JP5993150B2 - Diode, semiconductor module and power supply circuit - Google Patents

Description

  The present invention can suppress surge voltage and EMI noise, simplify or eliminate the snubber circuit and external circuit of the filter circuit on the power supply circuit, reduce the snubber loss, and save energy. The present invention relates to a diode capable of high-speed operation and a power supply circuit using the diode.

Recently, stable energy supply for urgent problems on a global scale, such as response to global warming due to greenhouse gases such as CO _2, and renewable energy Special Measures Law METI is submitted to the Diet , Passed in August 2011 by the Japanese Diet. Along with this, it is expected in Japan that the spread of distributed power sources such as sunlight, wind power, hydropower, biomass, geothermal heat, and solar heat, which has been difficult to spread in the market due to high cost, is promoted.

  On the other hand, in the United States, the spread of distributed power sources is also expected due to the Green New Deal policy. Since distributed power sources such as these solar cells and wind power generation tend to be introduced in large quantities into the power system, the demand for power converters for adjusting the produced power and power supply circuits used for it inevitably increases. The conversion of electric power produced from renewable energy to high efficiency is an extremely important issue in energy policy.

  In order to establish the distributed power supply in the market, from the viewpoint of energy saving, active elements such as MOSFETs, IGBTs, and diodes constituting the power supply circuit are required to reduce conduction loss, and from the viewpoint of downsizing of the power converter. Therefore, it is required to operate the power supply circuit at high speed, downsize passive elements such as capacitance, inductance, and resistance, reduce power loss, and downsize the cooling mechanism.

  At the same time as the spread of the distributed power source into the market, electronic devices or electric vehicles using wireless power supply tend to increase. Since such an electronic device has a high high-frequency output, EMC (electromagnetic compatibility) is required for electronic components used, particularly semiconductor elements including diodes.

  For diodes, silicon carbide, gallium nitride, gallium nitride, etc. in operation in a high withstand voltage region of 600 V or higher in order to reduce the size of the power supply circuit by operating at high speed. Active devices such as SBDs using wide-gap semiconductors are being developed. The effect that these elements operate at high speed is explained by the fact that the SBD operates monopolarly, whereas the PN diode operates bipolar. As described above, the diode, which is one of the active elements, is one of the important components in the power supply circuit, and is used for rectification of DC-DC converters, AC-DC converters, and commutation of IGBT elements. It is used.

  When the power supply circuit is operated at a high speed as described above, the power consumption on the circuit can be reduced and the power converter including the power supply circuit can be downsized. However, when the power supply circuit is miniaturized and operated at high speed, the following two problems arise due to high di / dt and dv / dt and the parasitic inductance on the circuit.

  As a first problem, a high surge voltage calculated by the product of high di / dt and parasitic inductance is generated, and a voltage higher than the power supply voltage and further higher than the reverse blocking voltage rating is applied to the diode element. May cause destruction.

  As a second problem, weak electromagnetic noise is generated from the diode due to circuit overcrowding and signal high frequency. In particular, in order to perform hard recovery during the OFF operation of the diode, parasitic inductance and capacitance undergo LC resonance, and harmonic EMI (electromagnetic interference) noise is generated from the diode element. This noise causes an increase in power loss and malfunction of peripheral circuits.

  Power converters using power supply circuits tend to improve circuit topology while complementing the drawbacks of each electronic component in order to achieve downsizing and higher efficiency. However, since the number of electronic components that serve as EMI noise sources with a single diode increases and the density of electronic components inevitably increases, it is ideal to reduce EMI noise from the electronic components.

As an example, EMI (electromagnetic interference) noise is also observed in a general rectifier diode used in a bridge rectifier in a rectifier circuit of a commercial power supply of 50 Hz / 60 Hz. In recent years, when the miniaturization of electrical equipment is progressing rapidly, it is necessary to cope with EMI noise countermeasures at the electronic component level.
With respect to these two points, those skilled in the art have attempted the following improvements in the prior art.

  Regarding the problem of surge voltage generation, which is the first problem, for example, Patent Document 1 discloses a technique for reducing the concentration profile of the drift layer of a diode in a region shallow from the junction and increasing it in a deep region. As a result, in the process in which the reverse voltage is applied to the diode and the depletion layer extends, the speed at which the depletion layer extends is high in the low concentration region and slow in the high concentration region. As a result, di / dt is early in the region where the reverse voltage is low and is slow in the region where the reverse voltage is high. Since the surge voltage is proportional to di / dt, its value becomes small. Patent Document 1 discloses that there is an effect of suppressing a surge voltage using such a concentration profile.

  Further, as a technique for suppressing a surge voltage, there are means for providing a snubber circuit in a power supply circuit, means for reducing parasitic inductance, and the like, which have been recognized as well-known techniques. For example, Patent Document 2 discloses a technique for creating a snubber circuit using a semiconductor device. Patent Document 2 discloses a diode in which a diode region and a snubber region are formed on one chip of a semiconductor device and equivalently a diode and a snubber circuit are coupled in parallel.

  Further, as a means for solving the problem 2, it is a well-known technique in the art that noise can be eliminated by installing a filter circuit having a capacitance such as a ceramic capacitor in parallel with the diode of the power supply circuit. .

JP 2008-251679 A JP 2010-206109 A

  As described above, the conventional technology solves the problems of suppressing the surge voltage and EMI noise when the diode is operated at high speed, and further reducing the number of components on the power supply circuit. Although it has been solved, the following problems still exist in the power supply circuit and the diode.

  In order to turn off the diode on the power supply circuit, a charge for turning off the diode must be charged, and a capacitor arranged in parallel with the diode or a capacitor integrated on the diode chip is charged. There must be.

  For this reason, the higher the speed of the power supply circuit, the more the diode off time is limited to the time for charging the capacitor than the charging time for turning off the diode.

That is, there is a problem that even if the diode can realize high-speed operation, it cannot be operated at high speed due to the capacitance of the snubber circuit when it is incorporated in the circuit.
Further, when the power supply circuit is operated at a high speed, the number of times of turning on / off per unit time increases, thereby increasing the power consumed by the capacitor.

  Even if the power consumption of the diode is suppressed, the power consumed by the capacitor increases, and there is a problem that the capacitor cancels the improvement in energy saving of the diode.

  That is, there is a problem that the power supply circuit increases the power consumption by inserting a snubber circuit and operating at high speed. Such disadvantages of hindering the high-speed operation of the circuit and increasing the snubber loss appear in a trade-off relationship with the elimination of the surge voltage.

  Further, when a method of providing a diode and a capacitor in different electrically isolated regions on one chip as in the cited document 2, wiring between the anode electrode pad of the diode and the electrode pad of the capacitor is used. Since routing is required, parasitic inductance is generated and an ESL (equivalent series inductance) component is generated, so that the capacitor does not act in a high frequency region.

  That is, there is a problem that the function of smoothing the current waveform at high speed is not performed, and all the problems cannot be solved by one technique. In addition, two regions, a diode region and a snubber circuit region, are separately arranged on an expensive chip, so that it is necessary to increase the element area and there is no cost merit. Furthermore, as shown in the graph of FIG. 19 of the cited document 2, there is a trade-off in which, when the capacitor capacitance ratio is increased, transient loss increases instead of reducing noise.

  If only EMI noise is to be suppressed, a method of soft switching in the diode element can be used, but the disadvantages of not being a high-speed operation and an increase in switching loss appear, and it will be a fundamental solution. There wasn't.

  Furthermore, in recent years, when SiC is used for a semiconductor substrate in SBD, a high breakdown voltage can be realized, but EMI noise has become prominent due to high-speed on / off at a high breakdown voltage.

  In recent years, power converters tend to be downsized, that is, power supply circuits are downsized, and the main circuit and the control circuit are often close to each other on the power supply circuit. For example, FWD (free wheel diode) using SiC is molded together with an IGBT which is a switching element and used as a main module of a power supply circuit as one module. As a control circuit, there is a drive IC which is a circuit for controlling a switching element, and it operates at a relatively low current. In such a state, the drive IC may malfunction due to EMI noise radiated from the SiC diode, resulting in erroneous ignition of the IGBT, which is a serious problem.

  The present invention was made paying attention to the above problems, and after suppressing surge voltage and EMI noise, simplification and useless external circuits such as snubber circuits and filter circuits on the power supply circuit, An object of the present invention is to provide a diode, a semiconductor module, and a power supply circuit that can operate at high speed and reduce energy consumption by reducing snubber loss.

In order to achieve the above object, the invention of claim 1
A semiconductor substrate having a first main surface and a second main surface opposite to the first main surface;
An anode electrode which is a first metal on the first main surface side;
A cathode electrode which is a second metal on the second main surface side;
A first semiconductor layer of a first conductivity type having a high concentration and formed in the semiconductor substrate facing the second main surface;
A second semiconductor layer having a low concentration of the first conductivity type, which is laminated from the semiconductor substrate in the first main surface direction to the first main surface facing the first semiconductor layer;
A first structure region having a substantially ring shape in which a termination structure for relaxing an electric field formed in the first semiconductor layer from the first main surface is formed;
When a negative voltage is applied from the anode electrode formed inside the first structure region to the cathode electrode, a depletion layer is formed on the second main surface from the first main surface side in the second semiconductor layer. A second structural region characterized by extending to the side;
In a Schottky barrier diode with
A third semiconductor region of a second conductivity type formed in the second semiconductor layer in the semiconductor substrate in the second structure region and located in the second semiconductor layer;
The third semiconductor is located in the second structure region so as to surround at least a part of the outer edge of the third semiconductor region, and has a second conductivity type dopant concentration deeper than the third semiconductor region and a depth of the third semiconductor region. A fourth semiconductor region deeper than the region and located in the second semiconductor layer;
The region surrounded by the inner edge of the third semiconductor region and the fourth semiconductor region surrounding the third semiconductor region and the portion including the inner edge between the first main surface and the first metal. A diode comprising a third structure region functioning as a capacitor composed of an intervening first dielectric.

  As a result, it is possible to reduce the off-loss of the diode element, suppress the surge voltage, remove the EMI noise, and realize the high-speed operation of the diode element and the reduction of the conduction loss.

For the first structure region, for example, a well-known termination structure such as a guard ring (GR), a field limiting ring (FLR), a trench breakdown voltage structure, or a field plate (FP) structure may be used.
For the second structure region, for example, a well-known structure of the region where the rectifying action of SBD, JBS, and TMBS is performed may be adopted.
Further, a known dielectric such as SiO2, Si3N4, TiBaO3, etc. may be used as the first dielectric. Alternatively, a stacked structure of these may be used.
When a laminated structure of two different dielectrics is used, it is regarded as one dielectric film, and the dielectric constant and film thickness of the whole dielectric are converted as follows.
The dielectric constant of the first dielectric film is ε2, the film thickness of the first dielectric film is Tox, the dielectric constant of the dielectric 1 is ε3, the film thickness is t3, and the dielectric constant of the dielectric 2 is ε4. The thickness is t4.
ε2 = ε3ε4 (t3 + t4) / (ε3t4 + ε4t3)
Tox = t3 + t4
When a laminated structure of three different dielectrics is used, it is regarded as one dielectric film, and the dielectric constant and film thickness of the whole dielectric are converted as follows.
The dielectric constant of the first dielectric film is ε2, the film thickness of the first dielectric film is Tox, the dielectric constant of the dielectric 1 is ε3, the film thickness is t3, and the dielectric constant of the dielectric 2 is ε4. The thickness is t4, the dielectric constant of the dielectric 3 is ε5, and the film thickness is t5.
ε2 = ε3ε4ε5 (t3 + t4 + t5) / (ε3ε5t4 + ε4ε5t3 + ε3ε4t5)
Tox = t3 + t4 + t5
Furthermore, Si, SiC, and GaN may be appropriately selected as the semiconductor substrate.

Furthermore the invention according to claim 2, in the diode according to claim 1, before SL as the second depth direction in a direction toward the main surface from the first major surface, the third integrated value with respect to the depth direction of the semiconductor substrate in a region with an impurity amount N _a of the second conductivity type in the semiconductor region, impurity amount N _D of the first conductivity type of said second semiconductor layer Is 1/3 or more times greater than the integrated value from the depth corresponding to the bottom surface of the fourth semiconductor region to the top surface of the first semiconductor layer with respect to the depth direction of the semiconductor substrate in the region. It is an invention characterized by being 9 times or less.
This realizes a diode that operates at a high speed while suppressing a surge voltage that is higher than the power supply voltage.

Further the invention described in claim 3 is the diode of claim 1 or 2, the Schottky barrier diode is characterized in that for unipolar operation.

The invention described in claim 4 is the diode according to claim 1, 2, or 3 , wherein the semiconductor substrate is silicon carbide.
This realizes the features that the withstand voltage of the diode can be increased and that it can operate at a high temperature.

Furthermore, the invention according to claim 5 is a semiconductor module comprising the diode according to any one of claims 1 to 4 and an external terminal electrically connected from the anode electrode and the cathode electrode. It is characterized by being a semiconductor module.

For example, a bridge diode module for full-wave rectification, an IGBT module integrated with a commutation diode connected in reverse parallel to the IGBT, a cathode common diode module, an anode common diode module, a semiconductor module which is a doubler diode module, The described diode may be used.
This reduces the possibility of malfunctioning in an integrated circuit that is driven with a low current (for example, an IGBT control circuit) that is particularly positioned close to the semiconductor module of claim 6.

Furthermore, the invention described in claim 6 is a power supply circuit, wherein the semiconductor module described above is used.
Accordingly, the semiconductor module can be used for the power circuit of the AC-DC converter, the DC-DC converter, and the inverter, circuits such as a snubber circuit and a filter circuit can be simplified, and the power circuit can be reduced in size.

The present invention operates as follows.
When a reverse voltage is applied to the diode, the capacitance decreases in proportion to the -1/2 power of the voltage in an SBD in which a normal drift layer has no concentration gradient. Even in an SBD or other diode using a substrate with an improved dopant profile of the semiconductor substrate, the depletion layer of the n-layer becomes thicker with the reverse voltage, so that the capacitance voltage change tends to decrease. Has characteristics. This characteristic continues until a reverse blocking voltage is applied.
When actually used on a circuit, the diode is not applied up to the reverse blocking voltage, and the rated reverse voltage is set lower than this in anticipation of the surge voltage.

  When the reverse voltage of the set value is applied to the diode, the set value voltage is overshooted by the surge voltage. When the voltage overshoots, the capacitance of the diode decreases. When the capacity is reduced, LC resonance is easily performed in the harmonic region. In order to shift the voltage value in the higher direction, charging with a small amount of charge is required, so dv / dt increases. In the process of voltage oscillation, when the voltage shifts to the lower side, the opposite phenomenon occurs and the vibration converges.

According to the present invention, in the voltage capacity characteristic, the voltage oscillation converges earlier by increasing the capacity even when the voltage shifts to a high voltage. In particular, when the surge voltage value exceeds the voltage value at which the capacity becomes minimum in the voltage capacity curve, this vibration suppression effect becomes significant.
A structure for realizing this characteristic is shown in FIG.

When a low voltage is applied in the region where the dielectric is formed, the depletion layer expands from the interface between the p ⁻ layer and the n ⁻ layer. While the depletion layer is expanding, the capacity decreases. Depletion p ^- depletion and the carrier layer are swept all p ^{- -} all spread in the area p of layer layers, n ^- can not spread in the layer both oxide film in order to keep the electric charge of the capacitor and p ^- the carrier is accumulated in the layer interface. When carriers accumulate at the interface, the depletion layer recedes and the formed depletion layer capacitance is equivalently short-circuited, so that the dielectric film capacitance occupies the entire capacitance component and the capacitance of the dielectric region increases.

In the diode element, since the capacitance has a minimum value below the reverse blocking voltage, it is a means of the present invention that the capacitance of the dielectric region when the reverse blocking voltage is applied is larger than the capacitance of other regions. . For this reason, it is necessary to satisfy the equation in paragraph 0029 in view of the ratio of the dielectric region to the rectifying area, the thickness of the dielectric film, the type of dielectric, and the dielectric constant of the semiconductor substrate. After the p ^- layer under the dielectric film is completely depleted, the depletion layer recedes and when a voltage having a depletion layer capacitance maximum with respect to the voltage is applied again, most of the electric field is dielectric. Comes on the membrane. A thin dielectric film tends to have a snubber function, but the minimum value of the dielectric film thickness is set for the reason described above.

Although must be as minimum value of the capacity is less than the reverse blocking voltage, which is p immediately under the dielectric region ^- net charge of the n-type impurity layer ^- p-type net charge amount below the n impurity layer If it is less than the amount, the entire n ^- layer is not depleted. Thereby, the minimum value of the capacity can be adjusted. The actual operating voltage of the diode is often used lower than the rated voltage. Preferably, the net charge amount of the n-type impurity in the n ⁻ layer is 1/3 to 0 of the net charge amount of the p-type impurity in the p ⁻ layer. .9 is good.

According to the present invention, when a reverse voltage is applied to the diode, after the thin p ⁻ layer under the dielectric is completely depleted, the capacitors formed in the p ⁻ layer and the n ⁻ layer are short-circuited. The dielectric works as a capacitor, and exhibits an equivalent snubber circuit characteristic when a high voltage is applied. On the other hand, when a low voltage is applied, it operates as a conventional diode at high speed.

For this reason, it is possible to operate at high speed while suppressing the surge voltage when the diode is off and reducing EMI (electromagnetic interference) noise. In addition, the present invention has a function of a snubber element with only a diode, and has no function of wiring, and thus has a function of smoothing a current waveform with a small ESL (equivalent series inductance) and a high capacitance. Furthermore, since the element area of the snubber region can be allocated to the diode region as compared with the case of the cited reference 2 in which the capacitor region is created separately from the region for creating the diode on the semiconductor substrate 1 chip, the n ⁻ layer of the diode Thus, not only the loss due to switching of the diode but also the conduction loss can be reduced. In addition, the heat generation density is reduced and the heat dissipation is increased by increasing the element area.
Furthermore, by using a wide gap semiconductor such as SiC as the semiconductor, it is possible to operate at a high temperature.
When a semiconductor module is configured with such a diode, a semiconductor module with less EMI noise can be configured.

  In addition, such a semiconductor module operates at high speed and can simplify the heat dissipation mechanism, the snubber circuit, and the filter circuit, so that the power supply circuit can be downsized and densified.

  Further, when such a semiconductor module is applied to a power supply circuit, since EMI noise is small, for example, the power supply circuit can be arranged near the control circuit, so that the power conditioner device can be downsized.

It is a fragmentary longitudinal cross-sectional view of the diode which concerns on one embodiment of this invention. It is a cross-sectional view of a diode according to an embodiment of the present invention. It is a schematic diagram of the diode which concerns on one embodiment of this invention. It is a graph which shows the characteristic of the diode which concerns on one embodiment of this invention. It is a graph which shows the turn-off speed characteristic of the diode which concerns on one embodiment of this invention. 1 is a power supply circuit using a diode according to an embodiment of the present invention. It is a graph which shows an example of the area ratio of the area | region enclosed by p ⁺ layer with respect to a rectification | straightening area.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiment, the first conductivity type is assumed to be n-type, and the second conductivity type is assumed to be p-type. When the symbols n ⁻ , n, and n ⁺ are used as the n-type impurity layer, the n-type impurity concentration in the layer is assumed to be higher in the order of n ⁻ <n <n ⁺ . The same applies to the p-type impurity layer. Further, unless otherwise specified, the impurity concentration refers to the net impurity concentration after compensation of each conductivity type.

  In addition, the drawings used in the description in the embodiments are schematic for ease of description, and the shape, dimensions, magnitude relationship, etc. of each element in the drawings are not necessarily shown in the drawings in actual implementation. It is not always the case. Furthermore, it is possible to change the shape, dimensions, magnitude relationship, impurity concentration, material, and the like within a range where the effects of the present invention can be obtained.

  Unless otherwise specified, a semiconductor substrate made of Si (silicon) is shown as an example unless otherwise noted, but other semiconductor substrates such as SiC (silicon carbide) or GaN (gallium nitride) are also possible. It is.

  A diode is a semiconductor that has an anode electrode and a cathode electrode. The resistance decreases when a positive voltage is applied from the anode electrode to the cathode electrode, and the resistance increases when a negative voltage is applied from the anode electrode to the cathode electrode. The active elements to be configured are shown.

  The second structural region described in the means for solving the problem is a so-called rectifying region, and indicates a region provided with a general structure having a function of forming a band barrier such as a Schottky barrier junction or a PN junction. For example, a general structure such as a PN junction, a JBS structure, an MPS structure, or a TMBS structure may be employed. Here, unless otherwise specified, a Schottky barrier diode (SBD) structure is employed.

  The first structural region shown in the claims shows an electric field relaxation structure for preventing the electric field from concentrating on the terminal portion of the junction surface. Generally, a guard ring, a field limited ring, a trench breakdown voltage structure, a field plate, etc. is there. Here, unless otherwise specified, the guard ring structure is adopted.

  The constituent requirements of the first structural region and the second structural region described above are not special technical features of the present invention, but are necessary configurations for solving the problems of the present invention. A structure may be used.

The technical feature of the present invention is that the disclosed problem can be solved by the diode using the third structure region, and therefore, the mode for carrying out the invention will be described focusing on the third structure region.
1 and 2 show an embodiment of a Schottky barrier diode which is a semiconductor device to which the present invention is applied. FIG. 1 is a partial longitudinal sectional view, and FIG. 2 is a transverse sectional view.

As shown in the figure, there are a first semiconductor layer 15 that is a high-concentration n ⁺ -type semiconductor layer of silicon, and an n ⁻ -type semiconductor layer (drift layer) that has a donor concentration lower than that of the first semiconductor layer 15. The semiconductor substrate 10 is constituted by the second semiconductor layer 20. An anode electrode 30 is bonded to the first main surface 21 on the n ⁻ -type second semiconductor layer 20 side, and a cathode electrode 31 is bonded to the second main surface 16 on the first semiconductor layer 15 side.

A breakdown voltage structure (first structure region 40) is formed in a substantially ring shape as a termination structure on the surface side of the second semiconductor layer 20 which is an n ⁻ layer. The first structure region 40 includes a p ⁺ guard ring 41, an oxide film 42, and an n ⁺ layer.

  A region surrounded by the guard ring 41 having a breakdown voltage structure is referred to as a rectification region (second structure region 50), and an area of the rectification region is defined as a rectification area. In the rectifying region (second structural region 50), when a negative voltage is applied from the anode electrode 30 formed inside the first structural region 40 to the cathode electrode 31, the depletion layer is in the second semiconductor layer 20. Thus, the first main surface 21 side extends to the second main surface 16 side.

  A third semiconductor region 60 is provided in the rectifying region (second structural region 50) of the diode, and surrounds at least a part of the outer edge of the third semiconductor region 60 in the second structural region 50. A fourth semiconductor region 70 located in the second semiconductor layer 20 and having a second conductivity type dopant concentration deeper than the third semiconductor region 60 and deeper than the third semiconductor region 60. Is provided.

  The third semiconductor region 60, the region surrounded by the inner edge of the fourth semiconductor region 70 surrounding the third semiconductor region 60, the first main surface 21 on the portion including the inner edge, and the first metal A dielectric 80 is interposed between the anode electrode 30 and the anode electrode 30.

The third semiconductor region 60, anode electrode 30 to the dielectric 80-p ^- third semiconductor region 60-n is a layer ^- a first semiconductor layer as the second semiconductor layer ^{20-n +} layer is a layer This is a region having a laminated structure of 15-cathode electrode 31 and has a structure in which the third semiconductor region 60 which is a p ⁻ layer is surrounded by a fourth semiconductor region 70 which is a p ⁺ layer.

As a result, a capacitance sandwiching the dielectric 80 is incorporated in the rectifying region (second structure region 50), and as shown in the equivalent circuit of FIG. The diode acts as a high resistance in the state where the voltage is applied. Above the rated reverse voltage, the diode acts as a circuit in which a high resistance and a capacitor are connected in series, that is, a snubber circuit.
The diode according to the first embodiment is an 80 V SBD, and the concentration of the n ⁻ layer 20 (drift layer) is 2e15 atms / cm ³ and the thickness is 6.5 μm.

The breakdown voltage structure uses GR. The p ⁺ layer 70 is selectively diffused in a substantially ring shape on the surface (rectification region) of the n ⁻ layer 20 surrounded by the GR. The concentration of the p ⁺ layer 70 is 1e18 atms / cm ³ and the diffusion depth is 2.5 μm. The p ⁻ layer 60 is selectively diffused in the surface region of the n ⁻ layer 20 surrounded by the p ⁺ layer 70 (area of the region surrounded by the inner edge of the fourth semiconductor region 70). The p ⁻ layer 60 has a diffusion depth of 0.5 μm at 2e16 atms / cm ³ . It is desirable to cover at least ^{p +} surface of the region surrounded by the layer 70 to the outer edge of the ^{p +} layer 70 apart distance above worthy of more than 0.8 times the diffusion depth of the ^{p +} layer 70 SiO2. The film thickness of SiO2 is 1000 mm.

Alternatively, a film thickness of 600 to 1000 mm in accordance with the current process is desirable. If the thickness is less than 600 mm, an electric field is intensively applied to the dielectric to cause dielectric breakdown. Therefore, care must be taken since the device does not function unless the dielectric film thickness is set to a film thickness corresponding to the breakdown voltage. An anode metal composed of a Mo barrier metal and an Al electrode metal covering the Mo barrier metal is laminated on the entire rectifying region. The barrier metal covers at least a region not surrounded by the p ⁺ layer. The area ratio of the region surrounded by the p ⁺ layer relative to the rectified area is preferably about 12% or more. The range is within the hatching range illustrated in FIG.

The impurity concentration, p ^- the depth direction of the layers are formed region p ^- layer and n ^- the ratio of Qp and Qn is the amount of charge in the layer (Qp / Qn) is 1/3 to 0.9 In designing, it is desirable that the capacitance value has a minimum value below the breakdown voltage. Preferably, the capacitance value has a minimum value at a value lower than the voltage value of the power supply voltage.

  The effect of the present invention can be achieved by showing the voltage-capacitance characteristics by setting the minimum value to be equal to or lower than the breakdown voltage. This is shown in FIG. As indicated by the arrows in the figure, from the low voltage side to around the rated voltage on the high voltage side, the capacity curve has a negative slope as before, exceeds the rated voltage and is lower than the surge voltage. Has a positive slope. Further, as shown in FIG. 5, the turn-off speed is improved.

In other embodiments, after changing the pressure resistance and the substrate material, main conditions are simply shown below.
In the 600V Si diode, the oxide film thickness is 5000 mm, and the area ratio of the region surrounded by the p ⁺ layer relative to the rectified area may be 10% or more.
In a 600 V SiC diode, the oxide film thickness is 5000 mm, and the area ratio of the region surrounded by the p ⁺ layer to the rectified area may be 50% or more.

Next, the operation will be described.
When a low reverse blocking voltage is applied to the region surrounded by the p ⁺ layer, the depletion layer extends from the junction surface between the p ⁻ layer 60 and the n ⁻ layer 20 in the same manner as the rectification region. Since the capacitance of the capacitor formed by the depletion layer is proportional to the -1/2 power of the applied voltage, the capacitance decreases as the reverse blocking voltage is increased.

As a characteristic action, the action appears when the reverse blocking voltage is further increased. When the reverse blocking voltage is further increased, the p ⁻ layer 60 is depleted similarly to the depletion of the n ⁻ layer 20 as the main function of the diode.

Then, the majority carriers are completely swept out by the lines of electric force from the p ⁺ layer 70 on the peripheral side of the region where the dielectric is laminated. After that, when an inversion layer in which minority carriers are accumulated at the interface between the p ⁻ layer 60 and the oxide film is formed, the capacitor capacity of the depletion layer formed by the junction of the p ⁻ layer 60 and the n ⁻ layer 20 is short-circuited on the equivalent circuit. The capacitor in the region where the dielectric is laminated is left by the MIS structure composed of the dielectric.

  Since the capacitor composed of the dielectric is arranged in parallel with the direction of the electric field, the capacity of the capacitor as viewed from the whole diode increases as the reverse blocking voltage increases.

  In general, the smaller the capacitance of the capacitor, the higher the LC resonance with the harmonics. However, with the conventional diode, the capacitor tends to become smaller when the reverse blocking voltage is increased. It has occurred. On the other hand, in the diode of this time, when the reverse blocking voltage is increased with a predetermined voltage as the starting point, the capacitance of the capacitor increases. Therefore, noise can be suppressed without causing LC resonance with parasitic inductance and harmonics.

  That is, when the reverse blocking voltage of the diode is increased, a resistor and a capacitor having a large capacity as seen in the equivalent circuit are connected in series, and this also functions as a harmonic filter circuit, so the external filter circuit is omitted. It becomes possible to simplify.

  In addition, since the capacitance of the capacitor increases after a predetermined voltage, the charge used for increasing the reverse blocking voltage increases. Therefore, dV / dt and di / dt are delayed, and a surge voltage corresponding to the product of the parasitic inductance component and di / dt is suppressed.

  That is, during reverse recovery when the reverse blocking voltage of the diode is increased, a resistor and a capacitor having a large capacity as seen in the equivalent circuit are connected in series, and this also functions as a snubber circuit. Omission and simplification can reduce the number of parts and reduce snubber loss.

Compared with a structure in which the p ^- layer is formed under the dielectric, this time there is a junction between the p ^- layer and the n ^- layer, so that the capacitance of the capacitor increases in the region where the reverse blocking voltage is low. Therefore, a small amount of charge is required to charge the diode, and high speed operation and low loss operation can be realized. Particularly, when the high-frequency operation is performed, the number of times of charging / discharging of the diode is increased, so that the power consumed by the diode element is drastically reduced when the charged charge per one time is reduced.

As another embodiment, there is an SBD using a silicon carbide substrate. The rectification region of the SBD has a laminated structure of anode electrode-dielectric-p ^- layer-n ^- layer-n ⁺ layer-cathode metal, and has a structure in which the p ^- layer is surrounded by a p ⁺ layer. .

In this region, when a low reverse blocking voltage is applied, the depletion layer extends from the junction surface of the p ⁻ layer and the n ⁻ layer as in the rectification region. Since the capacitance of the capacitor formed by the depletion layer is proportional to the -1/2 power of the applied voltage, the capacitance decreases as the reverse blocking voltage is increased.

  By using silicon carbide, it has the following characteristics. Since silicon carbide can operate at a high temperature, the heat dissipation mechanism and the cooling mechanism can be simplified when used in a power supply circuit.

  The snubber circuit, filter circuit, etc. used in the power supply circuit are a series circuit of a capacitor and a resistor. By making these equivalently integrated with a diode, a commercially available capacitor with a Tj of about 200 ° C operates. It becomes possible to operate in the temperature range that does not.

  FIG. 6 shows a diode bridge which is a rectifier circuit, and the diode bridge is configured without providing a snubber circuit marked with a cross in the drawing. On the power supply circuit, it is often arranged near the transformer where the EMI noise is large. By using the diode of the present invention, it is possible to realize EMS (Electromagnetic Interference Sensation) countermeasures.

  Further, when the element is used as a commutation diode and a semiconductor module together with a switching element such as an IGBT or MOSFET, malfunction due to the influence of EMI (electromagnetic interference) noise on the drive circuit IC of the switching element is suppressed. Can do.

  Since the diode according to the present invention is configured as described above, the power converter has the advantages of high frequency, energy saving, miniaturization, and noise-free. With the widespread use of power conditioners, renewable energy can be reduced. A distributed power source can be used as a power source. With this, it can be expected to realize an energy-saving society and a low-carbon society by so-called smart grid.

DESCRIPTION OF SYMBOLS 10 ... Semiconductor substrate 15 ... 1st semiconductor layer 16 ... 2nd main surface 20 ... 2nd semiconductor layer 21 ... 1st main surface 30 ... Anode electrode 31 ... Cathode electrode 40 ... 1st structure area 41 ... Guard Ring 42 ... oxide film 50 ... second structure region 60 ... third semiconductor region 70 ... fourth semiconductor region 80 ... dielectric

Claims (6)

A semiconductor substrate having a first main surface and a second main surface opposite to the first main surface;
An anode electrode which is a first metal on the first main surface side;
A cathode electrode which is a second metal on the second main surface side;
A first semiconductor layer of a first conductivity type having a high concentration and formed in the semiconductor substrate facing the second main surface;
A second semiconductor layer having a low concentration of the first conductivity type, which is laminated from the semiconductor substrate in the first main surface direction to the first main surface facing the first semiconductor layer;
A first structure region having a substantially ring shape in which a termination structure for relaxing an electric field formed in the first semiconductor layer from the first main surface is formed;
When a negative voltage is applied from the anode electrode formed inside the first structure region to the cathode electrode, a depletion layer is formed on the second main surface from the first main surface side in the second semiconductor layer. A second structural region characterized by extending to the side;
In a Schottky barrier diode with
A third semiconductor region of a second conductivity type formed in the second semiconductor layer in the semiconductor substrate in the second structure region and located in the second semiconductor layer;
The third semiconductor is located in the second structure region so as to surround at least a part of the outer edge of the third semiconductor region, and has a second conductivity type dopant concentration deeper than the third semiconductor region and a depth of the third semiconductor region. A fourth semiconductor region deeper than the region and located in the second semiconductor layer;
The region surrounded by the inner edge of the third semiconductor region and the fourth semiconductor region surrounding the third semiconductor region and the portion including the inner edge between the first main surface and the first metal. A diode comprising a third structure region functioning as a capacitor composed of an intervening first dielectric. Wherein as the first from said major surface a second depth direction in a direction toward the main surface, the depth of the semiconductor substrate in a region of impurities of said second conductivity type in the semiconductor region of the third integrated value with respect to the direction, depth corresponds to the bottom surface of the semiconductor region of the fourth impurity of the first conductivity type of the second semiconductor layer in the depth direction of the semiconductor substrate in the region Nitaishite integrated value from to the upper surface of the first semiconductor layer is, and less than 0.9 times 1/3 times or more, diode according to claim 1. Schottky barrier diode diode according to claim 1 or 2, characterized in that for unipolar operation. The semiconductor substrate according to claim 1, 2 or are described in third diode, which is a silicon carbide. The diode according to any one of claims 1 to 4, an external terminal electrically connected from an anode electrode and a cathode electrode,
A semiconductor module comprising: A power supply circuit using the semiconductor module according to claim 5 on a circuit.

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