TWI612008B - Micromechanical device - Google Patents

Abstract

The present invention achieves effective anti-adhesion measures in a micromechanical device using a highly insulating substrate.

According to the present invention, a conductive body (107 (107a)) is provided on a surface (101a) side and a surface (103a) side of a movable portion (103) opposite to each other in a region (122) where a convex portion (104) is formed. And (108 (108a)). The conductor (107) provided on the side (101a) of the substrate (101) is an independent conductor, and the independent conductor is an electrode (105) formed on the surface (101a) of the substrate (101). A gap (h) is provided so that the periphery is surrounded. A gap (annular gap) (h) surrounding the circumference of the independent conductor (independent conductor) (107) is set to an antistatic layer having a surface resistance of an antistatic level (10 ⁹ to 10 ¹⁴ Ω / □) ( 109).

Description

Micromechanical device

The present invention relates to a micromechanical device equipped with a fine movable portion.

In recent years, a microelectromechanical system (MEMS) that uses a micromechanical device that functions by mechanical action has been valued for a switch or a sensor. MEMS has been used as a pressure sensor or an acceleration sensor, and it has gradually become an important part together with LSI. MEMS has a three-dimensional structure, and the three-dimensional structure is provided with a fine movable structure by microfabrication using a thin film formation technology, a photolithography technology, and various etching technologies.

For example, in an electrostatic capacitance type pressure sensor, as shown in FIG. 8A, a fine diaphragm (movable portion) 401 that is displaced by pressure is supported by a support portion 403 and disposed on a substrate 402 in a spaced manner. on. There is a gap 404 between the substrate 402 and the diaphragm 401, and electrodes (not shown) are arranged opposite to each other facing the gap 404 to form a capacitor.

As shown in FIG. 8B, the pressure of the medium to be measured is applied to the side of the diaphragm 401 on the side opposite to the capacitor-forming side, and the diaphragm 401 is deformed under the pressure. The distance between the electrodes changes in response to the change, and the capacitance between the electrodes changes in response to the change, and becomes a sensor output. If the gap is vacuum, the pressure sensor can measure absolute pressure.

We know that in this kind of micromechanical device, the phenomenon of adsorption caused by the measured voltage is generated. Generally, when a voltage is applied between two electrodes that are opposed in parallel at a certain distance, Gravitational force (gravity induced by voltage) is inversely proportional to the square of the distance. Therefore, in the above-mentioned electrostatic capacitance type pressure sensor, when the diaphragm 401 deformed when a pressure is applied is close to the substrate 402 to a very close distance, since the distance between the diaphragm 401 and the substrate 402 is extremely narrow, Therefore, the gravity induced by the voltage is large, which causes the membrane 401 to be strongly attracted and bottomed (adsorbed).

Here, as soon as the bottom is reached, a short circuit occurs between the electrodes, so the gravity induced by the voltage disappears, causing the diaphragm 401 to separate from the substrate 402. However, just after detachment, the voltage-induced gravitational force was applied again, so the membrane 401 was strongly attracted and bottomed again. With extremely small distances between the electrodes, this bottoming and detachment can occur repeatedly.

In the case of an electrostatic capacitance type pressure sensor, in order to measure capacitance, a voltage must be applied, so that the attraction phenomenon caused by the voltage induced gravitational force is generated. As a result, the above-mentioned bottoming and detachment occur repeatedly, resulting in The output of the sensor is independent and unstable regardless of the pressure applied to the diaphragm. This adsorption phenomenon is more pronounced in MEMS sensors that are small and have a small distance between the electrodes, and the surface of the contact portion on the substrate or the electrode is relatively smooth.

In addition, the above-mentioned micromechanical device may be such that a part of the movable portion such as the bottom hits and the substrate are brought into contact with each other, and the movable portion is not restored by the rebound caused by the elastic force (refer to Patent Documents 1, 2 and 3) 3, 4, 5, 6). This phenomenon is called adhesion or fixation, and is a problem in micromechanical devices.

For example, pressure sensors that measure pressures lower than atmospheric pressure, such as electrostatic diaphragm vacuum gauges, are exposed to the atmosphere during transportation, installation, or maintenance. Excessive stress. When excessive pressure is applied in this way, the pressured diaphragm 401 will be largely bent beyond the actual use range as shown in FIG. 8C, and a part of the diaphragm 401 will contact the substrate 402 (bottom bottom).

Due to differences in design parameters such as the thickness of the diaphragm 401 and the size of the deformed area, as well as the material of the diaphragm 401, the above-mentioned bottoming state is different, but in most cases, bottoming will cause sticking. In particular, in a case where the electrode is not formed at the contact portion in order to suppress the adsorption phenomenon described above, sticking occurs significantly. The reason is considered to be that the materials constituting the diaphragm 401 and the substrate 402 are in direct contact with each other when the bottom is reached in an area where no electrode is formed in order to prevent the adsorption phenomenon.

When sticking occurs, even if the pressure is removed, the diaphragm 401 does not recover and gives an output as if pressure was applied, resulting in measurement errors. In particular, a micromechanical device made of an extremely flat substrate having a surface roughness (Rz) of 0.1 to several nm is a major problem. Moreover, in the case of a diaphragm vacuum gauge, since a vacuum state is maintained between the substrate and the movable portion, there is a tendency that adhesion is more likely to occur.

[Existing technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. Hei 10-512675

[Patent Document 2] Japanese Patent Laid-Open No. 11-340477

[Patent Document 3] Japanese Patent Laid-Open No. 2000-040830

[Patent Document 4] Japanese Patent Laid-Open No. 2000-196106

[Patent Document 5] Japanese Patent Laid-Open No. 2002-299640

[Patent Document 6] Japanese Patent Laid-Open No. 2007-078439

[Patent Document 7] Japanese Patent No. 3668935

In the conventional micromechanical device, in order to prevent the above-mentioned adsorption phenomenon and adhesion phenomenon caused by a voltage, a structure in which an electrode is not formed on a contact portion is provided on the one hand, and at least one of a movable portion and a substrate is provided on the other hand A fine structure such as a protrusion is formed on the opposite surface to reduce the contact area and suppress the contact force.

Specifically, using a well-known semiconductor device manufacturing technology, minute protrusions are formed on a semiconductor such as silicon or a substrate such as quartz constituting a micromechanical device. For example, by patterning using a known photolithography technique and etching technique, protrusions having a size of about several μm are formed on a substrate such as a semiconductor or quartz. The term "base material" as used in this specification refers to a member that collectively refers to a substrate and a movable portion.

However, although the adhesion countermeasures to reduce the contact area by the protrusions are effective to a certain extent, especially in the case of pressure sensors, since a large stress is applied when excessive pressure is applied, it is smaller. The protrusions can damage the diaphragm or substrate. On the other hand, if the protrusion is increased to prevent damage, the contact area is increased and the countermeasure effect itself cannot be obtained. In this way, the measures for preventing the adhesion of the protrusions must strictly control the size of the contact surface of the protrusions, and the control is complicated.

In addition, in the diaphragm vacuum gauge, in order to make the device resistant to acid or heat according to the use environment, a crystalline material such as sapphire or a material such as alumina ceramic is used. Compared with silicon or glass, this highly insulating material is more prone to adhesion.

In other words, repeated contact between the substrate and the movable portion that are not electrically charged at the initial stage and the movable portion may cause contact electrification and generate static electricity on the surface. The insulation resistance of the substrate is large, and the contact environment is also in a vacuum. As a result, there is no place for these static electricity to dissipate. When contact is made, static electricity is accumulated, and it is thought that electrostatic attraction is generated between the substrate and the movable part and adhesion occurs.

Especially when the structure of the film is thin, protrusions having a size of several μm are not an effective countermeasure against adhesion. In order to suppress the occurrence of such contact charging, it is more effective to reduce the contact area itself. Therefore, for example, it is considered to form minute irregularities with a size of sub-μm or less. However, materials such as sapphire or alumina ceramics are more difficult to process than materials such as silicon or glass in terms of high mechanical strength, high corrosion resistance, and chemical resistance. On the other hand, microfabrication with a size of sub-μm or less is extremely difficult.

In addition, although there is a technique for preventing adhesion by using a surface film that stabilizes the surface, in this case, the surface film is mostly made of an organic material, and when it is used in a high-temperature environment, or when the film and the substrate are used In a structure where the space between them is vacuum, organic materials cannot be used.

In addition, there are two conventional techniques for forming a concave-convex structure having a sub-μm thickness or less. One is a method of mechanically roughening the surface, such as sand blasting, but the roughness is difficult to control and a source of damage to the substrate is formed. This method is more risky for pressure sensors equipped with a movable part. The other is a method of drawing an exposure device using a stepping exposure machine or an electron beam used in a semiconductor manufacturing process. However, depending on the use or conditions of the vacuum gauge, there are also cases where, for example, the thickness of the movable part is thick, Products that do not require bumps of several to hundreds of nanometers, such as sensors that have a wide range of pressure to be measured. If this is taken into consideration, the proportion of processes or devices that can be used in common with products that do not need bumps will be reduced. , Is more disadvantageous in terms of manufacturing costs or production management. In addition, the following troublesome situations often occur: adhesion does not occur during the manufacture of the sensor or in the early stages of use, but adhesion occurs over a long period of use.

In addition, since it is easy to be charged when a surface such as a protrusion is formed using an insulator, there is a method of uniformly setting the contact portions to the same potential (for example, refer to Patent Document 7). However, in the method of uniformly setting the contact portions to the same potential, a voltage driving circuit including an electrical switching operation of a circuit or the like is required, and the problem cannot be solved by the device itself. Furthermore, silicon and silicon oxide are used in this method, and it is difficult to directly apply this method to materials with higher insulation properties.

For this reason, in particular, a micromechanical device using a highly insulating substrate such as sapphire or alumina ceramics is in a situation where it is difficult to take effective anti-adhesion measures.

The present invention is made to solve such a problem, and an object thereof is to obtain an effective anti-adhesion measure in a micromechanical device using a highly insulating substrate.

In order to achieve such an object, the present invention includes a substrate including an insulator, and a movable portion supported on the substrate by a supporting portion, which is spaced apart from the substrate in a movable region, and can be directed toward the movable region. The substrate is displaced in direction, and the movable portion is made of an insulator; the convex portion is formed on at least one of the substrate and the movable portion facing each other in the movable region; and the electrode is formed on each of the substrate and the movable portion opposed in the movable region. A surface; and a conductor provided on at least one of the substrate-side surface and the movable portion-side surface opposite to each other in the area where the convex portion is formed, and the conductor provided on the substrate-side surface and the movable portion-side surface. It is set as an independent conductor, and an independent conductor is formed by providing a gap on an electrode formed on a surface of a substrate or a movable portion on which the conductor is provided so as to surround the periphery, and a gap surrounding the independent conductor is set as a surface The resistance is an anti-static anti-static layer.

In the present invention, a conductive body is provided on the substrate-side surface and the movable portion-side surface opposite to each other in the area where the convex portion is formed, and at least one of the conductive bodies provided on the substrate-side surface and the movable portion-side surface is provided. One is an independent conductor, and the independent conductor is formed by providing a gap on an electrode formed on a surface of a substrate or a movable portion on which the conductor is provided so as to surround the periphery. A gap surrounding the independent conductive body is an antistatic layer having a surface resistance of an antistatic level (for example, 10 ⁹ to 10 ¹⁴ Ω / □).

In the present invention, by setting the gap surrounding the independent conductor as an antistatic layer, the independent conductor and the electrode surrounding the independent conductor are connected via the antistatic layer. Therefore, even if a charge caused by contact charging is generated, the charge can be dissipated to the surrounding electrodes through the antistatic layer to prevent adhesion. In addition, the potential of the independent conductive body can not follow the potential of the surrounding electrodes, thereby avoiding the phenomenon of adsorption.

In the present invention, the resistance formed between the independent conductor and the electrode surrounding the independent conductor is set to R, and the capacitance formed between the independent conductor and the electrode surrounding the independent conductor is R. Let C be the time constant RC of the product of the resistor R and the capacitor C, and set the vibration period of the AC voltage between the electrodes formed on the surfaces of the substrate and the movable part opposite to each other in the movable region during operation. In the case of T, the surface resistance of the antistatic layer is set such that the time constant RC is a value greater than the vibration period T of the AC voltage.

In the present invention, among the conductors provided on the substrate side and the movable portion side, at least the conductors provided on the side where the convex portion is formed are preferably closer to the material forming the convex portion. Hard material. Thereby, the convex portion does not penetrate into the conductor and is not plastically deformed or fixed, so that durability or reproducibility can be improved.

Further, in the present invention, it is preferable that the conductors provided on the substrate side surface and the movable portion side surface are made of different materials. As a result, intermolecular bonding is less likely to occur, and the conductors can be prevented from being directly bonded to each other.

According to the present invention, at least one of the conductors provided on the substrate-side surface and the movable portion-side surface is set to provide a gap on an electrode formed on the surface of the substrate or movable portion on which the conductor is provided, so that Independent conductive body surrounded by the surroundings, and the gap surrounding the independent conductive body is set to an antistatic layer with an antistatic surface resistance. Therefore, it can be effectively used in a micromechanical device using a highly insulating substrate. Anti-adhesion countermeasures.

100 (100A, 100B) ‧‧‧ micromechanical device

101‧‧‧ substrate

101a‧‧‧ side (the side on the substrate side)

102‧‧‧ support

103‧‧‧ Mobile

103a‧‧‧face (the side facing the movable part)

104‧‧‧ convex

105, 106‧‧‧ electrodes

107 (107a) ‧‧‧Conductor (independent conductor)

108 (108a) ‧‧‧Conductor

109‧‧‧Anti-static layer

121‧‧‧ movable area

122‧‧‧ convex formation area

h‧‧‧ clearance

FIG. 1A is a cross-sectional view illustrating a configuration example of a micromechanical device according to an embodiment of the present invention.

FIG. 1B is a cross-sectional view showing a partial configuration example of a micromechanical device according to the embodiment of the present invention.

FIG. 2 is a view of a region where a convex portion is formed on a substrate of a micromechanical device according to an embodiment of the present invention, as viewed from above.

FIG. 3 is a diagram illustrating an operation state of the micromechanical device according to the embodiment of the present invention.

4 is a cross-sectional view showing a partial configuration example of another micromechanical device according to the embodiment of the present invention.

5 is a cross-sectional view showing a partial configuration example of another micromechanical device according to the embodiment of the present invention.

6 is a cross-sectional view showing a partial configuration example of another micromechanical device according to the embodiment of the present invention.

7 is a cross-sectional view illustrating a configuration example of another micromechanical device according to the embodiment of the present invention.

FIG. 8A is a cross-sectional perspective view showing a partial configuration of a pressure sensor.

FIG. 8B is a cross-sectional perspective view showing a partial configuration of the pressure sensor.

FIG. 8C is a cross-sectional perspective view showing a partial configuration of the pressure sensor.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1A is a cross-sectional view illustrating a configuration example of a micromechanical device according to an embodiment of the present invention. FIG. 1B is a cross-sectional view showing a partial configuration example of a micromechanical device according to the embodiment of the present invention. FIG. 1B is an enlarged view of a part of FIG. 1A.

The micromechanical device 100 (100A) includes: a substrate 101 made of an insulator; and a movable portion 103 supported on the substrate 101 by a support portion 102. The movable portion 103 is spaced apart from the substrate 101 in a movable region 121 and can be mounted on the substrate 101. The movable region 121 is displaced toward the substrate 101 and is made of an insulator. The movable portion 103 is fixed to the support portion 102. The substrate 101 and the movable portion 103 have high insulation properties, and their insulation levels are greater than 10 ¹⁴ Ω / □.

In this micromechanical device 100A, a plurality of convex portions 104 are formed on the substrate 101 side surface 101 a of the substrate 101 and the movable portion 103 which are opposed in the movable region 121. The convex portion 104 is, for example, a pillar that is circular in plan view and has a diameter of 1 to several tens of μm. In this example, the interval L between the adjacent convex portions 104 is, for example, about 0.5 mm.

In addition, electrodes 105 and 106 are formed on the respective surfaces (surfaces) 101 a and 103 a of the substrate 101 and the movable portion 103 facing each other in the movable region 121. That is, the electrode 105 is formed on the surface 101a on the substrate 101 side, and the electrode 106 is formed on the surface 103a on the movable portion 103 side.

The micromechanical device 100A is, for example, a pressure sensor in which the movable portion 103 is a diaphragm. For example, the substrate 101 and the movable portion 103 are made of sapphire. The pressed movable portion 103 is displaced in the direction of the substrate 101. As a result, the interval between the electrode 105 and the electrode 106 in the movable region 121 is changed. To change the capacitance. The change in capacitance is used to measure the pressure applied to the movable portion 103. When the electrode formation region is set to a vacuum, it can be used as a pressure sensor capable of measuring absolute pressure.

In this micromechanical device 100A, in each region 122 where the convex portion 104 is formed, the surface 101a on the substrate 101 side and the surface 103a on the movable portion 103 side opposite to each other in the region 122 where the convex portion 104 is formed The conductors 107 (107a) and 108 (108a).

As shown in FIG. 2, when the area where the convex portion 104 is formed on the substrate 101 (hereinafter, referred to as a convex portion forming area) 122 is viewed from above, the conductive body 107 provided on the surface 101 a of the substrate 101 side is set to be independent conductive. The aforementioned independent conductive body is formed by providing a gap h on the electrode 105 formed on the surface 101 a of the substrate 101 so as to surround the periphery. The independent conductive body 107 covers the entire convex portion 104. Hereinafter, this conductive body 107 is referred to as an independent conductive body.

In contrast, the conductive body 108 provided on the surface 103 a on the side of the movable portion 103 is a part of the electrode 106 formed on the surface 103 a of the movable portion 103. That is, in the present embodiment, a region facing the independent conductor 107 on the substrate 101 side of the region where the electrode 106 is formed on the movable portion 103 side is referred to as a conductor 108.

In this embodiment, the surface resistances of the independent conductors 107 and 108 are set to a conductivity level of 10 ⁹ Ω / □ or less, but the independent conductors 107 and 108 are not the same material but are formed of different materials.

In the present embodiment, the independent conductive body 107 is made of a material that is closer to the hardness of sapphire that is the material of the convex portion 104, that is, the material of the substrate 101. In this example, a material having a Vickers hardness of 400 MPa or more is used. For example, materials such as W, Mo, Ti, Fe, Ni, Cu, Nb, Ta, Cr, Ga, Ir, Rh, Ru, V, Pd, and Zr are used. Moreover, about the guide The electrical body 108 may be a material having a Vickers hardness of 400 MPa or more.

In the substrate 101, a gap (annular gap) h surrounding the periphery of the independent conductive body 107 is an antistatic layer 109 having a surface resistance of an antistatic level. That is, the size of the gap h and the material within the gap h are determined and arranged so that the resistance value of the surface of the gap h is at an antistatic level, thereby forming the antistatic layer 109. In this embodiment, the surface resistance of the antistatic layer 109 is set to 10 ⁹ to 10 ¹⁴ Ω / □.

Such an antistatic layer 109 can be produced, for example, by a film formation method such as sputtering, vapor deposition, CVD (Chemical Vapor Deposition, Chemical Vapor Deposition), ALD (Atomic Layer Deposition), and the like. In the patterning, a film having a slightly lower resistance is formed only in the gap h surrounding the periphery of the independent conductive body 107. In this case, as a material for forming the antistatic layer 109, a material having a lower electrical resistance than an insulator constituting the substrate 101 and the movable portion 103 is used. Specific materials include semiconductors such as SiC and Si; oxides such as titanium oxide, indium oxide, zinc oxide, tin oxide, ruthenium oxide, and zirconia; aluminum nitride, titanium nitride, and nitride Nitride or carbide such as silicon and titanium carbide.

In addition, the antistatic layer 109 may be produced by reducing the surface resistance by performing ion implantation. Examples of the material in this case include iron, nickel, gold, silver, boron, copper, chromium, cerium, thorium, manganese, phosphorus, fluorine, argon, and the like.

In addition, the antistatic layer 109 can also be manufactured by the following operations: after the film is formed, the metal is thermally diffused at a high temperature, and then the excess metal is chemically and physically removed to reduce the surface resistance. In this case, examples of the metal to be diffused include titanium, niobium, tantalum, nickel, iron, chromium, and manganese.

In addition, the antistatic layer 109 may be made of a metal oxide layer having an atomic layer thickness. Make up. For example, the antistatic layer 109 may be formed using an atomic layer-thick oxide metal layer made of molybdenum oxide, tungsten oxide, or the like. Molybdenum oxide or tungsten oxide has a lower vapor pressure than sapphire. By heating this material together with the substrate 101 made of sapphire in the same furnace to about 900 ° C to evaporate (sublimate) the oxide metal, the oxide metal can be formed on the surface of the substrate 101 at the atomic layer level. Floor.

According to this micromechanical device 100A, when the compressed movable portion 103 is largely bent beyond the actual use range, a part of the surface 103 a of the movable portion 103 bottoms out on the upper surface of the convex portion 104 of the substrate 101. In this state, the conductive body 108 provided on the surface 103 a of the movable portion 103 is in contact with the independent conductive body 107 provided on the upper surface of the convex portion 104 of the substrate 101. Accordingly, even if a charge caused by contact charging is generated, the charge can be dissipated to the surrounding electrode 105 through the antistatic layer 109 to prevent adhesion. In addition, the potential of the independent conductive body 107 can be prevented from following the potential of the surrounding electrode 105, thereby avoiding an adsorption phenomenon. The reason will be described later.

In addition, in this embodiment, since the independent conductive body 107 and the conductive body 108 are made of different materials, it is possible to prevent the independent conductive body 107 and the conductive body 108 from being directly bonded. That is, when the independent conductor 107 and the conductor 108 are the same material, if the independent conductor 107 and the conductor 108 are in contact with each other in a vacuum, intermolecular bonding between the independent conductor 107 and the conductor 108 may occur. They join the case. In this embodiment, since the independent conductive body 107 and the conductive body 108 are made of different materials, such intermolecular bonding is unlikely to occur, and the independent conductive body 107 and the conductive body 108 can be prevented from being directly bonded.

In addition, in this embodiment, since the independent conductor 107 is made of a material that is closer to the hardness of the material forming the convex portion 104, even the independent conductor 107 and the conductor 108 Repeated contact prevents the convex portion 104 from intruding into the independent conductive body 107 and causing plastic deformation or fixing, thereby improving durability or reproducibility.

Here, the details of the present invention will be described. First, as described above, if the electrodes 101 are formed on the entire surface of the substrate 101 and the surface 103a of the movable portion 103 opposite to each other in the movable region 121, these electrodes will come into contact when they bottom out. It becomes a problem. In other words, bottoming and detachment caused by the adsorption phenomenon occur repeatedly and become a problem. In order to eliminate this problem, it is considered to be in a state where electrodes are not arranged at the contact portions. However, in a portion where no electrode is formed, the surface 101 a of the substrate 101 and the surface 103 a of the movable portion 103 are in direct contact.

When contact between the substrate 101 having a large insulation resistance and the movable portion 103 repeatedly occurs, contact charging occurs, and static electricity is generated on the surface. The insulation resistance of the substrate 101 and the movable portion 103 is large, and the contact environment is also in a vacuum. As a result, these static electricity are not dissipated. Therefore, static electricity is accumulated every time they are repeatedly contacted. As a result, electrostatic attraction is generated between the substrate 101 and the movable portion 103 and adhesion occurs.

In order to suppress the occurrence of such contact electrification, reducing the contact area itself is a relatively effective countermeasure. For this reason, the convex portion 104 is formed, thereby reducing the contact area when bottoming. However, in insulating materials such as sapphire, we know that the convex portions 104 can be easily formed into a pattern of several μm, but it is extremely difficult to perform microfabrication at the nm level. Therefore, the size of the convex portion 104 that can be easily realized is a unit of several μm. However, the convex portion 104 having a size of only several μm is not an effective countermeasure against the above-mentioned adhesion caused by static electricity.

On the other hand, by using the conductive bodies 107 and 108 as the parts that come into contact when reaching the bottom, contact electrification is unlikely to occur. However, if the conductive body 107 is formed as a part of the electrode 105 in the same manner as the conductive body 108, electricity is generated in the same manner as in the state where the electrode is formed. The connection between the electrode 105 and the electrode 106 causes an adsorption phenomenon, which is a problem.

In contrast, in this embodiment, the conductive body 107 is configured as an independent conductive body, and the gap h surrounding the independent conductive body 107 is set as an antistatic layer 109, so that The antistatic layer 109 connects the independent conductive body 107 and the surrounding electrode 105. Therefore, even if contact charging occurs, the charges generated by the contact charging can be dissipated to the electrode 105 through the antistatic layer 109 to prevent adhesion. . In addition, the potential of the independent conductive body 107 can be prevented from following the potential of the surrounding electrode 105, thereby avoiding an adsorption phenomenon.

That is, in this embodiment, the surface resistance of the antistatic layer 109 is set to 10 ⁹ to 10 ¹⁴ Ω / □. The resistance formed between the independent conductive body 107 and the electrode 105 surrounding the independent conductive body 107 is R, and the resistance formed between the independent conductive body 107 and the electrode 105 surrounding the independent conductive body 107 is R. The capacitance is set to C, the product of the resistance R and the capacitance C is set to a time constant RC, and are applied to the respective surfaces (surfaces 101a, 103b) of the substrate 101 and the movable portion 103 which are opposed to each other in the movable region 121 during operation. When the vibration period of the AC voltage of the electrodes 105 and 106 is set to T (the reciprocal of the vibration frequency f), the antistatic layer is set in a value (RC≫T) in which the time constant RC is greater than the vibration period T of the AC voltage. Surface resistance of 109.

The time constant RC of the antistatic layer 109 will be described in more detail with reference to FIG. 3. 3 is a cross-sectional view showing a part of a state in which the movable portion 103 of the micromechanical device 100A has bottomed on the substrate 101. In FIG. 3, the movable portion 103 of the micromechanical device 100A is a pressure sensor of a diaphragm, and the measurement voltage applied during operation is AC.

As shown in FIG. 3, the potential of the electrode 106, that is, the conductor 108 at the moment of bottoming is set to 0, and the potential of the electrode 105 is set to V ₀ sin (2 π ft). In this case, of course, the potential of the independent conductive body 107 that is in contact with the convex portion 104 of the conductive body 108 is also 0. However, if the resistance between the conductive body 107 and the electrode 105 on the same surface is too small, the movable portion 103 is separated from the substrate. At 101, the potential of the independent conductive body 107 will quickly follow the potential of the electrode 105 and become V ₀ sin (2 π ft), resulting in a potential difference from the conductive body 108 having a potential of 0. Therefore, a gravitational force caused by a voltage is generated, which causes repeated bottoming and detachment caused by the adsorption phenomenon.

In contrast, if the resistance formed between the independent conductive body 107 and the electrode 105 surrounding the independent conductive body 107 is R, the resistance between the independent conductive body 107 and the electrode 105 surrounding the independent conductive body 107 is set to R. When the capacitance formed between them is C, the independent conductor 107 and the electrode 105 to which the alternating current is applied can be regarded as only a primary filter (RC circuit). Therefore, if the cut-off frequency 1 / (2 π RC) of the RC circuit defined with respect to the alternating-current vibration frequency f applied to the electrode 105 is sufficiently small, the potential of the independent conductive body 107 will not follow the surrounding electrode 105 The potential is such that a potential difference does not occur with the conductor 108. As a result, a gravitational force caused by a voltage is not generated, that is, a suction phenomenon is not generated, and it is possible to prevent repeated bottoming and detachment from occurring.

On the other hand, since the electrostatically-charged diffusion of static electricity generated by contact is a direct current, if the initial charge is set to Q ₀ , the charge will be Q ₀ when it is dissipated to the electrode 105 through the antistatic layer 109. exp (-t / RC) decays. If the time constant RC is sufficiently small compared to the response speed of the pressure sensor, no sticking that causes charging will occur, but generally speaking, if the surface resistance of the independent conductor 107 is 10 ⁹ Ω / □ or less, it will not be easy to be charged. And, even if charging occurs, static electricity is quickly removed by the antistatic layer 109. In this way, in order to avoid abnormalities caused by the adhesion and adsorption phenomena, the lower limit of the resistance R for the cut-off frequency and the resistance for static electricity are limited for the resistance R between the independent conductor 107 and the electrode 105 surrounding the independent conductor 107. The upper limit is sufficient.

In addition, in the above-mentioned embodiment, it is the surface formed on the side of the movable part 103 A part of the electrode 106 of the 103a is the conductive body 108 on the movable portion 103 side, but a conductive body 108 (108b) different from the electrode 106 formed on the surface 103a of the movable portion 103 side may be provided, for example, as shown in FIG. 4. .

In addition, as shown in FIG. 5, an independent conductor 108 (108 c) can also be provided on the movable portion 103 side in the same manner as the independent conductor 107 on the substrate 101 side, and the independent conductor 108 c can be surrounded by the antistatic layer 110. Around.

In addition, as shown in FIG. 6, the conductive body 107 (107b) on the substrate 101 side may be a part of the electrode 105 formed on the surface 101a of the substrate 101 side, and an independent conductive body 108 (108c) may be provided on the movable portion 103 side. ), And the surrounding of the independent conductive body 108c is surrounded by the antistatic layer 110.

Further, in the above-mentioned embodiment, the convex portion 104 is provided on the substrate 101 side, but the surface 103 a of the movable portion 103 side opposite to the movable portion 121 may also be provided, like the micromechanical device 100 (100B) shown in FIG. 7. The convex portion 104 is formed and has the same configuration as described above. In addition, the convex portion 104 may be formed on both the substrate 101 side surface 101a and the movable portion 103 side surface 103a opposite in the movable region 121, and the same configuration as described above may be adopted.

In the above-described embodiment, the insulating material constituting the substrate 101 and the movable portion 103 is sapphire (single-crystal sapphire), but it may be alumina ceramic (polycrystalline alumina ceramic). In addition, it can also be silicon carbide, aluminum nitride, silicon nitride, zirconia, yttria, cordierite (2MgO-2Al2O3-5SiO2), mullite (3Al2O3-2SiO2), talc (MgO-SiO2), magnesium Any compound such as olivine (2MgO-SiO2) may be used as long as it is an insulating material having the same insulating properties as sapphire or alumina ceramics.

[Extension of Embodiment]

As mentioned above, although this invention was demonstrated with reference to embodiment, this invention is not limited to the said embodiment. Various changes that can be understood by those skilled in the art can be made to the configuration or details of the present invention within the scope of the technical idea of the present invention.

100 (100A) ‧‧‧Micro-mechanical device

101‧‧‧ substrate

101a‧‧‧ side (the side on the substrate side)

102‧‧‧ support

103‧‧‧ Mobile

103a‧‧‧face (the side facing the movable part)

104‧‧‧ convex

105, 106‧‧‧ electrodes

109‧‧‧Anti-static layer

121‧‧‧ movable area

h‧‧‧ clearance

Claims (7)

A micromechanical device is characterized in that it includes: a substrate composed of an insulator; a movable portion supported on the substrate by a support portion; and a spaced apart arrangement from the substrate in a movable region, and a movable portion capable of being disposed in the movable region. Displacement toward the substrate, the movable portion is made of an insulator; a convex portion is formed on at least one of the substrate and the movable portion that are opposed in the movable region; and an electrode is formed in the movable region. Surfaces of the substrate and the movable portion that are opposite to each other; and a conductor provided on the substrate side surface and the movable portion side that are opposite to each other in a region where the convex portion is formed, and disposed on the substrate side surface And at least one of the conductors on the side of the movable portion is an independent conductor, and the independent conductor is provided with a gap on an electrode formed on a surface of the substrate or the movable portion on which the conductor is provided, so that The periphery is surrounded, and the gap surrounding the independent conductor is set to have an antistatic surface resistance. Static layer. For example, in the micromechanical device of the first patent application scope, among the conductors provided on the side of the substrate side and the side of the movable portion, at least the conductors provided on the side where the convex portion is formed A material closer to the hardness of the material forming the convex portion. For example, the micro-mechanical device in the scope of patent application item 1, wherein, The conductors provided on the surface on the substrate side and the surface on the movable portion side are made of different materials. For example, the micromechanical device of any one of the items 1 to 3 of the scope of patent application, wherein the surface resistance of the antistatic layer is set to 10 ⁹ to 10 ¹⁴ Ω / □. For example, the micromechanical device according to any one of claims 1 to 3, wherein the resistance formed between the independent conductor and the electrode surrounding the independent conductor is set to R, and the independent The capacitance formed between the conductor and the electrode surrounding the independent conductor is set to C, the product of the resistance R and the capacitance C is set to a time constant RC, and is applied to the movable region during operation. When the vibration period of the AC voltage between the electrodes formed on the respective surfaces of the substrate and the movable portion is set to T, the time constant RC is set to a value greater than the vibration period T of the AC voltage. Surface resistance of the antistatic layer. For example, the micromechanical device according to any one of claims 1 to 3, wherein the insulator is sapphire. For example, the micromechanical device according to any one of claims 1 to 3, wherein the insulator is an alumina ceramic.