JP3388991B2 - Piezo-driven small valve - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric-actuated small valve that deforms a piezoelectric film by applying a voltage to change the flow path, and in particular, minute flow rate control of a reaction gas used in the manufacturing process of various semiconductor devices. The present invention relates to a small valve suitable for.

[0002]

2. Description of the Related Art In the manufacturing process of semiconductor devices, C
The VD (Chemical Vapor Deposition) method plays an important role as a process for forming various thin films, and high performance is required for the small valve used for controlling the flow rate of the reaction gas. With a conventional small valve that uses electromagnetic force, the flow rate is a minimum of 100 μl (microliter) due to problems such as manufacturing accuracy.
It has been difficult to control the minute flow rate stably, such that it can be controlled only up to about / min (minutes).

Therefore, the present inventors have proposed an electromagnetically driven small valve B as shown in FIG. This is one in which only the valve mechanism is miniaturized and the force by the electromagnetic force is applied by an external coil. In FIG. 6, the valve mechanism includes a valve lid 51 also serving as a spring and a valve seat 53 having a flow passage hole 52. The spring is a NiFe alloy soft iron magnetic material and has a swastika shape. The valve lid 51 is driven by the magnetic field gradient generated by the coil 55 outside the stainless pipe 54 for mounting the valve mechanism, and the valve lid 51 is displaced in the vertical direction in FIG. The flow rate can be controlled by opening and closing. With this small valve B, an extremely small flow rate of 10 μl / min or less can be controlled with high accuracy. 56 is a substrate and 57 is an O-ring.

[0004]

However, the single small valve B can flow only a very small flow rate as a whole, and even if a plurality of valves are used in parallel, the coil 55 for driving is downsized. Due to the limitation of 1, the overall size cannot be reduced, and as a result, it is difficult to arrange these small valves B in an integrated manner.

The object of the present invention is to solve the above problems,
It is intended to provide a small valve capable of stably controlling an extremely small flow rate and highly accurately controlling a wide range of flow rate.

[0006]

SUMMARY OF THE INVENTION The first aspect of the present invention, Ri Do a piezoelectric material polarized in the thickness direction the passage hole is provided in the central portion
The piezoelectric film whose periphery is fixed , and the periphery and one end of the piezoelectric film
A valve lid, which is supported by the other end of the integrated support beam and is capable of closing the flow path hole, and electrodes formed on both upper and lower surfaces of the piezoelectric film are provided, and a voltage is applied between the electrodes. Thus, the flow path hole of the piezoelectric film is deformed to change the flow path between the valve lid and the flow path hole.

A second invention according to the first invention, the shape Jomata of the passage hole, characterized in that the electrode was formed to have a directionality with respect to the center of the passage hole It was configured as a piezoelectrically driven small valve.

A third aspect of the invention is to provide a large number of first or first substrates on a substrate .
The piezoelectric drive type small valve according to the second aspect of the invention is integrated and arranged in a plane to form an integrated type piezoelectric drive type small valve.

The fourth invention is a large number of first or second inventions.
The piezoelectric drive type small valves of (1) are arranged in a matrix in a planar manner and each of them is provided with a switching element, thereby forming an integrated type piezoelectric drive type small valve.

[0010]

DETAILED DESCRIPTION OF THE INVENTION

[First Embodiment] FIG. 1 is a diagram showing a piezoelectric drive type small valve A according to a first embodiment of the present invention. FIG.
(B) is the bb sectional view taken on the line of (a). Reference numeral 1 is a piezoelectric film as a valve seat having a flow path hole 2 formed in the center thereof, and electrodes 3 and 4 are provided on both upper and lower surfaces thereof. This piezoelectric film 1
Is made of a piezoelectric material polarized in the thickness direction. Reference numeral 5 denotes a valve lid formed on the upper surface of the piezoelectric film 1 so as to cover the flow path hole (through hole) 2 and is supported by an integrated support beam 6. 7 is a silicon substrate. Reference numeral 8 indicates the direction in which the residual stress of the support beam 4 acts. Although the valve lid 5 is supported by the four support beams 6 here, it may be one or two.

The piezoelectric film 1 is PZT (lead zirconate titanate).
Is formed, and its thickness is several μm. The integrated valve lid 5 and support beam 6 are chemically stable permalloy (nickel iron alloy) or SiN (silicon nitride).
And has a thickness of 2 to 3 μm. Also, the electrodes 3, 4
Gold or platinum is used as the material, and in order to enhance the adhesiveness with the piezoelectric film 1, the piezoelectric film 1 and the electrodes 3 and 4 have a thickness of 0.01 μm.
It has a titanium film. The thickness of the electrodes 3 and 4 is 0.5 μm for gold and 0.2 to 0.3 μm for platinum.
Is. The overall size of the small valve A when viewed from above is several hundreds μm to 1 and 2 mm square.

Next, the operation of the small valve A will be described with reference to FIG. In a normal state, as shown in FIG. 2A, the valve lid 5 is pressed against the flow path hole 2 by the residual stress of the support beam 6 shown by the arrow 8 to close the flow path hole 2.
No holes are formed in the support beam 6 [(a) of FIG. 1]
[Reference] has been expressed in this way for the sake of convenience in order to make the gas flow passage easier to understand.

When a voltage is applied between the electrodes 3 and 4 in this state, the piezoelectric film 1 tends to extend in the thickness direction, so that the other portions shrink by that amount, and the periphery is fixed particularly in the plane direction. Therefore, as shown in FIG. 2B, the flow path hole 2 expands in the direction of arrow 9. As a result, the gas can flow through the generated gap in the direction of arrow 10. The size of this deformation is 300 μm × 300 μ when the size of the piezoelectric film 1 is changed.
m, the radius of the flow path hole 2 is 30 μm, and the magnitude of the electric field applied to the piezoelectric film 1 is about 1 V / μm, the order is 10 nm. If the thickness of the piezoelectric film 1 is 1 to 5 μm,
The applied voltage is 1 to 5 V, which can be sufficiently controlled by the control circuit formed on the same silicon substrate. Further, the opening / closing speed of the small valve A is determined by the expansion / contraction operation speed of the piezoelectric film 1, and therefore can be considerably increased.

FIG. 3 shows an example of the shape of the flow path holes 2 of the piezoelectric film 1 and the arrangement of the electrodes 3 and 4. (A) of FIG.
In the case shown in (c), the metal to be the electrodes 3 and 4 is the piezoelectric film 1.
(Not shown). When the flow path hole 2 is deformed into a shape similar to the original shape by applying a voltage to the piezoelectric film 1, the residual stress of the support beam 6 only presses the valve lid 5 deeper. In this case, since the deformation of the flow path hole 2 is not similar to the original shape, a gap is partially generated between the flow path hole 2 and the valve cover 5 even when the valve cover 5 is pressed. Gas flows there.

For example, as shown in FIG. 3A, even when a circular flow path hole 2 is formed at the center of a square piezoelectric film 1, the flow path after the deformation is greatly deformed in the diagonal direction. The shape of the hole 2 is no longer circular. Further, as shown in FIG. 3B, the electrodes 3 and 4 are partially arranged on the piezoelectric film 1, or as shown in FIG. 3C, the flow path hole 2 has an elliptical shape. By forming the shape of the flow path hole and the electrode so as to have directivity with respect to the center of the flow path hole, the deformation amount of the flow path hole 2 becomes directional, and as a result, the gap after the deformation is formed. Can be larger. Since the absolute size of such a gap is small, the amount of gas flowing through the gap is minute even when the valve is opened. That is, it becomes possible to control the flow of a small amount of gas by opening and closing the valve due to the deformation of the piezoelectric film.

[Second Embodiment] FIG. 4 shows a second embodiment of the present invention.
It is a figure which shows the embodiment of. 4A shows a case where a plurality of small valves A shown in FIG. 1 are planarly integrated in a row on a silicon substrate, and FIG. 4B shows a small number of small valves A arranged in a matrix on a silicon substrate. This is the case when they are integrated.
Reference numeral 11 denotes a control circuit for controlling opening / closing of each small valve A, which is formed on the same silicon substrate. Reference numeral 12 is a signal line formed on the same silicon substrate.

Here, one of the electrodes 3 and 4 of the piezoelectric film 1 is grounded, and the other is connected to the control circuit 11 by the signal line 12. The control signal to each small valve A is an ON / OFF binary signal, and the signal line 12 is used as a drive voltage for the piezoelectric film 1.
Through which the open / closed state of the valve is determined.

Also in this case, the flow rate that can be handled by each small valve A alone is very small. Therefore, the control of each valve is opened /
Even in the case of digital control of on / off of closing, the flow rate handled by a single valve is set as the minimum unit by adjusting the number of valves in the opened state by the control circuit 11 in the integrated plurality of valves as a whole. Precise flow rate control can be performed in the range from the fully closed flow rate 0 to the fully open flow rate. Further, since the control circuit 11 is also digitally controlled, it can have a simple structure.

[Third Embodiment] FIG. 5 shows a third embodiment of the present invention.
It is a figure which shows the embodiment of. Here, (b) of FIG.
Compared with the case shown in FIG. 5, this is a case where a large number of small valves A are integrated in a matrix as shown in FIG.
12a and 12b are signal lines. The signal line 12a serves as a control line and the signal line 12b serves as a drive line. When the number of small valves A integrated in this way is large, the method of directly controlling the individual small valves A causes a problem in the wiring method.
As shown in (b) of FIG.
3 and the auxiliary capacitor 14 for accumulating the piezoelectric film deformation operation signal, the number of signal lines is reduced to solve the problem.
A TFT (thin film transistor) is used as the switching element 13.

Next, the operation will be described. When the signal line 12a is in the active state, the switching element 13 becomes conductive between the source and the drain, and the same voltage as that of the signal line 12b is applied to the piezoelectric film 1 and the auxiliary capacitor 14. Therefore, the open / close state of the small valve A can be controlled by the signal line 12a. When the signal line 12a is made inactive, charges cannot move between the source and drain of the switching element 13, but the auxiliary capacitor 14
, The electric charge of the signal line 12b is kept held, and the piezoelectric film 1 is continuously driven for a predetermined time.

The signal line 12a corresponds to the scanning line of the display, and when the active state is generated in time division, the operation timing of the small valves A in each column is shifted by the time division, but the shift is caused by the auxiliary capacitor 14. Is compensated. Further, since the open / closed state of each small valve A can be determined by the signal lines extending vertically and horizontally, it is possible to adjust the number of opened valves to an arbitrary number in the plurality of integrated small valves A. it can. Therefore, it is possible to perform precise flow rate control from a completely closed flow rate of 0 to a fully opened flow rate.

[0022]

As described above, according to the first aspect of the present invention, it is possible to realize a highly precise and high-speed small valve that stably supplies a small amount and a fixed amount of gas as a simple substance. According to the second aspect of the invention, the shape of the flow path hole can be deformed to be dissimilar to the original shape by applying a voltage, and the gap when the valve is opened can be increased. Third
According to the invention, since the small valves are integrated, it becomes possible to control the flow rate of gas in a wide range with high accuracy. According to the fourth aspect, when realizing a wide control range, it is possible to reduce the number of signal lines that control the control range.

[Brief description of drawings]

FIG. 1 is a diagram showing a piezoelectrically driven small valve according to a first embodiment of the present invention, in which (a) is a plan view and (b) is b- of (a).
It is a b line sectional view.

2 (a) and 2 (b) are operation explanatory views of the small valve shown in FIG.

3 (a) is a diagram showing the shape of a flow passage hole of the small valve shown in FIG. 1, and FIG. 3 (b) is a diagram showing an example in which electrodes are partially arranged,
(C) is a figure which shows the case where the shape of a flow path hole was deformed into an ellipse.

FIG. 4 is a diagram showing a piezoelectrically driven small valve according to a second embodiment of the present invention, FIG. 4A is a diagram showing a case where a plurality of small valves are integrated and controlled in a single row arrangement, and FIG. It is a figure which shows the case where it integrates and is controlled by a small matrix arrangement.

FIG. 5 is a diagram showing a piezoelectrically driven small valve according to a third embodiment of the present invention, where (a) shows a case where a plurality of small valves are integrated and controlled in a matrix arrangement, and (b) shows It is a figure which shows the drive circuit of each small valve.

FIG. 6 is a sectional view schematically showing a conventional electromagnetically driven small valve.

[Explanation of symbols]

1: Piezoelectric film (valve seat) 2: Flow path hole (through hole) 3, 4:
Electrodes, 5: valve lid, 6: supporting beam, 7: silicon substrate, 8:
Direction in which residual stress of support beam 6 works, 9: direction of deformation of flow path hole, 10: flow path of gas, 11: control circuit, 12, 12
a, 12b: signal line, 13: switching element (TF
T), 14: Auxiliary capacitor for storing piezoelectric film deformation operation signal.

Continuation of the front page (56) Reference JP-A 4-136577 (JP, A) JP-A 62-204078 (JP, A) JP-B 7-29414 (JP, B2) JP-A 5-506706 (JP , A) (58) Fields investigated (Int.Cl. ⁷ , DB name) F16K 31/00-31/05

Claims (4)

(57) [Claims] 1. A piezoelectric film surrounding fixed Ri Do a piezoelectric material polarized in the thickness direction the passage hole is provided in the central portion, piezoelectric
A valve lid that is supported by the other end of a support beam , one end of which is integrated with the periphery of the electrolyte film, and that can close the flow path hole; and electrodes formed on both upper and lower surfaces of the piezoelectric film, A piezoelectric actuated small valve characterized in that a flow path between the valve lid and the flow path hole is changed by deforming the flow path hole of the piezoelectric film by applying a voltage between the electrodes. Wherein the shape Jomata is the electrode of the flow path hole, a piezoelectric-driven compact according to claim 1, characterized in that formed to have a directionality with respect to the center of the passage hole valve. 3. A plurality of pressures according to claim 1 or 2 on a substrate.
An integrated type piezoelectric actuated small valve in which electrically actuated small valves are arranged in a plane. 4. A plurality of piezoelectric drive types according to claim 1 or 2.
While arranging small valves in a matrix in a plane ,
Each is equipped with a switching element
Integrated type piezoelectric drive type small valve.