JP5678407B2 - Semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device having a reflux diode.

  In order to suppress the oscillation phenomenon (ringing) of the freewheeling diode that occurs during reverse biasing, a semiconductor device in which a capacitor having a predetermined capacitance value is connected in parallel with the freewheeling diode has been proposed (for example, see Patent Document 1). .

JP 2004-281462 A

  Although the amplitude of the vibration phenomenon can be suppressed by the semiconductor device proposed above, the convergence time of the vibration phenomenon cannot be shortened. For this reason, it is not possible to suppress the adverse effect of noise generated in the voltage / current due to the oscillation phenomenon of the freewheeling diode on the peripheral circuits.

  In view of the above problems, an object of the present invention is to provide a semiconductor device that is reduced in size and can shorten the convergence time of a vibration phenomenon that occurs in a free-wheeling diode during reverse bias.

The present invention includes a plurality of freewheeling diodes that operate unipolar, a capacitor and a resistor formed in one semiconductor chip, and a snubber circuit that is connected in parallel with the freewheeling diode and disposed adjacent to the freewheeling diode, A semiconductor chip on which a semiconductor snubber circuit is formed is disposed in a region between the plurality of free-wheeling diodes in a region sandwiched between the free-wheeling diodes so that the free-wheeling diodes are separated from each other.

  According to the present invention, since the reflux diode and the semiconductor snubber circuit connected in parallel are arranged adjacent to each other, it is possible to provide a semiconductor device that is reduced in size and can shorten the convergence time of the oscillation phenomenon that occurs in the reflux diode during reverse bias. .

1 is a schematic circuit diagram showing a configuration of a semiconductor device according to a first embodiment of the present invention. FIG. 5 is a schematic circuit diagram showing another configuration of the semiconductor device according to the first embodiment of the present invention. It is a schematic diagram which shows the example of the mounting form of the semiconductor device which concerns on the 1st Embodiment of this invention. 1 is a schematic diagram illustrating a mounting structure example of a semiconductor device according to a first embodiment of the present invention. It is sectional drawing which shows the structure of the free-wheeling diode which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the semiconductor snubber circuit which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor snubber circuit which concerns on the 1st Embodiment of this invention. 1 is a circuit diagram of a power conversion device using a semiconductor device according to a first embodiment of the present invention. It is a circuit diagram of other power converters using the semiconductor device concerning a 1st embodiment of the present invention. FIG. 5 is a schematic circuit diagram showing another configuration of the semiconductor device according to the first embodiment of the present invention. It is a schematic diagram which shows the other mounting structure example of the semiconductor device which concerns on the 1st Embodiment of this invention. It is a schematic diagram which shows the other mounting structure example of the semiconductor device which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor snubber circuit which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor snubber circuit which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor snubber circuit which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor snubber circuit which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor snubber circuit which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor snubber circuit which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor snubber circuit which concerns on the 1st Embodiment of this invention. It is a graph which shows the simulation result of the attenuation waveform of a vibration phenomenon. It is a graph which shows the relationship between a capacity | capacitance ratio, a vibration phenomenon convergence time ratio, and the increase margin of a transient loss. It is a typical circuit diagram which shows the structure of the semiconductor device which concerns on the 2nd Embodiment of this invention. It is a schematic diagram which shows the example of the mounting form of the semiconductor device which concerns on the 2nd Embodiment of this invention. It is sectional drawing along the XXIV-XXIV direction of FIG. It is sectional drawing along the XXV-XXV direction of FIG. It is sectional drawing which shows the structure of the switching element which concerns on the 2nd Embodiment of this invention. It is a circuit diagram of the power converter device using the semiconductor device which concerns on the 2nd Embodiment of this invention. It is a circuit diagram of other power converters using the semiconductor device concerning a 2nd embodiment of the present invention. It is sectional drawing which shows the structure of the free-wheeling diode which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the structure of the switching element which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the other structure of the switching element which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the other structure of the switching element which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the other structure of the free-wheeling diode which concerns on the 3rd Embodiment of this invention. It is a schematic diagram which shows the example of the mounting form of the semiconductor device which concerns on the 4th Embodiment of this invention. It is a schematic diagram which shows the example of a mounting structure of the semiconductor device which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the structure of the semiconductor chip which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor chip which concerns on the 4th Embodiment of this invention. It is a schematic diagram which shows the other mounting structure example of the semiconductor device which concerns on the 4th Embodiment of this invention. It is a schematic diagram which shows the other mounting example of the semiconductor device which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor chip which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor chip which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor chip which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor chip which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor chip which concerns on the 4th Embodiment of this invention. It is a schematic diagram which shows the other mounting structure example of the semiconductor device which concerns on the 4th Embodiment of this invention. It is a schematic diagram which shows the example of the mounting form of the semiconductor device which concerns on the 5th Embodiment of this invention. It is a schematic diagram which shows the mounting structural example of the semiconductor device which concerns on the 5th Embodiment of this invention. It is sectional drawing which shows the structure of the semiconductor chip which concerns on the 5th Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor chip which concerns on the 5th Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor chip which concerns on the 5th Embodiment of this invention. It is sectional drawing which shows the other structure of the semiconductor chip which concerns on the 5th Embodiment of this invention. It is a schematic diagram which shows the example of the mounting form of the semiconductor device which concerns on the 6th Embodiment of this invention. It is a schematic top view which shows the example of arrangement | positioning of the semiconductor device which concerns on the 6th Embodiment of this invention. It is a typical top view showing other examples of arrangement of a semiconductor device concerning a 6th embodiment of the present invention. It is a typical top view showing other examples of arrangement of a semiconductor device concerning a 6th embodiment of the present invention. It is a typical top view showing other examples of arrangement of a semiconductor device concerning a 6th embodiment of the present invention. It is a schematic diagram which shows the example of the mounting form of the semiconductor device which concerns on the 7th Embodiment of this invention. It is a typical top view which shows the example of arrangement | positioning of the semiconductor device which concerns on the 8th Embodiment of this invention. It is a typical top view which shows the other example of arrangement | positioning of the semiconductor device which concerns on the 8th Embodiment of this invention. It is a typical top view which shows the other example of arrangement | positioning of the semiconductor device which concerns on the 8th Embodiment of this invention. It is a typical top view which shows the other example of arrangement | positioning of the semiconductor device which concerns on the 8th Embodiment of this invention.

  Next, first to eighth embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the following first to eighth embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the embodiments of the present invention include components, The shape, structure, arrangement, etc. are not specified below. The embodiment of the present invention can be variously modified within the scope of the claims.

(First embodiment)
As shown in FIG. 1, the semiconductor device 10 according to the first embodiment of the present invention is configured to have a snubber function by including a freewheeling diode 100 that operates unipolar, at least a capacitor 210, and a resistor 220. A semiconductor snubber circuit 200 connected in parallel with the diode 100 and disposed adjacent to the freewheeling diode 100 is provided.

  The freewheeling diode 100 and the semiconductor snubber circuit 200 are connected in parallel between the anode terminal 300 and the cathode terminal 400. That is, the anode and cathode of the freewheeling diode 100 are connected to the anode terminal 300 and the cathode terminal 400, respectively. The free-wheeling diode 100 includes a free-wheeling diode that operates in the same manner as the unipolar operation. The capacitor 210 and the resistor 220 may be divided into a plurality of parts as long as they are at least connected in series, or may be formed alternately, for example.

  Hereinafter, a case where the semiconductor snubber circuit 200 is a so-called RC snubber circuit in which a capacitor 210 and a resistor 220 are connected in series will be described. FIG. 1 shows a configuration of the semiconductor snubber circuit 200 in which a capacitor 210 is connected to the anode terminal 300 and a resistor 220 is connected to the cathode terminal 400. However, as shown in FIG. 2, the resistor 220 may be connected to the anode terminal 300 and the capacitor 210 may be connected to the cathode terminal 400.

  In the first embodiment, as an example, a case where the freewheeling diode 100 and the semiconductor snubber circuit 200 are formed as separate semiconductor chips will be described. In the first embodiment, a case where the semiconductor device 10 is used for a large current application will be described, and a case where there are a plurality of chips constituting the freewheeling diode 100 will be described.

  The capacitor 210 is connected to the anode terminal 300, and the resistor 220 is connected to the cathode terminal 400. In the first embodiment, the semiconductor snubber circuit 200 is formed of, for example, silicon as a semiconductor base material, and is formed so that an electrode connected to the anode terminal 300 and an electrode connected to the cathode terminal 400 face each other. The case of a vertical semiconductor chip will be described.

  Further, it is assumed that the reflux diode 100 is a Schottky barrier diode using, for example, silicon carbide as a semiconductor substrate material. As for this Schottky barrier diode, a so-called vertical Schottky barrier diode formed so that an electrode connected to the anode terminal 300 and an electrode connected to the cathode terminal 400 face each other will be described as an example. For example, even in the structure of a PN junction diode, an operation equivalent to a unipolar operation is performed by controlling the lifetime of minority carriers that are the main components of excess carriers injected from the P-type region during conduction. Even a bipolar diode having a characteristic equivalent to that of a unipolar operation is also included in the unipolar operation diode described in the present invention.

  FIG. 3 shows an example of a specific mounting form of the semiconductor device 10 including the freewheeling diode 100 (for example, silicon carbide Schottky barrier diode) and the semiconductor snubber circuit 200 (for example, silicon semiconductor RC snubber circuit) shown in FIG.

  In FIG. 3, as an example of a semiconductor package on which the semiconductor device 10 is mounted, an anode-side metal film 310 and a cathode-side metal film 410 made of a metal material such as copper or aluminum are formed on an insulating substrate 500. A case where a ceramic substrate is disposed is shown. The insulating substrate 500 has an insulating property formed of, for example, a ceramic plate and functions as a support.

  On the ceramic substrate, two semiconductor chips (indicated by reference numeral 100 in the figure) on which the freewheeling diode 100 is arranged and a semiconductor chip in which the semiconductor snubber circuit 200 is arranged (indicated by reference numeral 200 in the figure) are arranged. Is done. Here, the free-wheeling diode 100 connected to the cathode terminal 400 and the cathode terminal of the semiconductor snubber circuit 200 are disposed so as to be electrically connected to the metal film 410 via a bonding material such as solder or brazing material. The free-wheeling diode 100 connected to the anode terminal 300 and the anode terminal of the semiconductor snubber circuit 200 are connected to the metal film 310 via metal wirings 320 and 330 such as aluminum wires and aluminum ribbons. The metal film 410 is connected to the cathode terminal 400, and the metal film 310 is connected to the anode terminal 300.

  As described above, the semiconductor device 10 according to the first embodiment of the present invention illustrated in FIG. 3 includes a plurality of free-wheeling diodes 100, and at least a part of the snubber circuit 200 is disposed between the free-wheeling diodes 100.

  The semiconductor package shown in FIG. 3 is incorporated, for example, in a mounting structure as shown in FIG. 4 in order to improve heat dissipation and stably exhibit performance. Although FIG. 3 illustrates the structure above the insulating substrate 500, FIG. 4 which is a cross-sectional view along the IV-IV direction in FIG. 3 illustrates an example of the mounting structure.

  As shown in FIG. 4, on the back surface side of the insulating substrate 500, for example, a back metal film 1000 made of the same metal film as the metal film 310 on the anode side and the metal film 410 on the cathode side is formed. The back surface metal film 1000 is formed on a base plate 1100 made of a metal material such as copper or aluminum via a bonding material such as solder or brazing material. The base plate 1100 preferably has a function as a semiconductor package support structure and a function of heat conduction. Furthermore, the base plate 1100 is in contact with the cooling structure 1200 so that the heat generated in the freewheeling diode 100 and the semiconductor snubber circuit 200 can be quickly dissipated. Note that the base plate 1100 and the cooling structure 1200 may be in direct contact with each other, or may be in contact with each other through an adhesive material such as silicon grease in order to increase adhesion and further enhance heat transfer. There are roughly two methods of dissipating heat by the cooling structure 1200, and there are an air-cooling method that dissipates heat by an air flow and a water-cooling method that dissipates heat by a liquid water flow such as water or oil. FIG. 4 shows an example of a water-cooling type cooling structure in which a water channel 1300 is formed in a predetermined part of the cooling structure 1200. Of course, the heat dissipation method in the first embodiment is not limited to the water cooling type cooling structure, but may be an air cooling type cooling structure.

  FIG. 5 and FIG. 6 show an example of a cross-sectional structure diagram of a semiconductor chip that constitutes the free wheel diode 100 and the semiconductor snubber circuit 200, respectively.

The freewheeling diode 100 shown in FIG. 5 is made of, for example, a substrate material in which an N ⁻ type drift region 2 is formed on an N ⁺ type substrate region 1 of a silicon carbide polytype of 4H type. As the substrate region 1, for example, a general low-resistance substrate having a resistivity of several mΩcm to several tens of mΩcm and a thickness of several tens to several hundreds μm can be used. Note that the resistivity and thickness may be outside the above ranges depending on the element structure and required breakdown voltage, but generally the smaller the resistivity and thickness can reduce the loss during conduction, so the resistivity and thickness are as much as possible. Small is preferable. The drift region 2 has, for example, an N-type impurity density of 10 ¹⁵ cm ⁻³ to 10 ¹⁸ cm ⁻³ and a thickness of 0.1 μm to several tens of μm. For the drift region 2 as well, the impurity density and thickness may be outside the above ranges depending on the element structure and the required breakdown voltage.

In the first embodiment, a case will be described in which the drift region 2 having an impurity density of 10 ¹⁶ cm ⁻³ , a thickness of 5 μm, and a breakdown voltage of 600 V class is employed. However, the withstand voltage is not limited to the 600V class. Although FIG. 5 shows the case where the substrate is composed of two layers of the substrate region 1 and the drift region 2, a substrate formed only by the substrate region 1 whose resistivity is not according to the above example is used. Alternatively, a multilayer substrate may be used. Note that although the case where the substrate material is formed of a silicon carbide material has been described, the substrate material may be formed of another semiconductor material such as silicon.

  Surface electrode 3 is formed on the main surface of drift region 2 that faces the bonding surface with substrate region 1. Further, a back electrode 4 is formed on the main surface facing the front electrode 3 and facing the bonding surface of the substrate region 1 with the drift region 2.

  The surface electrode 3 is composed of a single-layer or multi-layer metal material including at least a metal material that forms a Schottky barrier with the drift region 2. Examples of the metal material that forms the Schottky barrier include titanium, nickel, molybdenum, gold, and platinum. Further, since the surface electrode 3 is connected to an external electrode as the anode terminal 300, a multilayer structure using a metal material such as aluminum, copper, gold, nickel, silver or the like on the outermost surface of the surface electrode 3 may be used.

  On the other hand, the back electrode 4 is made of an electrode material that is in ohmic contact with the substrate region 1. Examples of the electrode material that is ohmic-connected to the substrate region 1 include nickel silicide and titanium material. Further, the back electrode 4 is connected to an external electrode as a cathode terminal 400, so that the outermost surface is made of aluminum, copper, or gold. Alternatively, a multilayer structure using a metal material such as nickel or silver may be used. 5 functions as a diode in which the front electrode 3 is an anode terminal and the back electrode 4 is a cathode terminal.

FIG. 6 is an example of a cross-sectional structure diagram of the semiconductor snubber circuit 200. In FIG. 6, a dielectric region 12 made of a dielectric material such as a silicon oxide film is formed on a substrate region 11 of, eg, silicon N ⁻ type. In the structure shown in FIG. 6, the substrate region 11 functions as a resistor 220, and the dielectric region 12 functions as a capacitor 210. For the substrate region 11, the resistivity and thickness of the substrate can be determined according to the required resistance value. For example, a substrate having a resistivity of several mΩcm to several hundred Ωcm and a thickness of about several tens to several hundreds of μm is used. In the first embodiment, a case will be described where, for example, the substrate region 11 having a resistivity of 100 Ωcm and a thickness of 300 μm is used so as to be at least larger than the resistance value included in the freewheeling diode 100. In the first embodiment, the case where the substrate region 11 is formed so as to have a single resistivity is illustrated, but the substrate region 11 includes a plurality of portions each having different resistivity. It may be. Further, in the first embodiment, the conductivity type of the substrate region 11 is N type, but it may be P type.

  The thickness and area of the dielectric region 12 are determined according to the required breakdown voltage and the required capacitor capacity. The breakdown voltage is preferably higher than that of the freewheeling diode 100 in order to prevent the dielectric region 12 from being broken. The capacitance of the capacitor 210 can be selected in a range of about 1/100 to about 100 times the capacitance due to the depletion layer that occurs when the free-wheeling diode 100 is cut off (when a high voltage is applied). . In consideration of a chip area necessary for exhibiting a sufficient snubber function and suppressing an increase in loss as much as possible, a range of about 1/10 to about 10 times is preferable as shown in the calculation results described later.

  In the first embodiment, the thickness of the dielectric region 12 is 1 μm so that the breakdown voltage is higher than that of the freewheeling diode 100, and the capacitance of the capacitor 210 is the same as the depletion layer capacitance formed when the freewheeling diode 100 is cut off. The case where it is about will be described. The dielectric region 12 may be any material other than a silicon oxide film as long as it has a predetermined withstand voltage and functions as the capacitor 210. However, the dielectric region 12 has a dielectric breakdown electric field and a relative dielectric constant. A material having a product value larger than that of the silicon oxide film is even better.

When such a material is used, a necessary capacitance can be obtained with a small area while maintaining the withstand voltage of the dielectric region 12. For example, when the dielectric breakdown electric field is 1 × 10 ⁹ V / m and the relative dielectric constant is 3.9 as a physical property value of a general silicon oxide film, when the thickness of the silicon oxide film is 1 μm, per 1 cm ² The capacitance is about 3.4 nF. On the other hand, when a silicon nitride (Si ₃ N ₄ ) film is used for the dielectric region 12 instead of the silicon oxide film, the dielectric breakdown electric field is 1 × 10 ⁹ V / m and the relative dielectric constant is 7.5. Then, with a thickness of 1 μm, a breakdown voltage equivalent to that of the silicon oxide film can be ensured. At this time, the capacitance per 1 cm ² when using the Si ₃ N ₄ film is about 6.6 nF.

As described above, when the Si ₃ N ₄ film is used, the capacitance can be increased by about twice as compared with the case where the silicon oxide film is used, and the dielectric breakdown voltage of the dielectric region 12 is maintained while being increased. A large capacitance can be obtained. Accordingly, the area efficiency is improved and the wafer cost can be reduced. This effect can be compared by the product of the dielectric breakdown electric field and the dielectric constant of the dielectric material. The value of the silicon oxide film is about twice the value of the Si ₃ N ₄ film. Further, if the material of the dielectric region is a ferroelectric such as BaTiO ₃ , this value is about 13 times that of the silicon oxide film, and the area can be reduced. Other ferroelectric films include Pb (Zr, Ti) O ₃ , SrBi ₂ Ta ₂ O ₉ and Ti ₄ Ti ₃ O _12, but the product of the dielectric breakdown electric field and the relative dielectric constant is that of the silicon oxide film. Any material may be used for the dielectric region 12 as long as it is larger than the value. In addition, the dielectric region 12 is not limited to a single dielectric material, and a laminate of a plurality of dielectric materials may be used. For example, as shown in FIG. 7, the ONO structure sandwiching the Si ₃ N ₄ film with a silicon oxide film, a leakage current in the Si ₃ N ₄ film can be minimized with a silicon oxide film.

  In the first embodiment, as will be described later, when, for example, a Schottky barrier diode is used as the freewheeling diode 100, the capacitance is reduced against the current / voltage oscillation phenomenon that is essentially generated by the unipolar operation. By connecting the semiconductor snubber circuit 200 having the small and small size capacitor 210 and the resistor 220 in parallel, the vibration phenomenon can be suppressed easily and effectively. That is, there is no need to use a technique of wiring an external discrete component such as a film capacitor or a metal clad resistor, which is conventionally used as a snubber circuit for reducing the vibration of a diode operating in bipolar operation, in a path through which a main current flows.

  Further, a relational expression of C = 1 / (2πfR) is generally known as a design expression that effectively exhibits the snubber function. Here, the capacitance value of the capacitor 210 is C, the resistance value of the resistor 220 is R, and the frequency of the vibration phenomenon is f. In the first embodiment, the capacitor 210 and the resistor 220 can be easily set using the semiconductor snubber circuit 200 having a small capacitance so as to satisfy the above design formula.

  Furthermore, a surface electrode 13 is formed on the dielectric region 12, and a back electrode 14 is formed on the substrate region 11 so as to face the surface electrode 13. The surface electrode 13 is formed of, for example, a metal material so as to connect to an external electrode as an anode terminal, and has a single layer structure or a multilayer structure using a metal material such as aluminum, copper, gold, nickel, or silver on the outermost surface. . Similarly, the back electrode 14 is also formed of, for example, a metal material so as to be connected to an external electrode as a cathode terminal, and a single layer structure using a metal material such as aluminum, copper, gold, nickel, silver or the like on the outermost surface. It has a multilayer structure. Thus, in the semiconductor snubber circuit 200 shown in FIG. 6, the front electrode 13 is connected to the anode terminal of the freewheeling diode 100 shown in FIG. 5, and the back electrode 14 is connected to the cathode terminal of the freewheeling diode 100 shown in FIG. It functions as a semiconductor RC snubber circuit.

  Next, the operation of the first embodiment will be described.

  The semiconductor device 10 according to the first embodiment of the present invention includes, for example, a converter (FIG. 8), an inverter (FIG. 9), and the like that are generally used as one of power energy conversion means shown in FIGS. For example, the power converter is connected to a power supply voltage (+ V) of 400 V so as to be reverse-biased and used as a passive element for circulating current. 8 and 9, the chip size and the number of chips can be determined according to the power capacity or current capacity required for the power converter for the semiconductor device 10 functioning as a passive element. It is preferable to realize a power conversion device that combines low cost.

  The operation mode of the semiconductor device 10 operates in conjunction with the switching operation of the switching element S such as a MOSFET or IGBT from a cut-off state in which current is cut off to a conductive state in which current is circulated, and from a conductive state to a cut-off state. In the power conversion device, as with the switching element S, a stable operation that requires low loss and is unlikely to malfunction is required for a passive element that circulates current. The operation will be described taking the converter circuit of FIG. 8 as an example. Note that the switching element S in FIG. 8 is formed of, for example, an IGBT. In the following, since a high current capacity is required, a case where the chips constituting the freewheeling diode 100 are two chips as shown in FIG. 3 will be described.

  In a state where the switching element S is turned on and a current flows through the switching element S, the semiconductor device 10 which is a passive element is in a reverse bias state and is in a cut-off state. In the freewheeling diode 100 shown in FIG. 5 (here, a Schottky barrier diode), since a reverse bias voltage is applied between the anode terminal 300 and the cathode terminal 400, the Schottky junction with the surface electrode 3 in the drift region 2. A depletion layer extending from the portion is generated, and the cutoff state is maintained. In the semiconductor snubber circuit 200 shown in FIG. 6, the dielectric region 12 functioning as the capacitor 210 is charged with a high voltage, and the cut-off state is maintained. As described above, in the cut-off state, the semiconductor device 10 functions in the same manner as in the case where the semiconductor device 10 is configured by only the Schottky barrier diode.

  Next, when the switching element S is turned off, the semiconductor device 10 enters a forward bias state and shifts to a conductive state in conjunction with the switching element S shifting to the off state. The depletion layer extending in the drift region 2 of the free-wheeling diode 100 shown in FIG. 5 recedes, and the Schottky junction formed between the surface electrode 3 and the drift region 2 corresponds to the Schottky barrier height. When the forward bias voltage is applied, the freewheeling diode 100 becomes conductive. At this time, the current flowing through the freewheeling diode 100 is substantially constituted only by the electron current from the electrons supplied from the back electrode 4 side into the drift region 2 and performs a unipolar operation. Also in the semiconductor snubber circuit 200 shown in FIG. 6, similarly to the freewheeling diode 100, the charge charged in the dielectric region 12 is discharged because the high voltage reverse bias state shifts to the low voltage forward bias state. And a transient current flows.

  However, in the semiconductor device 10 according to the first embodiment, the capacitor capacity of the dielectric region 12 is substantially the same as the depletion capacity formed when the free-wheeling diode 100 is cut off. For this reason, the magnitude of the transient current that flows due to the discharge is much smaller than the forward bias current that flows through the parallel free-wheeling diodes 100 and has little effect on the operation. The semiconductor snubber circuit 200 becomes a forward bias state after the transient current accompanying the change of the bias voltage flows, and enters a steady state, so that the semiconductor snubber circuit 200 is cut off and only the freewheeling diode 100 is turned on. When the freewheeling diode 100 is formed of a Schottky barrier diode made of a silicon carbide material semiconductor substrate, the resistance of the drift region 2 can be made lower than that of a general PN junction diode made of silicon material. , Conduction loss can be reduced.

  However, during this conduction, the free-wheeling diode 100 generates a steady conduction loss according to the magnitude of the current. This steady conduction loss is generated as heat, and this heat leads to performance degradation of the semiconductor chip itself, the entire semiconductor package, and further the entire power converter. It may be performance degradation due to heat rise or destruction due to exceeding the heat resistance temperature. For this reason, a cooling device for quickly radiating the heat generated from the semiconductor element is used.

  In the mounting structure illustrated in FIG. 4, the heat generated by the freewheeling diode 100 is a heat radiating portion through the metal film 410 on the cathode side, the insulating substrate 500, the back surface metal film 1000, the base plate 1100, and the cooling structure 1200. Heat is radiated to the fluid in the water channel 1300. The better the heat dissipation to the water flow path 1300 corresponding to the heat radiating portion, the lower the temperature of the reflux diode 100 associated with the increase in the loss of the reflux diode 100. That is, when the maximum temperature of the freewheeling diode 100 is limited to a predetermined temperature, the better the heat dissipation, the more the loss of the freewheeling diode 100 can be allowed, that is, the current can flow with a larger current density. Thus, the higher the heat dissipation, the greater the limit on the maximum usable current of the freewheeling diode 100.

  Here, the distance from the semiconductor chip in which the reflux diode 100 is disposed to the water flow path 1300 that is the heat radiating portion of the cooling structure 1200 is defined as a heat radiation distance t, and the distance between the semiconductor chips in which the reflux diode 100 is disposed is between the chips. Let the distance be d. The smaller the heat radiation distance t, the higher the heat radiation performance, and the smaller the heat resistance characteristic of the structural material arranged between the heat radiation distance t, the higher the heat radiation performance. On the other hand, up to the distance at which the heat generated from the semiconductor chips does not interfere with each other, the greater the inter-chip distance d, the higher the heat dissipation. However, as the inter-chip distance d increases, the mounting area increases, which is disadvantageous in terms of downsizing and cost reduction. In general, it can be approximated that the diffusion of heat from a predetermined heat source spreads at an angle of 45 degrees. Therefore, when the inter-chip distance d is approximately twice or more than the heat radiation distance t, the heat between the heat sources is increased. Interference is unlikely to occur.

  In the first embodiment, a chip mounting arrangement that improves the heat dissipation of the semiconductor device 10 having a plurality of semiconductor chips (freewheeling diode chips) on which the free-wheeling diodes 100 are arranged is realized without unnecessarily increasing the mounting area. Yes. As described above, the freewheeling diode chip generates heat due to a corresponding loss at the time of turn-on and steady conduction. On the other hand, the semiconductor snubber circuit 200 generates little heat at the time of turn-on transient operation compared to the freewheeling diode 100 and has almost no loss during steady-state conduction.

  As shown in FIGS. 3 and 4, a semiconductor chip (snubber chip) in which a semiconductor snubber circuit 200 is arranged is mounted between two free-wheeling diode chips. For this reason, even when the distance between the free-wheeling diode chips is limited to allowance for manufacturing variations, that is, even in the case of the highest density mounting, the free-wheeling diode chips as heat sources should be separated by at least the width of the snubber chip. Implemented.

  For this reason, for example, the heat dissipation of the freewheeling diode chip can be improved as compared with the case where the snubber chip is not mounted between the freewheeling diode chips and is mounted so as to be adjacent to only one of them. Furthermore, as shown in FIG. 4, if the inter-chip distance d is greater than or equal to twice the heat dissipation distance t, heat interference between the free-wheeling diode chips that are heat sources is less likely to occur. Rise. As a result, high cooling efficiency can be obtained with a minimum mounting area.

  As described above, the mounting arrangement suitable for the operation mechanism of the freewheeling diode 100 and the semiconductor snubber circuit 200 in the first embodiment further improves the performance of the semiconductor device 10 according to the first embodiment of the present invention. be able to.

  As the switching element S turns on and the switching element S shifts to the on state, the semiconductor device 10 enters the reverse bias state and shifts to the cutoff state. In the Schottky barrier diode shown in FIG. 5 that is the freewheeling diode 100, the electron current supplied from the back electrode 4 side into the drift region 2 decreases as the forward bias voltage decreases. When the forward bias voltage becomes equal to or lower than the voltage corresponding to the Schottky barrier height of the Schottky junction, and when the reverse bias voltage starts to be applied to the Schottky junction, The depletion layer extending from the Schottky junction spreads and the free-wheeling diode 100 shifts to a cut-off state.

  A reverse recovery current is a current that is transiently generated in the process in which excess carriers accumulated in the element of the free-wheeling diode 100 disappear when shifting from the conductive state to the cut-off state. This reverse recovery current flows as a transient current in the semiconductor device 10 and the switching element S, and a loss (herein called reverse recovery loss) occurs in each element. For this reason, the reverse recovery current generated in the freewheeling diode 100 should be as small as possible.

  When the freewheeling diode 100 is formed by a unipolar Schottky barrier diode formed of a semiconductor material made of silicon carbide, the reverse recovery current is much smaller than that of a general PN junction diode formed of silicon. That is, reverse recovery loss can be greatly reduced. This difference in reverse recovery loss can be explained by the difference in the cutoff / conduction mechanism between the Schottky barrier diode and the PN junction diode as follows.

A PN junction diode formed of general silicon has a drift region conductivity modulation effect by minority carrier injection during forward bias conduction. For this reason, in order to ensure a breakdown voltage while reducing conduction loss as much as possible, it is common to form the drift region with a small thickness and a low impurity concentration. For example, when trying to realize a PN junction diode with a breakdown voltage of 600 V class, for example, when the impurity density in the drift region is set to about 10 ¹⁴ cm ⁻³ due to the limitation of feasibility of low impurity concentration, the thickness is compared with about 50 μm. It is necessary to use a substrate having a thick drift region. When conducting, due to the conductivity modulation effect of bipolar operation, minority carriers and majority carriers are injected into the drift region in accordance with the magnitude of the flowing current, so that a low resistance can be obtained. For example, when a forward bias current of about several hundred A / cm ² flows, carriers are injected to the extent that the concentration of majority carriers (electrons) and minority carriers (holes) are both 10 ¹⁷ cm ⁻³ , and they are excessive. Operates as a carrier.

On the other hand, in a Schottky barrier diode, the current that flows during conduction is composed only of electrons that are majority carriers. For this reason, the amount of excess carriers generated when shifting to the cut-off state is generated only by the amount of carriers discharged from the depletion layer when the depletion layer is formed in the freewheeling diode 100. That is, for example, even when the drift region 2 having a breakdown voltage of 600 V class, an impurity density of 10 ¹⁶ cm ⁻³ , and a thickness of 5 μm is depleted, the carrier density is 10 minutes compared to the PN junction diode. 1. The thickness of the drift region in which carriers are distributed is 1/10, and only about 1/100 excess carriers are generated in total.

  As described above, when the freewheeling diode 100 is formed of an element that performs a unipolar operation, the reverse recovery current can be greatly reduced, and as a result, the reverse recovery loss can be greatly reduced. As described above, the effect of reducing the reverse recovery loss is the same as that in the case where the passive element is composed only of the Schottky barrier diode.

  Furthermore, the semiconductor device 10 according to the first embodiment has a reverse recovery operation that occurs when the passive element performs a unipolar operation, which cannot be essentially solved when the passive element is composed of only a Schottky barrier diode. It has a function to suppress current / voltage oscillation phenomenon.

  This oscillation phenomenon is caused by the mutual relationship between the parasitic inductance Ls generated in the circuit of the power converter such as an inverter incorporating the freewheeling diode and the cutoff speed (dIr / dt) of the reverse recovery current Ir generated in the freewheeling diode during the reverse recovery operation. It is generally known that a surge voltage is generated by the action, and is generated starting from the generation of the surge voltage. This vibration phenomenon of current / voltage causes element destruction due to surge voltage, increase of loss during vibration operation, malfunction of peripheral circuits, and the like. In other words, since it becomes an impediment to stable operation, it is required to reduce the current / voltage oscillation phenomenon. In order to reduce the vibration phenomenon, it is necessary to alleviate the current interruption speed (dIr / dt) during the reverse recovery operation, and further to have a mechanism that quickly attenuates the oscillating current and converges the vibration.

  However, with only a Schottky barrier diode that performs unipolar operation, the component of the reverse recovery current Ir is composed of majority carriers. Therefore, although the reverse recovery current Ir due to excess carriers is greatly reduced, the reverse is almost determined by the formation rate of the depletion layer. The recovery time t can hardly be controlled. For this reason, a vibration phenomenon is likely to occur in the current / voltage, and the vibration is not easily attenuated. There are two main reasons.

  One reason is that, as described above, in the Schottky barrier diode, the excess carriers injected from the cut-off state to the conductive state are composed only of majority carriers that supplement the depletion region formed in the drift region when cut off. It is a point. That is, the reverse recovery current cutoff speed (dI / dt) of the Schottky barrier diode almost depends only on the formation speed of the depletion region, and there are almost no minority carriers. Cannot be used as is. For this reason, when only the Schottky barrier diode is used, if the switching speed of the switching element is increased to reduce the transient loss, a more severe vibration phenomenon occurs. In other words, there is a trade-off relationship between reducing transient loss and suppressing vibration phenomena.

  Another reason is that the Schottky barrier diode operates with almost majority carriers only when conducting, so that the resistance inside the element does not change depending on the thickness of the drift region and the impurity concentration, both when conducting and immediately before shutting off. Is a point. As described above, although the PN junction diode has a low resistance due to the conductivity modulation effect when conducting, the drift region has a high resistance during the reverse recovery operation in which the conductivity modulation is canceled, and the reverse recovery current Ir is resistance limited. It has a mechanism. On the other hand, the Schottky barrier diode has its own resistance component having a low resistance both during conduction and immediately before interruption, and does not have a mechanism for limiting the reverse recovery current Ir. Therefore, a vibration phenomenon is likely to occur in the current / voltage, and the vibration is not easily attenuated. Further, by using a wide gap semiconductor such as silicon carbide as the semiconductor material, the resistance of the element itself is small, so that conduction loss can be reduced, but vibration phenomenon is more likely to occur. For this reason, when only the Schottky barrier diode is used, there is a trade-off relationship between the loss during conduction and the suppression of the vibration phenomenon.

  On the other hand, according to the semiconductor device 10 according to the first embodiment, a simple configuration in which the freewheeling diode 100 and the semiconductor snubber circuit 200 are connected in parallel suppresses the vibration phenomenon while reducing the transient loss and the conduction loss. can do.

  That is, in the semiconductor device 10, when the forward bias current decreases to zero in the freewheeling diode 100, a depletion layer due to the reverse bias voltage is formed in the drift region 2, and a reverse recovery current composed of excess carriers starts to flow. . Almost simultaneously with the application of the reverse bias voltage, an equivalent reverse bias voltage is also applied to the capacitor 210 formed of the dielectric region 12 in the semiconductor snubber circuit 200, and a corresponding transient current flows in the semiconductor snubber circuit 200. start. The transient current flowing through the semiconductor snubber circuit 200 is determined by the size of the capacitor 210 formed of the dielectric region 12 and the size of the resistance component of the substrate region 11, and can be designed freely. The semiconductor snubber circuit 200 connected in parallel has three effects.

  The first effect is that the semiconductor snubber circuit 200 does not operate unless there is a transient voltage fluctuation, so that the switching speed of the switching element S is not affected, and the loss depending on the switching speed can be kept low as in the conventional case. This is a possible point. That is, since the cutoff speed of the forward bias current flowing through the freewheeling diode 100 can be set at a high speed, the loss accompanying the cutoff of the main current can be reduced. The second effect is that when the freewheeling diode 100 enters the reverse recovery operation, the capacitor component and the resistance component of the semiconductor snubber circuit 200 connected in parallel to the freewheeling diode 100 act, and the reverse recovery current cutoff speed (dIr / dt) can be relaxed, and the surge voltage itself can be reduced. The third effect is that since the current flowing through the semiconductor snubber circuit 200 is consumed by the resistance component of the substrate region 11, the energy generated by the parasitic inductance Ls is absorbed and the vibration phenomenon is quickly converged.

  As described above, the semiconductor device 10 according to the first embodiment has the performance of reducing the transient loss and the conduction loss of the freewheeling diode 100, and at the same time, using the semiconductor snubber circuit 200, the vibration inherent in the unipolar operation. The phenomenon can be solved.

  The RC snubber configuration is a generally known circuit, but a semiconductor snubber circuit 200 in which a snubber circuit is formed on a semiconductor substrate is the first to be combined with a freewheeling diode 100 having an operation equivalent to a unipolar operation or a unipolar operation. A sufficient function can be achieved as a snubber circuit. Conventionally, with respect to a PN junction diode made of silicon that has been generally used in power conversion devices such as inverters, it has been practically difficult to form a snubber circuit on a semiconductor chip due to power capacity limitations. For this reason, it has been necessary to arrange a capacitor consisting of a film capacitor or the like, which is a discrete component, and a resistor consisting of a metal clad resistor or the like in a path through which a main current flows inside or outside the semiconductor package of the power converter. The reason for this is that in order for the snubber circuit to function sufficiently, the capacitance through which a transient current comparable to the reverse recovery current flowing in the freewheeling diode flows in order to reduce the reverse recovery current cutoff speed (dIr / dt). And a resistor having a power capacity capable of consuming the current flowing through the capacitor is required to attenuate the vibration phenomenon.

  As described above, in the PN junction diode, the magnitude of the reverse recovery current varies depending on the magnitude of the circulating current. In the above example, the reverse recovery current is 100 times that of the unipolar Schottky barrier diode. As the current density flowing through the freewheeling diode further increases or the withstand voltage class increases, the excess carriers injected during conduction increase and the reverse recovery current also increases. Therefore, when the free-wheeling diode is a PN junction diode, the thickness of the capacitor is limited by the required breakdown voltage when the capacitor is formed on the semiconductor chip. Therefore, the area of the capacitor is simply calculated as compared with the free-wheeling diode that operates unipolarly. Needs to be multiplied by 100. Further, since the power to be consumed with respect to the resistance is 100 times, the volume needs to be 100 times, and as a result, the snubber circuit needs a chip size 100 times that of the free wheel diode. For this reason, it has been practically difficult to form a snubber circuit in a power converter using a semiconductor chip.

  In the first embodiment, paying attention to the fact that the transient current flowing through the freewheeling diode 100 is a transient current consisting only of carriers generated when a depletion layer is formed in the drift region 2 at most, the snubber circuit is electrostatically The semiconductor snubber circuit 200 having a small capacity is different from the prior art. Furthermore, the configuration described in the first embodiment provides the following new effects not found in the prior art in terms of the function of reducing transient loss and conduction loss and the function of suppressing vibration phenomena.

  One effect is that when a semiconductor snubber circuit 200 having a predetermined capacitor capacity and resistance value is connected in parallel to the freewheeling diode 100 that performs unipolar operation, the snubber function is enabled in the entire current range and the entire temperature range in which the freewheeling diode 100 operates. It works effectively. As described above, the reverse recovery current of the Schottky barrier diode is composed only of excess carriers generated when a depletion layer is generated by the reverse bias voltage. For this reason, a substantially constant reverse recovery current flows every time regardless of the magnitude of the current flowing during the reflux operation. For the same reason, almost constant reverse recovery current flows without being affected by the operating temperature of the freewheeling diode. For this reason, transient loss can be reduced and the vibration phenomenon can be suppressed in all current ranges and temperature ranges. These are effects that cannot be obtained in combination with a general PN junction diode.

  Another effect is that by forming the snubber circuit with the semiconductor snubber circuit 200, for example, as shown in FIG. 3, the snubber circuit can be mounted in the immediate vicinity of the freewheeling diode 100 with a low inductance, further reducing the transient loss. In addition, the vibration phenomenon can be suppressed. This is because, as the parasitic inductance generated when the snubber circuit is connected in parallel to the freewheeling diode 100 is smaller, the transient current flows through the semiconductor snubber circuit 200 more easily, and the reverse recovery current (Ir) flowing through the freewheeling diode 100 is cut off (dIr / dt) can be easily relaxed, and since the back electromotive force generated by the parasitic inductance superimposed on the voltage applied to the capacitor 210 of the semiconductor snubber circuit 200 is small, the switching time can be increased in the withstand voltage range of the capacitor 210. by. For this reason, in the first embodiment, the parasitic inductance is reduced as compared with the case of a snubber circuit using a capacitor composed of a film capacitor or the like, which is a conventional discrete component, and a resistor composed of a metal clad resistor or the like. As a result, the switching time can be shortened to reduce the transient loss, and the reverse recovery current cutoff speed (dIr / dt) can be appropriately relaxed to suppress the vibration phenomenon.

  Further, mounting the semiconductor snubber circuit 200 in the immediate vicinity of the freewheeling diode 100 also reduces unnecessary noise emission. For example, in the case of a snubber circuit using capacitors and resistors of discrete components, the oscillating current generated in the freewheeling diode 100 passes through a current path that returns to the freewheeling diode 100 via these discrete components. At that time, the oscillating current is suppressed by the resistance, but until then, the surface formed by this current path works as a kind of loop antenna and radiates noise. In the case where the snubber circuit is formed by the semiconductor snubber circuit 200, the size of the surface formed by the current path of the oscillating current is reduced by mounting the semiconductor snubber circuit 200 in the immediate vicinity of the freewheeling diode 100 as compared with the case where discrete components are used. The noise emission due to the oscillating current is reduced significantly. Thereby, it is possible to prevent malfunction of the control circuit and the like due to noise.

  Furthermore, in the semiconductor device 10 according to the first embodiment, by forming the snubber circuit with the semiconductor snubber circuit 200, the power conversion device can be configured using the same mounting process as that of the freewheeling diode 100. For this reason, the vibration phenomenon can be easily and easily suppressed, and the required volume can be significantly reduced as compared with a snubber circuit using discrete components.

  Further, since the resistance component of the semiconductor snubber circuit 200 can be formed of a semiconductor substrate and directly mounted on a semiconductor package as shown in FIG. 3, high heat dissipation can be obtained. Therefore, it is possible to design a resistor with a higher density than an external resistor. That is, it has high resistance to destruction and can be further downsized.

  When a predetermined breakdown voltage is obtained, the resistance of the freewheeling diode 100 itself decreases as the depletion layer thickness is reduced by adopting a wide bandgap semiconductor element for the freewheeling diode 100, thereby reducing the low conduction loss. On the other hand, the reverse recovery current cutoff speed (dIr / dt) is increased and vibration energy is hardly consumed, so that the vibration phenomenon becomes more prominent. On the other hand, when a Schottky barrier diode made of silicon is used as the freewheeling diode 100, a certain level of effect can be obtained as an effect of the present invention. However, due to restrictions on the impurity concentration and thickness of the drift region 2, the silicon carbide material In comparison, the freewheeling diode 100 itself has a large resistance component, and the freewheeling diode 100 itself consumes vibration energy and is easily attenuated.

  However, in the semiconductor device 10 according to the first embodiment, by configuring the free wheel diode 100 with a wide bandgap semiconductor such as silicon carbide, it is possible to more remarkably reduce both the conduction loss and the vibration phenomenon. . That is, as exemplified in the first embodiment, the effect of the present invention can be maximized by configuring the freewheeling diode 100 with a Schottky barrier diode made of silicon carbide. In the first embodiment, the case where the semiconductor material of the free-wheeling diode 100 is silicon carbide is described. However, the same effect can be obtained by using a wide gap semiconductor such as gallium nitride or diamond. .

  Even during the reverse recovery operation, the heat dissipation of the two semiconductor chips in which the free-wheeling diodes 100 are arranged can be improved by using the mounting structure illustrated in FIG.

  In addition to the simple RC snubber circuit shown in FIG. 1, the semiconductor snubber circuit 200 may have a configuration including a diode 230 so as to be connected in parallel to the resistor 220 as shown in FIG. 10, for example. This is because the semiconductor snubber circuit 200 configured to have at least the capacitor 210 and the resistor 220 can obtain the same effect as described above.

  In addition to the semiconductor package using the ceramic substrate or the like shown in FIG. 3 and FIG. 4 shown as an example of the mounting form, for example, as shown in FIG. A mounting form in which the cooling structure 1200 and the metal substrate 420 are insulated by an insulating layer 1400 made of an insulating plate or insulating sheet having an insulating property may be used as the cathode terminal, or other mounting forms may be used. .

  Further, not only when the free-wheeling diode chip provided with the free-wheeling diode 100 is 2 chips, but also as shown in FIG. 12, the free-wheeling diode chip may be 3 chips or more. At this time, a snubber chip is disposed between the reflux diode chips. That is, at least a part of the semiconductor snubber circuit 200 is disposed between the freewheeling diodes 100.

  3, 4, 11, and 12, the back electrode 4 and the back electrode 14 on the cathode terminal side are mounted by solder or the like, and the anode terminal side is wired by the metal wirings 320 and 330. In addition, both the cathode terminal and the anode terminal may be mounted with solder or the like. The cooling performance is improved by mounting both the cathode terminal and the anode terminal with solder or the like. For this reason, the heat dissipation of the freewheeling diode 100 and the heat dissipation of the resistor 220 of the semiconductor snubber circuit 200 are increased, and mounting can be performed at a higher density.

  The capacitor 210 of the semiconductor snubber circuit 200 may be formed with the structure shown in FIGS. 13 to 16, and the resistor 220 may be formed with the structure shown in FIGS.

  FIG. 13 shows a case where, for example, a P-type opposite conductivity type region 15 is formed instead of the dielectric region 12 made of the silicon oxide film shown in FIG. In the case of the configuration shown in FIG. 6, the oscillation phenomenon is suppressed by charging the capacitor 210 in the dielectric region 12 with the voltage applied when the freewheeling diode 100 performs the reverse recovery operation. On the other hand, in the configuration example shown in FIG. 13, a depletion layer formed between the P-type opposite conductivity type region 15 and the N-type substrate region 11 is used as the capacitor 210. An advantage of using the depletion layer as a component of the capacitor 210 is that deterioration due to a transient current is relatively less than that of the dielectric region 12 such as a silicon oxide film. That is, it is advantageous in terms of long-term reliability.

  As another configuration for forming a depletion layer in the substrate region 11, for example, as shown in FIG. 14, a surface electrode 13 made of a metal material that forms a Schottky junction with the substrate region 11 is formed on the substrate region 11. A method can also be adopted. In addition to the Schottky junction, the same effect can be obtained with any configuration as long as a depletion layer is formed when a reverse bias voltage such as a heterojunction is applied.

  In the configurations of FIGS. 13 and 14, there is a concern that a forward current flows during forward bias. However, the resistance value of the substrate region 11 in FIGS. 13 and 14 is larger than the resistance value of the drift region 2 of the freewheeling diode 100. For this reason, most of the current flows through the low-resistance freewheeling diode 100 and hardly affects the conduction loss during forward bias.

  As shown in FIGS. 15 and 16, the capacitor 210 may be configured by forming a plurality of regions in series or in parallel. FIG. 15 is a circuit diagram in which the capacitor component by the dielectric region 12 shown in FIG. 6 and the capacitor component by the depletion layer obtained by forming the opposite conductivity type region 15 shown in FIG. An example is shown. FIG. 16 shows an example in which the capacitor 210 is formed by connecting the capacitor component by the dielectric region 12 and the capacitor component by the depletion layer shown in FIG. 10 in parallel. In any case, as long as the capacitor 210 is formed so as to be connected in series with the resistor 220, the capacitor 210 may be configured in any region.

FIG. 17 shows an example in which the resistor 220 including the substrate region 11 shown in FIG. In the configuration example shown in FIG. 17, instead of the substrate region 11 used in FIG. 6, the low resistance substrate region 16 made of an N ⁺ type low resistance substrate is used, and the resistor 220 is made of, for example, polycrystalline silicon. A resistance region 17 is formed on the dielectric region 12. An advantage is that the resistance value of the resistor 220 can be freely set by changing the thickness and impurity concentration of the resistor region 17 made of polycrystalline silicon. That is, the semiconductor snubber circuit 200 can be formed by using any substrate when selecting the substrate region as the support base. For this reason, it becomes possible to raise the freedom degree, such as material selection.

  The resistance region 17 may be made of any material other than polycrystalline silicon. However, the resistance region 17 is preferably made of a material having a higher dielectric breakdown field than silicon, and the manufacturing process of the resistance region 17 is performed. There is an effect of facilitating further. For example, when 100 V is applied as a surge voltage to both ends of the freewheeling diode 100 during reverse recovery, a transient current flows through the capacitor 210 in the semiconductor snubber circuit 200, so that the surge voltage is almost equivalent to both ends of the resistance region constituting the resistor 220. Of 100V is applied. At this time, a breakdown voltage greater than or equal to the breakdown voltage determined by the breakdown field and thickness corresponding to the material is required for the resistance region. In the case of silicon, in order to have a breakdown voltage of 100 V, a thickness of about 3 μm is required because the dielectric breakdown electric field of silicon is about 0.3 MV / cm. When poly silicon carbide having a higher breakdown electric field than silicon is used in the resistance region, the breakdown electric field of poly silicon carbide is about 3.6 MV / cm, so that the thickness can be reduced to about 1/10 of silicon. Therefore, the deposition time when forming the resistance region can be shortened, and the process can be facilitated. In addition, since silicon carbide has a thermal conductivity approximately three times better than that of silicon, there is an effect of improving the heat dissipation of the resistance region 17.

  FIG. 18 shows a case where the substrate region 11 described in FIG. 6 and the resistor region 17 described in FIG. 17 are connected in series as components of the resistor 220. As described above, the resistor 220 may be configured in any region as long as it is formed so as to be connected in series with the capacitor 210.

As described above, in the first embodiment, the case where the semiconductor material made of silicon is used as the support base of the semiconductor snubber circuit 200 is taken as an example. However, for example, an insulating substrate material such as silicon nitride, aluminum nitride, or alumina is used as the substrate region. It may be used as FIG. 19 shows an example in which an N ⁻ -type resistance region 19 is formed on an insulating substrate 18 made of silicon nitride as an example. As described above, any configuration may be used as long as it can be handled as a chip material and mounted as shown in FIG. 3 without using a semiconductor substrate such as silicon in the substrate region. FIG. 19 shows the case where the insulating substrate 18 and the resistance region 19 are in contact with each other, but a bonding material such as a metal film or solder may be formed between the insulating substrate 18 and the resistance region 19.

  20 and 21 use a circuit simulator for the relationship between the capacitance C of the capacitor used in the snubber circuit and the suppression effect of the vibration phenomenon and the increase in loss due to the transient current flowing in the capacitor. This is an example calculated. The vibration of the snubber circuit is reduced by the parasitic inductance Ls in the circuit, the capacitance C0 of the capacitor component of the free wheel diode, and the capacitance C of the snubber circuit connected in parallel to the free wheel diode and the resistance value R of the resistor. It can be calculated with a simple circuit simulator. In this calculation, as an example, the parasitic inductance Ls in the effect circuit is fixed to 99 nH and the resistance value R is 40 Ω, and the decay time of the vibration phenomenon and the transient loss generated in the snubber circuit depending on the size of the capacitance ratio C / C0. The change in the increase of the cost was calculated. The capacitance C0 of the capacitor component of the freewheeling diode was 150 pF.

  FIG. 20 shows a waveform of the vibration phenomenon when the capacity ratio C / C0 is 0.004 times to 40 times. As shown in FIG. 20, as the capacitance ratio C / C0 increases, the decay time of the vibration phenomenon decreases. In particular, the damping effect of the vibration phenomenon becomes remarkable from the capacity ratio C / C0 of about 0.1 times. On the other hand, when the capacity ratio C / C0 exceeds 10, the convergence time ratio value of the vibration phenomenon tends to be saturated.

  The axis on the left side of FIG. 21 indicates that the time until the voltage or current vibration is attenuated to 1/10 in the absence of the snubber circuit is t0, and when the snubber circuit is added, the vibration is equivalent to the case without the snubber circuit. The vibration phenomenon convergence time ratio t / t0 when the time until is t is shown. The axis on the right side of FIG. 21 shows the increase amount of excess loss E / E0 where E0 is the loss caused by the excess current flowing through the freewheeling diode and E is the loss caused by the excess current flowing through the capacitor of the snubber circuit. . Since a loss E due to a transient current proportional to the magnitude of the capacitance C of the capacitor occurs during the transient operation, it is preferable that the capacitance C of the capacitor is as small as possible.

  From the circuit simulator result, the capacitance of the capacitor 210 included in the snubber circuit 200 is selected in the range of 1/10 to 10 times the capacitance of the capacitor component in the cutoff state of the freewheeling diode 100. It is preferable. As a result, the vibration phenomenon can be reduced more significantly while suppressing an increase in loss. This effect can be obtained in any of the configuration examples described in the first embodiment.

  As described above, according to the semiconductor device of the first embodiment, the free-wheeling diode 100 and the semiconductor snubber circuit 200 connected in parallel are adjacent to each other, and at least the semiconductor snubber circuit 200 is interposed between the plurality of free-wheeling diodes 100. It is possible to provide a semiconductor device that is reduced in size by being partially disposed and that can shorten the convergence time of an oscillation phenomenon that occurs in a free-wheeling diode during reverse bias.

(Second Embodiment)
The semiconductor device according to the second embodiment will be described below. Below, the description of the same part as 1st Embodiment is abbreviate | omitted, and a different characteristic is demonstrated in detail.

  As shown in FIG. 22, the semiconductor device 10 </ b> A according to the second embodiment includes a free-wheeling diode 100 that performs the unipolar operation described in the first embodiment or an operation equivalent to the unipolar operation, at least a capacitor 210, and a resistor 220. In addition to the semiconductor snubber circuit 200 including the switching diode 600, the switching diode 600 connected in parallel to the freewheeling diode 100 and the semiconductor snubber circuit 200 is further provided. In the example shown in FIG. 22, the semiconductor snubber circuit 200 is an RC snubber circuit in which a capacitor 210 and a resistor 220 are connected in series. The emitter terminal 301 is connected to the emitter terminal of the switching element 600, the anode terminal of the freewheeling diode 100, and the resistor 220 of the semiconductor snubber circuit 200. The collector terminal 401 is connected to the collector terminal of the switching element 600, the cathode terminal of the freewheeling diode 100, and the capacitor 210 of the semiconductor snubber circuit 200.

  In the second embodiment, a case will be described in which the free wheeling diode 100, the semiconductor snubber circuit 200, and the switching element 600 are formed on different semiconductor chips. In the second embodiment, a case will be described in which there are a plurality of chips on which the freewheeling diode 100 and the switching element 600 are arranged in order to use the freewheeling diode 100 and the switching element 600 for a large current application.

  The configuration of the semiconductor snubber circuit 200 and the configuration of the free-wheeling diode 100 can employ the same configuration as in the first embodiment. Below, the case where the switching element 600 is IGBT which used silicon as a semiconductor base material, for example is demonstrated. Here, the case where the switching element 600 is a so-called vertical IGBT in which electrodes are formed so that the emitter terminal and the collector terminal face each other will be described as an example.

  FIG. 23 shows a semiconductor device 10A including the freewheeling diode 100 (for example, silicon carbide Schottky barrier diode) and the semiconductor snubber circuit 200 (for example, silicon semiconductor RC snubber) and the switching element 600 (for example, silicon IGBT) shown in FIG. It is the figure which showed the specific mounting example. As shown in FIG. 23, the semiconductor device 10A according to the second embodiment can be mounted on a semiconductor package using a ceramic substrate as in the example shown in FIG.

  In the example shown in FIG. 23, a semiconductor chip in which the freewheeling diode 100 is disposed on the metal film 410 (freewheeling diode chip, indicated by reference numeral 100 in the figure), and a semiconductor chip in which the semiconductor snubber circuit 200 is disposed (snubber chip). , And a semiconductor chip (switching element chip, indicated by reference numeral 600 in the drawing) on which the switching element 600 is disposed is disposed two by two. As shown in FIG. 23, a snubber chip is disposed between the freewheeling diode chips, and a snubber chip is disposed between the switching elements 600.

  The terminals connected to the collector terminals 401 of the freewheeling diode chip, the snubber chip, and the switching element chip are arranged so as to be in contact with the metal film 410 through a bonding material such as solder or brazing material. The terminals connected to the emitter terminals 301 of the freewheeling diode chip, the snubber chip, and the switching element chip are connected to the metal film 310 via metal wirings 320, 330, and 350 such as aluminum wires and aluminum ribbons, for example. Further, the gate terminal of the switching element 600 is connected to the metal film 700 connected to the gate terminal 510 through the metal wiring 710.

  The semiconductor package shown in FIG. 23 is used by being incorporated into a mounting structure as shown in FIGS. 24 and 25, for example, in order to improve heat dissipation and stably exhibit performance. FIG. 24 is a cross-sectional view along the XXIV-XXIV direction of FIG. 23 and shows an example of a mounting structure of a portion where the switching element 600 is mounted. FIG. 25 is a cross-sectional view along the XXV-XXV direction of FIG. 23 and shows an example of a mounting structure of a portion where the free-wheeling diode 100 is mounted. As shown in FIGS. 24 and 25, on the back surface side of the insulating substrate 500, for example, a back metal film 1000 made of a metal film similar to the metal film 310 on the emitter side and the metal film 410 on the collector side is formed.

  The mounting structure shown in FIGS. 24 and 25 has the same configuration as the mounting structure shown in FIG. That is, the back metal film 1000 is formed on the base plate 1100 having a function as a semiconductor package support structure and a function of heat conduction. Base plate 1100 contacts cooling structure 1200. As already described, the base plate 1100 and the cooling structure 1200 may be in direct contact with each other, or may be in contact with each other through an adhesive material such as silicon grease. In the example shown in FIGS. 24 and 25, an example of a water cooling type cooling structure in which a water flow path 1300 is formed in a predetermined portion of the cooling structure 1200 is shown. However, the cooling structure may be a water cooling type or an air cooling type. There may be.

  FIGS. 26, 5 and 6 show examples of cross-sectional structures of the switching element chip, the reflux diode chip and the snubber chip on which the switching element 600, the reflux diode 100 and the semiconductor snubber circuit 200 are respectively arranged. FIG.

FIG. 26 shows an example in which the switching element 600 is a general IGBT. For example, an IGBT using a substrate material in which an N ⁻ type drift region 23 is formed on a P ⁺ type substrate region 21 made of silicon via an N type buffer region 22. The substrate region 21 has, for example, a resistivity of several mΩcm to several tens of mΩcm and a thickness of about several μm to several hundred μm. The drift region 23 has, for example, an N-type impurity density of 10 ¹³ cm ⁻³ to 10 ¹⁶ cm ⁻³ and a thickness of several tens of μm to several hundreds of μm.

Note that the resistivity, impurity density, and thickness may be out of the above ranges depending on the element structure and required breakdown voltage, but in general, the smaller the resistivity and thickness, the more the resistance can be reduced. Is preferably reduced. In the second embodiment, for example, a drift region 23 having an impurity density of 10 ¹⁴ cm ⁻³ , a thickness of 50 μm, and a breakdown voltage of 600 V class is used.

  The buffer region 22 is formed to prevent punch-through with the substrate region 21 when a high electric field is applied to the drift region 23. In the second embodiment, the case where the substrate region 21 is used as a support base material is described as an example, but the buffer region 22 and the drift region 23 may be used as a support base material. The buffer region 22 may be omitted as long as the substrate region 21 and the drift region 23 do not punch through.

As shown in FIG. 26, a P-type well region 24 is formed in a part of the surface layer portion in the drift region 23, and an N ⁺ -type emitter region 25 is formed in a part of the surface layer portion in the well region 24. . A gate insulating film 26 made of, for example, a silicon oxide film is formed on the drift region 23, the well region 24, and the emitter region 25, and a gate electrode 27 made of, for example, N-type polycrystalline silicon is disposed on the gate insulating film 26. It is installed. Further, an emitter electrode 28 made of, for example, an aluminum material is formed in contact with the emitter region 25 and the well region 24 in the opening provided in the gate insulating film 26. An interlayer insulating film 29 made of, for example, a silicon oxide film is formed between the emitter electrode 28 and the gate electrode 27 so that the emitter electrode 28 and the gate electrode 27 are not in contact with each other. A collector electrode 30 is formed so as to be in ohmic contact with the substrate region 21. As described above, the IGBT that can be used in the switching element 600 shown in FIG. 26 is a so-called planar type in which the gate electrode 27 is formed on the semiconductor substrate plane.

  The configuration of the free wheel diode (here, the Schottky barrier diode) illustrated in FIG. 5 as the cross-sectional structure diagram of the free wheel diode chip shown in FIG. 23 is the same as that described in the first embodiment, and thus redundant description. Is omitted.

  Although the basic configuration of the semiconductor snubber circuit 200 illustrated in FIG. 6 as the cross-sectional structure diagram of the snubber chip illustrated in FIG. 23 is the same as that of the first embodiment, in order to effectively exhibit the snubber function. The capacitor 210 and the resistor 220 are preferably set in consideration of the switching element 600 newly connected in parallel. However, as will be described later, when a reverse recovery current flows through the freewheeling diode 100, the parallel switching elements 600 are always in a cut-off state. For this reason, the setting of the capacitor 210 and the resistor 220 of the semiconductor snubber circuit 200 corresponds to the setting according to the depletion capacity when the free wheel diode 100 and the switching element 600 are cut off, as in the case described in the first embodiment. Is possible.

  That is, for the substrate region 11, the resistivity and thickness of the substrate are set according to the magnitude of the resistance value necessary for the resistor 220. For example, the substrate region 11 having a resistivity of several mΩcm to several hundreds Ωcm and a thickness of about several tens of μm to several hundreds of μm is used. In addition, with respect to the capacitance of the capacitor 210, the thickness and area of the dielectric region 12 are set so that the required withstand voltage is satisfied at a minimum and the necessary capacitance is obtained. Capacitor 210 can be selected in the range of about 1/100 to about 100 times the sum of the depletion capacities in which freewheeling diode 100 and switching element 600 are charged in the cutoff state (when a high voltage is applied). However, if a sufficient snubber function is exhibited, the increase in loss is suppressed as much as possible, and the required chip area is taken into consideration, the capacitor is approximately in the range of about 1/10 to 10 times as shown in the calculation results described later. It is preferable to select 210. In the second embodiment, for example, the thickness of the dielectric region 12 is set to 1 μm so that the breakdown voltage of the freewheeling diode 100 and the switching element 600 is higher, and the capacitance of the capacitor 210 is the cutoff of the freewheeling diode 100 and the switching element 600. Assume that it is about the same as the sum of depletion capacities formed in the state.

  In the second embodiment in which the switching element 600 is connected in parallel with the free wheeling diode 100 and the semiconductor snubber circuit 200, as will be described later, for example, when a Schottky barrier diode is used for the free wheeling diode 100, the switching element 600 is essentially obtained by unipolar operation. The semiconductor snubber circuit 200 having the small capacitance 210 and the resistor 220 is connected in parallel to the current / voltage vibration phenomenon generated in the capacitor, and the vibration phenomenon can be easily and effectively suppressed. . That is, it is not necessary to use a conventional method of wiring an external discrete component such as a film capacitor or a metal clad resistor in a path through which a main current flows as a snubber circuit for reducing vibration of a free-wheeling diode that performs bipolar operation. Further, as already described, the semiconductor snubber circuit 200 is also provided in the second embodiment so as to satisfy C = 1 / (2πfR), which is generally known as a design formula that effectively exhibits the snubber function. The capacitor 210 and the resistor 220 can be easily set.

  The operation of the semiconductor device 10A according to the second embodiment will be described below.

  The semiconductor device 10A is used as a so-called inverter that moves a three-phase AC motor as shown in FIG. 27 as a general means for converting power energy, or a so-called H-bridge power converter as shown in FIG. Can do. For example, the inverter shown in FIG. 27 includes a semiconductor device 10A including a switching element E and a passive element B connected in parallel to form an upper arm, and a switching element G and a passive element F connected in parallel to form a lower arm. For example, the semiconductor device 10A is connected in series so as to be reverse-biased with respect to a power supply voltage (+ V) of 400V, for example. This connection is connected for three phases to form a three-phase inverter. With regard to the switching elements and passive elements used in FIG. 27, the chip size and the number of chips are determined according to the power capacity or current capacity required for the power converter, and the power has high performance, small size, and low cost. A conversion device is realized.

  The operation mode of the semiconductor device 10A shown in FIG. 27 is that when either the switching element of the upper arm or the lower arm performs a switching operation, the switching element and the passive element of the arm that is not switching operate in conjunction with each other, It operates from a cut-off state to cut off to a conductive state that circulates current and from a conductive state to a cut-off state. Here, the operation of the semiconductor device 10A will be described using the operation of one phase among the three phases shown in FIG. Further, as an example, a case where the switching element G of the lower arm performs a switching operation and the switching element E and the passive element B of the upper arm perform a reflux operation will be described. That is, the case where the semiconductor device 10A shown in FIG. 22 is one arm and the two arms are connected vertically is described. Further, in the following, a high current capacity is required for the power conversion device, and semiconductor chips on which the freewheeling diode 100, the semiconductor snubber circuit 200, and the switching element 600 are arranged are each used for two chips per arm. Will be described.

  In a state where the switching element G of the lower arm is turned on and a current flows through the switching element G, the switching element E and the passive element B of the upper arm are in a reverse bias state and are in a cut-off state.

  In the passive element F connected in parallel to the switching element G in the conductive state, the freewheeling diode 100 and the semiconductor snubber circuit 200 maintain the cutoff state. The freewheeling diode 100 is in a cut-off state because a low voltage such as the ON voltage of the switching element G is applied as a reverse bias across the Schottky barrier diode that is the freewheeling diode 100. In addition, in the semiconductor snubber circuit 200 shown in FIG. 6, the dielectric region 12 functioning as the capacitor 210 operates only when the voltage changes. Therefore, in a state where a voltage about the ON voltage of the switching element G is applied in a steady state. It is in a cut-off state.

  That is, in the lower arm, when the switching element G is turned on, a steady conduction loss corresponding to the magnitude of the current occurs in the switching element G. This steady conduction loss is generated as heat, and this heat leads to performance degradation of the semiconductor chip itself, the entire semiconductor package, and further the entire power converter. This may be performance degradation due to an increase in heat, or destruction due to exceeding the heat resistance temperature. For this reason, a cooling device for quickly dissipating the heat generated from the semiconductor device 10A is used.

  In the mounting structure illustrated in FIG. 24, the heat generated in the switching element 600 flows through the collector-side metal film 410, the insulating substrate 500, the back surface metal film 1000, the base plate 1100, and the cooling structure 1200. Heat is dissipated to the fluid in the path 1300. The better the heat dissipation to the water flow path 1300 corresponding to the heat radiating portion, the more the temperature rise of the switching element 600 accompanying the increase in the loss of the switching element 600 can be suppressed. That is, when the maximum temperature of the switching element 600 is limited to a predetermined temperature, the better the heat dissipation, the more loss of the switching element 600 can be allowed, that is, the current can flow with a larger current density. From this, the range of the maximum use current of the switching element 600 can be expanded, so that heat dissipation is high.

  Also in the second embodiment, as in the first embodiment, the smaller the heat radiation distance t, the higher the heat radiation performance, and the smaller the thermal resistance characteristic of the structural material formed between the heat radiation distance t, the higher the heat radiation performance. . On the other hand, the heat dissipation increases as the inter-chip distance d increases, but the mounting area increases, which is disadvantageous in terms of downsizing and cost reduction. Since the thermal diffusion from a predetermined heat source is approximated to spread at an angle of 45 degrees, if the size of the inter-chip distance d is about twice or more than the heat radiation distance t, the heat interference between the heat sources. Is unlikely to occur.

  In the second embodiment, a chip mounting arrangement is employed that improves the heat dissipation of the semiconductor device 10A including a plurality of switching element chips on which the switching elements 600 are arranged without unnecessarily increasing the mounting area. As described above, the switching element 600 generates heat due to a corresponding loss at the time of turn-on and steady conduction, but the semiconductor snubber circuit 200 has a smaller loss at the time of transient operation at turn-on than the freewheeling diode 100 and is steady. Since there is almost no loss during conduction, almost no heat is generated.

  Further, in the second embodiment, as shown in FIGS. 22 and 24, a snubber chip in which a semiconductor snubber circuit 200 is arranged is mounted between two switching element chips in which a switching element 600 is arranged. For this reason, even in the case of the highest density mounting in which the distance between the mounted chips is only a margin for manufacturing variations, the switching elements 600 serving as heat sources can be mounted at least as wide as the width of the snubber chip. it can. For this reason, for example, the heat dissipation of the switching element chip can be improved as compared with the case where the snubber chip is not mounted between the switching element chips but mounted adjacent to only one of the switching element chips. Furthermore, as shown in FIG. 24, if the inter-chip distance d is more than twice as large as the heat radiation distance t, heat interference between the switching elements 600 serving as the heat sources hardly occurs. Increases performance. As a result, high cooling efficiency can be obtained with a minimum mounting area.

  As described above, the mounting arrangement suitable for the operation mechanism of the switching element 600 and the semiconductor snubber circuit 200 according to the second embodiment can further improve the performance of the semiconductor device 10A according to the second embodiment. it can.

  The switching element E and the passive element B of the upper arm are also maintained in the cut-off state because the reverse bias voltage of about the power supply voltage is applied when the switching element G is conductive. This is because the reverse bias voltage is applied between the emitter terminal 301 and the collector terminal 401 for the IGBT which is the switching element 600 shown in FIG. 26, so that the drift region 23 extends from the PN junction with the well region 24. This is because a depletion layer is formed and the cutoff state is maintained. Further, in the Schottky barrier diode which is the freewheeling diode 100 shown in FIG. 5, a reverse bias voltage is applied between the front surface electrode 3 and the back surface electrode 4. A depletion layer extending from the junction is generated and the cut-off state is maintained. Also in the semiconductor snubber circuit 200 shown in FIG. 6, the dielectric region 12 functioning as the capacitor 210 is charged with a high voltage and maintains the cutoff state.

  As described above, when the switching element G of the lower arm is in the conductive state, both the upper and lower arms have the same effect as that of the prior art in which the passive element is configured only by the Schottky barrier diode.

  Next, the case where the switching element G of the lower arm is turned off and shifts to the cutoff state will be described.

  In the motor inverter circuit (L load circuit) as shown in FIG. 27, when the switching element G is turned off, the phase of the voltage rise and the current interruption is shifted. The voltage of the element G increases.

  On the other hand, a transient current flows through the passive element F connected in parallel to the switching element G to be turned off. That is, as the output voltage of the switching element G rises, the voltage applied to the passive element F changes from a low reverse bias voltage such as an on-voltage to a high reverse bias voltage such as a power supply voltage. In both 100 and the semiconductor snubber circuit 200, a transient current corresponding to the speed of voltage change flows.

  That is, in the free-wheeling diode 100 shown in FIG. 5, a depletion layer spreads from the surface electrode 3 side into the drift region 2 as the applied voltage increases, and electrons flow as a transient current to the back electrode 4 side. In the semiconductor snubber circuit 200 shown in FIG. 6, since the dielectric region 12 serving as the capacitance of the capacitor 210 is charged according to the applied voltage, a transient current flows. At this time, a transient voltage rise generated between the collector and the emitter of the switching element G is mitigated by the charging action of the capacitor capacitance in the dielectric region 12 of the semiconductor snubber circuit 200, and a surge voltage is generated due to the parasitic inductance included in the circuit. Is suppressed. That is, in the second embodiment, by connecting the switching element 600 in parallel with the free wheeling diode 100 and the semiconductor snubber circuit 200, even when the switching element 600 performs a turn-off operation, element breakdown and other peripheral circuits are prevented. Surge voltage causing malfunction or the like is reduced, and more stable operation can be realized.

  Then, after the voltage of the switching element 600 rises, the current is cut off at a predetermined speed. At this time, in the IGBT described as an example in the second embodiment, although the current interruption speed is limited and a loss occurs due to the influence of the hole current injected from the substrate region 21 during conduction, the vibration phenomenon due to the current interruption is unlikely to occur. As a result, it operates stably. After the current of the switching element 600 is cut off, the lower arm switching element G and the passive element F are in a steady off state and maintain the cut-off state.

  Even during the turn-off operation of the switching element 600, the heat dissipation of the two switching element chips formed of the switching element 600 can be improved by adopting the mounting structure illustrated in FIG.

  On the other hand, the passive element B connected in parallel with the switching element E of the upper arm becomes a forward bias state in conjunction with the turn-off operation of the switching element G and shifts to the conductive state. That is, the depletion layer extending in the drift region 2 of the free-wheeling diode 100 shown in FIG. 5 recedes, and the Schottky barrier height formed at the Schottky junction formed between the surface electrode 3 and the drift region 2 is increased. A forward bias voltage according to the above is applied, and the freewheeling diode 100 becomes conductive. At this time, the current flowing through the freewheeling diode 100 is constituted only by the electron current supplied from the back electrode 4 side in the drift region 2, and the freewheeling diode 100 performs a unipolar operation.

  Also, in the semiconductor snubber circuit 200 shown in FIG. 6, similarly to the freewheeling diode 100, the charge charged in the dielectric region 12 is discharged because the high voltage reverse bias state shifts to the low voltage forward bias state. , Transient current flows. However, in the second embodiment, the capacitor capacity of the dielectric region 12 is almost the same as the depletion capacity formed when the free wheel diode 100 and the switching element 600 are cut off, and is very small. For this reason, the magnitude of the transient current that flows due to the discharge is much smaller than the forward bias current that flows through the free-wheeling diode 100 connected in parallel to the semiconductor snubber circuit 200 and has little effect on the operation.

  In addition, for the switching element E connected in parallel to the passive element B, the voltage between the collector and the emitter shifts from the reverse bias voltage state to the forward bias state, but the gate signal is controlled to maintain the OFF state. Furthermore, since the PN junction between the substrate region 21 and the buffer region 22 is in a reverse bias state, the off state is maintained. However, since the voltage state between the collector and the emitter is displaced, a transient current due to the capacitor discharge accompanying the capacitance change of the depletion layer generated in the drift region 23 in the switching element 600 flows. However, similar to the semiconductor snubber circuit 200, this transient current is very small compared to the forward bias current flowing through the freewheeling diode 100 connected in parallel with the switching element 600, and hardly affects the operation. Then, the semiconductor snubber circuit 200 and the switching element 600 are cut off because a transition is made between the forward bias state and the steady state after the transient current accompanying the change in the bias voltage flows, and only the freewheeling diode 100 is turned on.

  In the second embodiment, when the freewheeling diode 100 is formed of a Schottky barrier diode made of a silicon carbide semiconductor substrate, the resistance of the drift region 2 is lower than that of a PN junction diode made of a general silicon material. It can be formed low. For this reason, although the conduction loss at the time of forward bias conduction | electrical_connection is reduced, the stationary conduction loss generate | occur | produces according to the magnitude | size of an electric current at the free-wheeling diode 100 at the time of this conduction | electrical_connection. Since this steady conduction loss is generated as heat, a cooling device is used for quickly radiating the heat generated from the semiconductor device 10A.

  As described above, in the mounting structure illustrated in FIG. 25, the heat generated by the freewheeling diode 100 is transmitted through the structure of the metal film 410, the insulating substrate 500, the back surface metal film 1000, the base plate 1100, and the cooling structure 1200. The heat is radiated to the fluid in the water flow path 1300. The better the heat dissipation to the water flow path 1300 corresponding to the heat radiating portion, the lower the temperature of the reflux diode 100 associated with the increase in the loss of the reflux diode 100. That is, when the maximum temperature of the freewheeling diode 100 is limited to a predetermined temperature, the better the heat dissipation, the more loss of the freewheeling diode 100 can be tolerated and the current can flow with a larger current density. From this, the range of the maximum working current of the free-wheeling diode 100 can be expanded as the heat dissipation is higher.

  Next, an operation in which the switching element G of the lower arm is turned on and the switching element G is turned on again will be described.

  In the motor inverter circuit (L load circuit) shown in FIG. 27, when the switching element G is turned on, the phases of current increase and voltage decrease are shifted. For this reason, a current starts to flow through the switching element G in a state where a relatively high voltage is applied. A transient current flows through the passive element F connected in parallel to the switching element G. This is because as the current flows through the switching element G and the voltage between the collector and the emitter decreases, the voltage applied to the passive element F decreases from a high reverse bias voltage such as a power supply voltage to a low ON voltage. It changes to a reverse bias voltage, and a transient current corresponding to the speed of this voltage change flows through the freewheeling diode 100 and the semiconductor snubber circuit 200. At this time, in the free-wheeling diode 100 shown in FIG. 5, the depletion layer that has spread in the drift region 2 as the voltage decreases gradually narrows to the surface electrode 3 side, and electrons enter the drift region 2 from the back electrode 4 side. Flows as a transient current. In the semiconductor snubber circuit 200 shown in FIG. 6, a transient current flows because the dielectric region 12 serving as a capacitor capacitance is discharged as the applied voltage decreases.

  This transient current has a magnitude that hardly affects the turn-on current flowing through the switching element 600 connected in parallel with the free wheeling diode 100 and the semiconductor snubber circuit 200. Thus, since the semiconductor snubber circuit 200 and the freewheeling diode 100 in the lower arm transition to a steady state after the transient current flows and the current is cut off, only the switching element 600 is in a conductive state.

  On the other hand, the passive element B connected in parallel with the switching element E of the upper arm enters a reverse bias state and shifts to a cutoff state in conjunction with the turn-on operation of the switching element G of the lower arm. In the Schottky barrier diode shown in FIG. 5, the electron current due to electrons supplied from the back electrode 4 side into the drift region 2 decreases as the forward bias voltage decreases. When the forward bias voltage becomes equal to or lower than the voltage corresponding to the Schottky barrier height of the Schottky junction, and when the reverse bias voltage starts to be applied to the Schottky junction, the surface electrode 3 is formed in the drift region 2. The depletion layer extending from the Schottky junction spreads out and shifts to the cutoff state.

  When transitioning from the conduction state to the cutoff state, the transiently generated current is the reverse recovery current in the process in which excess carriers accumulated in the element of the freewheeling diode 100 disappear. This reverse recovery current flows as a transient current through the passive element B and the switching element G of the lower arm, and a loss (herein referred to as reverse recovery loss) occurs in each element. For this reason, the reverse recovery current generated in the freewheeling diode 100 should be as small as possible.

  In the second embodiment, when the freewheeling diode 100 is formed of a unipolar Schottky barrier diode formed of a semiconductor material made of silicon carbide, this reverse recovery current is compared with a PN junction diode formed of general silicon. Is much smaller. That is, reverse recovery loss can be greatly reduced.

  Furthermore, in the second embodiment, the current / voltage at the time of reverse recovery operation due to unipolar operation, which could not be essentially solved in the case of the prior art in which the passive element is configured only by the Schottky barrier diode, Has the function of suppressing vibration phenomena. That is, in the second embodiment, when the forward bias current decreases and becomes zero in the freewheeling diode 100, a depletion layer due to the reverse bias voltage is formed in the drift region 2, and a reverse recovery current composed of excess carriers flows. start. At substantially the same time as the reverse bias voltage is applied, an equivalent reverse bias voltage is also applied to the capacitor 210 formed of the dielectric region 12 in the switching element 600 and the semiconductor snubber circuit 200, so that the switching element 600 and the semiconductor snubber circuit 200 The corresponding transient current begins to flow. The transient current flowing through the semiconductor snubber circuit 200 is determined by the size of the capacitor formed of the dielectric region 12 and the size of the resistance component of the substrate region 11, and can be designed freely.

  There are three effects of the semiconductor snubber circuit 200 connected in parallel as described in the first embodiment. That is, (1) since the cutoff speed of the forward bias current flowing through the freewheeling diode 100 can be set to a high speed, the loss accompanying the interruption of the main current can be reduced; (2) the freewheeling diode 100 has entered reverse recovery operation. Sometimes the surge voltage itself can be reduced; (3) The energy generated by the parasitic inductance Ls is absorbed and the vibration phenomenon can be quickly converged.

  Thus, the semiconductor device 10A according to the second embodiment has the performance of reducing the transient loss and conduction loss of the freewheeling diode 100, and at the same time, the vibration caused by the unipolar operation by using the semiconductor snubber circuit 200. The phenomenon can be solved.

  In the second embodiment of the present invention, the transient current flowing in the freewheeling diode 100 and the switching element 600 is a transient current consisting of only carriers generated when a depletion layer is formed in the drift region 2 and the drift region 23 at most. It is different from the prior art in that the snubber circuit is formed by a semiconductor snubber circuit 200 having a small electrostatic capacity, paying attention to a certain point. Further, the configuration described in the second embodiment provides the following new effects not found in the prior art in suppressing the performance and vibration phenomenon of reducing transient loss and conduction loss.

  One effect is that when the semiconductor snubber circuit 200 having a predetermined capacitor capacity and resistance value is connected in parallel to the freewheeling diode 100 and the switching element 600 that perform unipolar operation, in the entire current range and the entire temperature range in which the freewheeling diode 100 operates. The snubber function works effectively. As described above, the reverse recovery current generated at the time of reverse recovery of the Schottky barrier diode is composed only of excess carriers generated when a depletion layer is generated in the freewheeling diode 100 and the switching element 600 by the reverse bias voltage. Regardless of the magnitude of the current flowing during the reflux operation, a substantially constant reverse recovery current flows every time. For the same reason, the freewheeling diode 100 is hardly affected by the operating temperature, and a substantially constant reverse recovery current flows. For this reason, transient loss can be reduced and the vibration phenomenon can be suppressed in all current ranges and temperature ranges. These are effects that cannot be obtained in combination with a general PN junction diode.

  Another effect is that the semiconductor snubber circuit 200 is formed by the semiconductor snubber circuit 200 as shown in FIG. 23, so that the semiconductor snubber circuit 200 can be mounted with a low inductance in the immediate vicinity of the freewheeling diode 100 and the switching element 600. It is a point which can reduce a loss and suppress a vibration phenomenon. As described above, the smaller the parasitic inductance, the easier the transient current that flows in the snubber circuit flows, the easier it is to relax the reverse recovery current cutoff speed that flows in the freewheeling diode, and the switching time within the withstand voltage range of the capacitor. It depends on what you can do fast. Therefore, also in the second embodiment, by reducing the parasitic inductance as compared with the conventional snubber circuit using a discrete component capacitor or resistor, the switching time can be shortened and the transient loss can be reduced, and the reverse recovery current can be reduced. It is possible to appropriately relax the blocking speed of and suppress the vibration phenomenon.

  Further, as already described, unnecessary noise emission is reduced by mounting the snubber circuit in the immediate vicinity of the freewheeling diode. Thereby, it is possible to prevent malfunction of the control circuit and the like due to noise.

  Furthermore, in the second embodiment, by forming the snubber circuit with the semiconductor snubber circuit 200, it is possible to configure the power conversion device using the same mounting process as the free wheel diode 100 and the switching element 600. Therefore, the vibration phenomenon can be easily and easily suppressed, and the required volume can be greatly reduced as compared with the conventional snubber circuit.

  Further, the resistance component of the semiconductor snubber circuit 200 can be formed of a semiconductor substrate and directly mounted on a semiconductor package as shown in FIG. For this reason, high heat dissipation can be obtained. As a result, it is possible to design a resistor with a higher density than when an external resistor or the like is used. That is, the resistance to destruction is high and further downsizing can be realized.

  Further, as exemplified in the first embodiment, the effect of the present invention can be maximized by configuring the freewheeling diode 100 with a Schottky barrier diode made of silicon carbide. That is, by configuring the free-wheeling diode 100 with a wide band gap semiconductor such as silicon carbide, it is possible to more remarkably reduce both the conduction loss and the vibration phenomenon. Even when a wide gap semiconductor such as gallium nitride or diamond other than silicon carbide is used as the semiconductor material of the freewheeling diode 100, the same effect can be obtained.

  Even during the reverse recovery operation, the mounting structure illustrated in FIG. 25 can improve heat dissipation even when there are two free-wheeling diode chips.

  In the second embodiment, the resistor 220 and the diode 230 may be connected in parallel corresponding to the configuration shown in FIG. 10 described in the first embodiment. This is because the semiconductor snubber circuit 200 configured to have at least the capacitor 210 and the resistor 220 can obtain the same effect as described above.

  As for the mounting form, the mounting form corresponding to FIG. 11 may be used as in the first embodiment, or another mounting form may be used. In the second embodiment, the case where there are two free-wheeling diode chips, snubber chips, and switching element chips has been described. However, as shown in FIG. 12, there are 3 free-wheeling diode chips and 3 switching element chips. It may be the above. Moreover, it is good also as a system which mounts both surfaces of a collector terminal and an emitter terminal with solder. Since the cooling performance is improved by mounting both surfaces with solder or the like, the heat dissipation performance of the freewheeling diode 100 and the heat dissipation performance of the resistor 220 of the semiconductor snubber circuit 200 are increased.

  In the description of the second embodiment, the semiconductor snubber circuit 200 has been described with reference to FIG. 6 as an example of the structure of the semiconductor snubber circuit 200. As in the first embodiment, the capacitor 210 is illustrated in FIGS. The resistor 220 may be formed with the structure shown in FIGS.

  Also, in the second embodiment, the case where a semiconductor material made of silicon is used as the support base of the semiconductor snubber circuit 200 is taken as an example. For example, as shown in FIG. 19, silicon nitride, aluminum nitride, or alumina is used. Of course, an insulating substrate material such as a substrate region may be used. Although FIG. 19 shows the case where the insulating substrate 18 and the resistance region 19 are in contact with each other, a bonding material such as a metal film or solder may be formed between them.

  As described with reference to FIGS. 20 and 21 in the first embodiment, the capacitance C of the capacitor used in the snubber circuit and the static sum of the capacitor components of the freewheeling diode and the switching element in the cut-off state are static. When the capacitance is C0, the damping effect of the oscillation phenomenon becomes remarkable when the capacitance ratio C / C0 is around 0.1, and the convergence time ratio value of the oscillation phenomenon tends to be saturated when the capacitance ratio C / C0 exceeds 10. become. Further, during a transient operation, loss E is generated by a transient current proportional to the capacitance of the capacitor formed in the snubber circuit. Therefore, the capacitance of the capacitor 210 is preferably as small as possible.

  From this, the capacitance of the capacitor 210 of the semiconductor snubber circuit 200 used in the second embodiment is 10 times or more 10 times larger than the sum of the capacitor components in the cutoff state of the free-wheeling diode 100 and the switching element 600. By selecting within the range of twice or less, the vibration phenomenon can be reduced more significantly while suppressing an increase in loss. This effect can be obtained in any configuration example described in the second embodiment.

(Third embodiment)
In the third embodiment, in the configuration in which the free-wheeling diode 100, the semiconductor snubber circuit 200, and the switching element 600 described in the second embodiment are connected in parallel, the free-wheeling diode 100 and the switching element 600 are respectively a Schottky barrier diode and an IGBT. The case where it comprises with elements other than will be described. 29 shows an example of a cross-sectional structure of the freewheeling diode 100 corresponding to FIG. 5, and FIG. 30 shows an example of a cross-sectional structure of the switching element 600 corresponding to FIG. In the following, description of the same parts as those in the first embodiment or the second embodiment will be omitted, and different features will be described in detail.

The freewheeling diode 100 shown in FIG. 29 is made of a substrate material in which an N ⁻ type drift region 42 is formed on an N ⁺ type substrate region 41 of, for example, a silicon carbide polytype 4H type. The substrate region 41 has, for example, a resistivity of several mΩcm to several tens of mΩcm and a thickness of about several tens of μm to several hundreds of μm.

The drift region 42 has, for example, an N-type impurity density of 10 ¹⁵ cm ⁻³ to 10 ¹⁸ cm ⁻³ and a thickness of several μm to several tens of μm. Of course, the resistivity, impurity density, and thickness may be out of the above ranges depending on the element structure and required breakdown voltage, but in general, the smaller the resistivity and thickness, the more the loss during conduction can be reduced. It is preferable to reduce the resistance. In the third embodiment, for example, a drift region 42 having an impurity density of 10 ¹⁶ cm ⁻³ , a thickness of 5 μm, and a breakdown voltage of 600 V class is used.

  In the following, a case where the semiconductor substrate is a substrate composed of two layers of the substrate region 41 and the drift region 42 will be described. However, a substrate formed only of the substrate region 41 whose resistivity is not according to the above example is described. It may be used, or a multilayer substrate may be used. Moreover, although the case where a proof pressure is a 600V class is demonstrated as an example, a proof pressure class is not limited to this.

A hetero semiconductor region 43 made of polycrystalline silicon having a band gap smaller than that of silicon carbide is deposited in contact with the main surface of the drift region 42 facing the bonding surface with the substrate region 41. A heterojunction diode is formed at a junction of materials having different band gaps, that is, a drift region 42 made of silicon carbide and a hetero semiconductor region 43 made of polycrystalline silicon, and an energy barrier exists at the junction interface. In the heterojunction diode, the height of the energy barrier of the heterojunction portion can be controlled by changing the impurity density of the hetero semiconductor region 43. For this reason, the optimum barrier height can be set according to the required breakdown voltage. Here, as an example, it is assumed that the hetero semiconductor region 43 has a P-type impurity density of 10 ¹⁹ cm ⁻³ and a thickness of 0.5 μm.

  Further, as shown in FIG. 29, the front electrode 44 is formed on the hetero semiconductor region 43, and the back electrode 45 is formed in contact with the substrate region 41. Since the surface electrode 44 is connected to an external electrode as the anode terminal 302, the outermost surface may have a multilayer structure using a metal material such as aluminum, copper, gold, nickel, or silver. On the other hand, the back electrode 45 is made of an electrode material that is in ohmic contact with the substrate region 41. Examples of the electrode material to be ohmic-connected include nickel silicide and titanium material, and the back electrode 45 is connected as a cathode terminal 402 to an external electrode. 29 functions as a vertical diode in which the front electrode 44 is an anode terminal and the back electrode 45 is a cathode terminal.

On the other hand, FIG. 30 shows an example in which switching element 600 is a MOSFET made of silicon carbide. In FIG. 30, for example, a substrate material is used in which an N ⁻ type drift region 52 is formed on an N ⁺ type substrate region 51 having a polytype of silicon carbide of 4H type. For example, the substrate region 51 has a resistivity of several mΩcm to several tens of mΩcm and a thickness of about several μm to several hundred μm.

The drift region 52 has, for example, an N-type impurity density of 10 ¹⁴ cm ⁻³ to 10 ¹⁷ cm ⁻³ and a thickness of several μm to several tens of μm. In general, a smaller resistivity and thickness can reduce loss during conduction, and therefore it is preferable that the resistance is as small as possible. For example, a drift region 52 having an impurity density of 2 × 10 ¹⁶ cm ⁻³ , a thickness of 5 μm, and a breakdown voltage of 600 V class can be employed. In the third embodiment, a case where the substrate region 51 is used as a support base material will be described as an example, but the drift region 52 may be used as a support base material.

A P type well region 53 is formed in a part of the surface layer portion in the drift region 52, and an N ⁺ type source region 54 is formed in a part of the surface layer portion in the well region 53. Then, a gate insulating film 55 made of, for example, a silicon oxide film is formed on the surface layer portions of the drift region 52, the well region 53, and the source region 54, and a gate electrode 56 made of, for example, N-type polycrystalline silicon is formed on the gate insulating film 55. It is arranged on the top.

  Further, a source electrode 57 made of, for example, an aluminum material is formed in contact with the source region 54 and the well region 53 in the opening provided in the gate insulating film 55. An interlayer insulating film 58 made of, for example, a silicon oxide film is formed between the source electrode 57 and the gate electrode 56 so that the source electrode 57 and the gate electrode 56 do not contact each other. A drain electrode 59 that is in ohmic contact with the substrate region 51 is also formed. As described above, the MOSFET shown in FIG. 30 is a so-called planar type in which the gate electrode 56 is formed on the semiconductor substrate plane.

  In the description of the third embodiment, the case where the free wheeling diode 100 shown in FIG. 29 and the switching element 600 shown in FIG. 30 are used in parallel with the semiconductor snubber circuit 200 shown in FIG. explain. At this time, in order to effectively exhibit the snubber function, it is preferable to set the capacitor by the dielectric region 12 and the resistance by the substrate region 11 in consideration of the capacitor capacitance in the cutoff state of the freewheeling diode 100 and the switching element 600. . Similar to the first and second embodiments, in the third embodiment, for example, the thickness is set to 1 μm so as to be higher than the breakdown voltage of the freewheeling diode 100 and the switching element 600, and the electrostatic capacity of the capacitor 210 is increased. Assume that the capacitance is approximately the same as the sum of the depletion capacitances formed when the free-wheeling diode 100 and the switching element 600 are cut off.

  The operation of the third embodiment will be described below in correspondence with the operation of the inverter shown in FIG. 27 as in the second embodiment.

  In the state where the switching element G of the lower arm shown in FIG. 27 is turned on and a current flows through the switching element G, the switching element E and the passive element B of the upper arm are in a reverse bias state and are in a cut-off state.

  Since the switching element G in the conductive state is composed of a MOSFET made of a silicon carbide material, it is conductive with a lower on-resistance than the IGBT described in the second embodiment. This is because the band gap of the silicon carbide material is about three times larger than that of the silicon material and the maximum insulating electric field is about one digit larger, so that the thickness of the drift region 52 can be reduced and the impurity concentration can be increased. For this reason, the resistance of the drift region 52 can be lowered without the bipolar operation like the IGBT.

  In addition, in the passive element F connected in parallel with the switching element G in the conductive state, the free wheel diode 100 and the semiconductor snubber circuit 200 maintain the cutoff state. The reason why the heterojunction diode that is the freewheeling diode 100 is maintained in the cut-off state is that a reverse bias voltage as low as the ON voltage of the switching element G is applied across the freewheeling diode 100. In addition, the semiconductor snubber circuit 200 is maintained in the cut-off state because the dielectric region 12 functioning as the capacitor 210 operates only when the voltage changes, so that a voltage on the order of the ON voltage of the switching element G is applied in a steady state. This is because the state is a cut-off state.

  On the other hand, the switching element E and the passive element B of the upper arm are also maintained in the cut-off state because a reverse bias voltage of about the power supply voltage is applied. In the MOSFET that is the switching element 600, since a reverse bias voltage is applied between the source terminal 302 and the drain terminal 402, a depletion layer extending from the PN junction with the well region 53 is formed in the drift region 52, and is cut off. Is maintained. The reason why the heterojunction diode which is the freewheeling diode 100 is maintained in the cut-off state is that a reverse bias voltage is applied between the front electrode 44 and the back electrode 45, so that the heterojunction surface between the drift region 42 and the hetero semiconductor region 43 This is because the depletion layer extends from the first to the drift region 42. Also in the semiconductor snubber circuit 200, the dielectric region 12 functioning as the capacitor 210 is charged by a high voltage, and maintains the cutoff state.

  Thus, when the switching element G of the lower arm is in a conductive state, the passive elements of the upper and lower arms function in the same manner as in the second embodiment.

  Next, the case where the switching element G of the lower arm is turned off and shifts to the cutoff state will be described.

  In the motor inverter circuit (L load circuit) as shown in FIG. 27, when the switching element G is turned off, the phase of voltage increase and current interruption is shifted. For this reason, the voltage rise of the switching element G first occurs in a state where the current during conduction is substantially maintained.

  In the passive element F connected in parallel with the switching element G, a transient current flows through each of the freewheeling diode 100 and the semiconductor snubber circuit 200. This is because the voltage applied to the passive element F changes from a low reverse bias voltage such as an ON voltage to a high reverse bias voltage such as a power supply voltage as the voltage of the switching element G increases. This is because a transient current corresponding to the speed of the current flows. That is, in the freewheeling diode 100, when a depletion layer spreads from the hetero semiconductor region 43 side into the drift region 42 as the voltage rises, electrons flow as a transient current to the back electrode 45 side. In the semiconductor snubber circuit 200, since the dielectric region 12 serving as the capacitor 210 is charged according to the applied voltage, a transient current flows.

  As described above, the charging action of the capacitor capacitance in the dielectric region 12 of the semiconductor snubber circuit 200 alleviates the transient voltage rise generated between the collector and the emitter of the switching element G, and the surge voltage due to the parasitic inductance included in the circuit. Is suppressed. That is, in the third embodiment, the freewheeling diode 100 and the semiconductor snubber circuit 200 are connected in parallel to the switching element 600, so that even when the switching element 600 itself is turned off, element breakdown and other peripheral circuits are prevented. Surge voltages that cause malfunctions can be reduced.

  In a MOSFET made of silicon carbide, the current is sharply interrupted after the voltage rises. This is different from the IGBT described in the second embodiment, because the MOSFET performs a unipolar operation when conducting, and the electron current discharged from the depletion layer due to the voltage rise depends on the speed of the depletion layer extension. This is because it is blocked. That is, since the switching element 600 is a MOSFET made of silicon carbide, a low on-resistance can be realized when conducting, but the switching element 600 itself is easily turned off due to the speed of the cutoff performance of the switching element. . Furthermore, since the on-resistance is small, there arises a problem that the vibration phenomenon is not easily attenuated.

  However, in the third embodiment, even if the switching element 600 is a MOSFET made of silicon carbide, since the semiconductor snubber circuit 200 is arranged in parallel with the switching element 600, the vibration phenomenon can be effectively reduced. Can do. That is, when the current of the switching element 600 is interrupted, the current and voltage start to vibrate due to resonance with the parasitic inductance in the circuit, but the capacitor 210 including the dielectric region 12 of the semiconductor snubber circuit 200 has an equivalent voltage. Is applied and a corresponding transient current begins to flow. Then, the slope (dI / dt) of the current vibration is relaxed by the capacitor 210 and the resistor 220, and the energy generated in the parasitic inductance Ls by the resistance component of the substrate region 11 is consumed, so that the vibration phenomenon can be quickly converged. Therefore, as in the third embodiment, the vibration phenomenon can be suppressed even when the switching element 600 is a unipolar type and has a high-speed cutoff performance.

  Further, even if the switching element 600 is made of a wide gap semiconductor having a smaller conduction loss and the vibration phenomenon is difficult to attenuate, the vibration phenomenon can be easily attenuated without deteriorating the conduction loss. As described above, in the third embodiment, the switching element 600 has a configuration capable of achieving both suppression of conduction loss and transient loss at a high level, that is, the switching element 600 is a unipolar switching element capable of high-speed operation. In the case of a wide bandgap semiconductor that can realize low on-resistance, a higher effect can be obtained.

  After the current of the switching element 600 is cut off, the switching element G and the passive element F in the lower arm are in a steady off state and maintain the cut-off state.

  On the other hand, the passive element B connected in parallel with the switching element E of the upper arm enters a forward bias state and shifts to a conductive state in conjunction with the turn-off operation of the switching element G of the lower arm. The depletion layer that has spread into the drift region 42 of the free-wheeling diode 100 shown in FIG. 29 recedes, and the heterojunction formed between the hetero semiconductor region 43 and the drift region 42 is ordered according to the height of the hetero barrier. When the bias voltage is applied, the freewheeling diode 100 becomes conductive. In the heterojunction diode, although a forward current flows with a voltage drop determined by the sum of the built-in potentials spreading from the heterojunction to the drift region 42 side and the hetero semiconductor region 43 side, there is a heterobarrier against holes on the valence band side. Since the current is large, the current is almost constituted only by the electron current supplied from the back electrode 45 side in the drift region 42, and performs a unipolar operation. At this time, in the Schottky barrier diode described in the second embodiment, since the Schottky barrier height is uniquely determined by the work function difference inherent to the Schottky metal of the surface electrode 13, in order to obtain a predetermined breakdown voltage, The impurity concentration and thickness of the drift region 42 are limited. On the other hand, in the third embodiment, since the height of the hetero barrier of the heterojunction diode can be changed by controlling the impurity concentration of the hetero semiconductor region 43, the resistance of the drift region 42 is made lower. can do. That is, loss during conduction can be further reduced.

  In the semiconductor snubber circuit 200 shown in FIG. 6, when the freewheeling diode 100 shifts from the reverse bias state to the forward bias state, the charge charged in the dielectric region 12 is discharged as a transient current. In the third embodiment, the capacitance as the capacitor 210 by the dielectric region 12 is as small as the depletion capacitance formed in the free wheeling diode 100 and the switching element 600. For this reason, although a transient current flows due to the discharge, it has a magnitude that hardly affects the forward bias current flowing in the freewheeling diode 100 connected in parallel to the semiconductor snubber circuit 200. The semiconductor snubber circuit 200 shifts to a steady state after the transient current flows, and the current is cut off.

  For the switching element E connected in parallel to the passive element B, the gate-signal is controlled so as to be maintained in the OFF state, although the drain-source voltage shifts from the reverse bias voltage state to the forward bias state. Although the PN junction between the well region 53 and the drift region 52 is in a forward bias state, the off state is maintained because the built-in potential is as large as 2 to 3V. However, since the voltage state between the drain and the source changes, a transient current due to the discharge accompanying the capacitance change of the depletion layer generated in the drift region 52 of the switching element 600 flows. However, this transient current has a magnitude that hardly affects the forward bias current that flows through the freewheeling diode 100, as does the transient electricity that flows through the semiconductor snubber circuit 200 due to discharge. As described above, the semiconductor snubber circuit 200 and the switching element 600 of the upper arm shift to a steady state after the transient current flows, the current is cut off, and only the freewheeling diode 100 becomes conductive.

  Next, an operation in which the switching element G of the lower arm is turned on and the switching element G is turned on again will be described.

  As described above, in the motor inverter circuit (L load circuit) shown in FIG. 27, when the switching element G is turned on, a current starts to flow through the switching element G in a state where a relatively high voltage is applied. . As the current flows through the switching element G and the drain-source voltage decreases, the voltage applied to the passive element F changes from a high reverse bias voltage such as a power supply voltage to a low reverse bias voltage such as an on voltage. To change. A transient current corresponding to the speed of the voltage change flows through the free wheel diode 100 and the semiconductor snubber circuit 200 of the passive element F. In other words, in the freewheeling diode 100, the depletion layer that has spread in the drift region 42 gradually decreases toward the hetero semiconductor region 43 as the voltage decreases, and electrons flow from the back electrode 45 side into the drift region 42 as a transient current. Flowing. In the semiconductor snubber circuit 200, the dielectric region 12 serving as the capacitor 210 is discharged as the applied voltage decreases, and a transient current flows. This transient current has a magnitude that hardly affects the turn-on current flowing through the switching element 600. As described above, the semiconductor snubber circuit 200 and the freewheeling diode 100 in the lower arm shift to a steady state after the transient current flows, the current is cut off, and only the switching element 600 is turned on.

  On the other hand, the passive element B connected in parallel with the switching element E of the upper arm enters a reverse bias state and shifts to a cutoff state in conjunction with the turn-on operation of the switching element G of the lower arm. That is, in the free-wheeling diode 100 that is a heterojunction diode, the electron current supplied from the back electrode 45 side into the drift region 42 decreases as the forward bias voltage decreases. When the forward bias voltage becomes equal to or lower than the voltage corresponding to the hetero barrier height of the heterojunction, and when the reverse bias voltage is further applied to the heterojunction, the depletion layer extends from the heterojunction with the hetero semiconductor region 43. Occurs in the drift region 42, and the freewheeling diode 100 shifts to a cut-off state.

  The heterojunction diode used in the third embodiment performs a unipolar operation similarly to the Schottky barrier diode described in the first embodiment and the second embodiment. For this reason, the reverse recovery current is much smaller than that of a PN junction diode formed of general silicon. That is, reverse recovery loss can be greatly reduced.

  Furthermore, in the third embodiment, by combining a heterojunction diode capable of reducing conduction loss as compared with a Schottky barrier diode and the semiconductor snubber circuit 200, both conduction loss and transient loss can be achieved at a high level. . That is, in the third embodiment, when the freewheeling diode 100 performs the reverse recovery operation, a reverse bias voltage is applied and a reverse recovery current composed of excess carriers starts to flow into the drift region 42 at almost the same time. An equivalent reverse bias voltage is also applied to the capacitor 210 formed of the dielectric region 12 of the switching element 600 and the semiconductor snubber circuit 200, and a corresponding transient current starts to flow in the switching element 600 and the semiconductor snubber circuit 200. The size of the capacitor 210 is set so that the transient current due to the discharge is substantially equal to the transient current flowing through the freewheeling diode 100 and the switching element 600. For this reason, the reverse recovery current cutoff speed (dI / dt) can be relaxed without substantially changing the switching speed of the switching element G of the lower arm. Furthermore, since the current flowing through the semiconductor snubber circuit 200 is consumed by the resistance component of the substrate region 11, energy generated by the parasitic inductance Ls can be absorbed, and the vibration phenomenon can be quickly converged. That is, even if the freewheeling diode 100 is made a heterojunction diode and the conduction loss is reduced, the oscillation phenomenon caused by the unipolar operation is caused to occur in the semiconductor snubber circuit as in the case of using the Schottky barrier diode described in the second embodiment. 200.

As described above, by using a heterojunction diode that can realize a low on-resistance, a higher effect can be obtained.
Also in the third embodiment, paying attention to the fact that the transient current flowing through the freewheeling diode 100 and the switching element 600 is only the carriers generated when the depletion layer is formed in the drift regions 42 and 52, the snubber circuit is The semiconductor snubber circuit 200 is different from the prior art in that it is formed.

  Further, since the switching element 600 is also a unipolar type, the snubber function is effective in the entire current range and the entire temperature range when the switching element 600 is turned off in addition to the reverse recovery operation of the freewheeling diode 100. work.

  The same effect can be obtained by using other unipolar elements as shown in FIG. 31 and FIG.

In the switching element 600 shown in FIG. 31, for example, an N ⁻ type drift region 62 is formed on an N ⁺ type substrate region 61 in which the polytype of silicon carbide is 4H type. In this structure, a hetero semiconductor region 63 made of, for example, N-type polycrystalline silicon is formed on the main surface facing the bonding surface. That is, the junction between the drift region 62 and the hetero semiconductor region 63 is a hetero junction made of a silicon carbide material and a polycrystalline silicon material having different band gaps, and an energy barrier exists at the junction interface. A gate insulating film 64 made of, for example, a silicon oxide film is formed on the hetero semiconductor region 63 and the drift region 62, and a gate electrode 65 is formed on the gate insulating film 64. Further, a source electrode 66 in contact with the hetero semiconductor region 63 is formed in the opening formed in the gate insulating film 64, and an interlayer insulating film 67 made of, for example, a silicon oxide film is formed between the gate electrode 65 and the source electrode 66. Yes. A drain electrode 68 is formed in connection with the substrate region 61.

  Next, the operation of the switching element 600 shown in FIG. 31 will be described. In the switching element 600 shown in FIG. 31 as well as the MOSFET, the source electrode 66 is grounded and a positive potential is applied to the drain electrode 68 for use.

  When the gate electrode 65 is set to the ground potential or the negative potential, the switching element 600 maintains the cutoff state. This is because an energy barrier against conduction electrons is formed at the heterojunction interface between the hetero semiconductor region 63 and the drift region 62.

When a positive potential is applied to the gate electrode 65 in order to shift from the cut-off state to the conductive state, an electron accumulation layer is formed on the surface layer portions of the hetero semiconductor region 63 and the drift region 62 to which the gate electric field extends through the gate insulating film 64. Is formed. For this reason, the surface layer portions of the hetero semiconductor region 63 and the drift region 62 become potentials where free electrons can exist, the energy barrier extending toward the drift region 62 becomes steep, and the energy barrier thickness is reduced. As a result, an electronic current flows through the switching element 600. At this time, the length of the so-called channel portion that controls conduction / cutoff of the switching element 600 is about the thickness of the energy barrier formed by the hetero barrier, and is smaller than the channel length necessary for holding the breakdown voltage in the MOSFET. Conducts with lower resistance. For this reason, the semiconductor snubber circuit 200 can achieve both a conduction loss and a transient loss at a higher level. In the switching element 600 shown in FIG. 31, the gate electrode 65 is grounded again in order to shift from the conduction state to the cutoff state. Then, the accumulation state of conduction electrons formed at the heterojunction interface between the hetero semiconductor region 63 and the drift region 62 is released, and tunneling in the energy barrier is stopped. When the flow of conduction electrons from the hetero semiconductor region 63 to the drift region 62 stops and the conduction electrons in the drift region 62 flow to the substrate region 61 and are depleted, a depletion layer spreads from the hetero junction to the drift region 62 side. The switching element 600 is cut off.

  In the switching element shown in FIG. 31, reverse conduction (reflux operation) is also possible in which the source electrode 66 is grounded and a negative potential is applied to the drain electrode 68. For example, when the source electrode 66 and the gate electrode 65 are grounded and a predetermined positive potential is applied to the drain electrode 67, the energy barrier to the conduction electrons disappears, and conduction electrons flow from the drift region 62 side to the hetero semiconductor region 63 side, and vice versa. It becomes a conductive state. At this time, since there is no injection of holes and conduction is made only with conduction electrons, loss due to reverse recovery current when shifting from the reverse conduction state to the cutoff state is small. It is also possible to use the gate electrode 65 as a control electrode without grounding.

  Since the configuration shown in FIG. 31 can be used as a unipolar freewheeling diode, for example, the freewheeling diode 100 can be realized by the configuration shown in FIG. That is, when the configuration shown in FIG. 31 is used as the switching element 600, in addition to forming the switching element 600 and the free wheeling diode 100 as separate chips, the free wheeling diode 100 and the switching element 600 are made into one chip, and the semiconductor package is formed. It can be downsized. Thereby, the parasitic inductance generated in the wiring or the like is reduced, and the vibration phenomenon can be further reduced. Shortening the wiring length also has an effect of reducing radiation noise generated from the wiring by the oscillating current. Further, the manufacturing cost is reduced by reducing the chip size, and the capacitance of the capacitor 210 necessary for the semiconductor snubber circuit 200 is also reduced because the sum of the capacitor capacities of the freewheeling diode 100 and the switching element 600 is reduced. Can do. That is, the small semiconductor snubber circuit 200 can suppress the vibration phenomenon at low cost.

  In FIG. 31, the example in which polycrystalline silicon is used as the material of the hetero semiconductor region 63 has been described. However, as long as the material forms a heterojunction with silicon carbide, other silicon materials such as single crystal silicon and amorphous silicon, Any material may be used for the hetero semiconductor region 63, such as other semiconductor materials such as germanium and silicon germanium, and other polytypes of silicon carbide such as 6H and 3C. In addition, as an example, the description has been given using N-type silicon carbide as the drift region 62 and P-type polycrystalline silicon as the hetero semiconductor region 63. However, the drift region 62 and the hetero semiconductor region 63 may be formed of N-type. Any combination of silicon carbide and P-type polycrystalline silicon, P-type silicon carbide and P-type polycrystalline silicon, or P-type silicon carbide and N-type polycrystalline silicon may be employed.

Next, a junction type FET called a junction type FET (JFET) shown in FIG. 32 will be described. In the switching element 600 shown in FIG. 32, for example, an N ⁻ type drift region 72 is formed on an N ⁺ type substrate region 71 whose polytype of silicon carbide is 4H type, and a part of the surface layer portion of the drift region 72 is formed. Further, a P-type gate region 73 and an N ⁺ -type source region 74 are formed. An interlayer insulating film 77 is formed on the drift region 72, the gate region 73 and the source region 74. In the opening of the interlayer insulating film 77, the gate region 73 is connected to the gate electrode 75, and the source region 74 is connected to the source electrode 76. The substrate region 71 is in contact with the drain electrode 78.

  Since the JFET shown in FIG. 32 performs a unipolar operation like a MOSFET, the same effect as that obtained when the switching element 600 described above is a MOSFET can be obtained. Furthermore, since a gate insulating film that is essential for a MOSFET is not necessary for a JFET, operation at a high temperature exceeding, for example, 200 ° C. is relatively easy, which is advantageous in terms of ensuring reliability. For this reason, by using JFET for the switching element 600, the advantage that the vibration phenomenon can be suppressed irrespective of the operating temperature range, which is the effect of the present invention, can be utilized as a strength. In high temperature applications, for example, as shown in FIG. 13 and FIG. 14, the configuration using a depletion capacitor that does not use a silicon oxide film as the capacitor 210 of the semiconductor snubber circuit 200 is more effective while ensuring reliability. Can be demonstrated.

  As described above, the effect of using a switching element other than the MOSFET has been described for the switching element 600. However, the free-wheeling diode 100 is also described so far as long as it is a diode that operates in a unipolar operation or a unipolar operation. The effect similar to the effect of this invention which has been performed can be acquired.

  For example, even in the structure of a PN junction diode as shown in FIG. 33, by conducting measures such as heavy metal diffusion using gold or platinum, electron beam irradiation using an electron beam, ion irradiation using a proton or the like, By controlling the lifetime of minority carriers, which are the main components of excess carriers injected from the P-type region, an operation equivalent to the unipolar operation is performed. In this case, the effect of the present invention can be obtained even if the freewheeling diode 100 has a PN junction diode structure.

For example, the case where the PN junction diode shown in FIG. 33 is configured by a soft recovery diode will be described. The freewheeling diode 100 shown in FIG. 33 is made of a substrate material in which an N ⁻ type drift region 82 is formed on an N ⁺ type substrate region 81 made of, for example, silicon. The substrate region 81 has, for example, a resistivity of several mΩcm to several tens of mΩcm and a thickness of about several tens of μm to several hundreds of μm. The drift region 82 has, for example, an N-type impurity density of 10 ¹³ cm ⁻³ to 10 ¹⁷ cm ⁻³ and a thickness of several μm to several hundred μm. Here, it is assumed that the drift region 82 has an impurity density of 10 ¹⁴ cm ⁻³ , a thickness of 50 μm, and a breakdown voltage of 600 V class. FIG. 33 shows the case where the semiconductor substrate is a substrate composed of two layers of a substrate region 81 and a drift region 82, but the resistivity is a substrate formed only by the substrate region 81 that does not depend on the above example. May be used, or a multilayer substrate may be used. Of course, the withstand voltage is not limited to the 600V class.

  As shown in FIG. 33, a P-type opposite conductivity type region 83 is formed on the main surface of the drift region 82 facing the bonding surface with the substrate region 81, and a surface electrode 84 is formed on the opposite conductivity type region 83. ing. A back electrode 85 is formed in contact with the substrate region 81. Although the free wheeling diode shown in FIG. 33 is formed only by a PN junction, for example, a part may be configured to function as a Schottky diode, or may include other configurations.

  One method for allowing the PN junction diode shown in FIG. 33 to function as a soft recovery diode is to control the lifetime of minority carriers injected into the drift region 82 during conduction. For example, the lifetime of minority carriers in the drift region 82 is controlled to be different between the region near the opposite conductivity type region 83 and the region near the substrate region 81 by irradiating the drift region 82 with ions. As a result, the transient current due to the minority carriers flowing during reverse recovery is reduced, the reduction time of the minority carriers staying on the substrate region 81 side is relaxed, and the vibration phenomenon does not occur in the reverse recovery operation at a large current. Can be.

  However, in a PN junction diode in which the minority carrier lifetime is controlled, the minority carrier lifetime is shortened regardless of the magnitude of the current. For this reason, when the current is small, minority carriers disappear instantaneously at the time of reverse recovery, and the PN junction diode operates almost the same as the unipolar operation. In this case, the transient current flowing in the diode shown in FIG. 33 is a current due to the movement of majority carriers when the depletion layer spreads as in the unipolar diode described with reference to FIG. For this reason, a vibration phenomenon occurs when the semiconductor snubber circuit 200 is not present. However, by connecting the semiconductor snubber circuit 200 in parallel with the freewheeling diode 100, the vibration phenomenon at the time of low current can be reduced.

  Therefore, the vibration phenomenon can be alleviated even at a large current and a small current also by a combination of the freewheeling diode 100 which is a soft recovery diode and the semiconductor snubber circuit 200. Here, the effect of the third embodiment has been described by taking the soft recovery diode as an example. However, even when a fast recovery diode whose reverse recovery characteristic is not softened at the time of a large current is used, the operation is equivalent to the unipolar operation. If there is a current region for performing the above, an effect of suppressing at least a vibration phenomenon at a low current can be obtained. In addition, a material such as a PN junction diode made of silicon carbide, which is less prone to crystal recovery by heat treatment than a silicon material, has a minority carrier lifetime as in the case where a P-type region is formed by ion implantation. Even in the originally small diode, as described above, the effect of suppressing the vibration phenomenon can be obtained. In any structure, the effect of the present invention can be obtained when the PN junction diode is operated for reverse recovery under the condition that at least current does not flow and minority carriers are not injected.

  As described above, if the freewheeling diode 100 performs at least a part of the operation equivalent to the unipolar operation, the effect of the present invention can be obtained that the vibration phenomenon is reduced during the reverse recovery operation.

  33 has the same effect even when the switching element 600 described in the first embodiment is not connected in parallel to the free wheeling diode 100. That is, only the freewheeling diode 100 and the semiconductor snubber circuit 200 may be connected in parallel.

  Furthermore, in the third embodiment, the case where the combination of the elements of the free wheel diode 100 and the switching element 600 is different from the combination described in the second embodiment has been described. You may combine using any element demonstrated by the 1st-3rd embodiment. That is, for example, a combination using the Schottky barrier diode described in the second embodiment for the freewheeling diode 100 and the MOSFET described in the third embodiment for the switching element 600 may be used. Further, the reflux diode 100 and the switching element 600 may be formed on the same chip.

  Further, regardless of which element is used to combine the freewheeling diode 100 and the switching element 600, refer to FIGS. 4, 11, 12, 24, 25, etc. in the first and second embodiments. By adopting the mounting structure described above, it is possible to improve the heat dissipation of the chip in each of the free wheeling diode 100 and the switching element 600.

  Further, as described with reference to FIGS. 20 and 21 in the first embodiment, the capacitance C of the capacitor used in the snubber circuit and the capacitor capacitance component of the free-wheeling diode and the switching element in the cut-off state When the sum is the capacitance C0, the damping effect of the vibration phenomenon becomes remarkable when the capacitance ratio C / C0 is around 0.1, and the value of the convergence time ratio of the vibration phenomenon when the capacitance ratio C / C0 exceeds 10. Tends to be saturated. Further, since a loss E occurs due to a transient current proportional to the capacitance of the capacitor formed in the snubber circuit during the transient operation, the capacitance C of the capacitor is preferably as small as possible.

  Therefore, the capacitance of the capacitor 210 of the snubber circuit 200 used in the third embodiment is 10 times or more 10 times larger than the total capacitance of the capacitor components in the cutoff state of the freewheeling diode 100 and the switching element 600. Select within the range of double or less. As a result, the vibration phenomenon can be reduced more significantly while suppressing an increase in loss. This effect can be obtained in any configuration example described in the third embodiment.

(Fourth embodiment)
The fourth embodiment exemplifies a case where the free wheeling diode 100 and the semiconductor snubber circuit 200 are formed on the same chip.

  34 is an example of a mounting diagram of the semiconductor chip corresponding to FIG. 3, and FIG. 35 is an example of a mounting structure diagram corresponding to FIG. FIG. 36 is an example of a cross-sectional structure diagram of the semiconductor chip used in the mounting diagrams of FIGS. 34 and 35, and shows a cross-sectional structure of the semiconductor chip on which the free-wheeling diode 100 and the semiconductor snubber circuit 200 are formed. Below, the description of the same part as 1st Embodiment is abbreviate | omitted, and a different characteristic is demonstrated in detail.

  As shown in FIG. 34, a chip on which a snubber circuit built-in freewheeling diode 800 including a freewheeling diode 100 and a semiconductor snubber circuit 200 (snubber built-in freewheeling diode chip, indicated by reference numeral 800 in the figure) is a metal film on the cathode side. Two chips are arranged on 410. The cathode terminal of the snubber circuit built-in reflux diode 800 is in contact with the metal film 410 on the cathode side through a bonding material such as solder or brazing material. In the snubber circuit built-in freewheeling diode 800, a freewheeling diode region 2100 in which the freewheeling diode 100 is formed and a semiconductor snubber region 2200 in which the semiconductor snubber circuit 200 is formed are arranged. In the fourth embodiment, as shown in FIG. 34, two snubber built-in free-wheeling diode chips are arranged so that the regions where the semiconductor snubber regions 2200 are formed face each other. The anode terminal of the snubber circuit built-in reflux diode 800 is connected to the metal film 310 on the anode side through a metal wiring 320 such as an aluminum wire or an aluminum ribbon.

  Also in the fourth embodiment, the semiconductor package shown in FIG. 34 is used by being incorporated into a mounting structure as shown in FIG. 35, for example, in order to improve heat dissipation and stably exhibit performance. As shown in FIG. 35, a back surface metal film 1000 made of a metal film similar to the metal film 310 or the metal film 410, for example, is formed on the back surface side of the insulating substrate 500. As described with reference to FIG. 4 and FIG. 24, the back surface metal film 1000 is formed on the base plate 1100 having a function as a support structure of the semiconductor package and a function of heat conduction. Base plate 1100 is configured to contact cooling structure 1200. However, the base plate 1100 and the cooling structure 1200 may be in direct contact with each other, or may be in contact with each other through an adhesive material such as silicon grease. The cooling structure 1200 may dissipate heat in either an air-cooled type or a water-cooled type, but in the fourth embodiment, a water flow path 1300 is formed in a predetermined portion of the cooling structure 1200. An example of adopting a water-cooled cooling structure was shown.

  FIG. 36 shows a cross-sectional structure of a snubber built-in reflux diode chip. The semiconductor snubber built-in freewheeling diode 800 includes a freewheeling diode 100 formed on the right side of the right broken line in FIG. 36 and a semiconductor snubber circuit 200 formed on the left side of the left broken line in FIG. .

The part of the free-wheeling diode 100 is made of, for example, a substrate material in which an N ⁻ type drift region 2 is disposed on an N ⁺ type substrate region 1 of silicon carbide polytype 4H type. The substrate region 1 has a resistivity of, for example, several mΩcm to several tens of mΩcm and a thickness of about several tens to several hundreds of μm. The drift region 2 has, for example, an N-type impurity density of 10 ¹⁵ cm ⁻³ to 10 ¹⁸ cm ⁻³ and a thickness of several μm to several tens of μm. In the fourth embodiment, a drift region 2 having an impurity density of 10 ¹⁶ cm ⁻³ , a thickness of 5 μm, and a breakdown voltage of 600 V class can be employed. However, the breakdown voltage class is not limited to the 600V class. In the fourth embodiment, the case where the semiconductor substrate is a substrate composed of two layers of the substrate region 1 and the drift region 2 will be described, but only the substrate region 1 whose magnitude of resistivity does not depend on the above example. The substrate formed in (1) may be used, or a multilayer substrate may be used.

  In the part of the free-wheeling diode 100 formed on the right side of the right broken line shown in FIG. 36, the surface electrode 3 is formed on the main surface of the drift region 2 facing the junction surface with the substrate region 1 and is opposed to the surface electrode 3. Thus, the back electrode 4 that contacts the substrate region 1 is formed. The surface electrode 3 is made of a single-layer or multi-layer metal material including at least a metal material that forms a Schottky barrier with the drift region 2. As a metal material for forming the Schottky barrier, titanium, nickel, molybdenum, gold, platinum, or the like can be used. Further, since the surface electrode 3 is connected to an external electrode as the anode terminal 300, a multilayer structure may be formed by using a metal material such as aluminum, copper, gold, nickel, silver, or the like on the outermost surface. On the other hand, the back electrode 4 is made of an electrode material that is in ohmic contact with the substrate region 1. Examples of the electrode material to be ohmic-connected to the substrate region 1 include nickel silicide and titanium material, and the back electrode 4 is connected to an external electrode as a cathode terminal 400. Thus, the free-wheeling diode 100 shown in FIG. 36 functions as a diode having the front electrode 3 as an anode terminal and the back electrode 4 as a cathode terminal.

  Further, as shown in FIG. 36, a field insulating film 5 made of, for example, a silicon oxide film is formed between the drift region 2 and the surface electrode 3 except for the region where the freewheeling diode 100 is formed. The field insulating film 5 is a field insulating film that is generally used for relaxing the electric field concentration at, for example, a Schottky junction on the outer periphery of the chip when the freewheeling diode 100 is manufactured as a semiconductor chip. In FIG. 36, as an example of the end shape of the field insulating film 5, a case where the portion in contact with the surface electrode 3 is a right angle is shown, but the end portion may be an acute angle shape.

  Further, at the outer peripheral end of the free-wheeling diode 100 where the field insulating film 5 is formed, as shown in FIG. 37, for example, in the drift region 2 immediately below the portion where the surface electrode 3 and the field insulating film 5 are in contact with each other, The electric field relaxation region 7 may be formed. Furthermore, in addition to the configuration shown in FIG. 37, one or a plurality of guard rings may be formed so as to surround the outer periphery of the electric field relaxation region 7.

  Next, a semiconductor snubber circuit 200 formed on the left side of the left broken line in FIG. 36 will be described. A resistance region 6 made of, for example, polycrystalline silicon is formed on a predetermined region of the field insulating film 5 used for electric field relaxation at the outer peripheral end of the free-wheeling diode 100. Then, the surface electrode 3 is formed on the resistance region 6, and the surface electrode 3 is connected to the anode terminal 300 to which the anode terminal of the reflux diode 100 is connected. In the semiconductor snubber circuit 200 according to the fourth embodiment, the resistance region 6 functions as the resistor 220, and the field insulating film 5 functions as a part of the capacitor 210. The impurity concentration and thickness of the resistance region 6 can be set according to the resistance value required for the resistor 220. Also, the thickness and area of the field insulating film 5 can be set according to the withstand voltage and the capacitance required for the capacitor 210.

  With respect to the breakdown voltage, not only as a function of the semiconductor snubber circuit 200 but also from a Schottky barrier diode formed by the freewheeling diode 100 in order to satisfy the function of electric field relaxation of the freewheeling diode 100 to prevent the field insulating film 5 from being broken. It is preferable that the pressure resistance is high. The capacitance of the capacitor 210 can be selected in the range of about 1/100 to about 100 times the depletion capacity charged when the free-wheeling diode 100 is cut off (when a high voltage is applied). However, when a sufficient snubber function is exhibited and an increase in loss is suppressed as much as possible, and a necessary chip area is taken into consideration, a range of about 1/10 to about 10 times is preferable as shown in the calculation results described later. .

  In the fourth embodiment, for example, the thickness is 1 μm so that the breakdown voltage of the free-wheeling diode 100 is higher than that of the Schottky barrier diode, and the capacitance of the capacitor 210 is the depletion capacity formed when the free-wheeling diode 100 is cut off. A case where the same level is set will be described. The field insulating film 5 may be any material other than a silicon oxide film as long as it is a dielectric material having a predetermined withstand voltage and functioning as an electric field relaxation function and a capacitor 210. It is even better if the value of the product with the dielectric constant is larger than that of the silicon oxide film. When such a material is used for the field insulating film 5, it is possible to obtain a necessary capacitance with a smaller area than in the case of the silicon oxide film while maintaining the withstand voltage of the dielectric region 12.

For example, as described in the first embodiment, when the thickness is 1 μm, the capacitance per 1 cm ² is about 3.4 nF, whereas the silicon oxide film is replaced by Si ₃ N ₄ instead of the silicon oxide film. When the film is used, an equivalent breakdown voltage can be secured with a thickness of 1 μm, and the capacitance per cm ² when the Si ₃ N ₄ film is used is about 6.6 nF. In other words, when a Si ₃ N ₄ film is used for the field insulating film 5, the electrostatic capacity is increased about twice, and a larger electrostatic capacity can be obtained while maintaining the withstand voltage of the dielectric region. Therefore, the area efficiency can be improved and the wafer cost can be reduced.

  Further, as described above, the resistance size of the resistance region is preferably set so as to satisfy a general design formula C = 1 / (2πfR) that effectively exhibits a snubber function.

  As described above, even when the free-wheeling diode 100 and the semiconductor snubber circuit 200 are formed on the same chip, the operations and effects described in the first embodiment can be obtained.

  In the fourth embodiment shown in FIG. 36, the freewheeling diode 100 and the semiconductor snubber circuit 200 share the substrate region 1 and the drift region 2 as the support base, and the front electrode 3 and the back electrode 4 are used as the electrode materials. Shared. Further, the field insulating film 5 that functions as an electrolytic relaxation function of the freewheeling diode 100 functions as the capacitor 210 of the semiconductor snubber circuit 200. Since these shared portions can be formed by the same process, the manufacturing process can be simplified. Further, by mounting the free wheel diode 100 and the semiconductor snubber circuit 200 on one chip, the mounting area (site area) can be reduced, so that the semiconductor package can be reduced in size.

  Furthermore, when the fourth embodiment is used for an L load circuit, a new effect is achieved by integrating the freewheeling diode 100 and the semiconductor snubber circuit 200 into one chip. That is, as already described, when the freewheeling diode 100 is cut off and conducting, the semiconductor snubber circuit 200 does not operate and operates only during a transient, and is caused by the depletion capacity of the freewheeling diode 100 and the capacitor 210 of the semiconductor snubber circuit 200. The resistor 220 generates heat in order to consume the transient current that occurs. On the other hand, the freewheeling diode 100 does not generate much heat during the turn-on and turn-off transient operations due to the effect of phase shift between current and voltage. Therefore, the freewheeling diode 100 generates the most heat during steady state conduction. That is, the timing of generating heat during a series of operations differs between the free wheeling diode 100 and the semiconductor snubber circuit 200. For example, when the part of the freewheeling diode 100 is generating heat when conducting, the semiconductor snubber circuit 200 is in a cut-off state and does not generate heat. Compared to the case, it can be kept low. In other words, the conduction performance of the free-wheeling diode 100 can be improved by using one chip.

  Furthermore, as a feature of the fourth embodiment, the free-wheeling diode region 2100 in which the free-wheeling diode 100 of the free-wheeling diode 800 with a built-in snubber circuit is formed is mounted so as to face each other through the semiconductor snubber region 2200 for two chips. Therefore, it has higher heat dissipation. Of course, as shown in FIG. 38, even if the semiconductor snubber region 2200 for one chip is formed between the two free-wheeling diode regions 2100, the effect of improving the heat dissipation is obtained. However, by disposing the two snubber circuit built-in freewheeling diodes 800 so that the semiconductor snubber regions 2200 face each other, the distance between the freewheeling diode regions 2100 can be reduced by 2 as compared with the case where the freewheeling diode regions 2100 are arranged so as to face each other. Can be expanded to about double. For this reason, heat interference between the free-wheeling diode regions 2100 serving as the heat sources hardly occurs, and the heat dissipation performance is further improved.

  Further, even when three or more snubber built-in freewheeling diode chips are mounted in parallel, heat dissipation can be easily improved by disposing at least one semiconductor snubber region 2200 between the freewheeling diode regions 2100. Furthermore, for example, by changing the arrangement of the semiconductor snubber region 2200 in the freewheeling diode 800 with a built-in snubber circuit, various parallel numbers can be handled. For example, if the semiconductor snubber regions 2200 are formed on both sides of the snubber circuit built-in reflux diode 800, the semiconductor snubber regions 2200 can be arranged so as to face each other. As shown in FIG. In the case where the diode chips are arranged in a lattice shape, it can be easily handled by forming the semiconductor snubber region 2200 at positions facing each other. As a result, high cooling efficiency can be obtained with a minimum mounting area.

  As described above, the mounting arrangement suitable for the operation mechanism of the reflux diode 100 and the semiconductor snubber circuit 200 in the fourth embodiment can further improve the performance of the semiconductor device of the present invention. In the fourth embodiment, both the effect of further suppressing the vibration phenomenon and improving the transient performance and the conduction performance can be improved, and at the same time, the size and cost can be reduced.

  In FIGS. 36 and 37, the case where the free wheel diode 100 is a Schottky barrier diode has been described. However, for example, the heterojunction diode described in the third embodiment can be easily realized. FIG. 40 shows a cross-sectional view corresponding to FIG. 36 when the freewheeling diode 100 is a heterojunction diode.

  As shown in FIG. 40, a field insulating film 46 is formed in addition to the heterojunction diode including the substrate region 41, the drift region 42, the hetero semiconductor region 43, the front surface electrode 44, and the back surface electrode 45. The field insulating film 46 is formed between the drift region 42 and the hetero semiconductor region 43 except for the region where the freewheeling diode 100 is formed. On a predetermined region of the field insulating film 46, a resistance region 47 made of, for example, polycrystalline silicon is formed. Then, a surface electrode 44 is formed on the resistance region 47, and the surface electrode 44 is connected to an anode terminal 300 to which an anode terminal of the free-wheeling diode 100 is connected. As shown in FIG. 37, a P-type electric field relaxation region may be formed, or a guard ring may be formed so as to surround the outer periphery of the electric field relaxation region.

  The snubber circuit built-in free-wheeling diode 800 shown in FIG. 40 can realize the free-wheeling diode 100 and the switching element 600 described in the third embodiment with various elements, and the snubber circuit and the free-wheeling described in the fourth embodiment. It is possible to realize the effect of making the diode into one chip. Furthermore, a feature of the snubber circuit built-in free wheel diode 800 shown in FIG. 40 is that the resistance region 47 is formed of the same material as the hetero semiconductor region 43 of the free wheel diode 100. With the configuration shown in FIG. 40, in addition to the effect of using a heterojunction diode as the freewheeling diode 100, the manufacturing process can be further simplified and realized at low cost.

  In addition, the freewheeling diode 100 and the semiconductor snubber circuit 200 can be integrated into one chip with the configuration shown in FIGS.

  The configuration shown in FIG. 41 is different from the configuration shown in FIG. 36 in that the resistor 220 of the semiconductor snubber circuit 200 and a part of the drift region 42 are configured by the low concentration drift region 8. The configuration shown in FIG. 41 can be easily realized by forming the drift region 2 by introducing impurities and activating the impurities using, for example, a semiconductor material in which the substrate region 1 and the low concentration drift region 8 are stacked. With the configuration shown in FIG. 41, when the freewheeling diode 100 and the semiconductor snubber circuit 200 are made into one chip, the semiconductor substrate can be used as a resistance component, and the heat energy generated by the vibration phenomenon is dissipated through the semiconductor substrate. Therefore, the density of the resistance portion can be increased.

  The configuration shown in FIG. 42 is different from the configuration shown in FIG. 36 in that a PN junction diode having an operation equivalent to the unipolar operation shown in FIG. 33 is used as the freewheeling diode 100 instead of the Schottky barrier diode. Even if the configuration shown in FIG. 42 is adopted, the chip can be easily realized, and both the effect of further suppressing the vibration phenomenon and improving the transient performance and the conduction performance are improved, and at the same time, miniaturization and cost reduction are realized. it can.

  The configuration shown in FIG. 43 is different from the configuration shown in FIG. 42 in that the resistor 220 of the semiconductor snubber circuit 200 is configured by the low concentration drift region 88. The configuration shown in FIG. 43 can be easily realized by forming the drift region 82 by introducing impurities and activating the impurities using, for example, a semiconductor material in which the substrate region 81 and the low concentration drift region 88 are stacked. With the configuration shown in FIG. 43, even when the freewheeling diode 100 and the semiconductor snubber circuit 200 are made into one chip, the semiconductor substrate can also be used as a resistance component, and the heat energy generated by the vibration phenomenon passes through the semiconductor substrate. Since the heat is dissipated, the resistance portion can be densified.

  The configuration shown in FIG. 44 is that a part of the capacitor 210 of the semiconductor snubber circuit 200 is configured by a PN junction formed between the opposite conductivity type region 89 and the low concentration drift region 88. FIG. Different from the configuration shown. The structure shown in FIG. 44 uses, for example, a semiconductor material in which a substrate region 81 and a low concentration drift region 88 are stacked to form a drift region 82 by impurity introduction and impurity activation, and by impurity introduction and impurity activation. This can be easily realized by simultaneously forming the opposite conductivity type region 83 which is a part of the freewheeling diode 100 and the opposite conductivity type region 89 which is a part of the semiconductor snubber circuit 200. With the configuration shown in FIG. 44, since the freewheeling diode 100 and the semiconductor snubber circuit 200 can be formed by the same process, the manufacturing process can be simplified and the manufacturing cost can be reduced.

  Also, in the configuration shown in FIG. 44, a part of the semiconductor substrate can be used as the resistor 220, and the heat energy generated by the vibration phenomenon is radiated through the semiconductor substrate, so that the resistance portion can be densified. Become. In the configuration shown in FIG. 44, the capacitor 210 of the semiconductor snubber circuit 200 has a depletion capacity of a PN junction formed between the opposite conductivity type region 89 and the low concentration drift region 88 and a capacity of the field insulating film 86. Is a capacitor connected in series, but a configuration having only a PN junction capacitor may be used.

  In the above, a plurality of configurations in which the freewheeling diode 100 and the semiconductor snubber circuit 200 are integrated into one chip have been exemplified. However, in addition to the above examples, the combination of the elements of the freewheeling diode 100 and the semiconductor snubber circuit 200 is changed to 1 Of course, it may be a chip.

  In the fourth embodiment, the case where only the freewheeling diode 100 and the semiconductor snubber circuit 200 corresponding to the first embodiment are connected in parallel is illustrated, but the second embodiment and the third embodiment are exemplified. In the case where the switching element 600 is connected in parallel with the freewheeling diode 100 or the semiconductor snubber circuit 200 as shown in FIG. At this time, as shown in FIG. 45, by disposing the switching element chips one by one on the outside of the two-chip snubber built-in reflux diode chip, the distances between the switching elements 600 can be greatly separated. For this reason, heat interference between the free-wheeling diode regions 2100 and the switching element 600 hardly occurs, and the heat dissipation performance is further improved.

  As described above, according to the fourth embodiment, in any of the above-described configurations, at least the freewheeling diode 100 and the semiconductor snubber circuit 200 are integrated into one chip, thereby further suppressing the vibration phenomenon and transient performance. In addition to improving both the effect of improving the electrical conductivity and the conduction performance, it is possible to reduce the size and the cost.

  In addition, as described with reference to FIGS. 20 and 21 in the first embodiment, the damping effect of the vibration phenomenon becomes significant when the capacitance ratio C / C0 is around 0.1, and the capacitance ratio C / C0. The value of the convergence time ratio of the vibration phenomenon tends to saturate from around 10 above. In consideration of the generation of the loss E due to the transient current, the capacitance of the capacitor is preferably as small as possible. That is, the capacitor 210 of the semiconductor snubber circuit 200 used in the fourth embodiment is 1/10 times or more and 10 times or less of the total capacitance of the capacitor components in the cutoff state of the free wheel diode 100 and the switching element 600. By selecting the range, the vibration phenomenon can be reduced more remarkably while suppressing the increase in loss. This effect can be obtained in any of the configuration examples described in the fourth embodiment.

(Fifth embodiment)
In the fifth embodiment, the case where the switching element 600 and the semiconductor snubber circuit 200 are formed on the same semiconductor chip in the circuit of the second embodiment shown in FIG.

  46 is an example of a semiconductor chip mounting diagram corresponding to FIG. 23, and FIG. 47 is an example of a mounting structure diagram corresponding to FIG. FIG. 48 is an example of a cross-sectional structure diagram of the semiconductor chip corresponding to FIG. 26, and shows a cross-sectional structure of the switching element 600 and the semiconductor snubber circuit 200. In the following, description of the same parts as in the second embodiment will be omitted, and different features will be described in detail.

  As shown in FIG. 46, two chips each having a snubber built-in switching element 900 including a switching element 600 and a semiconductor snubber circuit 200 (a snubber built-in switching element chip, denoted by reference numeral 900 in the drawing), Are disposed on the cathode-side metal film 410. Two chips (reflux diode chips, indicated by reference numeral 100 in the figure) are disposed on the cathode side metal film 410. In the snubber built-in switching element 900, a switching element region 2600 in which a return diode is formed and a semiconductor snubber region 2200 in which a semiconductor snubber is formed are formed. As shown in FIG. 46, two snubber built-in switching element chips are arranged such that the portions where the semiconductor snubber regions 2200 are formed face each other. The free-wheeling diode chips are arranged one by one on the outside of the two snubber built-in switching element chips. That is, the semiconductor snubber circuit 200 is arranged between the freewheeling diodes 100.

  The collector terminal of the snubber built-in switching element 900 and the cathode terminal of the reflux diode 100 are in contact with the metal film 410 connected to the collector terminal 401 through a bonding material such as solder or brazing material. The emitter terminal of the snubber built-in switching element 900 is connected to the metal film 310 connected to the emitter terminal 301 through the metal wiring 350 such as an aluminum wire or an aluminum ribbon together with the anode terminal of the freewheeling diode 100. Further, the gate terminal of the switching element 600 is connected to the metal film 700 connected to the gate terminal 510 through the metal wiring 710.

  Also in the fifth embodiment, the semiconductor package shown in FIG. 46 is used by being incorporated in a mounting structure as shown in FIG. 47, for example, in order to improve heat dissipation and stably exhibit performance. A back surface metal film 1000 made of a metal film similar to the metal film 310 or the metal film 410, for example, is formed on the back surface side of the insulating substrate 500 of the mounting structure shown in FIG. As described with reference to FIG. 4 and FIG. 24, the back surface metal film 1000 is formed on the base plate 1100 having a function as a support structure of the semiconductor package and a function of heat conduction. The base plate 1100 is in contact with the cooling structure 1200. However, the base plate 1100 and the cooling structure 1200 may be in direct contact with each other, or may be in contact with each other through an adhesive material such as silicon grease. In addition, the cooling structure 1200 may dissipate heat by air cooling or water cooling. In the example shown in FIG. 47, a water cooling type cooling structure in which a water flow path 1300 is formed in a predetermined portion of the cooling structure 1200 is adopted.

  FIG. 48 is a cross-sectional structure diagram showing a cross-sectional structure of a semiconductor chip constituting the snubber built-in switching element 900. As shown in FIG. 48, the snubber built-in switching element 900 includes a switching element 600 formed on the right side of the right broken line and a semiconductor snubber circuit 200 formed on the left side of the left broken line.

The part of the switching element 600 shown in FIG. 48 is composed of a general IGBT as an example. For example, the switching element 600 is configured using a substrate material in which an N-type buffer region 22 and an N ⁻ -type drift region 23 are stacked on a P ⁺ -type substrate region 21 made of silicon. A P-type well region 24 is formed in a part of the surface layer portion in the drift region 23, and an N ⁺ -type emitter region 25 is formed in a part of the surface layer portion in the well region 24. A gate insulating film 26 made of, for example, a silicon oxide film is disposed on the surface layer portions of the drift region 23, the well region 24, and the emitter region 25, and a gate electrode 27 made of, for example, N-type polycrystalline silicon is formed on the gate insulating film 26. It is arranged. An emitter electrode 28 made of, for example, aluminum is formed in contact with the emitter region 25 and the well region 24 in the opening formed in the gate insulating film 26. A collector electrode 30 is formed in ohmic contact with the substrate region 21. Thus, the IGBT shown in FIG. 48 is a so-called planar type in which the gate electrode 27 is formed on the semiconductor substrate plane.

  Further, as shown in FIG. 48, a field insulating film 31 made of, for example, a silicon oxide film is formed on the drift region 23 and the well region 24 in the outer periphery of the region where the switching element 600 is formed. As already described, the field insulating film 31 is used to alleviate electric field concentration at the PN junction at the outer periphery of the chip. Further, as a configuration of the outer peripheral end portion where the field insulating film 31 is formed, a guard ring may be formed so as to surround the outer periphery of the well region 24.

  Next, the semiconductor snubber circuit 200 formed on the left side of the left broken line in FIG. 48 will be described. Formed, for example, when a gate insulating film 26, an interlayer insulating film (not shown), or the like of the switching element 600 is formed on a predetermined region of the field insulating film 31 used for electric field relaxation at the outer peripheral edge of the switching element 600. An insulating film 32 is disposed, and a resistance region 33 made of polycrystalline silicon is formed on the insulating film 32. FIG. 48 illustrates the case where the insulating film 32 is formed, but the resistance region 33 may be formed on the field insulating film 31 without forming the insulating film 32. An emitter electrode 28 is formed on the resistance region 33, and the emitter electrode 28 is connected to an emitter terminal 301 to which the emitter terminal of the switching element 600 is connected as a surface electrode of the semiconductor snubber circuit 200.

  In the semiconductor snubber circuit 200, the resistance region 33 functions as the resistor 220, and the field insulating film 31 and the insulating film 32 function as the capacitor 210. The impurity concentration and thickness of the resistance region 33 can be set according to the magnitude of the resistance value required for the resistor 220. The thickness and area of the field insulating film 31 can also be set according to the breakdown voltage required for the capacitor 210 and the required capacitance. The withstand voltage is set not only as a condition of the semiconductor snubber circuit 200 but also higher than the withstand voltage of the switching element 600 in order to prevent the field insulating film 31 functioning as an electric field relaxation of the switching element 600 from being destroyed. preferable.

  The capacitance of the capacitor 210 is about 1/100 of the depletion capacity charged when the freewheeling diode 100 connected in parallel with the semiconductor snubber circuit 200 is cut off (when a high voltage is applied). It can be selected in the range of about 100 times. However, as already described, when the sufficient snubber function is exhibited and the increase in loss is suppressed as much as possible and the necessary chip area is taken into consideration, the capacitance of the capacitor 210 is equal to the depletion capacitance charged in the freewheeling diode 100. A range of about 1/10 to about 10 times is preferable.

  In the semiconductor snubber circuit 200 shown in FIG. 48, for example, the thickness of the capacitor 210 is set to about 1 μm so as to be higher than the withstand voltage of the switching element 600, and the capacitance of the capacitor 210 is when the switching element 600 and the free wheel diode 100 are cut off. Suppose that it is about the same as the sum of the depletion capacities formed. The field insulating film 31 may be any material other than a silicon oxide film as long as it has a predetermined breakdown voltage and functions as an electric field relaxation function and a capacitor 210. Moreover, it is preferable to set the magnitude | size of resistance of the resistance area | region 33 so that the design formula C = 1 / (2 (pi) fR) which exhibits a snubber function effectively may be satisfy | filled.

  As described above, even when the switching element 600 and the semiconductor snubber circuit 200 are formed on one chip, the operations and effects described in the second embodiment can be realized.

  In the configuration shown in FIG. 48, the switching element 600 and the semiconductor snubber circuit 200 share the substrate region 21, the buffer region 22, and the drift region 23 as the support base, and share the emitter electrode 28 and the collector electrode 30. Yes. The field insulating film 31 that functions as an electric field relaxation function of the switching element 600 also functions as the capacitor 210. Furthermore, a polycrystalline silicon film serving as the gate electrode 27 of the switching element 600 can be formed in the same manner as the resistance region 33 that is the resistor 220. That is, these portions can be formed by the same process, and the manufacturing process can be simplified.

  Further, by mounting the semiconductor snubber circuit 200 and the switching element 600 on one chip, the mounting area (site area) can be reduced, so that the semiconductor package can be reduced in size. Further, the switching element 600 and the emitter electrode 28 of the semiconductor snubber circuit 200 serve as a common electrode, and the parasitic inductance generated in the wiring and the like is further reduced as compared with the case where the second embodiment is connected by the metal wiring 350 and 330. can do. For this reason, the vibration phenomenon at the time of reverse recovery of the reflux diode 100 connected in parallel can be further reduced.

  Further, when the fifth embodiment is applied to an inverter circuit as shown in FIG. 27, for example, a new effect in which the switching element 600 and the semiconductor snubber circuit 200 are integrated into one chip can be produced. That is, as described in the second embodiment and the third embodiment, when the freewheeling diode 100 performs a reverse recovery operation, the semiconductor snubber circuit 200 has the freewheeling diode 100 and the switching element to alleviate the oscillation phenomenon. The transient current generated due to the 600 depletion capacity and the capacitor 210 of the semiconductor snubber circuit 200 is consumed, and the resistor 220 generates heat. On the other hand, when the freewheeling diode 100 performs reverse recovery operation, the switching element 600 connected in parallel to the freewheeling diode 100 is not in a conductive state, and therefore hardly generates heat. As described above, when the semiconductor snubber circuit 200 generates heat during reverse recovery, the switching element 600 is in a cut-off state and does not generate heat. For this reason, by making the switching element 600 and the semiconductor snubber circuit 200 into one chip, the temperature rise of the entire chip can be suppressed to be lower than in the case of another chip. That is, by integrating the switching element 600 and the semiconductor snubber circuit 200 into one chip, high integration of the resistance region 33 due to improved heat dissipation can be expected.

  Furthermore, as a feature of the fifth embodiment, it has high heat dissipation. This is because the switching element region 2600 in which the switching element 600 of the snubber built-in switching element 900 is formed is mounted so as to face each other through the semiconductor snubber region 2200 for two chips. Of course, as described in the fourth embodiment, even if the semiconductor snubber region 2200 for one chip is formed between the switching element regions 2600, it has an effect of improving heat dissipation. However, if the semiconductor snubber regions 2200 are arranged so as to face each other, the distance between the switching element regions 2600 is about twice that of the case where the semiconductor snubber region 2200 for one chip is arranged between the switching element regions 2600. Can be enlarged. For this reason, heat interference between the switching element regions 2600, which is a heat source, hardly occurs, and the heat dissipation performance is further improved.

  Even when three or more switching element chips with a built-in snubber are mounted in parallel, heat dissipation can be easily improved by disposing the semiconductor snubber area 2200 for at least one chip between the switching element areas 2600. However, for example, as in the fourth embodiment, various parallel numbers can be accommodated by changing the arrangement of the semiconductor snubber region 2200 in the snubber built-in switching element 900. For example, if the semiconductor snubber region 2200 is formed on both sides of the snubber built-in switching element 900, the semiconductor snubber region 2200 can be disposed so as to face each other. Further, when there are four circuits with built-in snubber 900, as in the configuration shown in FIG. 39, the four snubber built-in switching elements chips are arranged so that the semiconductor snubber regions 2200 are arranged at the facing positions. By disposing in a shape, heat dissipation can be improved. In any case, high cooling efficiency can be obtained with a minimum mounting area.

  As described above, the performance of the semiconductor device of the present invention can be further improved by adopting a mounting arrangement suitable for the operation mechanism of the switching element 600 and the semiconductor snubber circuit 200 in the fifth embodiment. In addition, the free-wheeling diode chip disposed outside the snubber built-in switching element chip can sufficiently secure the distance between the two chips, so that the heat dissipation performance can be improved.

  As described above, in the fifth embodiment, both the effect of further suppressing the vibration phenomenon and improving the transient performance and the conduction performance can be improved, and at the same time, the size and cost can be reduced.

  46 and 48 described the case where the switching element 600 is an IGBT. For example, the various switching elements 600 described in the second embodiment and the third embodiment are integrated into one chip with the semiconductor snubber circuit 200. This can be easily realized as in the case where the switching element 600 is an IGBT. An example is shown in FIGS.

FIG. 49 shows an example in which a MOSFET made of, for example, a silicon carbide semiconductor substrate is used as the switching element 600 instead of using the IGBT shown in FIG. For example, the switching element 600 uses a substrate material in which an N ⁻ type drift region 52 is formed on an N ⁺ type substrate region 51. A P type well region 53 is formed in a part of the surface layer portion of the drift region 52, and an N ⁺ type source region 54 is formed in a part of the surface layer portion of the well region 53. A gate insulating film 55 made of, for example, a silicon oxide film is formed in contact with the surface layer portions of the drift region 52, well region 53, and source region 54, and a gate electrode 56 made of, for example, N-type polycrystalline silicon is formed on the gate insulating film 55. Is arranged. Further, a source electrode 57 in contact with the source region 54 and the well region 53 in the opening formed in the gate insulating film 55 is formed. A drain electrode 59 is formed in ohmic contact with the substrate region 51.
Further, as shown in FIG. 49, a field insulating film 31 made of, for example, a silicon oxide film is formed on the outer peripheral portion of the region where the switching element 600 is formed in contact with the surface layer portions of the drift region 52 and the well region 53. Yes.

  Next, the semiconductor snubber circuit 200 formed on the left side of the left broken line shown in FIG. 49 will be described. For example, an insulating film 32 or an interlayer insulating film (for example, formed when the gate insulating film 55 of the switching element 600 is formed on a predetermined region of the field insulating film 31 used for electric field relaxation at the outer peripheral edge of the switching element 600. (Not shown), and a resistance region 33 made of polycrystalline silicon is formed on the insulating film 32. FIG. 49 illustrates the case where the insulating film 32 is formed, but the resistance region 33 may be formed on the field insulating film 31 without forming the insulating film 32. A source electrode 57 is formed on the resistance region 33, and the source electrode 57 is connected to the source terminal 302 to which the source terminal of the switching element 600 is connected.

  In the semiconductor snubber circuit 200 illustrated in FIG. 49, the resistance region 33 functions as the resistor 220, and the field insulating film 31 and the insulating film 32 function as the capacitor 210. The impurity concentration and thickness of the resistance region 33 can be set according to the magnitude of the resistance value required for the resistor 220.

  With the configuration shown in FIG. 49, the effect that the free wheel diode 100 and the switching element 600 described in the third embodiment can be realized by various elements, and the semiconductor snubber circuit 200 and the switching element 600 described in the fifth embodiment are achieved. It is possible to realize the effect obtained by using one chip. Further, the feature of the configuration shown in FIG. 49 is that the resistance region 33 is formed of the same material as the gate electrode 56 of the switching element 600 as in the configuration shown in FIG. With such a configuration, in addition to the effect of using a MOSFET for the switching element 600, the manufacturing process can be further simplified and realized at low cost.

FIG. 50 shows a case where a transistor for driving the heterojunction portion shown in FIG. 16 with an insulated gate electrode is used as the switching element 600 instead of using the IGBT shown in FIG. For example, an N ⁻ type drift region 62 is formed on a substrate region 61 whose silicon carbide polytype is 4H type N ⁺ type. In the region where the switching element 600 is formed, a hetero semiconductor region 63 made of, for example, N-type polycrystalline silicon is formed on the drift region 62. A gate insulating film 64 made of, for example, a silicon oxide film is formed on the hetero semiconductor region 63 in contact with the drift region 62 at the opening of the hetero semiconductor region 63. A gate electrode 65 is formed on the gate insulating film 64, and a source electrode 66 is disposed in contact with the hetero semiconductor region 63. A drain electrode 68 is formed in contact with the substrate region 1. Further, a field insulating film 31 made of a silicon oxide film or the like is formed between the drift region 62 and the hetero semiconductor region 63 in the outer periphery of the region where the switching element 600 is formed.

  Next, the semiconductor snubber circuit 200 formed on the left side of the left broken line shown in FIG. 50 will be described. A resistance region 33 made of polycrystalline silicon is formed on a predetermined region of the field insulating film 31 used for the electric field relaxation at the outer peripheral edge of the switching element 600. A source electrode 66 is formed on the resistance region 33 as a surface electrode of the semiconductor snubber circuit 200, and this surface electrode is connected to the source terminal 302 to which the source terminal of the switching element 600 is connected. That is, in the semiconductor snubber circuit 200 shown in FIG. 50, the resistance region 33 functions as the resistor 220, and the field insulating film 31 and the insulating film 32 function as the capacitor 210. The impurity concentration and thickness of the resistance region 33 can be set according to the magnitude of the resistance value required for the resistor 220.

  50, the effect that the free wheel diode 100 and the switching element 600 described in the third embodiment can be realized by various elements, and the semiconductor snubber circuit 200 and the switching element 600 described in the fifth embodiment. It is possible to realize the effect of having been integrated into one chip. Further, as a feature of the configuration shown in FIG. 50, the resistance region 33 is formed of the same material as the hetero semiconductor region 63 of the switching element 600. 48 and 49, the resistance region 33 can be formed of the same material as that of the gate electrode 65 of the switching element 600.

FIG. 51 shows a case where the JFET shown in FIG. 32 is used as the switching element 600 instead of using the IGBT shown in FIG. In FIG. 51, for example, an N ⁻ type drift region 72 is formed on an N ⁺ type substrate region 71 whose polytype of silicon carbide is 4H type. An N ⁺ -type source region 73 and a P-type gate region 74 are formed in part of the surface layer portion in the drift region 72, respectively. The gate region 74 is connected to the gate electrode 75, and the source region 73 is connected to the source electrode 76. The substrate region 71 is connected to the drain electrode 78. Further, a field insulating film 31 made of, for example, a silicon oxide film is formed on the outer peripheral portion of the switching element 600 in contact with the surface layer portion of the drift region 72.

  A semiconductor snubber circuit 200 formed on the left side of the left broken line in FIG. 51 will be described. For example, an insulating film 32 or an interlayer insulating film formed when forming an insulating film 77 of the switching element 600 on a predetermined region of the field insulating film 31 used for electric field relaxation at the outer peripheral edge of the switching element 600 (see FIG. (Not shown) and the like, and a resistance region 33 made of polycrystalline silicon is formed in the insulating film 32. FIG. 51 illustrates the case where the insulating film 32 is formed, but the resistance region 33 may be formed on the field insulating film 31 without forming the insulating film 32. A source electrode 76 is formed on the resistance region 33 as a surface electrode of the semiconductor snubber circuit 200, and this surface electrode is connected to the source terminal 302 to which the source terminal of the switching element 600 is connected. That is, in the semiconductor snubber circuit 200 shown in FIG. 51, the resistance region 33 functions as the resistor 220, and the field insulating film 31 and the insulating film 32 function as the capacitor 210. The impurity concentration and thickness of the resistance region 33 can be set according to the magnitude of the resistance value required for the resistor 220.

  51, the effect that the free wheel diode 100 and the switching element 600 described in the third embodiment can be realized by various elements, and the semiconductor snubber circuit 200 and the switching element 600 described in the fifth embodiment. It is possible to realize the effect of having been integrated into one chip. With the configuration shown in FIG. 51, the manufacturing process can be further simplified and realized at low cost.

  Further, in the fifth embodiment, as described in the third embodiment, when the configuration employed in the switching element 600 can be used as a unipolar freewheeling diode, the freewheeling diode 100 is mounted on a separate chip. In addition to the formation, the free-wheeling diode 100, the switching element 600, and the semiconductor snubber circuit 200 can be made into one chip, and the semiconductor package can be downsized. Thereby, since the parasitic inductance generated in the wiring or the like can be further reduced, the vibration phenomenon caused by the semiconductor snubber circuit 200 can be further reduced. The shorter wiring length also has the effect of further reducing radiation noise generated from the wiring due to the oscillating current. Further, the cost is reduced by reducing the chip size, and the sum of the capacitor capacities of the freewheeling diode 100 and the switching element 600 is reduced, so that the capacitance required for the semiconductor snubber circuit 200 can also be reduced. That is, the suppression of the vibration phenomenon can be realized at a small size and at a low cost.

  The example in which the switching element 600 and the semiconductor snubber circuit 200 are made into one chip has been described above. However, when the chip is made into one chip, the resistance 220 of the semiconductor snubber circuit 200 is not limited to the resistance region 33 made of polycrystalline silicon. A substrate region or drift region in the semiconductor substrate may be used. In addition to the field insulating film 31 made of a silicon oxide film, the capacitor 210 of the semiconductor snubber circuit 200 employs a configuration in which a depletion layer is formed at the time of reverse bias such as a PN junction or a heterojunction. You may use as 210. Further, for example, a freewheeling diode 100 may be built in the switching element 600 such as a MOSFET having a Schottky barrier diode, and the semiconductor snubber circuit 200 may be integrated into one chip. In any configuration, the vibration phenomenon, which is a feature of the present invention, can be further suppressed, and both transient performance and conduction performance can be improved, and at the same time, miniaturization and cost reduction can be realized.

  In any combination, since heat interference between the switching elements 600 hardly occurs, the heat dissipation performance can be further improved, and the operation at a higher current density can be achieved.

  Also in the fifth embodiment, the damping effect of the vibration phenomenon becomes remarkable from the capacity ratio C / C0 of around 0.1, as described with reference to FIGS. 20 and 21 in the first embodiment. When the capacity ratio C / C0 exceeds 10, the convergence time ratio value of the vibration phenomenon tends to be saturated. In addition, since a loss E due to a transient current proportional to the capacitance of the capacitor 210 occurs during a transient operation, the capacitance of the capacitor 210 is preferably as small as possible. Therefore, as described above, the capacitance of the capacitor 210 of the semiconductor snubber circuit 200 used in the fifth embodiment is 1 as compared with the sum of the capacitances of the capacitor components in the cutoff state of the free-wheeling diode 100 and the switching element 600. By selecting within a range of / 10 times or more and 10 times or less, the vibration phenomenon can be reduced more significantly while suppressing an increase in loss. This effect can be obtained in any configuration example described in the fifth embodiment.

(Sixth embodiment)
In the sixth embodiment, as in the fourth embodiment, the freewheeling diode 100 and the semiconductor snubber circuit 200 are formed on the same chip, and the semiconductor snubber circuit 200 is disposed in the region where the freewheeling diode 100 is disposed (hereinafter, referred to as “return diode 100”). , Referred to as “freewheeling diode region”) will be described.

  For example, when the free-wheeling diode region is rectangular, a plurality of distributed semiconductor snubber circuits 200 are disposed adjacent to the plurality of sides of the rectangular region where the free-wheeling diode 100 is disposed. FIG. 52 shows an example in which a snubber circuit built-in freewheeling diode 800 having a structure in which two semiconductor snubber circuits 200 are arranged on both sides of one freewheeling diode 100 is mounted on a semiconductor package. In FIG. 52, a chip (a snubber built-in freewheeling diode chip) in which the snubber circuit built-in freewheeling diode 800 is arranged is denoted by reference numeral 800.

  The semiconductor package shown in FIG. 52 includes a ceramic substrate in which an anode side metal film 310 and a cathode side metal film 410 made of a metal material such as copper or aluminum are formed on an insulating substrate 500. The insulating substrate 500 is formed of, for example, a ceramic plate or the like, has an insulating property, and functions as a support. The free-wheeling diode 100 included in the snubber circuit built-in free-wheeling diode 800 and the cathode terminal of the semiconductor snubber circuit 200 are connected to the metal film 410 via a bonding material such as solder or brazing material. The anode terminals of the freewheeling diode 100 and the semiconductor snubber circuit 200 are connected to the metal film 310 via metal wirings 320 and 330 such as aluminum wires and aluminum ribbons. The metal film 410 is connected to the cathode terminal 400, and the metal film 310 is connected to the anode terminal 300.

  FIG. 53 shows an example of a top view of the snubber circuit built-in reflux diode 800 shown in FIG. The cross section along the II direction in FIG. 53 when the freewheeling diode 100 is a silicon carbide Schottky barrier diode is, for example, the cross sectional view shown in FIG. A cross section taken along the II-II direction, which is a cross-sectional structure diagram of the semiconductor snubber circuit 200, is, for example, the cross-sectional view shown in FIG. The cross section along the III-III direction showing the cross-sectional structure of the boundary portion between the free-wheeling diode 100 and the semiconductor snubber circuit 200 is, for example, the cross-sectional view shown in FIG. The snubber circuit built-in freewheeling diode 800 includes a freewheeling diode 100 portion formed on the right side of the right broken line in FIG. 36 and a semiconductor snubber circuit 200 portion formed on the left side of the left broken line.

  In the sixth embodiment, the free-wheeling diode 100 and the semiconductor snubber circuit 200 described in the first to fifth embodiments can be used. For this reason, the duplicate description about the structure and modification of the free-wheeling diode 100 and the semiconductor snubber circuit 200 that can be used in the sixth embodiment is omitted. The semiconductor device according to the sixth embodiment, like the semiconductor devices described in the first to fifth embodiments, is a converter (FIG. 8) or an inverter (FIG. 9) used as power energy conversion means. ) And the like are used as passive elements A and B that circulate current.

  As described in the fourth embodiment, by forming the freewheeling diode 100 and the semiconductor snubber circuit 200 on the same chip, it is possible to simplify the manufacturing process, reduce the size of the semiconductor package, and reduce the radiation noise due to the short wiring length. The effect of reducing the transient loss and suppressing the vibration phenomenon by mounting the semiconductor snubber circuit 200 in the immediate vicinity of the freewheeling diode 100 with a low inductance can be obtained. Further, as already described, when the freewheeling diode 100 is conducting and generating heat, the semiconductor snubber circuit 200 is in a cut-off state and does not generate heat, so the temperature rise of the entire chip is higher than that of another chip. The effect is that it can be kept low.

  In addition to these effects, the semiconductor device according to the sixth embodiment has the following effects. For example, as shown in FIG. 53, since the semiconductor snubber circuit 200 is distributed and arranged on two or more sides around the main surface of the semiconductor substrate on which the free-wheeling diode 100 is arranged, the oscillation current generated by the free-wheeling diode 100 is balanced. The semiconductor snubber circuit 200 can be well distributed, and as a result, local current concentration can be avoided. Furthermore, the heat generation of the semiconductor snubber circuit 200 generated by the passage of the transient current can be evenly distributed, and local heat generation can be avoided.

  In FIG. 53, the semiconductor snubber circuits 200 are arranged one by one on opposite sides, but may be arranged separately. Also, as shown in FIG. 54, by disposing the semiconductor snubber circuit 200 in the four sides of the region where the freewheeling diode 100 is disposed, the effect of dispersing the oscillating current and heat is further increased.

  Further, as shown in FIG. 55, the semiconductor snubber circuit 200 may be disposed outside the curved portion CR in the region where the free-wheeling diode 100 provided for relaxing the electric field of the free-wheeling diode 100 is disposed. If arranged as shown in FIG. 55, the principal surface outside the curved portion CR that is not originally used can be used as a region where the semiconductor snubber circuit 200 is arranged, and the area utilization efficiency of the semiconductor substrate can be improved. .

  Further, as shown in FIG. 56, the semiconductor snubber circuit 200 may be arranged so as to surround the entire circumference of the free-wheeling diode 100. If it arrange | positions as shown in FIG. 56, both the effect which improves the area utilization efficiency by using the four corners of the free-wheeling diode 100, and the effect which distributes an oscillating current and heat_generation | fever can be acquired. Further, for the semiconductor device according to the sixth embodiment, for example, by adopting the mounting structure illustrated in FIGS. 4 and 11, it is possible to improve the heat dissipation of the chip in which the snubber circuit built-in reflux diode 800 is disposed.

  In the sixth embodiment, since the semiconductor snubber circuit 200 is integrated with the freewheeling diode 100, the freewheeling diode and the snubber circuit can be mounted at the same time, so that the vibration phenomenon can be easily and easily suppressed. At the same time, the required volume can be greatly reduced as compared with the conventional snubber circuit.

  In the description of the sixth embodiment, FIG. 6 is used as an example of the structure of the semiconductor snubber circuit 200. However, the capacitor 210 of the semiconductor snubber circuit 200 has the structure shown in FIGS. Of course, the structure shown in FIGS. 17 and 18 may be used. In addition to the Schottky barrier diode, the freewheeling diode 100 is configured by a diode formed of a wide band gap semiconductor such as a heterojunction diode or a soft recovery diode, as described in the third embodiment. A PN junction diode or the like can be used.

(Seventh embodiment)
The semiconductor device according to the seventh embodiment further includes a switching element 600 in addition to the snubber circuit built-in free-wheeling diode 800 described in the sixth embodiment, and, similarly to the configuration shown in FIG. This is a semiconductor device connected in parallel with the freewheeling diode 100 and the semiconductor snubber circuit 200. That is, the seventh embodiment is an embodiment in which the second embodiment and the sixth embodiment are combined.

  As described in the sixth embodiment, various structures can be adopted for the semiconductor snubber circuit 200 and the free wheeling diode 100. As the switching element 600, for example, the IGBT described in the second embodiment can be used, and as described in the third embodiment, a MOSFET, a transistor having a heterojunction, a JFET, or the like can be used. .

  FIG. 57 is a snubber built-in freewheeling diode chip (indicated by reference numeral 800 in the figure) including the freewheeling diode 100 (for example, silicon carbide Schottky barrier diode) illustrated in FIG. 52 and the semiconductor snubber circuit 200 (for example, silicon semiconductor RC snubber). And a mounting diagram showing a specific embodiment of a semiconductor device composed of a switching element chip (indicated by reference numeral 600 in the figure) in which a switching element 600 (for example, silicon IGBT) is arranged.

  57, the case where a ceramic substrate is used as an example of a semiconductor package will be described as in FIG. 3 and FIG. The freewheel diode chip and the switching element chip with built-in snubber are on the metal film 410 so that the cathode terminal of the freewheel diode 100, the capacitor 210 of the semiconductor snubber circuit 200, and the collector terminal of the switching element 600 are connected to the metal film 410 on the cathode side. Has been placed. On the other hand, the anode terminal of the reflux diode 100, the resistor 220 of the semiconductor snubber circuit 200, and the emitter terminal of the switching element 600 are connected to the metal film 310 on the anode side through metal wirings 320, 330, and 350. A gate terminal of the switching element 600 is connected to the metal film 700 on the gate side through a metal wiring 710.

  Similarly to the semiconductor device according to the second embodiment, the semiconductor device according to the seventh embodiment includes, for example, a so-called inverter that moves a three-phase AC motor illustrated in FIG. 27, a so-called H bridge illustrated in FIG. It can be used for a power converter. Specifically, it is used as a switching element and a passive element of a power converter. At this time, as described in the second embodiment, by connecting the freewheeling diode 100 and the semiconductor snubber circuit 200 and the switching element 600 in parallel, the transient loss and the conduction loss of the freewheeling diode 100 are reduced, and at the same time, the unipolar operation. Occurrence of the vibration phenomenon caused by the above can be suppressed and more stable operation can be realized.

  As described above, according to the semiconductor device of the seventh embodiment, in addition to the effect of forming the free wheel diode 100 and the semiconductor snubber circuit 200 described in the sixth embodiment on the same chip, By connecting the freewheeling diode 100 and the semiconductor snubber circuit 200 and the switching element 600 in parallel, a stable operation of the power converter can be realized.

(Eighth embodiment)
In the eighth embodiment, as in the fifth embodiment, the switching element 600 and the semiconductor snubber circuit 200 are formed on the same chip, and the semiconductor snubber circuit 200 is adjacent to the region where the switching element 600 is disposed. The case where they are arranged so as to be dispersed will be described. For example, a snubber built-in switching element 900 having a structure in which a plurality of semiconductor snubber circuits 200 are arranged around one switching element 600 is an example of a semiconductor device according to the eighth embodiment.

  As for the switching element 600 of the semiconductor device according to the eighth embodiment, the capacitor 210 and the resistor 220 of the semiconductor snubber circuit 200, the various structures described in the first to seventh embodiments can be adopted. It is.

  FIG. 58 shows an example of a snubber built-in switching element 900 having a structure in which a plurality of semiconductor snubber circuits 200 are arranged around one switching element 600. In the snubber built-in switching element 900 shown in FIG. 58, two semiconductor snubber circuits 200 are distributed and arranged on two sides around the main surface of the semiconductor substrate on which the switching element 600 is arranged. 58, a cross section taken along the IV-IV direction, which is a cross-sectional structure diagram of the semiconductor snubber circuit 200, is, for example, the cross-sectional view shown in FIG. A cross section taken along the VV direction, which is a cross-sectional structure diagram of the switching element 600, is, for example, the cross-sectional view shown in FIG. The cross section along the VI-VI direction showing the cross-sectional structure of the boundary portion between the free-wheeling diode 100 and the switching element 600 is, for example, the cross-sectional view shown in FIG.

  According to the structure shown in FIG. 58, the oscillating current generated by the switching element 600 can be distributed to the semiconductor snubber circuit 200 in a well-balanced manner, and local current concentration can be avoided. Furthermore, the heat generation of the semiconductor snubber circuit 200 generated by the passage of the transient current can be evenly distributed, and local heat generation can be avoided. In the example shown in FIG. 58, the semiconductor snubber circuits 200 are arranged one by one on opposite sides, but the semiconductor snubber circuits 200 may be divided and arranged.

  Further, as shown in FIG. 59, when the semiconductor snubber circuit 200 is arranged in the four sides of the switching element 600, the effect of dispersing the oscillating current and heat is further increased.

  Further, the semiconductor snubber circuit 200 may be arranged outside the curved portion CR shown in FIG. 60 provided for the electric field relaxation of the switching element 600. By using a region outside the curved portion CR that is not originally used as a region where the semiconductor snubber circuit 200 is disposed, the area efficiency of the semiconductor substrate can be improved.

  Further, as shown in FIG. 61, the semiconductor snubber circuit 200 may be arranged so as to surround the entire circumference of the free-wheeling diode 100. With this arrangement, it is possible to obtain both the effect of improving the area efficiency by using the four corners of the switching element 600 and the effect of dispersing the oscillating current and heat generation. Also, with the semiconductor device according to the eighth embodiment, for example, by adopting the mounting structure illustrated in FIGS. 4 and 11, the heat dissipation of the chip in which the snubber built-in switching element 900 is disposed can be improved.

  As described above, according to the semiconductor device of the eighth embodiment, it is possible to realize a small and low-cost semiconductor device while suppressing the vibration phenomenon and improving the transient performance and improving the conduction performance.

(Other embodiments)
As described above, the present invention has been described according to the first to eighth embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

    For example, as a material of the freewheeling diode 100, the switching element 600, and the semiconductor snubber circuit 200, a silicon material, a silicon carbide material, and the like have been described as examples. However, if an effect of reducing the vibration phenomenon can be obtained, the substrate material is silicon germanium, nitride Other semiconductor materials such as gallium and diamond may be used. Moreover, although 4H type was demonstrated as a polytype of silicon carbide, other polytypes, such as 6H and 3C, may be sufficient. Further, the drift region of the switching element 600 and the free wheeling diode 100 has been described as being an N type, but may be configured as a P type.

  In addition, as a power converter to which the semiconductor device according to the embodiment of the present invention can be applied, a DC / DC converter, a three-phase AC inverter, or the like has been described as an example. Good. In any case, all types of power, such as inverters that convert DC voltage to AC voltage, rectifiers that convert AC voltage to DC voltage, DC / DC converters that change the voltage value of DC voltage, etc. It can be applied to a conversion device. And if it is a power converter device using the structure of embodiment of this invention, in any area | region of a large electric current area | region and a zero electric power area | region, Furthermore, a vibration phenomenon is reduced in both low temperature and high temperature. Can do. For this reason, the conduction loss and the transient loss can be reduced and the density can be increased, and the vibration phenomenon can be reduced and the operation can be stably performed, so that the basic performance of the apparatus can be improved at the same time.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  The semiconductor device of the present invention can be used in the electronic equipment industry including a manufacturing industry that manufactures a semiconductor device having a reflux diode.

DESCRIPTION OF SYMBOLS 1, 11, 21, 41, 51, 61, 71, 81 ... Substrate area | region 2, 23, 42, 52, 62, 72, 82 ... Drift area | region 3, 13, 44, 84 ... Surface electrode 4, 14, 45, 85 ... Back electrode 5, 31, 46, 86 ... Field insulating film 6, 17, 19, 33, 47 ... Resistance region 7 ... Electric field relaxation region 8, 88 ... Low concentration drift region 10, 10A ... Semiconductor device 12 ... Dielectric region 15, 83, 89 ... opposite conductivity type region 16 ... low resistance substrate region 22 ... buffer region 24, 53 ... well region 43, 63 ... hetero semiconductor region 100 ... freewheeling diode 200 ... semiconductor snubber circuit 210 ... capacitor 220 ... resistor 230 ... Diode 600 ... Switching element 800 ... Snubber circuit built-in reflux diode 900 ... Snubber built-in switching element 1000 ... Back surface metal film 100 ... base plate 1200 ... cooling structure 1300 ... water flow path 1400 ... insulating layer 2100 ... reflux diode region 2200 ... semiconductor snubber regions 2600 ... switching device region

Claims (15)

A plurality of freewheeling diodes that operate unipolar;
A semiconductor snubber circuit having a capacitor and a resistor formed in one semiconductor chip, and connected in parallel with the freewheeling diode and disposed adjacent to the freewheeling diode, from both sides between the plurality of freewheeling diodes. wherein by separating the freewheeling diode between the sandwiched reflux diode region, a semiconductor device, wherein the semiconductor chip in which the formed semiconductor snubber circuit is arranged.   The plurality of free-wheeling diodes are disposed on a cooling structure, and a distance between the free-wheeling diodes is at least twice as long as a distance from the free-wheeling diodes to a heat radiation portion of the cooling structure. A semiconductor device according to 1.   The semiconductor device according to claim 1, further comprising a switching element connected in parallel to the reflux diode.   The semiconductor device according to claim 3, comprising a plurality of the switching elements, wherein at least a part of the semiconductor snubber circuit is disposed between the plurality of switching elements.   5. The plurality of switching elements are disposed on a cooling structure, and a distance between the switching elements is at least twice as long as a distance from the switching element to a heat radiation portion of the cooling structure. A semiconductor device according to 1.   6. The semiconductor device according to claim 1, wherein the semiconductor snubber circuit is disposed on the same chip as the free wheel diode.   A plurality of snubber built-in freewheeling diode chips in which the semiconductor snubber circuit and the freewheeling diode are arranged, and the semiconductor snubber circuit is arranged in a region adjacent to the plurality of snubber built-in freewheeling diode chips. The semiconductor device according to claim 6.   The plurality of snubber built-in freewheeling diode chips are disposed on a cooling structure, and the distance between the freewheeling diodes disposed in each of the plurality of snubber built-in freewheeling diode chips is from the freewheeling diode to the heat dissipation part of the cooling structure. The semiconductor device according to claim 7, wherein the distance is at least twice the distance to 9. The semiconductor device according to claim 3, wherein the semiconductor snubber circuit is disposed on the same chip as the switching element.   A plurality of snubber built-in switching element chips in which the semiconductor snubber circuit and the switching element are arranged are provided, and the semiconductor snubber circuits are arranged in adjacent regions of the plurality of snubber built-in switching element chips. The semiconductor device according to claim 9.   The plurality of snubber built-in switching element chips are disposed on a cooling structure, and a distance between the switching elements disposed in each of the plurality of snubber built-in switching element chips is a heat dissipation of the cooling structure from the switching element. 11. The semiconductor device according to claim 10, wherein the semiconductor device is at least twice the distance to the portion.   2. The semiconductor device according to claim 1, wherein the semiconductor snubber circuit is distributed on the same chip as the free wheel diode, and the distributed semiconductor snubber circuit is arranged around the free wheel diode. .   The semiconductor device according to claim 12, further comprising a switching element connected in parallel to the reflux diode.   The semiconductor snubber circuit further includes a switching element connected in parallel to the freewheeling diode, the semiconductor snubber circuit is distributed on the same chip as the switching element, and the distributed semiconductor snubber circuit is disposed around the switching element. The semiconductor device according to claim 12, wherein:   The semiconductor device according to claim 1, wherein the semiconductor snubber circuit has a configuration in which a capacitor and a resistor are connected in series.

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