JP2007002924A - Micro valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro valve capable of preventing a fluid from leaking even if the pressure of the fluid flowing into an inflow port side internal space is low by increasing an outflow port closing force by a valve element when the valve element is not displaced by a drive means. <P>SOLUTION: This micro valve comprises a valve element forming substrate 20 having a first diaphragm part 22 forming an outflow port side internal space S2 in the clearance thereof from a valve seat forming substrate 10, the valve element 23 opening and closing an outflow port 12, and a second diaphragm part 25 forming the inflow side internal space S1 in the clearance thereof from the valve seat forming substrate 10 and a closed space forming substrate 30 forming a closed space in the clearance thereof from the valve element forming substrate 20. The micro valve further comprises a bias means in which a stress imparting film 28 laminated on the first diaphragm part 22 of the valve element forming substrate 20 and the peripheral part of the first diaphragm part 22 of a frame 21 increases the closing force when the valve element 23 is not displaced by the drive means. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microvalve that controls the flow of fluid.

  Conventionally, a microvalve that uses a structure formed by processing a semiconductor substrate such as a silicon substrate with micromachining technology as a pump that controls the flow of a small amount of fluid in the field of microelectronics or medical electronics. Have been researched and developed in various places. For example, an integrated electrostatic actuator that drives a valve body formed on a structure using electrostatic attraction has been proposed (see Patent Document 1). .

  In this type of microvalve, for example, as shown in FIG. 17 (a), a fluid inflow port 11 and an outflow port (valve port) 12 are provided in the thickness direction so as to penetrate one surface side (the upper surface on FIG. 17 (a)). The valve seat forming substrate 10 in which the valve seat 13 protrudes from the peripheral portion of the outlet 12, the frame 21 fixed to the one surface side of the valve seat forming substrate 10, and the frame 21 continuously and integrally. The first diaphragm portion 22 provided and spaced from the one surface of the valve seat forming substrate 10 and a valve body that projects from the central portion of the first diaphragm portion 22 toward the valve seat forming substrate 10 and opens and closes the outlet 12. 23 and a closed space forming substrate 30 which is fixed to the valve body forming substrate 20 on the side opposite to the valve seat forming substrate 10 side and forms a closed space 36 between the valve body forming substrate 20 and the valve body forming substrate 20. And. Here, in the above-described microvalve, the valve body forming substrate 20 is formed using a silicon substrate, and the valve seat forming substrate 10 and the closed space forming substrate 30 are each formed using a glass substrate. The body forming substrate 20 and the valve seat forming substrate 10 are fixed by anodic bonding, and the valve body forming substrate 20 and the closed space forming substrate 30 are fixed by anodic bonding.

  The above-described microvalve has an impurity diffusion layer (for example, boron at a high concentration) provided at the center of the first diaphragm portion 22 as a driving means for displacing the valve body 23 in the direction to open the outlet 12. A movable electrode 24 made of a diffused impurity diffusion layer) and a fixed electrode 31 made of a metal film provided on the closed space forming substrate 30 and facing the movable electrode 24, and is electrically connected to the movable electrode 24. When the voltage is applied between the pad 27a and the pad (not shown) electrically connected to the fixed electrode 31, the outlet 12 is caused by the electrostatic force generated between the movable electrode 24 and the fixed electrode 31. The valve body 23 is displaced in the opening direction. That is, in the above-described microvalve, the outlet 12 is closed by the valve body 23 as shown in FIG. 17A when no voltage is applied between the movable electrode 24 and the fixed electrode 31. On the other hand, when a voltage higher than the specified voltage is applied between the movable electrode 24 and the fixed electrode 31 from the drive voltage source E, the valve element 23 is moved away from the outlet 12 as shown in FIG. Displacement opens the outlet 12. In short, the above-described microvalve constitutes a normally closed type microvalve. FIG. 17A shows a state in which the fluid is introduced into the outlet side inner space S2 between the first diaphragm portion 22 and the valve seat forming substrate 10 through the inlet 11, and FIG. When the outlet 12 is opened as shown in b), the fluid introduced into the outlet-side inner space S2 through the inlet 11 flows out through the outlet 12 (in FIG. 17B). Arrows indicate fluid flow paths).

By the way, in the above-described microvalve, in a state where the outlet 12 is closed by the valve body 23, the valve body 23 is lifted by the pressure of the fluid flowing into the outlet side internal space S2 through the inlet 11, and the outlet 12 is opened. In order to prevent this, the second diaphragm portion 25 is formed on the one surface side of the frame 21 of the valve body forming substrate 20. In the closed space 36, for example, an inert gas or air is used. The pressure receiving medium made of the gas is sealed at a pressure equal to the atmospheric pressure. Accordingly, in the above-described microvalve, the valve body 23 is not displaced by the driving means, and flows into the inlet side internal space S1 between the valve seat forming substrate 10 and the second diaphragm portion 25 through the inlet 11. By receiving the pressure of the fluid, the second diaphragm portion 25 that partitions the inflow side internal space S1 and the closed space 36 is bent (deformed in a shape that protrudes toward the closed space forming substrate 30). A closing force which is a force in a direction in which 23 closes the outlet 12 is applied.
JP 2004-176802 A

  However, in the above-described microvalve, the closing force is reduced as the pressure of the fluid introduced into the inlet side internal space S1 is reduced in a state where the valve body 23 is not driven by the driving means. Depending on the pressure of the fluid flowing into the space S1, the fluid may leak through the outlet 12.

  The present invention has been made in view of the above-mentioned reasons, and the object thereof is to increase the closing force of the outlet by the valve body in a state where the valve body is not displaced by the driving means, compared to the conventional one. An object of the present invention is to provide a microvalve capable of preventing the fluid from leaking even when the pressure of the fluid flowing into the inlet side internal space is low.

  The invention according to claim 1 is formed using a semiconductor substrate and a valve seat forming substrate having a fluid inlet and outlet penetrating in the thickness direction and having a valve seat protruding from a peripheral portion of the outlet on one surface side. And a first diaphragm portion and a first diaphragm portion that are provided on the inner surface of the valve seat forming substrate and are formed inside the frame to form an outlet side inner space with the valve seat forming substrate. A second diaphragm that forms an inlet side internal space communicating with the inlet and the outlet side internal space between the valve body that protrudes from the center of the valve seat to the valve seat forming substrate side and opens and closes the outlet and the valve seat forming substrate A valve body forming substrate having a portion, a closed space forming substrate which is fixed to the valve body forming substrate on the opposite side of the valve seat forming substrate and forms the closed space between the valve body forming substrate and an outlet Drive to displace the valve body And a second diaphragm part that partitions the inlet side internal space and the closed space in a state in which the valve body is not displaced by the driving means and receives the pressure of the fluid flowing into the inlet side internal space and bends Thus, the valve body is a microvalve on which a closing force, which is a force in a direction to close the outlet, acts, and is provided with a biasing means for increasing the closing force when the valve body is not displaced by the driving means. It is characterized by that.

  According to the present invention, since the biasing means for increasing the closing force when the valve body is not displaced by the driving means is provided, the outlet of the outlet by the valve body when the valve body is not displaced by the driving means is provided. The closing force can be increased as compared with the conventional case, and it is possible to prevent the fluid from leaking even if the pressure of the fluid flowing into the inlet side internal space is low.

  According to a second aspect of the present invention, in the first aspect of the present invention, the driving means includes a movable electrode formed of an impurity diffusion layer provided in a central portion of the first diaphragm portion on the valve body forming substrate, and the closed space. A fixed electrode provided on the forming substrate and opposed to the movable electrode, and the outlet is formed by an electrostatic force generated between the movable electrode and the fixed electrode when a voltage is applied between the movable electrode and the fixed electrode. The valve body is displaced in an opening direction, and the biasing unit is configured to displace the first diaphragm portion and the first frame in the frame on the side of the valve body forming substrate facing the closed space forming substrate. The first diaphragm portion is stressed so that the closing force is increased in a state where the valve body is not displaced by the driving means, which is stacked across the periphery of the diaphragm portion of the first diaphragm portion. Characterized by comprising the stress applying film.

  According to the present invention, the bias means can be formed with high accuracy by a general semiconductor manufacturing process.

  According to a third aspect of the present invention, in the first aspect of the present invention, the biasing means is a peripheral portion of the first diaphragm portion and is formed in a concave cross section so as to approach the valve seat forming substrate side as it approaches the frame. It consists of the site | part made.

  According to the present invention, it is possible to form the bias means by appropriately designing a mask when the first diaphragm portion is formed by a semiconductor manufacturing process. Can be simplified.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the driving means is provided on the movable electrode provided in the central portion of the first diaphragm portion on the valve body forming substrate and on the closed space forming substrate. A fixed electrode opposed to the movable electrode, and when the voltage is applied between the movable electrode and the fixed electrode, the electrostatic outlet generated between the movable electrode and the fixed electrode causes the outlet to open. The valve body is displaced, and the closed space forming substrate is a first recess formed in a portion facing the first diaphragm portion and securing a displacement space of the first diaphragm portion. A gap forming recess provided with a fixed electrode on the bottom surface, and a second recess formed in a portion facing the second diaphragm portion to secure a displacement space of the second diaphragm portion, the first recess Yo A deep recess for pressure adjustment space, and a communication recess comprising a third recess for communicating the gap formation recess and the pressure adjustment space recess on the side facing the valve element forming substrate, and the bias The means is configured to reduce the depth of the portion corresponding to the peripheral portion of the second diaphragm portion in the concave portion for pressure adjustment space as compared with the depth of the portion corresponding to the central portion of the second diaphragm portion. It consists of the step protrusion protrudingly provided in the inner surface of the recessed part for adjustment space.

  According to the present invention, the bias means determines the depth of the portion corresponding to the peripheral portion of the second diaphragm portion in the concave portion for pressure adjustment space to the depth of the portion corresponding to the central portion of the second diaphragm portion. In the space corresponding to the peripheral portion of the second diaphragm portion in the recessed portion for the pressure adjustment space in the closed space. The pressure loss can be reduced, and the closing force can be increased.

  According to a fifth aspect of the present invention, in the first aspect of the invention, the driving means is provided on the valve body forming substrate at a movable electrode provided at a central portion of the first diaphragm portion and on the closed space forming substrate. A fixed electrode opposed to the movable electrode, and when the voltage is applied between the movable electrode and the fixed electrode, the electrostatic outlet generated between the movable electrode and the fixed electrode causes the outlet to open. A valve body is displaced, and the valve body forming substrate has a plurality of annular concave grooves concentrically formed on a surface of the second diaphragm portion facing the closed space forming substrate, and the closed space The forming substrate is a first recess that is formed in a portion facing the first diaphragm portion and secures a displacement space of the first diaphragm portion, and a gap forming recess provided with a fixed electrode on the inner bottom surface. When, A second concave portion that is formed in a portion facing the second diaphragm portion and secures a displacement space of the second diaphragm portion and is deeper than the first concave portion, and the valve body formation A communication recess composed of a third recess for communicating the gap forming recess and the pressure adjusting space recess on the side facing the substrate, and the biasing means is provided on each inner bottom surface of the pressure adjusting space recess. It is characterized by comprising a plurality of small protrusions projecting from each part facing each of the concave grooves.

  According to this invention, the plurality of annular concave grooves are formed concentrically on the surface of the second diaphragm portion facing the closed space forming substrate, so that the second diaphragm portion has a flat plate shape. Compared with the case of forming the shape, the bias means is composed of a plurality of small protrusions projecting from the respective portions facing the respective concave grooves on the inner bottom surface of the pressure adjusting space concave portion. Pressure loss in the space formed between the second diaphragm portion and the pressure adjusting space recess in the closed space can be reduced, and the closing force can be increased.

  According to a sixth aspect of the present invention, in the first aspect of the invention, the bias means is a flow path formed between the outlet side internal space and the inlet side internal space, and the outlet side internal space. It is characterized by comprising a pressure adjusting flow path that causes a pressure loss so that the pressure of the gas is lower than the pressure in the inlet side internal space.

  According to this invention, since the pressure in the outlet side internal space is lower than the pressure in the inlet side internal space in a state where the valve element is not displaced by the driving means, The relative pressure of the closed space with respect to the pressure can be increased, and the closing force can be increased.

  According to a seventh aspect of the present invention, in the first aspect of the present invention, the bias means is made of a gas sealed in the closed space at a pressure higher than atmospheric pressure.

  According to the present invention, the closing force can be increased by appropriately setting the pressure of the gas sealed in the closed space during manufacturing.

  According to an eighth aspect of the present invention, in the first aspect of the present invention, the driving means is provided on a movable electrode provided at a central portion of the first diaphragm portion in the valve body forming substrate and on the closed space forming substrate. A fixed electrode opposed to the movable electrode, and when the voltage is applied between the movable electrode and the fixed electrode, the electrostatic outlet generated between the movable electrode and the fixed electrode causes the outlet to open. The valve body is displaced, and the closed space forming substrate is a first recess formed in a portion facing the first diaphragm portion and securing a displacement space of the first diaphragm portion. A gap forming recess provided with a fixed electrode on the bottom surface, and a second recess formed in a portion facing the second diaphragm portion to secure a displacement space of the second diaphragm portion, the first recess Yo A deep recess for pressure adjustment space, a communication recess comprising a third recess for communicating the gap formation recess and the pressure adjustment space recess on the side facing the valve element forming substrate, and the valve element forming substrate Forming a wiring formed on the inner bottom surface of the groove formed continuously on the gap forming concave portion on the opposite surface side to connect the fixed electrode and the pad provided on the portion not overlapping the valve body forming substrate An air passage formed by the wiring forming groove in a state in which the valve body forming substrate and the closed space forming substrate are fixed to each other, and the biasing means includes the closed space. It is characterized by comprising a gas sealed at a pressure higher than atmospheric pressure.

  According to the present invention, the closing force can be increased by appropriately setting the pressure of the gas sealed in the closed space during manufacturing. In addition, there is an advantage that the manufacturing is facilitated as compared with a case where a through-hole that communicates between the closed space and the outside is separately formed for pressure-sealing the closed space.

  In the first aspect of the invention, the closing force of the outlet by the valve body in a state where the valve body is not displaced by the driving means can be increased as compared with the conventional one, and the pressure of the fluid flowing into the inlet side internal space is low. However, there is an effect that the fluid can be prevented from leaking.

(Embodiment 1)
Hereinafter, the microvalve of the present embodiment will be described with reference to FIGS. The microvalve of this embodiment can be used by being provided on a supply path for liquid fuel (for example, methanol, pure water, aqueous methanol solution, etc.) to a small fuel cell or fuel reformer, for example. It can be used for other purposes. In the microvalve of this embodiment, an inflow port 11 and an outflow port (valve port) 12 for a fluid (for example, liquid fuel) are provided in the thickness direction, and the outflow port 12 is formed on one surface (upper surface in FIG. 1). A valve seat forming substrate 10 having a valve seat 13 projecting from its peripheral portion, a frame 21 fixed to the one surface side of the valve seat forming substrate 10, and a valve seat forming substrate 10 provided continuously and integrally inside the frame 21. The valve body forming board which has the valve body 23 which protrudes from the center part of the 1st diaphragm part 22 and the 1st diaphragm part 22 which were spaced apart from the said one surface of this to the valve seat formation board | substrate 10 side, and opens and closes the outflow port 12 20 and a closed space forming substrate 30 which is fixed to the valve body forming substrate 20 opposite to the valve seat forming substrate 10 side and forms a closed space 36 between the valve body forming substrate 20 and the valve body forming substrate 20. Here, in the microvalve of this embodiment, the valve body forming substrate 20 is formed by using a low impurity concentration p-type silicon substrate 200 (see FIG. 7A), and the valve seat forming substrate 10 is made of Pyrex. The first glass substrate 100 made of (registered trademark) (see FIG. 9A), and the closed space forming substrate 30 is also made of a second glass substrate 300 made of Pyrex (registered trademark) (FIG. 10 ( a), the valve body forming substrate 20 and the valve seat forming substrate 10 are fixed by anodic bonding, and the valve body forming substrate 20 and the closed space forming substrate 30 are anodic bonded. It is fixed. The p-type silicon substrate 200 is a p-type silicon substrate having a main surface of (100). In the present embodiment, the silicon substrate 200 constitutes a semiconductor substrate serving as the basis of the valve body forming substrate 20.

  The microvalve of the present embodiment is a high-concentration impurity diffusion layer (for example, provided in the center of the first diaphragm portion 22 as a driving means for displacing the valve body 23 in the direction to open the outlet 12. A movable electrode 24 made of an impurity diffusion layer in which boron is diffused at a high concentration) and a metal film (for example, a laminated film of a platinum film and a chromium thin film) provided on the closed space forming substrate 30 and facing the movable electrode 24. A fixed electrode 31, which is movable when a voltage is applied between a pad 27 a electrically connected to the movable electrode 24 and a pad 37 a (see FIG. 5) electrically connected to the fixed electrode 31. The valve body 23 is displaced in the direction to open the outlet 12 by the electrostatic force generated between the electrode 24 and the fixed electrode 31. That is, the basic operation principle of the microvalve of the present embodiment is the same as that of the conventional example shown in FIG. 17, and in the state where no voltage is applied between the movable electrode 24 and the fixed electrode 31, the valve body 23 As a result, the outlet 12 is closed. On the other hand, when a voltage higher than the specified voltage is applied between the movable electrode 24 and the fixed electrode 31 from the drive voltage source E (see FIG. 17B), the valve body 23 is displaced in a direction away from the outlet 12. Thus, the outlet 12 is opened. In short, the microvalve of the present embodiment constitutes a normally closed type microvalve. The material of the metal film constituting the fixed electrode 31 is not limited to platinum or chromium, and for example, aluminum, nickel, titanium, tungsten, gold, or the like may be employed.

  Moreover, in the microvalve of this embodiment, in the state where the outflow port 12 is closed by the valve body 23, the outflow side internal space S <b> 2 between the valve seat forming substrate 10 and the first diaphragm portion 22 through the inflow port 11. In order to prevent the valve body 23 from being lifted due to the pressure of the fluid that has flowed into the outlet and opening the outlet 12, a second diaphragm portion 25 is formed on the one surface side of the frame 21 of the valve body forming substrate 20. In the closed space 36, for example, a pressure receiving medium made of a gas such as an inert gas or air is sealed at a pressure equal to the atmospheric pressure. Therefore, in the microvalve of the present embodiment, the inlet 23 is located in the inlet-side inner space S1 between the valve seat forming substrate 10 and the second diaphragm portion 25 through the inlet 11 while the valve body 23 is not displaced by the driving means. In response to the pressure of the fluid that has flowed in, the second diaphragm portion 25 that partitions the inlet-side inner space S1 and the closed space 36 bends (deforms so as to protrude toward the closed space forming substrate 30). A closing force that is a force in a direction in which the valve body 23 closes the outlet 12 is applied.

  On one surface of the valve seat forming substrate 10 described above, a channel recess 15 serving as a fluid channel is formed between the inlet 11 and the outlet 12 so as to surround the inlet 11 and the outlet 12. The inlet side internal space S1 and the outlet side internal space S2 communicate with each other. Here, the opening shape of the inflow port 11 and the outflow port 12 is circular, and the inner peripheral shape of the recess 15 for flow paths is rectangular. In addition, the above-described valve seat 13 is formed continuously and integrally on the peripheral portion of the outlet 12 in the valve seat forming substrate 10 so as to protrude from the inner bottom surface of the flow path recess 15. For example, a metal thin film (for example, a chromium thin film) that prevents the valve body 23 and the valve seat 13 from being bonded when the frame 21 of the valve body forming substrate 20 and the valve seat forming substrate 10 are fixed together by anodic bonding. ) Is formed.

  The valve body forming substrate 20 is formed by processing the above-described silicon substrate 200 by a micromachining technique. Specifically, the valve body forming board 20 uses a lithography technique, an etching technique, and the like, and the valve body 23 is the first one. It is supported by the frame 21 via the diaphragm portion 22. The valve body 23 has an octagonal cross-sectional shape perpendicular to the thickness direction of the valve seat forming substrate 10, and the cross-sectional area gradually decreases as the valve body 23 moves away from the first diaphragm portion 22 (closer to the valve seat 13). . The valve body forming substrate 20 has a high concentration impurity diffusion layer (for example, an impurity diffusion layer in which boron is diffused at a high concentration) 204 formed on one surface side opposite to the valve seat formation substrate 10 side. A portion of the impurity diffusion layer 204 formed at the center of the first diaphragm portion 22 constitutes the movable electrode 24. The first diaphragm portion 22 has a corrugated plate-shaped cross section that intersects in the circumferential direction, and a plurality of annular concave grooves 22a are concentrically formed on the side facing the closed space forming substrate 30. Is formed. The second diaphragm portion 25 also has a corrugated plate-like cross section that intersects in the circumferential direction, and a plurality of annular concave grooves 25a are concentrically formed on the side facing the closed space forming substrate 30. Is formed. Thus, by making each diaphragm part 22 and 25 into a cross-sectional corrugated shape, it can be made to bend easily compared with the case where each diaphragm part 22 and 25 is formed in the shape of a flat plate, respectively.

  The pad 27a electrically connected to the movable electrode 24 is provided on the closed space forming substrate 30 together with the pad 37a electrically connected to the fixed electrode 31, and the movable electrode 24 is formed of an impurity diffusion layer. It is electrically connected to the pad 27a through a part of 204 and a metal wiring 26a that is continuously and integrally formed on the pad 27a in the closed space forming substrate 30.

  In addition, the outer peripheral shape of the closed space forming substrate 30 is formed in a rectangular shape, but the long side dimension (so that the pads 27a and 37a described above are exposed in a state of being fixed to the valve body forming substrate 20). The dimension in the left and right direction in FIG. 1A is set to be longer than the dimension of the long side of the valve body forming substrate 20 (the dimension in the left and right direction in FIG. 1A). Here, the closed space forming substrate 30 is fixed to the peripheral portion of the valve body forming substrate 20 by anodic bonding. The surface facing the valve body forming substrate 20 in the Heisei space forming substrate 30 is a groove formed continuously with the gap forming recess 33 and does not overlap the fixed electrode 31 and the valve body forming substrate 20. A wiring forming groove 38 (see FIG. 5B and FIG. 6) provided on the inner bottom surface is formed with a wiring 39a made of a metal wiring connecting the provided pad 37a, and the valve body forming substrate 20 is closed. The air passage formed by the wiring forming groove 38 in a state in which the space forming substrate 30 is fixed is a sealing portion 40 (FIG. 11C) made of resin (for example, silicone resin, epoxy resin, etc.) as described later. ))).

  On the surface of the closed space forming substrate 30 facing the valve body forming substrate 20, a displacement space of the valve body 23 in the thickness direction of the valve seat forming substrate 10 is secured at a portion facing the first diaphragm portion 22. A gap forming recess 33, which is one recess, is formed, and a fixed electrode 31 made of the above-described metal film is formed on the inner bottom surface of the gap forming recess 33. Further, the gap forming recess 33 is opened in a circular shape. When the frame 21 of the valve body forming substrate 20 and the closed space forming substrate 30 are fixed to the closed space forming substrate 30 by anodic bonding, the inner bottom surface of the gap forming recess 33 and the first diaphragm portion are used. A groove 41 deeper than the gap-forming recess 33 is also formed in order to prevent bonding with the groove 22.

  Further, a portion of the closed space forming substrate 30 facing the valve element forming substrate 20 is a second recess that secures a displacement space of the second diaphragm portion 25 at a portion facing the second diaphragm portion 25. A pressure adjusting space recess 34 deeper than the first recess is formed, and the frame 21 of the valve body forming substrate 20 and the closed space forming substrate 30 are anodic bonded to the inner bottom surface of the pressure space recess 34. A bonding prevention film made of a metal film (for example, a laminated film of a platinum film and a chromium film) that prevents the second diaphragm portion 25 and the inner bottom surface of the pressure adjusting space concave portion 34 from being bonded when fixed. 32 is formed. Here, the pressure adjusting space recess 34 is opened in a circular shape.

  In addition, the closed space forming substrate 30 is formed with a communication recessed portion 35 including a third recessed portion that allows the gap forming recessed portion 33 and the pressure adjusting space recessed portion 34 to communicate with each other on the surface facing the valve body forming substrate 20. ing. Here, the closed space forming substrate 30 and the valve body formation are formed in a state where the closed space forming substrate 30 and the valve body forming substrate 20 are fixed by providing the recessed portions 33, 34, and 35 in the closed space forming substrate 30. The above-described pressure receiving medium is sealed in the closed space 36 formed between the substrates 20.

  Therefore, also in the microvalve of the present embodiment, the closed space 36 receives the pressure of the fluid flowing into the inlet side internal space S1 between the valve seat forming substrate 10 and the second diaphragm portion 25 through the inlet 11. When the second diaphragm portion 25 is deformed so as to reduce the volume (bends in a convex shape toward the closed space forming substrate 30), the pressure receiving medium in the closed space 36 is compressed and pressure is increased. Since a closing force that is a force in the direction in which the valve body 23 closes the outlet 12 (that is, the direction in which the valve body 23 is pushed down) is applied, no voltage is applied between the movable electrode 24 and the fixed electrode 31. Then, the 2nd diaphragm part 25 deform | transforms similarly to Fig.17 (a), and the outflow port 12 is closed by the valve body 23. FIG. On the other hand, if a voltage higher than a specified voltage required for the valve body 23 to open the outlet 12 against the closing force is applied between the movable electrode 24 and the fixed electrode 31, the movable electrode 24 and Since the first diaphragm portion 22 is bent and the outlet 12 is opened so that the movable electrode 24 approaches the fixed electrode 31 by the electrostatic force generated between the fixed electrode 31 and the fluid, the fluid flows. If the stroke amount of the valve body 23 is set to about several μm, even a fluid with good responsiveness and high viscosity can control a small amount of fluid of several μl / min level with high accuracy and high speed. Moreover, since the stroke amount of the valve body 23 is small, the outlet 12 can be opened and closed by applying a voltage of about several volts.

By the way, in the microvalve of the present embodiment, as the biasing means for increasing the closing force when the valve body 23 is not displaced by the driving means, the valve body forming substrate 20 is opposed to the closed space forming substrate 30. The first diaphragm portion 22 and the peripheral portion of the first diaphragm portion 22 in the frame 21 are stacked so as to increase the closing force in a state where the valve body 23 is not displaced by the driving means. A stress applying film 28 for applying stress to the diaphragm portion 22 is provided, and a compressive stress is applied to the first diaphragm portion 22 where tensile stress is applied when the stress applying film 28 is not provided. Here, the peripheral portion of the stress applying film 28 overlaps a portion where the thickness of the frame 21 is constant. In this embodiment, the stress applying film 28 is composed of a silicon oxide film deposited by a plasma CVD method using TEOS (Si (OC ₂ H ₅ ) ₄ ) and O ₂ as source gases. For example, the silicon oxide film may be formed of a silicon nitride film deposited by a CVD method. The film thickness when the above-described silicon oxide film is used as the stress applying film 28 may be set to about 1 μm, for example, and the film thickness when the above-described silicon nitride film is used as the stress applying film 28 is, for example, about 120 nm. Should be set.

  Hereinafter, each of the valve body forming substrate 20, the valve seat forming substrate 10, and the closed space forming substrate 30 will be described individually with respect to the microvalve manufacturing method of the present embodiment.

  First, a method for forming the valve body forming substrate 20 will be described with reference to FIGS.

  By forming silicon oxide films 201 and 202 by pyrogenic oxidation on the main surface side (upper surface side in FIG. 7A) and back surface (lower surface side in FIG. 7A) of the above-described silicon substrate 200, FIG. The structure shown in (a) is obtained. In the pyrogenic oxidation process, for example, if the oxidation temperature is 1100 ° C. and the oxidation time is 145 minutes, the thickness of each of the silicon oxide films 201 and 202 is about 1000 nm. It is not limited.

  Thereafter, in order to expose the portions of the silicon substrate 200 corresponding to the concave grooves 22a and 25a of the diaphragm portions 22 and 25, the diaphragms are formed on the silicon oxide film 201 on the main surface side of the silicon substrate 200. After forming a first resist layer (not shown) in which portions corresponding to the concave grooves 22a and 25a of the portions 22 and 25 are opened, the main surface of the silicon substrate 200 using the first resist layer as a mask The silicon oxide film 201 is patterned by dry etching the silicon oxide film 201 on the side, and then the first resist layer is removed to obtain the structure shown in FIG. 7B.

Then, using the patterned silicon oxide film 201 as a mask, the main surface of the silicon substrate 200 is etched by isotropic etching using a hydrofluoric acid-based chemical (for example, HF: HNO ₃ : CH ₃ COOH = 1: 3: 8). By forming the concave grooves 22a and 25a, the structure shown in FIG. 7C is obtained. In addition, although the depth of each concave groove 22a, 25a is set to 25 micrometers, this value does not specifically limit.

  Thereafter, the silicon oxide film 202 on the back surface side of the silicon substrate 200 is covered with a second resist layer (not shown), and then the silicon oxide film 201 on the main surface side of the silicon substrate 200 is removed by etching. By removing the resist layer 2, the structure shown in FIG. 7D is obtained.

  Thereafter, boron is solid-phase diffused on the main surface side of the silicon substrate 200 to form a high-concentration impurity diffusion layer 204, and a silicon oxide film 205 is formed on the surface side of the impurity diffusion layer 204, whereby FIG. The structure shown in (e) is obtained. In the solid phase diffusion process, for example, if the diffusion temperature is 1125 ° C. and the diffusion time is 12 hours, the thickness of the silicon oxide film 205 is about 400 nm.

  Thereafter, a third resist layer (not shown) patterned to form the respective diaphragm portions 22 and 25 is formed on the silicon oxide film 202 on the back surface side of the silicon substrate 200, and then the third resist is formed. The silicon oxide film 202 on the back surface side of the silicon substrate 200 is dry-etched using the layer as a mask to pattern the silicon oxide film 202, and then the third resist layer is removed, and then the main surface of the silicon substrate 200 is removed. The structure shown in FIG. 7F is obtained by etching away the silicon oxide film 205 on the side.

Thereafter, a silicon oxide film 208 serving as a basis for the stress applying film 28 is formed on the main surface side of the silicon substrate 200 by a plasma CVD method using TEOS (Si (OC ₂ H ₅ ) ₄ ) and O ₂ as source gases. By depositing, the structure shown in FIG.

  Thereafter, a chromium film 209 is formed on the silicon oxide film 208 on the main surface side of the silicon substrate 200 to obtain the structure shown in FIG.

  Thereafter, a fourth resist layer (not shown) patterned to form a stress applying film 28 having a desired pattern is formed on the chromium film 209 on the main surface side of the silicon substrate 200, and then the fourth resist layer is formed. The chromium film 209 is patterned by etching the resist film as a mask, and then the fourth resist layer is removed to obtain the structure shown in FIG. 8B.

  Then, after the dicing, the first diaphragm portion 22 is etched by etching the silicon substrate 200 from the back side to a depth reaching the impurity diffusion layer 204 using the patterned silicon oxide film 202 on the back side of the silicon substrate 200 as a mask. And the structure shown in FIG.8 (c) is obtained by forming the 2nd diaphragm part 25. FIG. As a chemical solution in this etching step, for example, by using a solution of EPW (ethylenediamine pyrocatechol), the impurity diffusion layer 204 in which boron is diffused at a high concentration can be used as an etching stopper layer, and each diaphragm portion 22, 25 is constituted by a part of the impurity diffusion layer 204, and can be prevented from becoming too thick or too thin. The central portion of the first diaphragm portion 22 constitutes the movable electrode 24.

  Thereafter, unnecessary portions of the silicon oxide film 208 are wet-etched using the patterned chromium film 209 as a mask to form the stress applying film 28 made of the remaining silicon oxide film 202, and then the chromium film 209 is removed. Thus, the valve body forming substrate 20 having the structure shown in FIG. 8D is obtained.

  Next, a method for forming the valve seat forming substrate 10 will be described with reference to FIG.

  First, after a chromium film 101 is formed on the entire surface of one surface side of the first glass substrate 100 (the upper surface side in FIG. 9A) by sputtering or the like, a flow path is formed on the one surface of the first glass substrate 100. After forming a patterned fifth resist layer (not shown) to form the concave portion 15 and the valve seat 13, the chromium film 101 is etched by using the fifth resist layer as a mask. Then, the fifth resist layer is removed to obtain the structure shown in FIG.

  Then, using the patterned chromium film 101 as a mask, a flow path recess 15 is formed on the one surface of the first glass substrate 100 using a hydrofluoric acid chemical (for example, BHF, HF having a concentration of 50%). After the formation, the chromium film 101 is removed to obtain the structure shown in FIG.

  Then, the structure shown in FIG.9 (c) is obtained by forming the inflow port 11 and the outflow port 12 which penetrate the 1st glass substrate 100 in the thickness direction by drilling.

  Thereafter, a chromium film 104 serving as the basis of the above-described bonding prevention film 14 is formed on the one surface side of the first glass substrate 100 by a sputtering method or the like, thereby obtaining the structure shown in FIG.

  Thereafter, a sixth resist layer (not shown) patterned to form the bonding prevention film 14 is formed on the chromium film 104 on the one surface side of the first glass substrate 100, and then the sixth resist layer is formed. The unnecessary portion of the chromium film 104 is wet-etched using the resist layer as a mask to form the bonding prevention film 14 made of the remaining chromium film 104, and then the sixth resist layer is removed and then dicing is performed. Thus, the valve seat forming substrate 10 having the structure shown in FIG. 9E is obtained.

  Next, a method for forming the closed space forming substrate 30 will be described with reference to FIG.

  First, a chromium film 301 is formed on the entire surface of one surface side of the second glass substrate 300 (the upper surface side in FIG. 10A) by sputtering, and then pressure adjustment is performed on the one surface of the second glass substrate 300. After the seventh resist layer 301 patterned to form the space recess 34 and the groove 41 is formed, the chromium film 301 is patterned by etching the chromium film 301 using the seventh resist layer 302 as a mask. As a result, the structure shown in FIG.

  Then, using the patterned chromium film 301 as a mask, a pressure adjusting space concave portion 34 and a groove portion are formed on the one surface of the second glass substrate 300 using a hydrofluoric acid chemical (for example, HF having a concentration of 50%). By forming 41, the structure shown in FIG.

  Thereafter, a chromium film 303 is formed on the entire surface of the second glass substrate 300 on the one surface side by a sputtering method or the like, thereby obtaining the structure shown in FIG.

  Thereafter, an eighth resist layer (not shown) patterned to form the gap forming recess 33 and the communication recess 35 is formed on the chromium film 303 on the one surface side of the second glass substrate 300. Then, using the eighth resist layer as a mask, unnecessary portions of the chromium film 303 are etched to pattern the chromium film 303, and then the eighth resist layer is removed to obtain the structure shown in FIG. Get the structure shown.

  Thereafter, the gap forming recess 33 and the communication recess 35 are formed on the one surface of the second glass substrate 300 using the patterned chromium film 303 as a mask, and then the chromium film 303 is removed to remove the chromium film 303 as shown in FIG. The structure shown in e) is obtained.

  Thereafter, a fixed electrode 31 and a bonding prevention film 32 made of a laminated film of a platinum film and a chromium film are formed by sputtering using a metal mask, and then dicing is performed, as shown in FIG. A closed space forming substrate 30 having a structure is obtained.

  Next, when forming a microvalve with the above-described valve body forming substrate 20, the valve seat forming substrate 10, and the closed space forming substrate 30, as shown in FIG. And the closed space forming substrate 30 are overlapped, and then heated to a first predetermined temperature (for example, 400 ° C.) in a vacuum to form a closed space between the valve body forming substrate 20 and the closed space forming substrate 30. A first predetermined voltage (for example, 600 V) is applied from the DC voltage source E1 with the formation substrate 30 at the low potential side, and then anodically bonded. Thereafter, as shown in FIG. After the valve seat forming substrate 10 is overlaid, the valve seat forming substrate 10 is heated between the valve body forming substrate 20 and the valve seat forming substrate 10 by heating to a second predetermined temperature (for example, 400 ° C.) in a vacuum. As the low potential side, a second predetermined voltage (from the DC voltage source E2) For example, 600V) is applied to perform anodic bonding. Subsequently, as shown in FIG. 11C, the air passage formed by the above-described wiring forming groove 38 is made of resin (for example, silicone resin, The sealing portion 40 is formed by sealing with an epoxy resin or the like.

  In the microvalve of the present embodiment described above, the biasing means for increasing the closing force when the valve body 23 is not displaced by the driving means is provided, so that the valve body 23 is not displaced by the driving means. The closing force of the outlet 12 by the valve body 23 can be increased as compared with the prior art, and the fluid can be prevented from leaking even if the pressure of the fluid flowing into the inlet side internal space S1 is low. Further, since the bias means is composed of the stress applying film 28, the bias means can be formed with high accuracy by a general semiconductor manufacturing process.

(Embodiment 2)
By the way, in the first embodiment, the stress applying film 28 described above constitutes a bias unit that increases the closing force in a state where the valve element 23 is not displaced by the driving unit, but in the microvalve of the present embodiment, As shown in FIG. 12, a portion 22b which is a peripheral portion of the first diaphragm portion 22 and is formed in a concave shape so as to approach the valve seat forming substrate 10 side as it approaches the frame 21, is driven by a valve body 23 by a driving means. Biasing means for increasing the closing force in a state in which is not displaced is configured. Further, in the present embodiment, when the frame 21 of the valve body forming substrate 20 and the closed space forming substrate 30 are fixed by anodic bonding, the movable electrode 24 and the fixed electrode 31 are not bonded to each other so that the movable electrode 24 and the fixed electrode 31 are not bonded. A bonding prevention film 29 is formed on the surface facing 31. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  Thus, in the microvalve of the present embodiment, a portion 22b that is formed in a concave section so as to approach the valve seat forming substrate 10 side as it approaches the frame 21 in the peripheral portion of the first diaphragm portion 22 is provided. Thus, the valve body 23 is moved to the valve seat forming substrate 10 side as compared with the case where the portion 22b is not provided in the first diaphragm portion 22 constituted by a part of the impurity diffusion layer 204 described in the first embodiment. The force in the direction of pushing down acts. In forming the valve body forming substrate 20 in the present embodiment, in the method for forming the valve body forming substrate 20 described in the first embodiment, the shape of the mask when forming the concave grooves 22a and 25a may be changed. In short, in the microvalve of the present embodiment, it is possible to form a bias means by appropriately designing a mask for forming the first diaphragm portion 22 and the second diaphragm portion 25 by a semiconductor manufacturing process. Compared to the first embodiment, the manufacturing process can be simplified.

(Embodiment 3)
The basic configuration of the microvalve of the present embodiment is substantially the same as that of the first embodiment, and the biasing means for increasing the closing force when the valve body 23 is not displaced by the driving means is shown in FIG. For the pressure adjusting space, the depth of the portion corresponding to the peripheral portion of the second diaphragm portion 25 in the concave portion for adjusting space 34 is made smaller than the depth of the portion corresponding to the central portion of the second diaphragm portion 25. It is different in that it is constituted by a step projection 34b projecting from the inner surface of the recess 34. Further, in the present embodiment, when the frame 21 of the valve body forming substrate 20 and the closed space forming substrate 30 are fixed by anodic bonding, the movable electrode 24 and the fixed electrode 31 are not bonded to each other so that the movable electrode 24 and the fixed electrode 31 are not bonded. A bonding prevention film 29 is formed on the surface facing 31. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  Therefore, in the microvalve of the present embodiment, the depth of the portion corresponding to the peripheral portion of the second diaphragm portion 25 in the concave portion 34 for pressure adjustment space is set to the depth of the portion corresponding to the central portion of the second diaphragm portion 25. Since the step projection 34b that is shallower than the height is provided on the inner surface of the pressure adjusting space recess 34, the volume of the closed space 36 can be reduced as compared with the case where the step projection 34b is not provided. The space corresponding to the peripheral portion of the second diaphragm portion 25 in the closed space 36 is narrowed when the diaphragm portion 25 is bent toward the inner bottom surface side of the pressure adjusting space recess 34 by the pressure in the inlet side internal space S1. Therefore, pressure loss in the space corresponding to the peripheral portion of the second diaphragm portion 25 in the pressure adjusting space recess 34 in the closed space 36 can be reduced, and the closing force can be increased. Kill.

  In addition, since the above-mentioned step protrusion 34b can be formed by changing the shape of the mask in the method for forming the closed space forming substrate 30 described in the first embodiment, the manufacturing process is not complicated.

(Embodiment 4)
The basic configuration of the microvalve of the present embodiment is substantially the same as that of the third embodiment, and the biasing means for increasing the closing force when the valve body 23 is not displaced by the driving means is the same as that described in the third embodiment. Instead of the projections 34b, as shown in FIG. 14, a plurality of small projections 34a projecting from the respective portions facing the respective concave grooves 25a of the second diaphragm portion 25 on the inner bottom surface of the pressure adjusting space concave portion 34. The only difference is the construction. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 3, and description is abbreviate | omitted.

  Thus, in the microvalve of the present embodiment, the bias means has a plurality of small protrusions protruding from the respective portions facing the respective concave grooves 25a of the second diaphragm portion 25 on the inner bottom surface of the pressure adjusting space concave portion 34. Since the projection 34a is formed, the volume of the closed space 36 can be reduced as compared with the case where each of the small projections 34a is not provided, and the pressure adjusting space recess 34 of the closed space 36 is located between the second diaphragm portion 25. Pressure loss in the formed space can be reduced, and the closing force can be increased.

(Embodiment 5)
The basic configuration of the microvalve of the present embodiment is substantially the same as that of the first embodiment. In the first embodiment, the inner peripheral shape of the channel recess 15 provided on the one surface of the valve seat forming substrate 10 is the inlet 11. 15 and the outflow port 12, the flow path recess 15 formed on the one surface of the valve seat forming substrate 10 has a shape as shown in FIG. Is different. Since other configurations are the same as those in the first embodiment except that the stress applying film 28 described in the first embodiment is not provided, illustration and description thereof are omitted.

  The channel recess 15 formed in the valve seat forming substrate 10 in the present embodiment includes an outlet-side recess 15b that surrounds the outlet 12 and has a rectangular inner peripheral shape, and an inner peripheral shape that surrounds the inlet 11 and is rectangular. The inlet-side recess 15a, the outlet-side recess 15b and the inlet-side recess 15a are connected to each other and are formed between the outlet-side inner space S2 and the inlet-side inner space S1. The pressure adjusting recess 15c is used to form a pressure adjusting flow path that causes a pressure loss so that the pressure in the internal space S2 is lower than the pressure in the inlet side internal space S1. The pressure adjusting recess 15c is formed in a zigzag shape. In order to form such a channel recess 15, the shape of the mask when the channel recess 15 is formed in the method for forming the valve seat forming substrate 10 described in the first embodiment may be changed.

  Thus, in the microvalve of the present embodiment, the biasing means for increasing the closing force when the valve body 23 is not displaced by the driving means is used as the outflow side internal space S2 and the inflow side internal part described in the first embodiment. A flow path formed between the space S1 and a pressure adjusting flow path that causes a pressure loss so that the pressure in the outlet side internal space S2 is lower than the pressure in the inlet side internal space S1. Therefore, the pressure in the outlet side internal space S2 is lower than the pressure in the inlet side internal space S1 when the valve body 23 is not displaced by the driving means. The relative pressure of the closed space 36 with respect to the can be increased, and the closing force can be increased.

(Embodiment 6)
The basic configuration of the microvalve of this embodiment is substantially the same as that of the first embodiment, and a closed space is formed as shown in FIG. 16 without providing the stress applying film 28 provided as the bias means in the first embodiment. The substrate 30 is provided with a through hole 42 penetrating in the thickness direction, and the pressure receiving medium made of a gas such as dry air is higher than the atmospheric pressure by a specified pressure (for example, about 5 kPa to 50 kPa) in the closed space 36. A characteristic is that the gas enclosed in the closed space 36 at a pressure higher than atmospheric pressure constitutes the bias means. Further, in the present embodiment, when the frame 21 of the valve body forming substrate 20 and the closed space forming substrate 30 are fixed by anodic bonding, the movable electrode 24 and the fixed electrode 31 are not bonded to each other so that the movable electrode 24 and the fixed electrode 31 are not bonded. A bonding prevention film 29 is formed on the surface facing 31. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  In the present embodiment, in order to seal the space to be the closed space 36 in a pressurized state, the valve body forming substrate 20 and the closed space forming substrate 30 are fixed by anodic bonding, and the valve body forming substrate 20 and the valve seat are fixed. After fixing the forming substrate 10 by anodic bonding, the through hole 42 of the closed space forming substrate 20 and the wiring forming groove described in the first embodiment in a pressurized container in which the internal space is pressurized with dry air. 38 may be sealed with resin or the like.

  Therefore, in the microvalve of the present embodiment, the closing force can be increased by appropriately setting the pressure of the gas sealed in the closed space 36 during manufacture.

  In the present embodiment, both the through hole 42 and the wiring forming groove 38 are used as a ventilation path for pressurizing the space that becomes the closed space 36. However, the through hole 42 and the wiring are used as the ventilation path. It is sufficient if at least one of the formation grooves 38 is formed, and if only the wiring formation groove 38 is formed as a ventilation path, that is, if the wiring formation groove 38 is also used as a ventilation path. There is an advantage that manufacture is facilitated as compared to the case where the above-described through hole 42 that communicates between the closed space 36 and the outside in order to seal the closed space 36 under pressure is formed separately.

1 is a schematic cross-sectional view showing a first embodiment. The valve body formation board | substrate in the same as the above is shown, (a) is a schematic plan view, (b) is a schematic sectional view, (c) is a schematic bottom view. The valve body formation board | substrate in the same as the above is shown, (a) is the schematic perspective view seen from upper direction, (b) is the schematic perspective view seen from the downward direction. The valve seat formation board | substrate in the same as the above is shown, (a) is a schematic perspective view seen from the top, (b) is a schematic sectional drawing, (c) is a schematic perspective view seen from the bottom. The closed space formation board | substrate in the same as the above is shown, (a) is a schematic perspective view seen from the top, (b) is a schematic sectional drawing, (c) is a schematic perspective view seen from the downward direction. It is a schematic sectional drawing same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of the valve body formation board | substrate in the same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of the valve body formation board | substrate in the same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of the valve seat formation board | substrate in the same as the above. It is principal process sectional drawing for demonstrating the manufacturing method of the board | substrate for closed space formation same as the above. It is explanatory drawing of a manufacturing method same as the above. FIG. 6 is a schematic cross-sectional view showing a second embodiment. FIG. 6 is a schematic cross-sectional view showing a third embodiment. FIG. 6 is a schematic cross-sectional view showing a fourth embodiment. It is a schematic plan view of the valve seat formation board in Embodiment 5. FIG. 9 is a schematic cross-sectional view showing a sixth embodiment. It is operation | movement explanatory drawing of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Valve seat formation board 11 Inflow port 12 Outlet 13 Valve seat 15 Recess for flow path 20 Valve body formation board 21 Frame 22 1st diaphragm part 23 Valve body 24 Movable electrode 25 2nd diaphragm part 28 Stress application film | membrane 30 Closure Space forming substrate 31 Fixed electrode 36 Closed space S1 Inlet side internal space S2 Outlet side internal space

Claims (8)

  A valve seat forming substrate having a fluid inlet and outlet penetrating in the thickness direction and having a valve seat protruding from the periphery of the outlet on one surface side, and a valve seat forming substrate formed using a semiconductor substrate Forming a valve seat from the frame fixed to the one surface side and the center part of the first diaphragm part and the first diaphragm part that forms an outlet side internal space provided between the frame and the valve seat forming substrate provided inside the frame A valve body forming substrate having a second diaphragm portion that forms an inflow port side internal space communicating with the inflow port and the outflow port side internal space between the valve body that protrudes toward the substrate side and opens and closes the outflow port and the valve seat forming substrate And a closed space forming substrate which is fixed to the valve body forming substrate on the opposite side of the valve seat forming substrate and forms the closed space between the valve body forming substrate and the valve body is displaced in a direction to open the outlet. Drive means When the valve body is not displaced by the step, the second diaphragm portion that partitions the inlet side internal space and the closed space receives the pressure of the fluid flowing into the inlet side internal space and bends to cause the valve body to flow. A microvalve on which a closing force, which is a force in a direction to close the outlet, acts, and is provided with biasing means for increasing the closing force when the valve body is not displaced by the driving means. valve.   The driving means includes a movable electrode made of an impurity diffusion layer provided at a central portion of the first diaphragm portion in the valve body forming substrate, a fixed electrode provided on the closed space forming substrate and facing the movable electrode, The valve body is displaced in a direction to open the outlet by an electrostatic force generated between the movable electrode and the fixed electrode when a voltage is applied between the movable electrode and the fixed electrode. The biasing unit is stacked across the first diaphragm portion and the peripheral portion of the first diaphragm portion in the frame on the side of the valve body forming substrate facing the closed space forming substrate. 2. A stress applying film that applies stress to the first diaphragm portion so that the closing force increases when the valve body is not displaced by the means. Micro valve according.   The said biasing means is a peripheral portion of the first diaphragm portion, and comprises a portion formed in a concave section so as to approach the valve seat forming substrate side as it approaches the frame. Micro valve.   The driving means includes a movable electrode provided in a central portion of the first diaphragm portion in the valve body forming substrate, and a fixed electrode provided in the closed space forming substrate and facing the movable electrode. The valve body is displaced in a direction to open the outflow port by an electrostatic force generated between the movable electrode and the fixed electrode when a voltage is applied between the movable electrode and the fixed electrode. The substrate is a first concave portion that is formed in a portion facing the first diaphragm portion and secures a displacement space of the first diaphragm portion, and a gap forming concave portion provided with a fixed electrode on the inner bottom surface; A second recess that is formed in a portion facing the second diaphragm portion and secures a displacement space of the second diaphragm portion and is deeper than the first recess, and the valve body formation A communication recess comprising a third recess that allows the gap forming recess and the pressure adjustment space recess to communicate with each other on the side facing the plate, and the biasing means includes the second recess in the pressure adjustment space recess. A step projection protruding from the inner surface of the pressure adjusting space recess so that the depth of the portion corresponding to the peripheral portion of the diaphragm portion is shallower than the depth of the portion corresponding to the central portion of the second diaphragm portion. The microvalve according to claim 1, comprising:   The driving means includes a movable electrode provided in a central portion of the first diaphragm portion in the valve body forming substrate, and a fixed electrode provided in the closed space forming substrate and facing the movable electrode. The valve body is displaced in a direction to open the outflow port by an electrostatic force generated between the movable electrode and the fixed electrode when a voltage is applied between the valve body and the fixed electrode. In the second diaphragm portion, a plurality of annular concave grooves are concentrically formed on a surface facing the closed space forming substrate, and the closed space forming substrate faces the first diaphragm portion. Formed in a first recess that is formed in a part and secures a displacement space of the first diaphragm part, and in which a fixed electrode is provided on the inner bottom surface, and a part that faces the second diaphragm part A second concave portion that secures a displacement space of the second diaphragm portion and deeper than the first concave portion, and a gap forming concave portion on the side facing the valve element forming substrate, A communication recess comprising a third recess that communicates with the pressure adjustment space recess, and the biasing means protrudes from each portion facing the respective groove on the inner bottom surface of the pressure adjustment space recess. The microvalve according to claim 1, further comprising a plurality of small protrusions.   The bias means is a flow path formed between the outlet side internal space and the inlet side internal space, and the pressure in the outlet side internal space is higher than the pressure in the inlet side internal space. 2. The microvalve according to claim 1, comprising a pressure adjusting flow path that causes a pressure loss to be lowered.   2. The microvalve according to claim 1, wherein the bias means is made of a gas sealed in the closed space at a pressure higher than atmospheric pressure.   The driving means includes a movable electrode provided in a central portion of the first diaphragm portion in the valve body forming substrate, and a fixed electrode provided in the closed space forming substrate and facing the movable electrode. The valve body is displaced in a direction to open the outflow port by an electrostatic force generated between the movable electrode and the fixed electrode when a voltage is applied between the movable electrode and the fixed electrode. The substrate is a first concave portion that is formed in a portion facing the first diaphragm portion and secures a displacement space of the first diaphragm portion, and a gap forming concave portion provided with a fixed electrode on the inner bottom surface; A second recess that is formed in a portion facing the second diaphragm portion and secures a displacement space of the second diaphragm portion and is deeper than the first recess, and the valve body formation A communication recess composed of a third recess for communicating the gap forming recess and the pressure adjusting space recess on the surface facing the plate, and the gap forming recess on the surface facing the valve body forming substrate. A wiring for connecting a fixed electrode and a pad provided at a portion that does not overlap the valve body forming substrate, and a wiring forming groove provided on an inner bottom surface of the valve body forming substrate, In the state where the closed space forming substrate is fixed, the air passage formed by the wiring forming groove is sealed with resin, and the bias means is formed from a gas sealed in the closed space at a pressure higher than atmospheric pressure. The microvalve according to claim 1, wherein:

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