JP2005224934A - Movable microstructure and semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a movable microstructure increasing a rate of a movable component of a static capacitance between electrodes by reducing the static capacitance between an electrode structure of the movable microstructure and the substrate. <P>SOLUTION: This movable microstructure 100 is provided with a first electrode 110 formed on the substrate and a second electrode 123 disposed oppositely to the first electrode, and at least one of the first electrode and the second electrode is movably constituted. This movable microstructure is so constituted that the electrostatic force is generated between the first electrode and the second electrode, so that the first electrode and the second electrode are relatively moved. This microstructure is characterized in that the second electrode is disposed in the upper part of the first electrode, the first electrode and the second electrode are provided with recessed/projecting structure 110a and 123a corresponding vertically, and the first electrode and the second electrode are vertically and relatively moved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a minute movable structure and a semiconductor device, and more particularly, to a structure having a movable portion configured to move by electrostatic force, and a structure of a semiconductor device including the structure.

  In general, there is known a fine movable structure having a movable portion that is configured to form a fine structure on a surface of a silicon substrate or the like and operate by electrostatic force. Such fine movable structures are expected to be applied as electrostatic actuators, optical switches, micromirror devices, thin film vibrators, and the like.

Examples of the fine movable structure include a thin film vibrator that can form a thin film vibrator filter used for signal processing such as communication and a thin film resonator of a clock source used in various electronic devices. In such a thin film vibrator, a comb-shaped movable electrode is slidably disposed between the comb-shaped drive electrodes along the surface of the substrate, and the movable electrode is vibrated by vibrating the movable electrode. There is known a vibrator configured by utilizing the change in capacitance between the two (for example, see Non-Patent Document 1 below).
“Laterally Driven Resonant Microstructures” WILLIAM C.I. TANG, TU-CUONG, H. NGUYEN and ROGER T. HOWE Sensors and Actuators, 20 (1989) p. 25-32

  However, since the conventional thin film vibrator requires a large electrostatic force at the initial stage of driving the movable electrode, the drive electrode and the movable electrode are configured in a comb shape to increase the electrostatic force. Increases the electrostatic capacitance between the driving electrode and the movable electrode, and also increases the planar projection area of the comb-shaped driving electrode and the movable electrode, so that the electrostatic capacitance between these electrodes and the substrate is increased. Is also getting bigger. On the other hand, the fluctuation amount of the electrostatic capacitance due to the planar sliding operation of the movable electrode is considerably smaller than the above-mentioned sum of electrostatic capacitances. Therefore, since the ratio of the capacitance fluctuation component (variable capacitance) generated by the vibration of the capacitance movable electrode is small, it is necessary to increase the drive voltage in order to obtain a sufficient signal output. There is a problem that it is difficult to reduce the voltage and power saving is difficult.

  Therefore, the present invention solves the above-mentioned problems, and its problem is to reduce the capacitance between the electrode structure of the fine movable structure and the substrate, thereby varying the capacitance component between the electrodes. It is an object of the present invention to provide a fine movable structure capable of increasing the ratio of. In addition, by reducing the parasitic capacitance between the electrode structure of the micro movable structure and the semiconductor substrate, the ratio of variable capacitance resulting from the operation of the movable part of the micro movable structure is increased, and the micro movable structure is driven. An object of the present invention is to provide a semiconductor device in which the voltage is reduced.

  The micro movable structure according to the present invention includes a first electrode formed on a substrate and a second electrode disposed to face the first electrode, and at least one of the first electrode and the second electrode. And a movable structure in which the first electrode and the second electrode move relatively by generating an electrostatic force between the first electrode and the second electrode. In the body, the second electrode is disposed above the first electrode, the first electrode and the second electrode have a concavo-convex structure corresponding to a vertical direction, and the first electrode and the second electrode are It is characterized by relatively moving in the vertical direction.

  According to this invention, the 1st electrode and the 2nd electrode arranged above have an uneven structure corresponding to the up-and-down direction, and the 1st electrode and the 2nd electrode are relative to the up-and-down direction. By moving, the opposing area between the first electrode and the second electrode can be increased by the concavo-convex structure to enhance the driving force based on the electrostatic force, and the second electrode is disposed above the first electrode. Therefore, it is possible to reduce the planar projection area on the substrate as compared with the conventional configuration in which the driving electrode and the movable electrode having a comb-tooth structure are arranged on a plane. Therefore, the electrostatic capacity between the electrode structure and the substrate can be reduced. Therefore, when the drive voltage is applied to generate an electrostatic force and the first electrode and the second electrode are moved relatively to take out the output resulting from the change in capacitance, the output can be efficiently obtained. Therefore, it is possible to reduce the drive voltage and to save power.

  In this case, it is desirable that the relative movement direction between the electrodes is a direction perpendicular to the surface of the substrate. However, the present invention is not limited to this, and a wide range of movement components in the vertical direction can be used. Include. That is, as long as it has a moving component in the vertical direction, it may move obliquely with respect to the surface of the substrate.

  Further, the first electrode and the second electrode are opposed to each other in a state in which the first electrode and the second electrode mesh with each other in a reference state in which no voltage is applied between the first electrode and the second electrode, or the first electrode It is desirable that at least one of the second electrode and the second electrode has a structure inserted into the other. In the reference state, electrostatic force does not work between the electrodes, but even in this reference state, the first electrode and the second electrode are arranged to face each other, or of the first electrode and the second electrode. Since at least one of them is inserted into the other, the mutual distance between the first electrode and the second electrode is small and the opposing area is large, so that the electrostatic force acting between the electrodes is large, Responsiveness of relative operation between the electrodes and the S / N ratio of the output signal can be improved, and the input signal can be reduced in voltage or power saving.

  Conventionally, there is known a comb-like electrode structure in which a pair of comb-like electrodes each having comb teeth extending parallel to the surface of the substrate are arranged to face each other, but in the present invention, for example, When each of the first electrode and the second electrode is a comb-like electrode, the first electrode and the second electrode each having comb teeth extending in a direction intersecting (preferably orthogonal) with the surface of the substrate are mutually connected. Are arranged so as to face each other.

  In the present invention, it is preferable that at least one of the first electrode and the second electrode is provided with a concave hole configured such that the other can be inserted from above or below. Since one of the first electrode and the second electrode is provided with a concave hole, and the other electrode is fitted into the concave hole, the two electrodes are two-dimensionally engaged. Therefore, since the facing area between both electrodes can be increased, the driving force can be further increased.

  In the present invention, it is preferable that the first electrode is fixed on the substrate and the second electrode is configured to be movable. According to this, since the 1st electrode arranged below is fixed on a substrate and the 2nd electrode arranged above it is constituted movably, it becomes possible to constitute a structure simply, When the first electrode and the second electrode are configured by the thin film structure formed on the substrate, the first electrode and the second electrode can be manufactured very easily by a normal thin film manufacturing process.

  In the present invention, it is preferable that the second electrode is fixed to the substrate via an elastic deformation portion. According to this, it is possible to improve the accuracy of the moving direction and the moving amount of the second electrode by providing the elastically deforming portion.

  In the present invention, the electrostatic force is preferably configured to exert only an electrostatic repulsive force. According to this, since the first electrode and the second electrode are in the closest state when no electrostatic force is generated, the driving force at the initial stage of driving can be increased without increasing the driving voltage. Further, since only the electrostatic repulsive force is exerted when the electrostatic force is generated, the first electrode and the second electrode are always separated from each other than the initial state. Since the capacitance between the electrodes is reduced, the rate of change in capacitance during driving can be further increased. Therefore, when the drive voltage is applied to generate an electrostatic force and the first electrode and the second electrode are moved relatively to take out the output resulting from the change in capacitance, the output can be efficiently obtained. Therefore, it is possible to reduce the drive voltage and to save power. In addition, since driving is performed only by electrostatic repulsion, collision between electrodes does not occur even if the driving voltage becomes excessive, and there is an advantage that a countermeasure against short circuit destruction by overvoltage driving becomes unnecessary.

  In each of the above inventions, it is preferable that an electrical signal based on a change in capacitance between the first electrode and the second electrode can be output. According to this, since the relative movement state between the electrodes can be electrically output, the movement speed and positional relationship of the electrodes can be electrically observed, or the electrical frequency characteristics resulting from the relative movement state Or earn.

  Further, it is preferable that the first electrode and the second electrode are relatively vibrated based on the electrostatic force. As a result, an electric signal having a waveform corresponding to the relative vibration between the electrodes can be output, so that an electrostatic vibrator that can be used as a frequency filter, a resonator, or the like can be configured.

  Further, the semiconductor device of the present invention includes a semiconductor substrate, an insulating film formed on the semiconductor substrate, a first electrode formed on the insulating film, and a second electrode disposed to face the first electrode. And at least one of the first electrode and the second electrode is configured to be movable, and an electrostatic force is generated between the first electrode and the second electrode, A second movable electrode configured to move relative to the second electrode, wherein the second electrode is disposed above the first electrode, and the first electrode and the second electrode are The first electrode and the second electrode move relative to each other in the up-down direction.

  According to this invention, the 1st electrode and the 2nd electrode arranged above have an uneven structure corresponding to the up-and-down direction, and the 1st electrode and the 2nd electrode are relative to the up-and-down direction. By moving, the opposing area between the first electrode and the second electrode can be increased by the concavo-convex structure to enhance the driving force based on the electrostatic force, and the second electrode is disposed above the first electrode. Therefore, it is possible to reduce the planar projection area on the substrate as compared with the conventional configuration in which the driving electrode and the movable electrode having a comb-tooth structure are arranged on a plane. Therefore, the parasitic capacitance between the electrode structure and the semiconductor substrate can be reduced. Therefore, when the drive voltage is applied to generate an electrostatic force and the first electrode and the second electrode are moved relatively to take out the output caused by the variable capacitance, the output can be efficiently obtained. The drive voltage can be lowered, and power saving can be achieved.

  Furthermore, the semiconductor device of the present invention is a semiconductor device including a vibrating body having an oscillating portion that vibrates due to an electrostatic force, an electrode, an insulating film, and a semiconductor substrate, wherein the vibrating body and the semiconductor substrate are joined to each other. At least a part of the rear surface of the semiconductor substrate is hollowed out, and a region where the vibrating body and the semiconductor substrate are joined in the hollowed-out portion is composed of only the insulating film.

  According to the present invention, the parasitic capacitance between the semiconductor substrate and the vibrating body can be reduced by eliminating the semiconductor substrate directly below the vibrating body. Therefore, it is not necessary to drive the vibrating body with a high voltage, and it becomes easy to catch the variable capacitance due to vibration, and the driving voltage can be further reduced.

  According to another aspect of the present invention, there is provided a semiconductor device including a vibrating body having an oscillating portion that vibrates by electrostatic force and an electrode, a semiconductor substrate, and an insulating film formed between the vibrating body and the semiconductor substrate. A surface recess is provided in at least a part of the surface of the semiconductor substrate in a region where the vibrator and the semiconductor substrate are joined, and the resonator and the semiconductor are provided in the region provided with the surface recess than in other regions. It is characterized in that the distance from the substrate is separated.

  According to the present invention, since the distance between the vibrating body and the semiconductor substrate is separated from the other regions by the surface recess of the semiconductor substrate, the parasitic capacitance between the vibrating body and the semiconductor substrate can be reduced. In this case, the internal space of the surface recess may be configured as a hollow as it is, or the internal space of the surface recess may be filled with the insulating film.

  Furthermore, the semiconductor device of the present invention has a first electrode formed on a semiconductor substrate and a second electrode disposed to face the first electrode, and at least one of the first electrode and the second electrode. The first movable electrode is movable, and the first electrode and the second electrode are relatively moved by generating an electrostatic force between the first electrode and the second electrode. A semiconductor device having a structure and an insulating film, wherein at least a part of a back surface of the semiconductor substrate in a region where the minute movable structure and the semiconductor substrate are joined is hollowed out, and the minute movable structure in the hollowed-out portion A region where the body and the semiconductor substrate are joined is composed of only the insulating film.

  According to the present invention, the parasitic capacitance between the semiconductor substrate and the minute movable structure can be reduced by eliminating the semiconductor substrate directly under the minute movable structure. Therefore, it is not necessary to drive the minute movable structure with a high voltage, and it becomes easy to grasp the variable capacitance due to the minute movement, and the drive voltage can be further lowered.

  In addition, the semiconductor device of the present invention includes a first electrode formed on a semiconductor substrate and a second electrode disposed to face the first electrode, and at least one of the first electrode and the second electrode. The first movable electrode is movable, and the first electrode and the second electrode are relatively moved by generating an electrostatic force between the first electrode and the second electrode. A semiconductor device comprising a structure and an insulating film formed between the semiconductor substrate and the micro movable structure, wherein at least a surface of the semiconductor substrate in a region where the micro movable structure and the semiconductor substrate are joined A surface concave portion is provided in part, and the distance between the micro movable structure and the semiconductor substrate is greater in the region where the surface concave portion is provided than in other regions.

  According to the present invention, since the distance between the vibrating body and the semiconductor substrate is separated from the other regions by the surface recess of the semiconductor substrate, the parasitic capacitance between the vibrating body and the semiconductor substrate can be reduced. In this case, the internal space of the surface recess may be configured as a hollow as it is, or the internal space of the surface recess may be filled with the insulating film.

  In the present invention, the second electrode is disposed above the first electrode, and the first electrode and the second electrode have a concavo-convex structure corresponding to each other in the vertical direction. The second electrode is characterized by relatively moving in the vertical direction.

  According to this invention, the 1st electrode and the 2nd electrode arranged above have an uneven structure corresponding to the up-and-down direction, and the 1st electrode and the 2nd electrode are relative to the up-and-down direction. By moving, the opposing area between the first electrode and the second electrode can be increased by the concavo-convex structure to enhance the driving force based on the electrostatic force, and the second electrode is disposed above the first electrode. Therefore, it is possible to reduce the planar projection area on the substrate as compared with the conventional configuration in which the driving electrode and the movable electrode having a comb-tooth structure are arranged on a plane. Therefore, the parasitic capacitance between the electrode structure and the semiconductor substrate can be reduced. Therefore, when the drive voltage is applied to generate an electrostatic force and the first electrode and the second electrode are moved relatively to take out the output caused by the variable capacitance, the output can be efficiently obtained. The drive voltage can be lowered, and power saving can be achieved.

  In this case, it is desirable that the relative movement direction between the electrodes is a direction perpendicular to the surface of the semiconductor substrate, but the present invention is not limited to this, and has a movement component in the vertical direction. Widely encompass. That is, as long as it has a moving component in the vertical direction, it may move obliquely with respect to the surface of the semiconductor substrate.

  In the present invention, it is preferable that at least one of the first electrode and the second electrode is provided with a concave hole configured such that the other can be inserted from above or below. Since one of the first electrode and the second electrode is provided with a concave hole, and the other electrode is fitted into the concave hole, the two electrodes are two-dimensionally engaged. Therefore, since the facing area between both electrodes can be increased, the driving force can be further increased.

  In the present invention, it is preferable that the first electrode is fixed on the semiconductor substrate and the second electrode is configured to be movable. According to this, since the 1st electrode arrange | positioned below is fixed on the semiconductor substrate and the 2nd electrode arrange | positioned above it is comprised movably, it becomes possible to comprise a structure simply. When the first electrode and the second electrode are formed by a thin film structure formed on a semiconductor substrate, the first electrode and the second electrode can be manufactured very easily by a normal thin film manufacturing process.

  In the present invention, it is preferable that the second electrode is fixed to the semiconductor substrate via an elastic deformation portion. According to this, it is possible to improve the accuracy of the moving direction and the moving amount of the second electrode by providing the elastically deforming portion.

  In the present invention, the electrostatic force is preferably configured to exert only an electrostatic repulsive force. According to this, since the first electrode and the second electrode are in the closest state when no electrostatic force is generated, the driving force at the initial stage of driving can be increased without increasing the driving voltage. Further, since only the electrostatic repulsive force is exerted when the electrostatic force is generated, the first electrode and the second electrode are always separated from each other than the initial state. Since the capacitance between the electrodes is reduced, the rate of change in capacitance during driving can be further increased. Therefore, when the drive voltage is applied to generate an electrostatic force and the first electrode and the second electrode are moved relatively to take out the output resulting from the change in capacitance, the output can be efficiently obtained. Therefore, it is possible to reduce the drive voltage and to save power. In addition, since driving is performed only by electrostatic repulsion, collision between electrodes does not occur even if the driving voltage becomes excessive, and there is an advantage that a countermeasure against short circuit destruction by overvoltage driving becomes unnecessary.

  In each of the above inventions, it is preferable that an electrical signal based on a change in capacitance between the first electrode and the second electrode can be output. According to this, since the relative movement state between the electrodes can be electrically output, the movement speed and positional relationship of the electrodes can be electrically observed, or the electrical frequency characteristics resulting from the relative movement state Or earn.

  Further, it is preferable that the first electrode and the second electrode are relatively vibrated based on the electrostatic force. As a result, an electric signal having a waveform corresponding to the relative vibration between the electrodes can be output, so that an electrostatic vibrator that can be used as a frequency filter, a resonator, or the like can be configured.

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Each embodiment described below is a micro movable structure and a semiconductor device including the same, and is configured as a so-called MEMS (Micro Electro Mechanical System).

[First Embodiment]
First, with reference to FIG.1 and FIG.2, the micro movable structure 100 of 1st Embodiment which concerns on this invention is demonstrated. FIG. 1 is a schematic longitudinal sectional view (a) and (b) showing a cross section of the micro movable structure 100 cut by planes orthogonal to each other, and FIG. 2 (a) is a schematic perspective view of the micro movable structure 100.

In this micro movable structure 100, an insulating film 102 made of SiO ₂ or the like is formed on a substrate 101 made of a silicon substrate or the like, and a first electrode layer 110 and a second electrode made of polysilicon or the like are formed thereon. An electrode layer 120 is formed. Here, the insulating film 102 is for electrically insulating the substrate 101 from the first electrode layer 110 and the second electrode layer 120, and the substrate 101 is an insulating substrate or an intrinsic semiconductor. It does not have to be formed.

  The first electrode layer 110 is fixed to the substrate 101 (insulating film 102). The first electrode layer 110 is provided with a concave hole 110a that opens upward. In the illustrated example, as shown in FIG. 1B, a plurality of concave holes 110a are provided. These concave holes 110 a are arranged in a line on the surface of the substrate 110.

  The second electrode layer 120 includes a base 121 fixed on the substrate 101 (insulating film 102), an elastic support 122 having a base connected to the base 121, and a first connected to the tip of the elastic support 122. 2 electrodes 123. The elastic support part 122 is connected between the horizontal part extending in parallel to the surface of the substrate 101 from the base part 121 and between the horizontal part and the second electrode 123, and is refracted with respect to the horizontal part and orthogonal to the surface of the substrate 101. And a vertical portion. However, the shape of the elastic support portion 122 is not limited to the shape shown in the illustrated example, and may be configured to extend obliquely between the base portion 121 and the second electrode 123.

  The second electrode 123 is disposed above the first electrode layer 110. The second electrode 123 is provided with a convex portion 123a extending downward, and the convex portion 123a is configured to be inserted into the concave hole 110a of the first embodiment. A plurality of convex portions 123a are provided, and each convex portion 123a is configured to fit into each of the plurality of concave holes 110a. There is a gap between the convex portion 123a and the concave hole 110a. More specifically, there is a gap between the outer surface of the convex portion 123a and the inner surface of the concave hole 110a, and there is also a gap between the end surface of the convex portion 123a and the inner bottom surface of the concave hole 110a. Exists.

  The second electrode 123 is configured to be movable in a substantially vertical direction when the elastic support portion 122 is bent. Thus, the fitting state of the convex portion 123a changes so as to enter and exit the concave hole 110a. More specifically, when the second electrode 123a moves up and down, the insertion depth of the convex portion 123a with respect to the concave hole 110a is increased or decreased. That is, the interval between the end surface of the convex portion 123a and the inner bottom surface of the concave hole 110a is increased or decreased. The moving direction of the second electrode 123 is not necessarily a direction orthogonal to the surface of the substrate 101, and the second electrode may be configured to move up and down obliquely with respect to the surface of the substrate. That is, the moving direction of the second electrode 123 only needs to have an orthogonal component orthogonal to the surface of the substrate 101. In this case, it is preferable that the concavo-convex structure provided so as to correspond to each other in the first electrode and the second electrode is also arranged so as to be diagonally opposed in correspondence with the relative movement direction between the electrodes.

  In the present embodiment, the first electrode layer 110 and the second electrode 123 have a concavo-convex shape on the surface opposed to each other, and a structure in which the concavo-convex shape is engaged with each other, that is, a comb-tooth structure have. In the present embodiment, the first electrode layer 110 is provided with a plurality of concave holes 110a, and the second electrode 123 is also provided with a plurality of convex portions 123a correspondingly. However, the number of concave holes and convex portions is arbitrary and may be one by one. Also, the second electrode 123 may be provided with a concave hole, and the first electrode layer may be provided with a corresponding convex portion.

  In the present embodiment, since the concave hole 110a of the first electrode layer 110 and the convex portion 123a of the second electrode 123 form a concavo-convex structure corresponding to the vertical direction, the first electrode layer 110 and the second electrode layer 110 Since the facing area between the electrodes 123 can be increased, when an electrostatic force is generated between the electrodes by supplying a predetermined potential to both electrodes, a driving force based on the electrostatic force can be increased. it can.

  In particular, in a reference state in which no voltage is applied between the first electrode layer 110 and the second electrode layer 123, the first electrode layer 110 and the second electrode layer 123 are arranged to face each other, Alternatively, since at least one of the first electrode layer 110 and the second electrode layer 123 is inserted into the other, the first electrode layer 110 and the second electrode layer 110 can be connected to each other even in a reference state where no electrostatic force is applied between the electrodes. The two electrode layers 123 are opposed to each other so that they are meshed with each other, or at least one of the first electrode layer 110 and the second electrode layer 123 is inserted into the other. And the second electrode layer 123 have a small mutual distance and a large facing area between them, so that the electrostatic force acting between the electrodes is increased, whereby the response of the second electrode layer 123 and the S / N ratio Can be above, also, it is possible to lower voltage or power consumption of the input signal.

  In the present embodiment, since the second electrode 123 is disposed above the first electrode layer 110, the driving electrode and the movable electrode, each of which is configured in a comb shape, are arranged in a plane on the substrate surface. Compared with the case where it is made, the electrostatic capacitance between both electrodes and the board | substrate 101 can be made small.

  FIG. 2B is a schematic perspective view showing a modification of the embodiment. In the above embodiment, the first electrode layer 110 is provided with the concave hole 110a, and the second electrode 123 is provided with the convex portion 123a corresponding to the concave hole 110a. However, in the micro movable structure 100 ′ of this modified example, The first electrode layer 110 ′ is provided with a concave groove 110a ′ having an open end, while the second electrode 123 ′ is provided with a convex rib 123a ′ corresponding to the concave groove. Even in such a configuration, the first electrode layer and the second electrode are provided with the concavo-convex structure corresponding to each other in the vertical direction, so that the driving force based on the electrostatic force can be secured. In this modification as well, the first electrode layer 110 ′ and the second electrode layer 123 ′ are mutually connected in a reference state in which no voltage is applied between the first electrode layer 110 ′ and the second electrode layer 123 ′. It is desirable to have a structure in which at least one of the first electrode layer 110 ′ and the second electrode layer 123 ′ is inserted into the other.

  Next, with reference to FIG. 3, the manufacturing method of the micro movable structure of the first embodiment will be described. FIG. 3 is a schematic process cross-sectional view (a) to (c) showing a manufacturing method, and in each of the processes (a) to (c), a cross-sectional view corresponding to FIG. 1 shows a cross-sectional view corresponding to FIG.

When manufacturing the micro movable structure 100 described above, first, as shown in FIG. 3A, an insulating film such as SiO ₂ is formed on the surface of the substrate 101 by thermal oxidation, coating and baking, vapor deposition, sputtering, or the like. 102 is formed. The insulating film 202 is used to ensure insulation between the substrate 101 and the structure composed of the first electrode layer 110 and the second electrode layer 120 when the substrate 101 has a certain degree of conductivity. belongs to. Therefore, the insulating film 102 is not necessary when the substrate 101 is an insulating substrate or an intrinsic semiconductor substrate. The substrate 101 is preferably a semiconductor substrate such as a silicon substrate in order to integrally form the circuit structure.

  Next, the first electrode layer 110 is formed in a predetermined region on the substrate 101 (insulating film 102). The first electrode layer 110 may be formed by patterning a predetermined structural layer and then etching through a mask or the like to form the concave hole 110a, or by stacking a plurality of structural layers. Also good. In the latter case, a sacrificial layer may be formed in a region where the concave hole 110a is provided, and the sacrificial layer may be removed after the first electrode layer 110 is formed. The sacrificial layer may be a material that can be removed with high selectivity with respect to the material constituting the first electrode layer 110 and may be formed of an inorganic material such as PSG (phosphorus-doped glass), a resist, or other synthetic resin. The material constituting the first electrode layer 110 is made of, for example, polysilicon (polycrystalline silicon). In any case, this step is performed by a film formation stage (evaporation, sputtering, coating, etc.) of the first electrode layer 110 and a patterning stage (photolithography method, etching, etc.).

  Next, as shown in FIG. 3B, a sacrificial layer 105 is formed on the first electrode layer 110. The sacrificial layer 105 is formed so as to cover the upper surface of the first electrode layer 110 and further spread to the position where the first electrode layer 110 is out of the plane. The sacrificial layer 105 can be made of the same material as the sacrificial layer. The sacrificial layer 105 is configured to cover the inner surface, that is, the inner surface and the inner bottom surface of the concave hole 110a of the first electrode layer 110 with a predetermined thickness.

  Next, as shown in FIG. 3C, the second electrode layer 120 is formed on the sacrificial layer 105. The second electrode layer 120 extends from the region on the sacrificial layer 105 above the first electrode layer 110 to the region on the sacrificial layer 105 where the first electrode layer 110 is not formed. It is configured so as to extend to a region outside the formation region. The portion formed in the region outside the sacrificial layer 105 serves as the base 121, and the portion formed in the region on the sacrificial layer 105 in the range where the first electrode layer 110 is not formed serves as the elastic support portion. The portion formed in the region on the sacrificial layer 105 above the first electrode layer 110 becomes the second electrode 123. At this time, the convex portion 123a is formed in the concave hole 110a so as to have a predetermined distance from the first electrode layer 110 by the sacrificial layer 105.

  Thereafter, the sacrificial layer 105 is removed by wet etching or the like, thereby forming the structure shown in FIG. At this time, since the sacrificial layer 105 is exposed at the outer periphery of the second electrode layer 120 as shown in FIG. 2A, it is removed through this exposed portion. In order to facilitate the removal of the sacrificial layer 105, the shape of the second electrode layer 120 may be changed. For example, a gap is formed between the plurality of second electrodes or between the elastic support portions by forming the second electrode 123 into a plurality of divided shapes or forming the elastic support portion 122 into a plurality of divided structures. Therefore, the sacrificial layer can be more easily removed through this gap.

  3C, the portion corresponding to the elastic support portion 122 of the second electrode layer 120 is removed, and a film forming process is performed on the removed portion with a different material. The support part 122 can be configured. In this way, the elastic support portion 122 can be made of a material different from the base portion 121 and the second electrode 123, such as a metal thin film.

  FIG. 4 shows an equivalent circuit of a structure configured by the first electrode layer 110 and the second electrode layer 120 configured on the substrate 101 in the micro movable structure 100. Here, Ca is a fluctuation component of capacitance between the first electrode layer and the second electrode layer, R is resistance (loss), L is inductance, and Co is a steady component of capacitance. Here, Ca and Co are based on the capacitance between the electrodes, the capacitance between the structure and the substrate 101, and the like. The capacitance variation component Ca is caused by relative movement between the first electrode layer and the second electrode layer, typically due to a change in gap between the electrodes.

  The performance of this micro movable structure, particularly when configured as a vibrator, is greatly influenced by the ratio γ = Ca / Co of the capacitance fluctuation component and the steady component. When this γ value increases, the charge / discharge current due to the capacitance fluctuation component Ca increases, so that the output potential can be increased even when the drive voltage (excitation voltage) is low. Accordingly, the drive voltage can be lowered, and power saving can be achieved.

FIG. 5 shows a specific example of a circuit structure connected to the fine movable structure 100 of the above embodiment. This circuit structure includes an AC power supply E, a load resistance R _L , and a DC bias voltage Vdc. The AC power source E is connected to the first electrode layer 110, and the DC bias voltage Vdc is connected to the second electrode 123. When a predetermined AC potential vi is applied to the first electrode by the AC power source E, the first electrode and the second electrode relatively vibrate due to variations in electrostatic force. Since the gap between the electrodes changes due to the mechanical vibration, the capacitance Cs between the electrodes fluctuates. Therefore, the current flowing through the load resistance _RL based on the DC bias voltage Vdc in synchronization with the mechanical vibration. As a result, the potential of the output terminal Vo vibrates, and a vibration waveform corresponding to mechanical vibration is output. The configuration of such a circuit structure is an example, and other appropriate circuit configurations can be adopted. It is also possible to configure the vibrator structure to be incorporated in various electronic circuits such as communication circuits.

  FIG. 6 shows temporal fluctuations of the driving waveform A of the first electrode layer 110, the driving waveform B of the second electrode 123, and the potential difference C between the first electrode layer 110 and the second electrode 123 in the micro movable structure 100. It is a graph. Generally, the electrostatic actuator is configured to operate by an electrostatic attractive force between the electrodes. However, in the present embodiment, the electrostatic actuator can be driven so as to generate an electrostatic repulsive force between the electrodes. The driving method shown in FIG. 6 is one-side bias driving that shows an example of a mode driven by electrostatic repulsion, and a positive AC voltage + Va is applied to the first electrode layer 110 and an AC voltage is applied to the second electrode 123. A DC voltage + Vd having the same polarity (positive) as + Va is applied. As a result, an electrostatic repulsive force is generated between the first electrode layer 110 and the second electrode 123, and the second electrode 123 vibrates as the electrostatic repulsive force increases or decreases as the potential difference C increases or decreases.

  FIG. 7 is a graph showing a driving mode different from the above. In this graph, AC voltages + Va, + Va ′ having the same polarity in the driving waveforms A, B and the potential difference between the electrodes when the driving waveforms A, B are applied to the first electrode layer 110 and the second electrode 123, respectively. C is shown. This driving method is phase difference driving, and by applying an alternating current waveform having the same polarity to both electrodes with a slight phase shift, a potential difference C that varies periodically is generated between the electrodes. The electrostatic repulsive force between 110 and the second electrode layer 123 increases or decreases, which causes the second electrode 123 to vibrate.

  In any of the above driving methods, the first electrode layer 110 and the second electrode 123 are closest to each other in the initial state where no electrostatic force is generated because the driving is performed by the electrostatic repulsive force generated between the electrodes. In the state where the same polarity voltage is always applied as described above, the distance between the electrodes is always larger than the initial state due to electrostatic repulsion. Therefore, since the electrode interval is small before driving, the electrode interval is small, so that the driving can be started even with a smaller driving voltage. Since the steady component Co becomes small, the γ value can be increased. Therefore, the drive voltage can be lowered and power saving can be achieved. Further, since the electrode interval is minimized in the initial state, it is possible to prevent an accident such as collision of both electrodes when the drive voltage becomes excessive. In other words, it is possible to prevent short-circuit breakdown of the electrode due to overvoltage driving, and it is naturally unnecessary to take such a countermeasure against short-circuit breakdown.

  In the first embodiment, the first electrode is fixed to the substrate and the second electrode is movable. However, the first electrode may be movable and the second electrode may be fixed to the substrate. Alternatively, both the first electrode and the second electrode may be configured to be movable. Moreover, although the said embodiment described the case where it comprised as a vibrator | oscillator fundamentally used as a high frequency filter, a resonator, etc., the micro movable structure concerning this invention is not restricted to a vibrator | oscillator, but as various drive sources. It can be used as various micro electrostatic operation mechanisms such as an electrostatic actuator used, an optical switch for switching light propagation paths, and a micromirror device having a variable reflection angle.

[Second Embodiment]
Next, a second embodiment of the present invention will be described in detail with reference to the accompanying drawings. First, a semiconductor device having a micro movable structure similar to that of the first embodiment according to the present invention will be described with reference to FIGS. FIGS. 8A and 8B are schematic longitudinal sectional views showing a cross section of the semiconductor device having the micro movable structure 100 cut along planes orthogonal to each other, and FIGS. 9A and 9B are micro movable structures. 1 is a schematic perspective view of a semiconductor device having 100, 100 ′. Here, in the present embodiment, since the substrate 101 of the first embodiment is the same as the above except that it is a semiconductor substrate 101 ′ composed of a silicon substrate or the like, the same parts are denoted by the same reference numerals, Those explanations are omitted.

  In this embodiment, as shown in FIGS. 8 and 9, the back surface of the semiconductor substrate 101 ′ in the region where the semiconductor substrate 101 ′ (insulating film 102) and the micro movable structure 100 are joined is cut out to the insulating film 102. A recess 107 is formed.

  Next, with reference to FIG. 10, the manufacturing method of the micro movable structure of the said embodiment is demonstrated. FIG. 10 is a schematic process cross-sectional view (a) to (d) showing the manufacturing method. In each of the processes (a) to (d), a cross-sectional view corresponding to FIG. FIG. 8 shows a cross-sectional view corresponding to FIG. Here, since each process shown in FIGS. 10A to 10C is the same as each process described in the first embodiment, corresponding parts are denoted by the same reference numerals, and description thereof is omitted. To do.

  After the same micro movable structure 100 as that of the first embodiment is formed by the steps shown in FIGS. 10A to 10C, the region in which the micro movable structure 100 is formed as shown in FIG. The back surface of the semiconductor substrate 101 ′ is cut out to the insulating film 102 to form a recess 107. Etching can be performed by wet etching or dry etching by forming a resist in a portion that is not drilled. The etching stop is performed according to a difference in etching rate between the semiconductor substrate 101 and the insulating film 102. Therefore, it is preferable to perform etching with a large difference in etching rate, that is, with a large selectivity.

  For example, KOH or TMAH solution (tetramethylammonium hydroxide) can be used for wet etching. As dry etching, RIE (reactive ion etching) or etching by a combination of RIE (reactive ion etching) and CDE (chemical dry etching) can be used.

  Furthermore, it is also possible to form the concave portion 107 by hollowing out by FIB (focused ion beam) processing or by lasering without forming a resist.

  The semiconductor substrate 101 may be punched either before the micro movable structure 100 is formed or after the micro movable structure 100 is formed. When the micro movable structure 100 and the circuit are bonded by, for example, wire bonding, solder bumps, or metal bumps, the strength of the semiconductor substrate 101 with respect to the pressure at the time of bonding is taken into consideration and the micro movable structure 100 and the circuit are cut out after bonding. It is desirable to form the recess 107 by the above.

  The equivalent circuit of this semiconductor device is the same as the equivalent circuit of the first embodiment and is shown in FIG. As described above, the performance of this micro movable structure, particularly when used as a vibrator, is greatly influenced by the ratio γ = Ca / (Co + Cp) of the variable component of the capacitance and the steady component (including parasitic capacitance). Receive. When this γ value increases, the charge / discharge current due to the capacitance variable component Ca increases, so that the output potential can be increased even when the drive voltage (excitation voltage) is low, so the S / N ratio of the output signal. Becomes higher. Accordingly, the drive voltage can be lowered, and power saving can be achieved. In particular, in this embodiment, since the back surface of the semiconductor substrate 101 in the region where the micro movable structure 100 is formed is cut out, the first electrode 110 and the second electrode 120 through the insulating film 102, the semiconductor substrate 101, and the like. Cp, which is a parasitic capacitance between the two, can be reduced. As a result, the performance as a vibrator can be further enhanced.

  FIG. 11 is a diagram schematically showing the frequency characteristics of the impedance of the micro movable structure 100 of the present embodiment. A dotted line represents the frequency characteristic in a state where the back surface of the semiconductor substrate 101 ′ in the region where the micro movable structure 100 is formed is not hollowed and the concave portion 107 is not formed, and a solid line is the surface of the semiconductor substrate 101 ′. This represents the frequency characteristics in the state. When the back surface of the semiconductor substrate 101 is removed, Cp, which is a parasitic capacitance between the first electrode 110 and the second electrode 120, and the semiconductor substrate 101 is reduced, and the impedance change at the resonance frequency is increased. It becomes easy to use.

  A specific example of the circuit structure connected to the minute movable structure 100 of the present embodiment is shown in FIG. 6 as in the first embodiment. Since this circuit structure is the same as that described in the first embodiment, description thereof is omitted. The driving waveform of the minute movable structure 100 is also the same as that shown in FIGS.

[Third Embodiment]
FIG. 12 illustrates still another third embodiment. The third embodiment includes a micro movable structure 100 similar to that of the first embodiment, and a part of the semiconductor substrate 101 ″ is pulled out as in the second embodiment. Unlike the second embodiment, the semiconductor substrate 101 ″ is hollowed out only at a portion where the first electrode 110 and the base 121 and the semiconductor substrate 101 ″ (insulating film 102) are joined. Specifically, the above structure is provided. A concave portion 107 ′ is provided by hollowing out a portion to be joined to the first electrode layer 110, and a concave portion 107 ″ is provided by hollowing out a portion to be joined to the base portion 121. The punching out may be a part of the part to be joined, but if the whole part to be joined is perforated, it is effective in reducing the parasitic capacitance through the electrode and the insulating film 102 of the semiconductor substrate 101 ″. Although it is effective to reduce parasitic capacitance if it passes through other than the junction as in the embodiment, in this embodiment, the region to be punched out is selected in consideration of the strength of the semiconductor substrate and the like. By punching out the semiconductor substrate 101 ″ only at the high bonding portion, the parasitic capacitance can be efficiently reduced while ensuring the rigidity of the substrate.

[Modification 1]
In each of the above embodiments, the first electrode is fixed to the substrate and the second electrode is movable. However, the first electrode may be movable and the second electrode may be fixed to the substrate. Both the first electrode and the second electrode may be configured to be movable. Moreover, although the said embodiment described the case where it comprised as a vibrator | oscillator fundamentally used as a high frequency filter, a resonator, etc., the micro movable structure and semiconductor device which concern on this invention are not restricted to a vibrator | oscillator, but various kinds. It can be used as various micro electrostatic operation mechanisms such as an electrostatic actuator used as a drive source, an optical switch for switching a light propagation path, and a micromirror device having a variable reflection angle.

[Modification 2]
The substrate of the semiconductor device can be applied to GaAs, SiGe, or the like other than silicon, and the structure is not limited to silicon, and can be formed of GaAs, SiGe, or the like.

[Modification 3]
Each of the above embodiments can be applied to any semiconductor device provided with a vibrating body. For example, the present invention can be applied to a structure having a linear type, a bent type, a bent improved type, a radial vibration basic type, or the like.

[Modification 4]
The insulating film of the above embodiment is not limited to silicon oxide, and any insulating film can be applied. For example, an insulating film used in semiconductor manufacturing such as silicon nitride is preferable.

[Fourth Embodiment]
Next, a fourth embodiment according to the present invention will be described with reference to FIG. In this embodiment, the micro movable structure 100 similar to that in each of the above embodiments is included, but the semiconductor substrate 201 on which the micro movable structure 100 is formed has a structure different from that in each of the above embodiments. On the surface of the semiconductor substrate 201, surface recesses 201a and 201b provided in the formation range of the micro movable structure 100 are provided, and the insulating film 102 similar to the above is provided on the surface recesses 201a and 201b via a space. The minute movable structure 100 is formed on the insulating film 102.

  In this embodiment, since the surface recesses 201a and 201b are formed, a space (cavity) is provided between the micro movable structure 100 and the semiconductor substrate 201. The parasitic capacitance generated between the one electrode 110 and the base 121) and the semiconductor substrate 201 is reduced.

  In order to form the above structure, for example, the surface recesses 201a and 201b are formed by performing selective etching (such as wet etching or dry etching) processing or selective stacking processing on the surface of the semiconductor substrate 201. Then, after the sacrificial layer is formed so as to fill the surface recess, the insulating film 102 is formed, and then the sacrificial layer may be removed by etching or the like.

  According to this embodiment, since the parasitic capacitance can be reduced without completely hollowing out the semiconductor substrate 201, a long-time etching process for completely hollowing out the semiconductor substrate 201 becomes unnecessary. The manufacturing time can be shortened and a decrease in the rigidity of the semiconductor substrate 201 can be suppressed.

  In this embodiment, the surface recesses 201a and 201b include a portion where the micro movable structure 100 (the first electrode 110 and the base 121 thereof) and the semiconductor substrate 201 are joined, and are formed in a wider range. It may be formed only in the part to be joined, or may be formed in only a part of the part to be joined.

[Fifth Embodiment]
Finally, a fifth embodiment according to the present invention will be described with reference to FIG. In this embodiment, the same semiconductor substrate 201 as that of the fourth embodiment is provided. That is, on the surface of the semiconductor substrate 201, surface concave portions 201a and 201b provided in the formation range of the micro movable structure 100 are provided. However, in this embodiment, the insulating film 202 is formed so as to fill the insides of the surface recesses 201 a and 201 b and also be disposed on the surface of the semiconductor substrate 201, and the minute movable structure is formed on the insulating film 202. A body 100 is formed.

  In this embodiment, since the surface recesses 201a and 201b are formed, the thickness of the insulating film 202 between the micro movable structure 100 and the semiconductor substrate 201 is increased. 100 (the first electrode 110 and the base 121 thereof) and the parasitic capacitance generated between the semiconductor substrate 201 are reduced.

  In the above structure, for example, the surface recesses 201a and 201b are formed by subjecting the surface of the semiconductor substrate 201 to selective etching (such as wet etching or dry etching) or selective stacking, and the surface recesses. The insulating film 202 is formed by stacking an insulating film after the insulating film is formed so as to be filled in the insulating film.

  According to this embodiment, since the parasitic capacitance can be reduced without providing a space between the minute movable structure 100 and the semiconductor substrate 201, the support rigidity of the minute movable structure 100 can be increased. it can.

  Also in this embodiment, the surface recesses 201a and 201b include a portion where the micro movable structure 100 (the first electrode 110 and the base 121 thereof) and the semiconductor substrate 201 are joined, and are formed in a wider range. It may be formed only in the part to be joined, or may be formed in only a part of the part to be joined. In these cases, the insulating film 202 may be formed so as to fill the surface recess.

  The micro movable structure according to the present invention is not limited to the illustrated examples described above, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

The schematic longitudinal cross-sectional view (a) and (b) of the micro movable structure of 1st Embodiment. The schematic perspective view (a) of the micro movable structure of 1st Embodiment, and the schematic perspective view (b) of a modification. Schematic process sectional drawing (a)-(c) which shows the manufacturing method of the micro movable structure of 1st Embodiment. The equivalent circuit diagram of a micro movable structure. The circuit diagram which shows the example of the circuit structure connected to 1st Embodiment. The graph which shows the drive aspect using electrostatic repulsion. The graph which shows the different drive aspect using electrostatic repulsion. The schematic longitudinal cross-sectional view (a) and (b) of the semiconductor device of 2nd Embodiment. The schematic perspective view (a) of the semiconductor device of 2nd Embodiment, and the schematic perspective view (b) of a modification. Schematic process sectional drawing (a)-(c) which shows the manufacturing method of the semiconductor device of 2nd Embodiment. The figure which shows the frequency characteristic of the impedance at the time of forming a recessed part. The schematic sectional drawing of 3rd Embodiment. The schematic sectional drawing of a 4th embodiment. The schematic sectional drawing of 5th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100,100 '... Minute movable structure, 101 ... Substrate, 102 ... Insulating film, 110, 110' ... 1st electrode layer, 120, 120 '... 2nd electrode layer, 121 ... Base, 122 ... Elastic support part, 123 ... second electrode, 101 ', 101 ", 201 ... semiconductor substrate, 107, 107', 107" ... concave portion formed by hollowing out semiconductor substrate, 201a ... surface concave portion

Claims (19)

A first electrode formed on the substrate; and a second electrode disposed opposite to the first electrode, wherein at least one of the first electrode and the second electrode is configured to be movable, and the first electrode In the micro movable structure configured to move the first electrode and the second electrode relatively by generating an electrostatic force between the electrode and the second electrode,
The second electrode is disposed above the first electrode;
The first electrode and the second electrode have a concavo-convex structure corresponding to the vertical direction,
The micro movable structure characterized in that the first electrode and the second electrode move relatively in the vertical direction.   2. The micro movable structure according to claim 1, wherein at least one of the first electrode and the second electrode is provided with a concave hole configured such that the other can be inserted from above or below. .   The micro movable structure according to claim 1 or 2, wherein the first electrode is fixed on the substrate and the second electrode is configured to be movable.   The micro movable structure according to claim 3, wherein the second electrode is fixed to the substrate via an elastic deformation portion.   The micro movable structure according to any one of claims 1 to 4, wherein only the electrostatic repulsive force is exerted as the electrostatic force.   The micro movable structure according to any one of claims 1 to 5, wherein an electric signal based on a change in capacitance between the first electrode and the second electrode can be output. body.   The minute movable structure according to any one of claims 1 to 6, wherein the first movable electrode and the second electrode are configured to vibrate relative to each other based on the electrostatic force. . A semiconductor substrate;
An insulating film formed on the semiconductor substrate;
A first electrode formed on the insulating film; and a second electrode disposed opposite to the first electrode, wherein at least one of the first electrode and the second electrode is configured to be movable, A micro movable structure configured to move the first electrode and the second electrode relatively by generating an electrostatic force between the first electrode and the second electrode, and
The second electrode is disposed above the first electrode;
The first electrode and the second electrode have a concavo-convex structure corresponding to the vertical direction,
The semiconductor device according to claim 1, wherein the first electrode and the second electrode move relatively in the vertical direction. A vibrating body having an oscillating portion and an electrode that vibrate by an electrostatic force;
An insulating film;
A semiconductor device comprising a semiconductor substrate,
At least a part of the rear surface of the semiconductor substrate in a region where the vibrating body and the semiconductor substrate are bonded is hollowed out, and a region where the vibrating body and the semiconductor substrate are cut out is composed of only the insulating film. Semiconductor device. A vibrating body having an oscillating portion and an electrode that vibrate by an electrostatic force;
A semiconductor substrate;
A semiconductor device comprising an insulating film formed between the vibrator and the semiconductor substrate,
A surface recess is provided in at least a part of the surface of the semiconductor substrate in a region where the vibrating body and the semiconductor substrate are joined, and the region between the vibrating body and the semiconductor substrate is more than in other regions in the region where the surface recess is provided. A semiconductor device characterized in that the distance is separated. A first electrode formed on a semiconductor substrate; and a second electrode disposed opposite to the first electrode, wherein at least one of the first electrode and the second electrode is configured to be movable, A micro movable structure configured to move the first electrode and the second electrode relatively by generating an electrostatic force between the first electrode and the second electrode; and an insulating film. A semiconductor device,
At least a part of the back surface of the semiconductor substrate in the region where the micro movable structure and the semiconductor substrate are joined is hollowed out, and the region where the micro movable structure and the semiconductor substrate are joined in the hollowed out portion is only from the insulating film. A semiconductor device comprising: A first electrode formed on a semiconductor substrate; and a second electrode disposed opposite to the first electrode, wherein at least one of the first electrode and the second electrode is configured to be movable, A micro movable structure configured to move the first electrode and the second electrode relatively by generating an electrostatic force between the first electrode and the second electrode; the semiconductor substrate; A semiconductor device comprising an insulating film formed between the micro movable structure,
A surface concave portion is provided in at least a part of the surface of the semiconductor substrate in a region where the micro movable structure and the semiconductor substrate are joined, and the micro movable structure and the region are provided in the region where the surface concave portion is provided more than other regions. A semiconductor device characterized in that a distance from the semiconductor substrate is separated. The second electrode is disposed above the first electrode;
The first electrode and the second electrode have a concavo-convex structure corresponding to the vertical direction,
The semiconductor device according to claim 11, wherein the first electrode and the second electrode move relatively in the vertical direction.   14. The semiconductor device according to claim 8, wherein at least one of the first electrode and the second electrode is provided with a concave hole configured such that the other can be inserted from above or below. .   The semiconductor device according to claim 8, wherein the first electrode is fixed on the substrate, and the second electrode is configured to be movable.   The semiconductor device according to claim 15, wherein the second electrode is fixed to the substrate via an elastic deformation portion.   The semiconductor device according to claim 8, wherein only the electrostatic repulsive force is exerted as the electrostatic force.   18. The semiconductor according to claim 8, wherein the semiconductor is configured to be capable of outputting an electrical signal based on a change in capacitance between the first electrode and the second electrode. apparatus. 19. The semiconductor device according to claim 8, wherein the semiconductor device is configured to relatively vibrate the first electrode and the second electrode based on the electrostatic force. 19. .

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