JPH0415377A - Electrostatic drive type microvalve - Google Patents

Abstract

PURPOSE:To permit the high speed control of gas with high precision, permit baking and permit the use in the superhigh vacuum and superclean environment for a long period, by carrying out the opening/closing control of a gas flow passage by a valve seat by the electrostatic attractive force generated between the first and second rod driving electrodes and a valve rod. CONSTITUTION:The electrostatic attractive force in the vertical direction is applied arbitrarily to a valve rod 64 by selectively applying a voltage through terminals 76A - 76C, and an outlet 44A is opening/closing-controlled. Accordingly, the electrostatic attractive force is generated between the valve rod 64 and the first silicone substrate 30 by applying a voltage between body, and the valve rod 64 is shifted upward, together with a valve seat 50, and the outlet 44A is cut off. Further, the valve rod 64 is shifted downward, together with the valve seat 50, by applying a voltage between the valve rod 64 and the second rod driving electrode 72, and the outlet 44A is released. Since, the opening and closing operations of the valve seat 50 is carried out by utilizing the electrostatic attractive force, the high speed control for gas with high precision is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatically driven microvalve, and particularly to an electrostatically driven microvalve that is capable of high-speed gas control.

[Prior Art] As semiconductor elements become smaller and more sophisticated, gas valves for semiconductor processing equipment are required to be extremely lean and have high-speed response.

Gas valves commonly used in the past have been manufactured by machining, such as electromagnetic valves and air valves. For this reason, there is a limit to the miniaturization of the gas flow path or the overall shape, and there are many dead spaces, which has been a major obstacle to achieving cleanliness and high-speed response. Additionally, this type of gas valve has the problem that it cannot be baked depending on the sealing member, making it unsuitable for ultra-high vacuum applications.

To solve this problem, a micro valve using a silicon substrate has been proposed (Noh Esashi, "Integrated Thermal Mass Flow Controller", IEICE Technical Report, SDM87-72).
．． 1987), and FIG. 4 shows an example of a conventional microvalve that can be controlled at high speed.

This microvalve includes a silicon substrate 10 and a Pyrex glass 2 bonded to the top of the silicon substrate 10.
Including 0. The silicon substrate 10 has a flow path 12. Valve rod 14. A diaphragm 16 is formed by etching.

Further, the Pyrex gas 20 is hermetically bonded to the silicon substrate 10 by anodic bonding, and the valve rod 1
An outlet 22 is formed at a location corresponding to 4, and an inlet 24 is formed at a location corresponding to a part of the flow path 12.

Furthermore, a flow meter 18 is provided in the middle of the flow path 12.

Further, a valve rod 14 is provided at the bottom of the silicon substrate 10.
A piezo actuator 26 supports 28 at a location corresponding to
The installation is fixed.

Next, the operation of this microvalve will be explained.

First, when no voltage is applied to the piezo actuator 26, there is a gap between the valve rod 14 and the outlet 22, and gas flows therethrough.

When a voltage is applied to the piezo actuator 26, the piezo actuator 26 extends, deforms the diaphragm 16 upward, and pushes the valve rod 14 upward. This blocks the outlet 22 and stops the gas.

At this time, the substantial dead space of the valve is after the gas cutoff section. In this microvalve, only the hole of the outlet 22 made in the Pyrex glass 20 becomes a dead space, and since this area is extremely small, high-speed response is possible.

[Problem to be solved by the invention] In this way, in the conventional microvalve, when the gas is cut off, the cutting blade can be adjusted by driving the piezo actuator, and the driving speed is also determined by the performance of the piezo actuator. It has excellent characteristics.

However, when opening the valve, the elasticity of the diaphragm is used, so the valve cannot be forcibly opened from the outside. For this reason, there was a problem in that the response speed of the valve could not be sufficiently increased, and furthermore, the conductance of the valve decreased.

Further, the micro valve is connected to a piezo actuator 2.
Since an adhesive is used for the 6 itself and its support 28, there is a problem in that it cannot be baked and can only be used for ultra-high vacuum applications.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a structure that enables high-speed and high-precision control of gas, and also has a structure that can be baked, and which is suitable for use in ultra-high vacuum. Another purpose is to provide an electrostatically driven microvalve that can withstand use in ultra-clean environments.

[Means for Solving the Problems] In order to achieve the above object, the electrostatically driven microvalve of the present invention includes: a first silicon substrate formed such that a part of the gas flow path passes through the back surface; a first glass substrate that is bonded to the front side of the first silicon substrate and forms a gas flow path between it and the first silicon substrate; and a gas flow path that is opened and closed on the back side of the first silicon substrate. a valve seat made of polycrystalline silicon attached to the substrate; a valve rod provided on the back side of the first silicon substrate for driving the valve seat; and a diaphragm for supporting the valve rod, formed as part of the substrate. a first rod drive electrode and a second rod drive electrode, which are installed to face the front and back surfaces of the valve rod with a gap therebetween; It is characterized in that the opening and closing of the gas flow path by the valve seat is controlled by electrostatic attraction generated by applying a voltage between the drive electrode and the second rod drive electrode and the valve rod.

The following method may be used to form microvalves with such a configuration minutely and with high precision. That is, the gas flow path, valve rod, and diaphragm are the same as the first. The second silicon substrate can be formed with high precision by, for example, silicon crystal anisotropic etching using a KOH solution.

Also, processing of glass substrates, such as gas inlets.

Glass processing for forming the outlet can be performed with high performance by electric discharge processing.

Further, the microvalve of the present invention includes a second glass substrate bonded to the back side of the second silicon substrate and provided with the second rod driving electrode so as to face the valve rod with a gap therebetween. Preferably, the first silicon substrate and the second silicon substrate are bonded via an insulating layer, and the first silicon substrate itself is used as the first rod driving electrode.

Further, in the microvalve of the present invention, the first silicon substrate and the first glass substrate are anodically bonded, the first silicon substrate and the second silicon substrate are bonded by a low temperature anodic bond, and the second silicon substrate and the second glass substrate are anodically bonded. It is preferable that the silicon substrate and the second glass substrate be formed in a bakeable manner by anodic bonding.

Further, in the microvalve of the present invention, it is preferable that a pressure adjustment hole is provided in the valve rod region or the diaphragm region of the second silicon substrate.

principle of invention Next, the present invention will be explained in detail.

Conventionally, in a microvalve using a piezo actuator, the valve rod is moved while the piezo actuator and the Hull plot are brought into direct contact to open and close the gas flow path. Therefore, in order to use piezo actuators to both open and close the gas flow path, piezo actuators should be placed on both sides of the valve rod, or
The piezo actuator must be fixed to the valve rod.

However, in order to increase the driving force of the piezo actuator, it is necessary to stack the piezo actuators in layers, resulting in a large volume. Therefore, the former method poses a problem in that the microvalve itself cannot be miniaturized. Also,
The latter method requires the use of some kind of adhesive to secure the valve rod and piezo actuator, making it difficult to control the micron-order gap (the gap between the valve rod and the outlet) required for this type of valve. A problem arises.

In contrast, the present invention is characterized in that electrostatic attraction is used as the driving force used in the microvalve. Since this electrostatic attraction is a force acting on a surface, a relatively large force can be obtained without increasing the size of the drive system.

That is, when considering that a circular valve rod is driven by electrostatic attraction P, the displacement W of the valve rod is given by the following equation.

where, E is the Young's modulus of silicon 1, h is the plate thickness of the diaphragm, a is the outer radius of the diaphragm, h is a coefficient depending on the shape of the diaphragm, and F is the drag force of the valve (closing edge). Further, the electrostatic force P is given by the following equation when the applied voltage is V.

Tatashi, ε. is the dielectric constant of vacuum 1s is the electrode area.

! is the distance between the electrodes.

From equations (1) and (2), F becomes F import... (3) however,! . is the distance between the electrodes when no voltage is applied. From equation (3), the applied voltage or valve withstand voltage required to drive the valve rod can be determined.

As is clear from the above equations (2) and (3), by forming the electrode area S to be large, a relatively large electrostatic attractive force P can be generated.

Focusing on this point, the microvalve of the present invention has a planar configuration in which a first rod driving electrode and a second rod driving electrode are installed so as to face the front and back surfaces of the valve rod with a gap between them. It is designed to generate large electrostatic attraction. This makes it possible to realize a microvalve that is small and capable of high-speed control and high-precision control.

Furthermore, in the present invention, since the microvalve is formed using a silicon substrate, a glass substrate, polycrystalline silicon, etc., special assembly techniques as in the past are not required, and the IC
Manufacturing technology makes it possible to form with high precision.

In particular, in the present invention, the microvalve itself can be formed using IC technology, and there is no need to use adhesives as in the past.
Even if the drive system is baked, the same problem will not occur, and the micro valve 't-14 can be used in ultra-high vacuum or ultra-clean environments.

[Function] The present invention consists of the above structure, and its function will be explained next.

In the microvalve of the present invention, the valve can be opened and closed by applying a voltage from the outside.

That is, in the present invention, the first rod drive electrode and the valve rod form a capacitor with a gap therebetween, and the second rod drive electrode and the valve rod form a capacitor with a gap in between. Therefore, by applying a voltage between the first rod driving electrode and the valve rod, an electrostatic attractive force P shown in equation (2) above is generated between the two, which causes the valve seat to close the gas flow path. to drive.

Conversely, by applying a voltage between the valve rod and the second rod driving electrode, an electrostatic attraction shown by the above equation (2) is generated between the two, and the gas flow path is opened. drive the valve seat so that

In this way, both the opening and closing operations of the valve are performed using electrostatic attraction, allowing for high-speed gas control.

High precision control becomes possible.

Furthermore, by adopting a configuration that uses electrostatic attraction to open and close the valve, the entire valve can be made smaller in plan view, and can be directly attached to a chamber in, for example, a semiconductor processing device.

Furthermore, since the microvalve of the present invention is basically formed using a silicon substrate, a glass substrate, etc., it can be formed using a manufacturing technology such as an IC. Therefore, it is possible to achieve a micro-order distance between electrodes with extremely high precision, and it is possible to drive with a relatively low voltage.
There is no need to worry about electrical discharge. Furthermore, the gas flow path, inlet,
Since the outlet can also be formed finely, dead space can be kept to a minimum. In particular, dead space in the outlet section has a large negative effect on high-speed gas switching, but in the present invention, this outlet section can be made structurally small, so there is no problem.

Furthermore, since the microvalve of the present invention can basically be manufactured by batch processing using IC manufacturing technology, it is possible to mass-produce electrostatically driven microvalves with uniform quality and small variations between elements. can be manufactured.

Furthermore, since the microvalve of the present invention can use a thermally stable method, such as an anodic bonding cap, for assembly, sealing, etc. of the whole, baking, especially baking of its actuator part, becomes possible.

By the way, if the gaps formed on the front and back sides of the valve rod are respectively hermetically sealed, pressure fluctuations will occur between the two due to movement of the valve rod, and unnecessary force will be generated. Therefore, in the present invention, it is preferable to provide a through hole for pressure adjustment in the valve loft region or diaphragm region of the second silicon substrate. As a result, no differential pressure is generated between the gaps formed on the front and back sides of the valve rod, and the damping factor of the valve rod can be changed by adjusting the number and size of the through holes. Furthermore, by sealing air pressure within each of the gaps, high-speed response of the valve rod can be achieved.

[Effects of the Invention] As explained above, according to the present invention, all valves are opened and closed using electrostatic attraction, which makes it possible to control gas at high speed and with high precision. This has the effect of providing an electrostatically driven microvalve that can be miniaturized.

Further, the present invention provides a method for anodic bonding a first silicon substrate and a first glass substrate, and low temperature anodic bonding for the first silicon substrate and a second silicon substrate;
By anodically bonding the silicon substrate and the second glass substrate, the assembly and sealing of the entire bulb can be performed using a thermally stable method, and baking, especially the driving part, can be performed easily. A possible electrostatically actuated microvalve can be obtained.

Furthermore, the present invention has a configuration in which a through hole is provided between the gap formed on the front side of the valve rod and the gap formed on the back side so that a pressure difference does not occur in a steady state. By adjusting the number and size, the damping factor of the valve rod can be adjusted, and high-speed operation of the valve rod is also possible.

[Example] Next, a preferred example of the present invention will be described in detail based on the drawings.

First Embodiment FIG. 1 shows a preferred first embodiment of the electrostatically driven microvalve according to the present invention. The microvalve of the embodiment includes a first silicon substrate 30 on which a gas flow path 32 is formed, and inlets 42 and 2 of the gas flow path 32.
The first glass substrate 40 on which two outlets 44A and 44B are formed is hermetically sealed by anodic bonding.

The gas flow path 32 is formed to pass from the front side of the first silicon substrate 30 to the back side, and then return from the back side to the front side.
It is formed with high precision by anisotropically etching a silicon crystal using an OH solution. Further, the inlet 42. The outlets 44A, 44B are formed with high precision using electric discharge machining.

Furthermore, a valve seat 50 for opening and closing the gas flow path 32 is attached to the back side of the first silicon substrate 30. This valve seat 50 is made of polycrystalline silicon, and is airtightly fixed to its periphery or to the back side of the silicon substrate 30, and is configured to open and close the outlet 44A by moving the central part of the seat up and down.

Further, on the back side of the first silicon substrate 30, a second
A silicon substrate 60 is bonded thereto.

In the embodiment, the periphery of the second silicon substrate 60 is bonded to the back side of the first silicon substrate 30 by low-temperature anodic bonding using a low melting point glass 62. This second silicon substrate 60 is connected to the valve rod 6 that drives the valve seat 50.
4 and a diaphragm 66 that supports the periphery of the valve rod 64 form a movable structure formed by machining and sawing.

A valve seat 50 is joined to the center of the valve rod 64, and operates to open and close the outlet 44A in accordance with the vertical movement of the valve rod 64.

Further, a second glass substrate 70 is anodically bonded to the back side of the second silicon substrate 60. On this second glass substrate 70, there is a gap 100A between the valve rod 64 and the gap 100A.
A second rod driving electrode 72 is arranged so as to face each other via the second rod driving electrode 72 .
For example, it is formed into a plate shape using AI or the like. Thereby, this second rod drive electrode 72 and the valve rod 64 form a capacitor with the gap 100A interposed therebetween.

Further, since the first silicon substrate 30 and the second silicon substrate 60 are electrically insulated by the low melting point glass 62, a capacitor is formed between them with a gap 100B between them.

Then, the first silicon substrate 30. Second silicon substrate 60. The second rod drive electrode 72 has terminals 76A, 76B electrically connected to the outside via through holes 74A, 74B, 74C.

76C is connected. Thereby, the first silicon substrate 30 functions as a first rod driving electrode that faces the valve rod 64 through the gap 100B.

Therefore, by selectively applying a voltage through each of the terminals 76A, 76B, and 76C, an electrostatic attraction force directed upward and downward can be applied to the valve rod 64, thereby controlling the opening and closing of the outlet 44A. can.

That is, the valve rod 64 and the first silicon substrate 30
By applying a voltage between them, the above (2
), the valve rod 64 is moved upward together with the valve seat 50, and the outlet 4
4 can be blocked.

Also, a valve rod 64 and a second rod driving electrode 72
By applying a voltage between them, the valve rod 60 is moved downward together with the valve seat 50, and the outlet
4A can be opened.

As described above, according to the present invention, since both the opening and closing operations of the valve seat 50 are performed using electrostatic attraction, high-speed control and high-precision control of gas is possible.

Furthermore, it will be understood that according to the present invention, the entire valve can be downsized in its entirety, so that it can be directly attached to a chamber or the like, for example.

Furthermore, according to this embodiment, the first silicon substrate 30 and the first glass substrate 40 are anodically bonded, and the second silicon substrate 60 and the second glass substrate 70 are similarly anodically bonded. A first silicon substrate 30 and a second silicon substrate 60 are bonded by low-temperature anodic bonding using a low-melting glass 62. As described above, since the microvalve of the present invention uses a thermally stable method for assembling and sealing the entire valve, it is possible to bake it, and in particular, it is possible to bake its actuator part. It will be understood that it can be used in lean environments and ultra-high vacuum applications.

FIG. 2 shows the Hull plot 64 and the first silicon substrate 30.
This is actually measured data showing the relationship between the voltage applied between the valve seat 50 and the cutoff pressure of the gas flow path 32 by the valve seat 50.

In the microvalve of the embodiment, the valve seat 50 blocks the gas flow path 32 by applying an applied voltage of 8 V, and by applying a higher voltage, the blocking voltage increases.

From this, it will be understood that even if the actuator portion is formed in a planar manner, a relatively large driving force for opening and closing the valve seat 50 can be obtained.

Second Embodiment FIG. 3 shows a second preferred embodiment of the electrostatically driven microvalve according to the present invention.

In the electrostatically driven microvalve according to the first embodiment, since the gap 100B is hermetically sealed, pressure fluctuations occur due to the movement of the valve rod 64, and unnecessary force is generated. hinders response. In addition, the gap 100A communicates with the outside, which raises the question of whether external humidity or the like will affect the valve operation.

The feature of this embodiment is that in order to solve such a problem, a through hole for pressure adjustment is provided in either the valve rod region or the diaphragm region of the second silicon substrate 60, and a steady state is maintained between the gaps 100A and 100B. The reason is that the structure is such that no differential pressure occurs. In this embodiment, a through hole 80 is formed in the valve rod 64.

Further, in this embodiment, the through hole 74C is sealed with a cap 82 made of silicon, for example, to enable feedthrough from the second rod drive electrode 72 without breaking the airtightness.

With the above configuration, according to this embodiment, the damping factor of the valve rod 64 can be changed by adjusting the number and size of the through holes 80, and as described above, the gas can be sealed inside. This makes it possible to achieve high-speed response of the valve rod 64. According to experiments, it was confirmed that chattering of the valve 64 was sufficiently suppressed.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible within the scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory diagram of a first preferred embodiment of the electrostatically driven microvalve according to the present invention, FIG. 2 is a gas cutoff characteristic diagram of the first embodiment, and FIG. 3 is a diagram of the present invention. FIG. 4 is a cross-sectional explanatory view of a second preferred embodiment of the electrostatically driven microvalve according to the present invention, and FIG. 4 is a cross-sectional explanatory view of a conventional microvalve. 30... first silicon substrate, 32... gas flow path,
40... First glass substrate, 42... Inlet,
44A, 44B... Outlet, 50... Valve seat, 60... Second silicon substrate, 62... Low melting point glass, 64... Valve rod, 66
...Diaphragm, 70...Second glass substrate, 7
2... Second rod drive electrode, 80... Through hole, 8
2...Cap, 100A, 100B...Gap.

Claims (1)

[Claims] (1) A first silicon substrate formed such that a part of the gas flow path passes through the back surface thereof, and a gas flow path bonded to the front surface side of the first silicon substrate between the first silicon substrate and the first silicon substrate. a first glass substrate forming a polycrystalline silicon substrate; a valve seat made of polycrystalline silicon attached to the back side of the first silicon substrate to open and close a gas flow path; A valve rod that drives the valve seat and a diaphragm that supports the valve rod face a second silicon substrate formed as a part of the substrate with a gap between the front and back surfaces of the valve rod. a first rod driving electrode and a second rod driving electrode arranged so as to generate a voltage by applying a voltage between the first rod driving electrode and the second rod driving electrode and the valve rod. An electrostatically driven microvalve that uses electrostatic attraction to control the opening and closing of a gas flow path using a valve seat.