JPH08210519A - Microminiature device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve thermal insulation between a thermal driving substrate and a substrate including a valve orifice and a valve seat in a thermally-driven microactuator. SOLUTION: This device has (a) opposite main surfaces 130, 118A, a flow passage 114 extended from the main surface 130 to the main surface 118A, (b) an integral annular wall structure 131 projected from the main surface 130 to surround the flow passage 114 and provided with a vale seat, and (c) a valve seat substrate 112 installed adjacent to the integral annular wall structure 131 and provided with a recess 130A in the periphery of the main surface 130. Further the device has an upper substrate 113 including a valve surface which is installed adjacent to the valve seat substrate 128 and can be installed in a position to close to a valve seat 128 to obstruct a fluid flow passing through the flow passage 114 and in a position to open to the valve seat to pass the fluid flow through the flow passage.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates generally to microminiature devices, and more particularly to microfluidic devices.

[0002]

BACKGROUND OF THE INVENTION The evolution of microminiature mechanical devices has advanced by using techniques commonly referred to as micromachining or microfabrication. For example, "S by Angell, et al.
ilicon Micromechanical De
Vices ”, Scientific America
n, (April 1983), pp. See the description of the microfabrication of mechanical devices 44-55.

A basic requirement of micromechanical actuators (hereinafter "microactuators") is that some mechanical actuation means must be provided. Yet another requirement is that the actuation means must generate sufficient force for reliable actuation. For example, the microactuator can comprise a portion of a microvalve used to control the flow of carrier gas through the capillary column of a gas chromatograph. Microactuators move fluid members by moving a moving member (typically a moving membrane, diaphragm, or boss) through a distance of 100 microns against a pressure of 200 pounds per square inch (1375 kilopascals). May need to be opened and closed.

Power from an external power supply is typically supplied to the microactuator. Microactuators employ one of a variety of techniques to convert the applied power into actuating force. Often, the applied power is partially or wholly converted to thermal power, and such microactuators can be considered thermally driven.

Arrays of bimetal legs machined by micromachining have been used to generate thermally actuated actuation forces in microminiature valves. As the bimetal leg heats up, stresses are created in its structure to deflect the protruding boss adjacent the orifice, increasing or decreasing fluid flow to the attached fluid support system.
For example, referring to FIG. 1, reproduced from commonly assigned US Pat. No. 5,333,831, issued to Barth et al., A valve seat substrate 12 on which a microminiature valve 10 serves as a base. And an upper substrate 13 is shown. A central flow passage (via) 14 is formed through the valve seat base plate 12. Supported on the upper substrate 13 above the valve seat substrate 12: a fixed periphery 16, a central boss 18, preferably made of silicon, and legs 20,
There are 22. The length and width of the upper substrate 13 match the dimensions of the valve seat substrate 12.

The structure and operation of the upper substrate 13 is Gor
Commonly assigned US Pat. No. 5,058,856 to Don et al. Briefly, a layer of nickel has been deposited and patterned on top substrate 13 using sputtering, photolithographic, and electroplating techniques. The array of legs 20 and 22 joins the fixed perimeter 16 to the boss 18. A resistive layer of nickel is present on the top surface of the boss and can be used to heat the boss and legs. When the upper substrate 13 is heated, the difference in the coefficient of thermal expansion between silicon and nickel causes the legs 20,
22 is an arc, and the boss 18 is lifted away from the valve seat 28 so as to project upward from the upper main surface of the valve seat base plate 12. When the boss 18 is separated from the valve seat base plate 12, the flow passage 1
4 is in fluid communication with the surrounding volume 24. On the other hand, this volume 2
4 is in fluid communication with the device which seeks to regulate the flow therethrough by means of a microminiature valve 10 (alternatively there may be actuation by means other than arcuate legs). The valve seat 28 includes a bearing surface 32 against which the boss 18 sits when the boss is in the closed position.

The performance of the microminiature valve 10 is largely determined by its thermal resistance characteristics. For example, if the microminiature valve 10 is normally closed when no power is applied, and if the thermal resistance from the actuator to its surroundings is low, the microminiature valve 10 requires a relatively large amount of power to open. , It cools rapidly when power is removed and therefore closes rapidly. If the thermal resistance from the microminiature valve 10 to the surroundings is high, the microminiature valve 10 requires less power to open, but cools more slowly and therefore more slowly.

Thermal power flows from upper substrate 13 through several paths and in several ways. When the microminiature valve 10 is closed, the boss 18 contacts the valve seat 28. Thermal power is then passed from the boss 18 through the valve seat 28 to the valve seat substrate 1
It flows to most of 2 by solid state conduction. Thermal power also flows from the actuator legs 20, 22 to the fixed perimeter 16 and thus to the valve seat substrate 12 by solid state conduction. Gas-phase conduction of thermal power is also performed from the lower surface of the upper substrate 13 to the valve seat substrate 12 and from the upper surface of the upper substrate 13 to a surrounding package (not shown). The thermal power flowing into the valve seat substrate 12 also flows into the thermally conductive package structure in contact with the valve seat substrate 12, such as the structure in contact with the lower surface 38.

It is often desirable to minimize the power consumed by a microminiature device, especially for microminiature valves where high speed operation is not critical. However, the prior art methods have not paid sufficient attention to the power lost by solid phase conduction or vapor phase conduction from the upper substrate 13 to the lower substrate 12.

[0010]

OBJECTS OF THE INVENTION The present invention is a thermally actuated microactuator (and particularly in a microminiature valve 10 such as that shown in FIG. 1), the heat between a thermally driven substrate and a substrate containing a valve orifice and a valve seat. Intended to improve insulation.

[0011]

SUMMARY OF THE INVENTION A device for controlling fluid flow can be constructed in accordance with the present invention. The device includes opposing first and second major surfaces and a flow passage extending from the first major surface to the second major surface, projecting from the first major surface, surrounding the flow passage, and closing the valve. An integral toroidal wall structure having a seat, and a valve seat base plate peripherally disposed within the first major surface and having a recess adjacent the integral toroidal wall structure. There is. An upper substrate is installed adjacent to the valve seat substrate, closed to the valve seat to impede fluid flow through the flow passage, and open to the valve seat to allow fluid flow through the flow passage. It has a valve face that can be installed in position. The depressions have a sufficient combination of surface area and depth compared to the overall upward surface area and the overall thickness of the valve seat substrate, respectively, such that vapor phase conduction between the upper substrate and the valve seat substrate is reduced. ing. The annular wall structure can be configured to minimize solid phase conduction from the top substrate to the valve seat substrate.

Another advantage of the present invention is that the method of forming the microminiature valve self aligns the orifice and valve seat of the central flow passage so that the fabrication process is not subject to over-etching and under-etching. Anisotropic etching keeps the valve seat geometry constant regardless of etching time. The duration of the etching affects the depth of the valve seat, but the cross-sectional configuration of the valve seat is generally fixed after the formation of parallel {111} direction walls.

Fabrication of a microminiature valve includes a ladder that masks selected portions of both the upper and lower major surfaces of the valve seat substrate. The first region remains exposed on the lower major surface. Etching the exposed first region partially or wholly forms a passage through the substrate. Preferably, the etching process is performed on the etched path with {11
Employ direction-dependent etching that forms walls in the 1} direction. The front surface is patterned and subsequently etched to form mask areas that will form depressions and torus wall structures. Direction-dependent etching from the front also further shapes the passages, creating {111} walls that form a central flow passage whose area is smallest at the orifice and whose cross-sectional area increases with increasing distance from the orifice.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Although the following description is directed to a microactuator in the form of a microminiature valve, the teachings of the present invention apply to other types of thermally actuated microdevices that operate at high temperatures with minimal power consumption. It is considered to have uses. Microdevices are thus "thermally driven"
Is meant to include those that operate by converting the applied power into an actuating force that moves a movable member, where the conversion benefits from the conservation or separation of thermal energy generated during the conversion. . Examples include microactuators driven by forces generated in the process of expansion / contraction of a gas or liquid according to the phase change of the gas or liquid or the change of the bimetal or shape memory material. Accordingly, the present invention is a mechanical device or system, or fluids (including gases and liquids).
Physical phenomena such as current flow, electrical and electronic parameters (such as capacitance, current, and voltage potential), acoustic and optical parameters (such as reflection, absorption, or diffraction), and simple dimensional parameters There are applications in a variety of microactuators that can be used to operate at (such as acceleration, pressure, length, depth, etc.).

Referring to FIGS. 2 and 2 (enlarged view of the dashed portion of FIG. 2), a first preferred embodiment of a novel microactuator in the form of a microminiature valve 110 is a valve seat substrate 112 which serves as a base. Is equipped with. The valve seat substrate 112 is preferably a silicon orifice chip that has been fabricated from a wafer using a batch processing process as described below with respect to FIGS. A central flow passage 114 is formed through the valve seat substrate 112 (the term "passage" is used herein to describe the fine through holes in the fabricated layer). Supported on the top of the valve seat substrate 112 is an upper substrate 113 formed of silicon with a fixed periphery 116 and a thermally actuated member in the form of a central boss 118. Upper substrate 113
The lengths and widths of the are substantially matched to the respective dimensions of the valve seat substrate 112.

The thermal actuator is the upper substrate 113.
In addition, preferably provided in the form of an array of bimetal elements, some of the bimetal elements have a higher coefficient of thermal expansion than the rest of the bimetal elements, so that when the temperature of the bimetal elements changes, movement occurs. The terms "bimetal" and "bimetallic" are not limited to their conventional meaning, eg, one or two parts within a bimetal element may actually be non-metallic. Preferably, in the illustrated embodiment, a portion of the bimetal element is nickel and the other portion of the bimetal element is the semiconductor silicon.

The bimetal element in the form of legs 120, 122 comprises a layer of nickel on top of a silicon layer, the thickness of the nickel layer and the silicon layer each being, for example, 30 microns. Legs 120 and 122 join fixed perimeter 116 to central boss 118. A resistive heater (not shown) is placed adjacent to the top surface of upper substrate 113 and in close proximity to legs 120 and 122. Upper substrate 11
When 3 is heated by introducing an electric current into the resistive heater, the difference in the coefficient of thermal expansion of silicon and nickel is
Bend 20, 122 into an arc and lift the boss 118 farther from the valve seat 128. When the boss 118 separates from the valve seat 112, the flow passage 114 provides fluid communication between the throat 132 and the surrounding volume 124. Meanwhile, the surrounding volume 124 is in fluid communication with a device (not shown) whose flow is intended to be regulated by the microminiature valve 110. The preferred embodiment of the thermal start-up operation and the structure and operation of the upper substrate 113 are
Commonly assigned Gordon et al. US Pat. No. 5,
No. 058,856, and the commonly assigned Bar
Th, et al., U.S. Pat. No. 5,333,831. These disclosures are incorporated herein by reference.

The microminiature valve 110 has a leg 120.
And 122, but the invention is not limited to actuation by arcuate legs. For example, the structure connecting the central boss 118 to the fixed perimeter 116 may instead be provided as a rigid circular diaphragm that selectively flexes to regulate fluid flow between the flow passage 114 and the surrounding volume 124.

The valve seat substrate 112 comprises an annular wall structure 119, preferably in the form of a hollow truncated pyramid. For the purposes of this description, the term "annular" is meant to include polygonal as well as circular or conical structures. Annular wall structure 119
Has an orifice 127 surrounded by a valve seat 128. The valve face 118A sits against the valve seat 128 when the central boss 118 is in the closed position. Valve seat 128
Is formed on the valve seat wall 129 protruding from the throat wall 131. The annular wall structure 119 is surrounded by a perimeter 112C defining a recess 130A formed in the upper main surface 130 of the valve seat substrate 112. As described more fully below, the annular wall structure 119 and the recess 130A are preferably formed in the upper major surface 130 and the lower major surface 138 by direction dependent etching of the valve seat substrate 112. The width of the valve seat 128 may vary, but should be chosen large enough not to be destroyed when the valve seat repeatedly contacts between the valve seat 128 and the valve surface 118A.

The recess 130A, the throat wall 131, the valve seat 128,
Also, due to the particular configuration of the orifice 127 of the valve seat substrate 112, the aerodynamic and thermal properties are improved over the prior art. As noted above, the goal of the thermal actuation valve 110 design is to minimize wasted thermal power. Typically, power is derived from the top substrate 113 in several ways: by conductance through the valve seat 128.
Due to the heat conduction path through the legs 120, 122, the surrounding volume 1
Due to convective heating of the gases in 24 and above the upper substrate 113, vapor conduction from the top surface of the upper substrate 113, to the package members above the top substrate 113, and to the surroundings. It flows by a vapor-phase conduction flow through a gas of volume 124.

The valve seat substrate 112, and thus the upper substrate 1,
13 is configured to have a recess 130A so as to reduce gas phase conduction between the valve 13 and the valve seat substrate 112. Preferably, the valve seat substrate 112 is configured to obtain a sufficient combination of the surface area and depth of the recesses 130A as compared to the overall upward surface area of the valve seat substrate 112 and the overall thickness 112D, respectively. The gas phase conduction between the valve seat substrate 112 and the valve seat substrate 112 is reduced as compared with the prior art. Further around 11
It is also desirable to make 2C thick enough to maximize the depth of the recess 130A and to make the mechanical strength of the valve seat substrate 112 as a whole suitable.

The teachings herein of the annular wall structure 119 also aim to minimize the overall thermal conductance between the upper substrate 113 and the valve seat substrate 112. For example, in order to minimize the solid-state thermal conductance from the valve surface 118A to the valve seat substrate 112, the valve seat wall 12
Make 9 thin enough without compromising strong mechanical strength,
The valve seat 128 is made sufficiently thin. Further, the throat wall 131 is made sufficiently thin to minimize solid-phase heat conduction from the valve seat wall 129 to the valve seat substrate 112. As a result, the power consumption of the legs 120, 122 to achieve a given displacement of the boss 118 at a given temperature is significantly reduced.

In the first preferred embodiment, the recess 130A covers a surface area of at least 10 times the cross-sectional area enclosed by the valve seat 128. The depth of the recess 130A is substantially equal to the vertical height of the annular wall structure 119. In the second embodiment of the valve seat substrate 112, the vertical height of the annular wall structure 119 is greater than 2 to 5 times the minimum lateral thickness of the throat wall 131. In the third embodiment of the valve seat substrate 112, the surface area of the recess 130A is preferably 25-95% of the total upward surface area of the valve seat substrate 113, and the depth of the recess 130A is preferably as large as the entire valve seat substrate 112. The thickness of 112
Between 25 and 95% of D, or the thickness of the perimeter 112C is selected from the range of about 5 to 75% of the total thickness 112D of the valve seat substrate 112.

In a fourth embodiment of the valve seat substrate 112, the total thickness 112D is less than 500 microns and the perimeter 11
The thickness of 2D is less than 300 microns and the recess 130A
Depth is greater than 200 microns or the cross-sectional area of the flow orifice is less than 360,000 square microns.

A method of making the valve seat substrate 112 on the orifice tip will now be generally described, and specific steps in the fabrication of the valve seat substrate 112 will be described below with respect to FIGS.
Further details on the fabrication of the actuator substrate are Gord.
disclosed in commonly assigned US Pat. No. 5,058,856 to On and Barth.

FIGS. 4-11 illustrate a first preferred method of making the valve seat substrate 112 of FIG. The fabrication process is preferably performed in a batch mode in which multiple valve seat substrates 112 are simultaneously fabricated on one silicon wafer and multiple silicon wafers are processed simultaneously in a cassette. The fabrication process consists of three silicon etching operations in addition to some operations that mask and etch the thin film on the wafer surface.

The fabrication process begins with FIG. Silicon wafer 260 is coated both top and bottom by low pressure chemical vapor deposition (LPCVD) with first and second layers 262 and 264 of silicon nitride. Preferentially, the first and second silicon nitride layers 262 and 264 are low stress layers achieved by the silicon rich deposition method. Subsequently, a chrome layer 266 is deposited on the first silicon nitride layer 262 by sputter deposition.

Using a double sided photomask aligner, such as the Karl Suss MA-25 aligner,
A photoresist pattern is simultaneously formed on the chrome layer 266 and the second silicon nitride layer 264. Central area 26
9 is defined in photoresist and is then etched through the second silicon nitride layer 264 using a conventional plasma etching method and later etched to form the cavity 279A.
Exposing a portion of the silicon wafer that will form the. The photoresist pattern on chrome layer 266 is etched using a wet etching method known to fabricate a chrome photomasking pattern on glass. The inner ring 272 forms the area that will later become the valve seat 128, and the outer ring 274 will form the area that will later become the upper surface of the shoulder region around the valve seat substrate 112. For the purposes of this description,
The terms "ring" and "ring" are meant to include circular as well as polygonal forms. In particular, although the preferred embodiment of the valve seat 128 forms a linear configuration (when viewed from above), other configurations are contemplated by the present invention.

In FIG. 5, the central region 2 is formed by using an aqueous solution of potassium hydroxide (KOH) in the first silicon etching operation.
At 69, etch into the bottom of the silicon wafer 260. Preferably, the silicon wafer 260 has a <100> crystal orientation of the silicon wafer 26 with respect to the silicon crystal lattice.
It is oriented so that it is perpendicular to the principal plane of 0. In such an orientation of the silicon wafer 260, the etching with the KOH aqueous solution proceeds rapidly in the <100> direction perpendicular to the wafer surface, and along the <111> plane oriented 54.7 degrees away from the <100> direction. However, etching proceeds much slower. As a result, the etching substantially terminates at the {111} crystal plane, resulting in a cavity 279A having a flat roof and four beveled throat walls composed of the {111} crystal planes. In FIG. 5, the four sloping wall first and second throat walls 278, 280 can be seen. First and second throat walls 278, 28
0 is an angle of 5 from the horizontal plane of the silicon wafer 260.
It is in the direction of 4.7 degrees.

Preferably, the resulting cavity 279A depth in this step should be greater than the thickness of the required perimeter region 112C, so that the results of subsequent etching steps form a passage through the silicon wafer 260. Also preferably, the extent of the central region 269 should be small enough that the protrusions of the first and second throat walls 278, 280 are completely within the boundaries of the inner annulus 272. Cavity 279A may be completely etched through silicon wafer 260 to the stop of silicon nitride layer 262 at this point in the fabrication process, but to save fabrication time, the etching process may be performed with a depth of cavity 279A that surrounds peripheral region 112C.
It is desirable to stop when the thickness exceeds the required thickness. For example, if one wishes to have a thickness of the peripheral region 112C of 250 microns, the cavity 2 at this point in the fabrication process.
The 79A depth can be 300 microns to provide a comfortable margin of 50 microns. Also, at this point in the fabrication process, the cavity 279A should not be completely etched down to the first silicon nitride layer. This is because a subsequent photomasking operation must be performed, and the first silicon nitride layer 262 cannot be strong enough to survive mechanical handling during the subsequent photomasking process.

Next, a second photomasking operation is performed. Plasma etching is performed on the first silicon nitride layer 26.
2 and leave an outer ring region 270 of silicon nitride and an inner ring region 276 of silicon nitride. A second silicon etching operation is performed with an aqueous KOH solution, resulting in the features shown in FIGS. 6 and 7 (enlarged view of the dashed portion of FIG. 6).
The second silicon etching operation etches the exposed portion of the silicon wafer 260 in the area between the ring regions 270 and 276, creating an annular cavity with a recessed surface 282. The second silicon etching operation also deepens the cavity 279A. The second silicon etching operation creates the throat wall 281. In the preferred embodiment, the second silicon operation etches 725 microns deep into the top surface of silicon wafer 260, etching the roof of cavity 279A to create a central flow passage 279B that extends completely through silicon wafer 260.

Preferably, as shown in FIGS. 6 and 7,
Inner ring region 276 is the central passageway for silicon wafer 260.
Allow silicon etching from above. However, the annulus is not strictly necessary and the inner annulus region 276 helps to ease manufacturing tolerances for manufacturing convenience. Tolerances calculate the original range of widths of the central region 269 according to known principles of crystallographic and direction dependent etching as the downward moving {100} direction etch plane fits into the upward moving {100} direction etch plane. The second silicon etching operation is easy because it can be reduced in any way. Moreover, it is not strictly necessary to form a complete passage through the silicon wafer 260 during the second silicon etching operation. However, the fabrication of a complete passage can ensure that the upper and lower masking patterns are properly aligned with each other visually. Therefore, the second silicon etching operation involves the central flow passage 2
79B is preferably formed completely through the silicon wafer 260.

Inner ring 272 and outer ring 274 are then employed as masking regions in a plasma etching operation that etches the exposed silicon nitride in inner circular region 276 and outer annular region 270. Inner annular sub-region 276A of silicon nitride replicating the lateral shape of ring 272 and outer annular sub-region 2 replicating the lateral shape of ring region 274.
70A is formed. The annular sub-region 276A, when viewed from above, forms the particular shape shown as feature 702 in FIG. 20 and described below. The concave surface 282 shown in FIGS. 8 and 9 (enlarged view of the broken line portion of FIG. 8), and the first, second, and
Third and fourth opposed recess walls 294A, 294B, 2
The now exposed silicon regions such as 95A and 295B are etched with a KOH solution in a third silicon etching operation. Preferably, the flat {100} face is etched in the <100> direction in the third silicon etching operation less than in the same plane in the first and second etching operations. For example, recessed surface 282 is typically over 25 microns overetched during the third silicon etch operation.

Referring to FIGS. 8 and 9, the third silicon etching operation performed on the top major surface is {111}.
Four side walls with inner and outer lateral walls in the direction, the combined upper surface of which has the same shape as that of the valve seat. The first and second tilted valve seat inner walls 296, 298 are shown in cross section in FIGS. 8 and 9. First and second substantially vertical walls 290 and 292 connect the first and second angled valve seat inner walls 296, 298 to the first and second inner throat walls 278, 280 previously formed. The first and second vertical walls 290, 292 consist essentially of crystal planes in the {110} direction, and the etch rate in the <110> crystal direction with aqueous KOH is typically <10 in the {100} plane.
It is about 1.9 times higher than the vertical etch rate in the 0> direction.
Thus, the first and second vertical walls 290, 292 project downwardly and outwardly, thus increasing their lateral dimension while maintaining substantially the same vertical dimension.
The horizontal upper surface of the throat wall 281 is also etched downward in the <100> crystal direction. However, the first and second tilted valve seat inner walls 296, 298 are established early in the third silicon etching operation, and the first and second vertical walls 29,
It is essentially unchanged during the lateral etching of 0,292 and the vertical etching of the horizontal upper surface of the throat wall 281.

As shown in FIGS. 10 and 11 (enlarged view of the dashed portion of FIG. 10) and after the third silicon etching operation, the second silicon nitride layer 264 is removed from underneath the silicon wafer 260 by plasma etching. It Next, during a third silicon etching operation, a plasma etch is performed on the upper surface of the silicon wafer 260 to etch the portion of the inner ring sub-region 276A below the inner ring 272 exposed by the undercuts of the inner ring sub-region 276A. Exposed to. The lateral extent of the remainder of the inner annular sub-region 276A is defined by the second and fourth opposed recess walls 294.
B and 295B are spread in substantially the same space. Therefore, the first and second tilted valve seat inner walls 296, 29
8 between the etched silicon features on the top and the edges of the inner annular sub-region 276A, so that the edges of the inner annular sub-region 276A have first and second inclined valve seat inner walls 296. , 298 laterally coincide with the edges of the top surface of subassembly 298 with sub-micron accuracy.

As a final step in the batch fabrication process, wet chemical etching is used to remove the remaining chromium regions from the silicon wafer 260. As a result, a silicon wafer 2 having a plurality of individual orifices and seats
60 results. The silicon wafer 260 can then be separated into individual orifice tips in a dicing process using a conventional high speed dicing saw. The final dicing step can generate dust that can later interfere with the operation of the orifice tip. Thus, if the modified fabrication process is justified by certain considerations, the dicing step can be performed before the third silicon etching operation, and the individual silicon chips obtained after dicing can be processed by a third silicon etch, It can be exposed to two plasma etches and a chrome etch as described above. Except when the individual tips are mounted in a fixture that facilitates such individual huddle. The modified fabrication process is beneficial in some cases because the third silicon etching operation tends to dissolve the fine silicon dust that remains in the orifice tip after the dicing step.

12 and 13 (enlarged view of the broken line portion in FIG. 12) are cutaway perspective views of the orifice region of the valve seat substrate 112 completed in the individual orifice tip.

14 and 15 (enlarged view of broken line portion of FIG. 14), FIG. 16 and FIG. 17 (enlarged view of broken line portion of FIG. 16), FIG. 18 and FIG. 19 (enlarged view of broken line portion of FIG. 18) Show the second, third and fourth preferred embodiments of the valve seat base plate, respectively, formed according to the above process, but with minor modifications, as shown below.

In FIGS. 14 and 15, the second valve seat substrate 412 is used.
Is the second central flow passage 414, the second valve seat 428, the second
Seat wall 429 and second throat wall 431.
This embodiment controls the first silicon etching operation described above to control the valve seat substrate 412 surrounding the second throat wall 431 from below.
By etching to a depth equal to the desired thickness. Then, during the third silicon etching operation, the etching stops when the second central flow passage 414 extends completely through the wafer. Overetching results in lateral undercuts or destruction of the second valve seat 428.

In FIGS. 16 and 17, the third valve seat substrate 512 is shown.
Is the third central flow passage 514, the third valve seat 528, the third
Seat wall 529 and third throat wall 531.
This example is performed using the first and second silicon etching operations and is easier to perform.

In FIGS. 18 and 19, the fourth valve seat substrate 612 is used.
Is the fourth central flow passage 614, the fourth valve seat 628, the fourth
Seat wall 629 and a fourth throat wall 631.
This embodiment is conceptually the same as the embodiment shown in FIGS. 16 and 17 except that extended contact portions 618A, 618B are added to the lower surface of the central boss 618.

FIG. 20 illustrates a valve seat etch mask 702 that is preferably used to control the etch of the various valve seats described herein in the present invention. Valve seat etching mask 70
2 overlaps above the orifice area of the valve seat substrate 112 for the purpose of indicating its relative arrangement. The mask is composed of features that are oriented along the <110> direction on the {100} plane of the silicon wafer 260 and a straight frame with diagonal tabs at its corners that face the <110> direction on the {100} plane. There is. The purpose of the diagonal tabs is to improve the shape of the corners, ensuring that the {111} planes that are subsequently formed on the outer edge of the frame without undercutting the linear features meet at sharp corners. That is.

FIG. 21 shows a photographic plate corner compensation mask 802 suitable for use in controlling the etch of the valve seat support structure described herein in the present invention. The purpose of this corner compensation mask is to ensure that the very deeply etched {111} planes that form the outer surface of the annular wall structure 119 form the proper corners. For more details on etching the convex corners of {100} silicon with an aqueous KOH solution, see Mayer.
Others are "Fabrication of Non-Und
eretched Convex Corners i
n Anisotropic Etching of of
(100) -Silicon in Aqueous
KOH with Respect To Novel
Micromechanical Element ”,
J. Electrochem. Soc. , Vol. Thirteen
7, No. 12, p. 3947-3951.

The structure of the above-disclosed embodiment can be modified by changing the pattern of the etch resistant film. Alternatively, alternative coatings such as silicon dioxide or polyimide are contemplated as deposited or grown on the surface of the finished structure. Further, while the disclosed embodiments of the invention have been described as being fabricated from a silicon substrate, other materials such as metals, glass, ceramics, or polymers, and other semiconductors or crystalline substrates such as gallium arsenide may be used. Can also be used. For example, the structures described herein can be made according to one or more of the following alternatives. Borosilicate glass can be made using ultrasonic machining, photosensitive glass can be lithographically formed, ceramic material can be ultrasonically machined, or can be cast and baked. The metal or machinable ceramic can be formed by conventional machining, or the polymer can be machined, cast, or injection molded.

As described above, the microminiature device of the present invention is [1] a microminiature device for controlling the flow of a fluid, comprising: a. Opposing first and second major surfaces, and a flow passage extending from the first major surface to the second major surface, b. Projecting from the first major surface and surrounding the flow passage,
An integral annular wall structure with a valve seat, c. A valve seat substrate disposed adjacent the integral annular wall structure and having a recess around the first major surface; and a fluid disposed adjacent the valve seat substrate and passing through the flow passage. A top substrate having a valve face that can be placed in a closed position relative to the valve seat to obstruct flow and in an open position relative to the valve seat to allow fluid flow through the flow passage, The recesses have a sufficient combination of surface area and depth, respectively, as compared to the overall upward surface area and the overall thickness of the valve seat substrate to reduce vapor phase conduction between the upper substrate and the valve seat substrate. It is constructed and has an embodiment as shown in the following [2] to [20].

[2] The apparatus according to [1], wherein the peripheral portion is thick enough to make the mechanical strength of the valve seat base plate as a whole suitable while making the depth of the recess as large as possible.

[3] The apparatus according to [2], wherein the annular wall structure exhibits a vertical height sufficient to reduce vapor phase conduction between the upper substrate and the valve seat substrate.

[4] The annular wall structure further includes a throat wall, and the throat wall is thin enough to minimize the solid-state thermal conductance from the valve surface to the valve seat substrate [1].
An apparatus according to claim 1.

[5] The annular wall structure further comprises a valve seat supported by the valve seat wall, and the recess encloses a surface area of at least 10 times the cross-sectional area surrounded by the valve seat. Equipment.

[6] The device according to [1], wherein the depth of the recess is substantially equal to the vertical height of the annular wall structure.

[7] The device according to [1], wherein the surface area of the recess is between 25% and 95% of the total upward surface area of the valve seat substrate.

[8] The device according to [1], wherein the depth of the recess is between 25% and 95% of the total thickness of the valve seat base plate.

[9] The apparatus according to [1], wherein the peripheral thickness is selected from the range of about 5 to 75% of the total thickness of the valve seat substrate.

[10] The apparatus according to [1], wherein the valve seat substrate has a total thickness of more than 500 microns and a peripheral thickness of less than 300 microns.

[11] The device according to [1], wherein the depth of the recess is larger than 200 microns.

[12] The annular wall structure further includes a throat wall, and the vertical height of the annular wall structure is 2 which is the minimum lateral thickness of the throat wall.
The apparatus according to [1], which is larger than the range of 3 times.

[13] The apparatus according to [1], wherein the flow passage is installed at the center of the annular wall structure, and the cross-sectional area of the flow passage is reduced when the flow passage exits from the valve seat.

[14] The apparatus according to [1], wherein the valve seat substrate is made of a semiconductor material.

[15] The apparatus according to [14], wherein the annular wall structure is formed by a {111} crystal plane.

[16] The valve seat substrate is made of metal, glass,
The device according to [1], which is composed of a material selected from a material group of ceramics and polymers.

[17] The apparatus according to [1], wherein the annular wall structure forms a truncated cone structure.

[18] The apparatus according to [17], wherein the flow passage is formed by a four-sided throat wall.

[19] The apparatus according to [1], wherein the upper substrate further comprises a thermal actuator that operates to position the valve surface at a selected one of the open position and the closed position.

[20] The apparatus according to [19], wherein the thermal actuator is further composed of first and second materials having different thermal expansion coefficients.

[0065]

Since the present invention is constructed as described above, it is possible to improve the thermal insulation between the thermally driven substrate and the substrate containing the valve orifice and the valve seat in the thermally actuated microactuator.

[Brief description of drawings]

FIG. 1 is a cross-sectional side view of a prior art microminiature valve.

FIG. 2 is a cross-sectional side view of a microminiature valve with a flow orifice and valve seat constructed in accordance with the present invention.

3 is a partially enlarged detailed sectional side view of the microminiature valve of FIG.

FIG. 4 is a diagram showing a process of manufacturing the valve seat and the flow orifice of the microminiature valve shown in FIG.

5 is a diagram showing a process of manufacturing an embodiment of the valve seat and the flow orifice of the microminiature valve of FIG. 2, showing a state in which a central region is etched.

FIG. 6 is a view showing an example of a process subsequent to that of FIG. 5, showing a state in which a central flow passage and the like are formed.

7 is an enlarged view of the central flow passage portion of FIG.

8 is a view showing another example of the post-process of FIG. 5, showing a state in which a central flow passage and the like are formed.

9 is an enlarged view of the central flow passage portion of FIG.

FIG. 10 is a diagram showing an example of a further post process of FIGS. 6 to 8;

11 is an enlarged view of the central flow passage portion of FIG.

12 is a detailed side perspective, cross-sectional view of a portion of a valve seat and flow orifice of a microminiature valve made using the process of FIGS. 4-11.

13 is an enlarged view of an inner wall portion of the tilted valve seat of FIG.

FIG. 14 is a cross-sectional side view of a second preferred embodiment of a microminiature valve constructed in accordance with the present invention.

15 is a detailed cross-sectional side view of a portion of the valve of FIG.

FIG. 16 is a sectional side view of a third preferred embodiment of a microminiature valve constructed in accordance with the present invention.

17 is a detailed cross-sectional side view of a portion of the valve of FIG.

FIG. 18 is a cross-sectional side view of a fourth preferred embodiment of a microminiature valve constructed in accordance with the present invention.

19 is a detailed cross-sectional side view of a portion of the valve of FIG.

FIG. 20 is a plan view of an orifice region of a valve seat substrate manufactured by the steps of FIGS. 4 to 11 in the present invention, and is a view showing a suitable valve seat etching mask in an overlapping manner for the purpose of illustration.

FIG. 21 is a plan view of a corner compensation mask suitable for controlling the outside of the throat wall manufactured by the process of FIGS. 4 to 11 according to the present invention.

[Explanation of symbols]

 110 Micro Miniature Valve 112 Valve Seat Substrate 112A Central Region 112B Peripheral Region 112C Peripheral 112D Overall Thickness of Valve Seat Substrate 113 Upper Substrate 114 Central Flow Passage 116 Fixed Perimeter 118 Central Boss 118A Valve Face 119 Annular Wall Structure 120, 122 Leg 124 Perimeter Volume 127 Orifice 128 Valve seat 129 Seat wall 130 Upper main surface 130A Recess 131 Throat wall 132 Throat 138 Lower main surface

Claims (1)

[Claims] 1. A microminiature device for controlling fluid flow, comprising: a. Opposing first and second major surfaces, and a flow passage extending from the first major surface to the second major surface, b. Projecting from the first major surface and surrounding the flow passage,
An integral toroidal wall structure with a valve seat, c. A valve seat substrate disposed adjacent to the integral annular wall structure and having a recess around the first major surface, and disposed adjacent to the valve seat substrate and through the flow passage. A top substrate having a valve face that can be placed in a closed position relative to the valve seat to impede fluid flow and in an open position relative to the valve seat to pass the fluid flow through the flow passage. , The recess has a sufficient combination of surface area and depth compared to the overall upward surface area and the overall thickness of the valve seat substrate, respectively, so that gas phase conduction between the upper substrate and the valve seat substrate is reduced. Is a micro miniature device.