JP2004354105A - Electric capacitance pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the temperature characteristic and pressure responsiveness of a capacitance pressure sensor by reducing the mount of minute substances, contained in a measurement medium and deposited/heaped up on a strain part of a diaphragm, even if a coarse-meshed filter is used. <P>SOLUTION: A first substrate 21 with a fixed electrode 25 formed thereon is joined to the diaphragm 22 to form a vacuum capacitance chamber 31 between these two members. In the middle of an inner face of the strain part 22B of the diaphragm 22, a movable electrode 26 is formed in correspondence with the fixed electrode 25 while a joining/fixing part 24A of a movable body 24 is joined to a middle part of an outer face of the strain part 22B. The movable body 24 integrally comprises a cover part 24B for covering the strain part 22B of the diaphragm 22 from above. A minute gap 33 is formed between an outer circumferential surface part of the cover part 24B and an inner wall surface 40 of a second substrate 23 to prevent minute substances from permeating into an internal space 32 in the second substrate 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a capacitance type pressure sensor having a diaphragm structure for detecting a change in measured pressure as a change in capacitance, and more particularly to a capacitance type pressure sensor suitable for use in a semiconductor etching process or the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various types of capacitance type pressure sensors used for pressure gauges and the like have been known (for example, see Patent Documents 1, 2, and 3).
[0003]
[Patent Document 1]
JP-A-9-126929
[Patent Document 2]
JP-A-11-351978
[Patent Document 3]
JP-A-6-265428
The applicant has not found any prior art documents closely related to the present invention by the time of filing, except for the prior art documents specified by the prior art document information described in the present specification.
[0004]
One of them is a capacitance type pressure sensor for measuring an absolute pressure (hereinafter, such a sensor is also referred to as an absolute pressure sensor). This absolute pressure sensor isolates the gap between the capacitor electrodes, whose capacitance value changes due to a change in the pressure to be measured, from the atmosphere and evacuates the inside, and is usually configured as shown in FIG. In brief, the absolute pressure sensor 1 includes a silicon substrate 2 and a glass substrate 3 that are stacked and anodically bonded (electrostatically bonded), and a sealed space formed between the two substrates is a capacity chamber (vacuum chamber). It is set to 4. The silicon substrate 2 has a thick outer peripheral portion forming a joint 2A with the glass substrate 3 and a central portion having a measured pressure P ₁ The diaphragm is formed by forming a thin strain-generating portion 2B which elastically deforms when it receives the pressure. A movable electrode 5 is provided on the outer surface side of the strain generating portion 2B. The movable electrode 5 is electrically connected to a capacitance detection IC chip 6 provided on the outer surface of the glass substrate 3 via a lead wire 7. ing. On the other hand, on the back surface of the glass substrate 3 facing the diaphragm, a fixed electrode 8 is provided so as to be close to and face the movable electrode 5.
[0005]
In the absolute pressure sensor 1 having such a structure, the measured pressure P is applied to the strain generating portion 2B side of the diaphragm 2. ₁ Is applied, the strain generating portion 2B elastically deforms in accordance with the pressure, and changes the minute gap G between the movable electrode 5 and the fixed electrode 8. For this reason, the capacitance of the capacitor composed of the movable electrode 5 and the fixed electrode 8 changes, and this is taken out as an electric signal and subjected to signal processing to obtain the measured pressure P. ₁ Can be detected.
[0006]
When pressure measurement is performed using such a conventional absolute pressure sensor 1 in, for example, an etching step of a semiconductor manufacturing apparatus, a film forming step by CVD, or the like, a minute substance contained in a measurement medium, for example, a reactive substance. Generate gas plasma to generate Si, Si ₃ N ₄ , Al, etc., the etching gas contains minute substances such as gasified materials and reaction products, and these minute substances are contaminants, and the strain-causing portions of the diaphragm 2 are contaminated. It adheres and deposits on 2B. When such a substance is deposited, the temperature characteristic of the absolute pressure sensor 1 changes, and the temperature compensation of the sensor output is invalidated. That is, since the material properties (particularly the thermal expansion coefficient) of the minute substance attached to and deposited on the strain-generating portion 2B and the strain-generating portion 2B are different, when the temperature changes due to the so-called bimetal effect with the deposit, the strain-generating portion 2B This will cause deflection. Since the amount of deflection depends on the type and amount of the deposit, the temperature compensation performed at the start of use of the sensor becomes invalid. In addition, since the compliance (= volume change / pressure change) of the strain generating portion 2B also decreases, there is a problem that a minute pressure change cannot be measured with high accuracy.
[0007]
In order to solve such a problem, a pressure sensor that captures a minute substance contained in the measurement medium with a filter to prevent the minute substance from adhering and accumulating on the strain generating portion has been conventionally used. (For example, see Patent Document 4).
[0008]
[Patent Document 4]
U.S. Pat. No. 5,811,686
[0009]
[Problems to be solved by the invention]
However, the conventional pressure sensor described in the above-mentioned U.S. Pat. No. 5,811,885 uses a filter having a large mesh number (fine mesh) in order to reduce adhesion and deposition of minute substances contained in a measurement medium. When used, the measurement medium is difficult to pass, so that a change in pressure cannot be quickly transmitted to the diaphragm, and the pressure responsiveness of the sensor decreases. Conversely, if you try to increase the pressure responsiveness by using a filter with a small mesh number (coarse), the fine substance contained in the measurement medium easily passes through and adheres to the strain-causing part and deposits. Since the amount increases, there is a problem that the temperature characteristic of the sensor changes and a measurement error increases. Therefore, conventionally, as long as a filter is used, it has not been possible to design and manufacture a sensor capable of simultaneously satisfying both measurement accuracy and pressure responsiveness.
[0010]
The present invention has been made in order to solve the above-described conventional problems, and an object of the present invention is to use a coarse filter so that a minute substance contained in a measurement medium causes distortion of a diaphragm. It is an object of the present invention to provide a capacitance type pressure sensor capable of reducing the amount of adhesion and deposition on a part and simultaneously improving both temperature characteristics and pressure responsiveness.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a first invention is a diaphragm-type capacitance pressure sensor that detects a change in measured pressure as a change in capacitance, wherein a substrate provided with a fixed electrode, A diaphragm having a strain-generating portion and forming the capacity chamber together with the substrate by joining the joining portion to the substrate, and a movable electrode provided in the strain-generating portion corresponding to the fixed electrode; A movable body that covers the strain-generating portion of the diaphragm and is displaced integrally with the strain-generating portion by the measured pressure, and the movable body is bonded to a center of an outer surface of the strain-generating portion of the diaphragm; A cover is formed integrally with the joint fixing portion and covers the strain generating portion of the diaphragm, and a minute gap is formed between the covering portion and the strain generating portion.
[0012]
In the first invention, when the strain generating portion of the diaphragm is elastically deformed by the pressure of the measurement medium, the movable body is also displaced integrally with the strain generating portion, and changes the distance between the fixed electrode and the movable electrode. Since the covering part of the movable body covers the strain generating part of the diaphragm with a small gap, the minute substance contained in the measurement medium enters this gap and adheres to and accumulates on the strain generating part. To prevent
The part that mainly determines the pressure sensitivity of the diaphragm is the strain generating part. If the fixed joint of the movable body is regarded as a rigid body, the central part of the strain-generating part to which the fixed joint of the movable body is joined cannot be elastically deformed. Deform. Even if a minute substance contained in the measurement medium adheres and accumulates on the joint fixed part of the rigid movable body and the covering part connected to the strain generating part via the rigid body, the pressure sensitivity of the diaphragm will Has almost no effect, so that the measurement accuracy can be maintained in a stable state for a long time. In addition, as described in the embodiment of the present invention, this structure also improves the output response to a transient change in pressure.
[0013]
According to a second aspect of the present invention, in the first aspect, the substrate, the diaphragm, and the movable body are respectively formed of the same material, and these are integrally joined by direct joining.
[0014]
In the second aspect, since the substrate and the diaphragm are directly joined, a sensor having a desired inter-electrode distance can be obtained. That is, in the method of joining using a joining material, the inter-electrode distance varies due to variation in the thickness of the joining material itself after joining. On the other hand, direct bonding is a method in which the bonding surfaces of the bonding members are mirror-finished and bonded to each other simply by bringing them into close contact with each other. Therefore, there is no need to use a bonding material at all, and therefore, the variation in the distance between the electrodes due to the variation in the thickness of the bonding material. Does not occur, and a highly accurate distance between electrodes can be obtained.
At the time of direct joining, basically, it is only necessary to mirror-finish the joining surfaces of the two joining members and to laminate them together. However, in order to obtain more reliable joining, appropriate pressure and temperature (for example, 200 to 1300 °) (Approximately C).
Further, since the substrate, the diaphragm and the movable body are formed of the same material, no stress is generated between these members due to a difference in thermal expansion coefficient.
[0015]
According to a third aspect of the present invention, in a capacitance type pressure sensor having a diaphragm structure for detecting a change in measured pressure as a change in capacitance, a first substrate provided with a fixed electrode; A diaphragm having a movable chamber corresponding to the fixed electrode in the strain-generating portion, and a diaphragm formed with the substrate by the bonding portion being bonded to the substrate. A second substrate joined on the joining portion and surrounding the strain generating portion; and a movable body located in the second substrate and displaced integrally with the diaphragm by a measured pressure. A joint portion joined to the center of the outer surface of the strain-generating portion of the diaphragm, and a cover portion formed integrally with the joint portion and covering the strain-generating portion of the diaphragm; Form a small gap between Those were.
[0016]
In the third invention, the amount of the minute substance contained in the measurement medium that has penetrated into the second substrate through the minute gap is small, and is prevented from adhering and accumulating on the strain generating portion of the diaphragm. I do.
[0017]
In a fourth aspect based on the third aspect, a minute gap is formed between the inner wall surface of the second substrate and the outer peripheral surface of the cover of the movable body, and the diaphragm is bonded to the first substrate. The inner edge of the portion is located substantially inside the minute gap from the inner wall surface of the second substrate.
[0018]
In the fourth aspect, a part of the surface of the joint of the diaphragm joined to the first substrate is located inside the inner wall surface of the second substrate and faces the minute gap. The fine substance contained in the measurement medium that has penetrated into the second substrate through the substrate adheres and deposits mainly on the portion of the joint portion opposed to the gap, and adheres and deposits on the strain generating portion. The amount is small.
[0019]
According to a fifth aspect, in the third or fourth aspect, the first substrate, the diaphragm, the second substrate, and the movable body are respectively formed of the same material, and these are integrally joined by direct joining. .
[0020]
In the fifth invention, a sensor having a desired inter-electrode distance can be obtained because of direct bonding. Further, no stress is generated between the first and second substrates, the diaphragm, and the movable body due to a difference in thermal expansion coefficient.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings.
FIG. 1 is an external perspective view showing a first embodiment of a capacitance type pressure sensor according to the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, FIG. 3 is a plan view of a first substrate, FIG. 4 is a bottom view of the diaphragm. This embodiment shows an example in which the present invention is used for pressure measurement of a semiconductor manufacturing apparatus for physically and chemically dry-etching a silicon wafer. In the following drawings, the dimensions in the thickness direction are extremely exaggerated for convenience of explanation.
[0022]
In these figures, an absolute pressure sensor indicated by reference numeral 20 is composed of a sensor element S and a package PK for housing the sensor element S, and is disposed in an etching chamber of a semiconductor manufacturing apparatus.
[0023]
In the semiconductor manufacturing apparatus, the degree of vacuum inside is about several Pa, and a filter F is provided in front of the absolute pressure sensor 20. As the filter F, a relatively coarse filter is used so as not to affect the pressure responsiveness of the absolute pressure sensor 20, and facilitates the passage of the measurement medium (etching gas).
[0024]
The components of the sensor element S will be described in detail. The sensor element S includes a first substrate 21, a diaphragm 22, a second substrate 23, a movable body 24, a fixed electrode 25, a movable electrode 26, and a reference. It is composed of electrodes 27 and 28 and four electrode extraction pins 29a to 29d. The first substrate 21, the diaphragm 22, the second substrate 23, and the movable body 24 are made of the same material, for example, a sapphire substrate (Al ₂ O ₃ ) Or a quartz substrate, are sequentially laminated with their centers aligned, and are integrally joined by direct joining.
[0025]
Direct joining is a method of joining only the physicochemical bonding force between joining members without using any joining material or the like. A method of joining by joining mirror surfaces of two joining members and bringing them into close contact with each other. It is. At the time of joining, there is no particular need to apply pressure, and it is sufficient to simply overlap them. However, more preferably, joining is performed by heating to about 200 to 1300 ° C.
[0026]
The method of joining the first substrate 21, the diaphragm 22, the second substrate 23, and the movable body 24 is not limited to direct joining, and when a silicon single crystal substrate is used as a substrate material for these members, diffusion joining is performed. What is necessary is just to join. When silicon and glass are used as substrate materials, anodic bonding may be performed. Such a joining method is a method of joining without interposing a joining material at the interface between the substrates, similarly to the direct joining described above.
[0027]
A closed space surrounded by the first substrate 21 and the diaphragm 22 forms a capacity chamber 31. The capacity chamber 31 is evacuated to form a vacuum chamber having a predetermined degree of vacuum.
[0028]
On the other hand, the internal space of the second substrate 23, that is, the space 32 formed by the diaphragm 22, the second substrate 23, and the movable body 24 is formed between the second substrate 23 and the movable body 24. The measurement medium 34 is communicated with the inside of the semiconductor manufacturing apparatus through the filter F through the formed annular minute gap 33.
[0029]
The first substrate 21 is formed in the shape of a square thin plate having a side length of about 9 mm and a thickness of about several hundred μm, and is provided at the center of a surface to which the diaphragm is bonded (referred to as a diaphragm bonding surface or a bonding surface). Is formed with a concave portion 35 forming the capacity chamber 31. As shown in FIG. 3, the recess 35 is formed of a rectangular recess slightly smaller than the first substrate 21. The fixed electrode 25 and one reference electrode 27 are formed on the bottom surface. Further, at the four corners of the bottom surface of the recess 35, pin holes 36a to 36d through which the respective electrode extraction pins 29a to 29d penetrate, and a protective wall 37 are formed. 38 are formed.
[0030]
The fixed electrode 25 is formed in the center of the bottom surface of the recess 35 in a circular pattern, and is connected to the electrode extraction pin 29a by a conductive film 39a. The reference electrode 27 is formed in a C-shaped pattern with one portion open, surrounds the periphery of the fixed electrode 25, and is connected to the electrode extraction pin 29b by a conductive film 39b. The protective wall 37 is for preventing a molten metal material (such as platinum) from scattering around when the conductive films 39a and 39b are formed by thermal spraying. It is made of a body and protrudes from each corner of the recess 35. The evacuation hole 38 is formed at an opening of the reference electrode 27, and is sealed after the capacity chamber 31 is evacuated by a vacuum pump.
[0031]
The diaphragm 22 is formed of a rectangular plate having a thickness of about several tens of μm and formed into a thin film. The outer peripheral edge is directly bonded to the bonding surface of the first substrate 21 to form a bonding portion 22A. The portion inside the joint 22A is the measured pressure P ₁ Thus, a strain-generating portion 22B that is elastically deformed is formed. The strain generating portion 22B is circular, and the movable body 24 is directly joined to the center of the outer surface (the surface on the movable body side). In this case, since the movable body 24 is regarded as a rigid body, the elastically deformable strain-causing portion of the diaphragm 22 after being formed into an actual product is formed by a central portion where the movable body 24 is joined and the joint 22A. It is an annular part between.
[0032]
In FIG. 4, the movable electrode 26 and the other reference electrode 28 are connected to the fixed electrode 25 and one reference electrode 27 on the back surface side of the strain generating portion 22B of the diaphragm 22 which is joined to the first substrate 21. It is formed correspondingly. The movable electrode 26 has a circular pattern having substantially the same diameter as the fixed electrode 25 and is formed at the center of the back surface of the strain-flexing portion 22B, thereby maintaining a predetermined distance (about several μm) between the fixed electrode 25 and the electrode. And is connected to an electrode extraction pad 42a by a conductive film 41a. The reference electrode 28 is formed in a C-shaped pattern having substantially the same size as the one reference electrode 27, surrounds the movable electrode 26, and is connected to the electrode extraction pad 42b by a conductive film 41b. I have. Needless to say, the reference electrode 28 also faces the reference electrode 27 while maintaining a predetermined distance between electrodes (about several μm). Note that the fixed electrode 25, the movable electrode 26, and the reference electrodes 27 and 28 are formed by vapor deposition or sputtering.
[0033]
The second substrate 23 is formed in a frame shape having a thickness of about 1 mm, an outer shape of a square having the same size as the first substrate 21 and the diaphragm 22, and an inner shape of a circle. The outer peripheral surface of the joint 22A of the diaphragm 22 is directly joined to the outer peripheral surface of the diaphragm 22 to thereby surround the strain generating portion 22B and the movable body 24.
[0034]
The movable body 24 includes a joint fixing portion 24A joined to the center of the outer surface of the strain generating portion 22B of the diaphragm 22, and a covering portion integrally formed at the tip of the joint fixing portion 24A to cover the upper part of the strain generating portion 22B. 24B constitutes a rigid body, and is located in the second substrate 23. The joint fixing portion 24A is formed in a disk shape having substantially the same diameter as the fixed electrode 25 and the movable electrode 26. Similarly, the covering portion 24B is also a disk having a diameter substantially equal to that of the strain generating portion 22B of the diaphragm 22, and the gap 33 is formed between the outer peripheral surface 43 and the inner wall surface 40 of the second substrate 23.
[0035]
In this case, the inner diameter of the joint 22A of the diaphragm 22 is R ₁ , The inner diameter of the third substrate 23 is R ₂ , The outer diameter of the cover 24B of the movable body 24 is R ₃ Then R ₁ ≤R ₃ <R ₂ As shown in FIG. 2, the inner edge a of the joint portion 22A of the diaphragm 22 is located at least the width W of the gap 33 inside the inner wall surface 40 of the second substrate 23 as shown in FIG. ing. The width W of the gap 33 is small within a range in which a minute substance contained in the measurement medium 34 does not easily pass and the measurement medium 34 easily passes and does not affect the pressure responsiveness of the absolute pressure sensor 20. The width, preferably the ratio of the length L to the width W, is set to about 20 μm or more.
[0036]
The electrode extraction pins 29a to 29d respectively penetrate the electrode holes 36a to 36d formed in the first substrate 21 and protrude to the rear surface side, and are connected to a signal processing circuit of a printed circuit board (not shown). .
[0037]
In such an absolute pressure sensor 20, when the measurement medium 34 is guided to the absolute pressure sensor 20 through the filter F during measurement, the pressure P ₁ Thereby, the movable body 24 is pushed down, and the strain generating portion 22B of the diaphragm 22 is elastically deformed. As a result, the distance between the fixed electrode 25 and the movable electrode 26 changes, and the capacitance of the capacitor formed by these two electrodes changes. ₁ Can be detected.
[0038]
The pressure of the measurement medium 34 guided to the absolute pressure sensor 20 is P ₁ To P ₂ When the pressure changes to ₂ After passing through the filter F, the measuring medium 34 enters the second substrate 23 through the minute gap 33 and increases the pressure in the internal space 32 to P ₁ To P ₂ Requires a long time, the pressure P in the internal space 32 transiently changes. ₁ And the pressure P applied to the outer surface of the cover 24B of the movable body 24 (the surface exposed to the outside of the package PK) ₂ Pressure difference (| P ₁ −P ₂ |) Occurs. However, in this structure, the displacement of the movable electrode 26 is caused by the pressure P ₂ (The pressure in the internal space acts in the opposite direction on the cover 24B facing the strain-generating portion 22B so as to offset the displacement of the movable electrode 26. Therefore, the small gap 33 formed between the second substrate 23 and the movable body 24 does not lower the pressure responsiveness of the sensor.
[0039]
In addition, the minute gap 33 between the inner wall surface 40 of the second substrate 23 and the outer peripheral surface of the cover 24B of the movable body 24 prevents intrusion of minute substances contained in the measurement medium 34, In addition, even if it passes through the gap 33, the R ₁ = R ₃ <R ₂ According to the condition (1), the liquid crystal falls and adheres and accumulates mainly on the surface of the joining portion 22A of the diaphragm 22 located immediately below, so that the amount of adhesion and accumulation on the strain generating portion 22B can be reduced. Therefore, a measurement error due to a temperature change is small, and the temperature characteristics of the sensor can be improved.
[0040]
Further, when the first substrate 21, the diaphragm 22, the second substrate 23, and the movable body 24 are formed of the same material made of sapphire or quartz, the residual stress generated at the joint during the manufacturing is reduced as compared with the case of manufacturing the different materials. Can be reduced. Since this aging of the residual stress causes an error in pressure measurement, it is desirable to minimize the change as much as possible. In addition, even if there is a temperature change or the like during use, no thermal stress is generated at the joint, and the elastic deformation of the diaphragm 22 is not affected.
[0041]
In addition, since the first substrate 21, the diaphragm 22, the second substrate 23, and the movable body 24 are integrally joined by direct joining, a highly accurate inter-electrode distance can be obtained. That is, in the case of joining using a joining material, the inter-electrode distance varies due to the variation in the thickness of the joining material. However, in the case of direct joining, since the joining material is not used at all, the variation due to the thickness of the joining material is small. The distance between the electrodes is determined only by the dry etching amount of the concave portion 35 of the first substrate 21 and the thicknesses of the fixed electrode 25 and the movable electrode 26 without occurrence. Therefore, an inter-electrode distance substantially equal to the design value can be obtained, and an absolute pressure sensor capable of extremely highly accurate and highly reliable pressure measurement can be obtained.
[0042]
In addition, when each constituent member of the sensor element S is formed of a sapphire substrate, sapphire is a single crystal and has no grain boundaries such as alumina and ceramics. Even a highly corrosive measurement medium can be directly contacted to measure pressure. Therefore, there is no need to separate the sensor element S from the measurement medium 34 by covering the surface of the sensor element S with a sealing liquid, and the size of the sensor can be reduced.
[0043]
Furthermore, the sapphire substrate employs a manufacturing process similar to the batch process used in semiconductor manufacturing, so that variations between sensor elements such as electrode spacing are small, and a large number of sensor elements having the same characteristics can be manufactured. Yes, excellent mass productivity.
[0044]
Next, a method of manufacturing the above-described absolute pressure sensor will be schematically described with reference to FIGS.
The absolute pressure sensor 20 has a large number of sensor elements manufactured on a 4-inch square sapphire substrate having a thickness of, for example, about 1.5 mm and having a three-layer structure in which three plates are stacked, and then individually formed by dicing. The sensor element is manufactured by cutting and separating the sensor element into a package and storing the package in a package. For convenience of description, a manufacturing procedure will be described using one of the sensor elements.
[0045]
5 and 6 are a plan view and a cross-sectional view for explaining a step of forming the second substrate and the movable body.
First, a plate material 100 made of a square sapphire substrate is prepared. This plate material 100 has the same size and thickness as the second substrate 23, and the joining surface with the diaphragm 22 is mirror-finished by polishing. After the mirror finish, the material is heated to about 1500 ° C. to remove distortion (melting point of sapphire: about 1800 ° C.).
[0046]
Next, a first groove 101 having a groove width W is formed near the outer periphery of the diaphragm joining surface of the mirror-finished plate material 100 by ultrasonic processing, laser processing, blast processing, or the like (FIG. 5). The first groove 101 is a groove that becomes a part of a minute gap 33 formed between the second substrate 23 and the cover 24B of the movable body 24, and has an outer diameter of the inner diameter of the second substrate 23. R ₂ And the inner diameter is the outer diameter R of the cover 24B of the movable body 24. ₃ Is set equal to
[0047]
Next, a predetermined portion of the diaphragm joining surface of the plate material 100 is masked with a mask 102, and a second groove 103 is formed by dry etching, blasting, or the like (FIG. 6). A portion of the diaphragm joining surface of the plate material 100 covered by the mask 102 is a portion outside the first groove 101 to be the joining fixed portion 24A of the movable body 24, a central portion to be the joining fixing portion 24A, and a protection portion. This is the portion that becomes the wall 37. The second groove 103 has the same outer diameter as the first groove 101, a sufficiently small inner diameter, and serves as the internal space 32 of the second substrate 23. When the second groove 103 having a predetermined depth is formed, the first groove 101 is dug down and located below the second groove 103. As a result, disc portions 104a and 104b having different diameters are formed in two steps in the center of the inside of the plate material 100, and the upper small-diameter disc portion 104a is a non-etched portion and This is a portion to be the joint fixing portion 24A. On the other hand, the large-diameter disk portion 104b on the lower side is the remaining portion of the etching and the portion that becomes the cover portion 24B of the movable body 24. Further, the frame wall portion 105 of the plate material 100 outside the first and second grooves 101 and 103 is a portion to be the second substrate 23. After the processing of the second groove 103, the mask 102 is removed from the plate material 100.
[0048]
FIGS. 7A and 7B are a plan view and a cross-sectional view for explaining a step of joining the plate material and the diaphragm.
The sapphire substrate is formed in a predetermined thin film shape, and the front and rear surfaces thereof are mirror-finished by polishing, whereby the diaphragm 22 having a uniform thickness is manufactured. Next, the diaphragm 22 is positioned and placed on the diaphragm joining surface of the plate material 100, and the center of the back surface and the outer peripheral edge of the back surface are directly joined to the surface of the small-diameter disk portion 104a and the surface of the frame wall portion 105, respectively. In the case where the diaphragm 22 and the plate material 100 are directly joined, it is desirable to heat the material to about 1000 ° C.
[0049]
FIGS. 8A and 8B are a plan view and a cross-sectional view illustrating a step of forming an electrode on a diaphragm.
A conductive thin film is formed on the central part of the surface of the diaphragm 22 and on the inner side of the frame wall part 105 of the plate material 100, which is close to the outer periphery, and is patterned by the engraving technique so that the movable electrode 26 having a predetermined shape and the reference An electrode 28 is formed. The conductive thin film can be formed by a dry film forming method, such as CVD, vacuum evaporation, or sputtering, which is usually used in a semiconductor process. Further, the conductive films 41a and 41b and the pads 42a to 42db are simultaneously formed.
[0050]
FIGS. 9A and 9B are a plan view and a cross-sectional view illustrating a step of forming a pin hole and a vacuum exhaust hole in the first substrate.
First, a first substrate 21 made of a square sapphire substrate is prepared. The surface of the first substrate 21 which is the bonding surface with the diaphragm 22 is mirror-finished by polishing, and then heated to about 1500 ° C. to remove distortion. Next, pin holes 36a to 36d and a vacuum exhaust hole 38 are formed at predetermined positions of the first substrate 21 by laser processing. The pin holes 36a to 36d are formed so as to face the pads 42a to 42d shown in FIG.
[0051]
FIGS. 10A and 10B are a plan view and a cross-sectional view for explaining a step of forming a recess serving as a capacitance chamber in the first substrate.
A predetermined portion of the surface of the first substrate 21 is covered with a mask 110 to form a recess 35 having a predetermined depth by dry etching or blasting. The concave portion 35 is a portion that becomes a sealed space by joining the diaphragm 22 in a later step, and becomes the capacity chamber 31 by being further evacuated. After the formation of the recess 35, the mask 110 is removed.
[0052]
FIGS. 11A and 11B are a plan view and a cross-sectional view for explaining a step of forming an electrode on the first substrate.
A fixed electrode 25 and a reference electrode 27 having a predetermined shape are formed by forming a conductive thin film on the bottom surface of the concave portion 35 of the first substrate 21 and patterning the conductive thin film by an engraving technique. Like the movable electrode 26 and the reference electrode 28 described above, the conductive thin film can be formed by a dry deposition method such as CVD, vacuum deposition, or sputtering, which is usually used in a semiconductor process. Thereafter, conductive films 39a and 39b are formed by thermal spraying or the like.
[0053]
FIGS. 12A and 12B are a plan view and a cross-sectional view for explaining a step of joining the first substrate and the diaphragm.
The diaphragm 22 is positioned and mounted on the surface of the first substrate 21, and the movable electrode 26 and the reference electrode 28 are opposed to the fixed electrode 25 and the reference electrode 27, respectively. Then, the first substrate 21 and the diaphragm 22 are directly joined. It is desirable that the direct bonding between the first substrate 21 and the diaphragm 22 is also performed by heating to about 1000 ° C.
[0054]
FIGS. 13A and 13B are a plan view and a cross-sectional view for explaining a process of cutting and separating a plate material into an outside and an inside to form a second substrate and a movable body.
A ring-shaped third groove 112 is formed in the outer peripheral portion of the surface of the plate material 100 opposite to the diaphragm joining surface by laser processing, dry etching, or the like, and communicates with the first groove 101. The third groove 112 has the same size and groove width as the first groove 101. As a result, the plate material 100 is completely cut and separated into an outer portion and an inner portion from the first groove 101 and the third groove 112, and the outer portion is formed of the frame-shaped body shown in FIG. 23, the inner part forms the movable body 24, and the first groove 101 and the third groove 112 form the minute gap 33 having the groove width W.
[0055]
Next, a solder stopper layer is formed by spraying a conductive material on the pads 42a to 42d on the diaphragm 22 through the pin holes 36a to 36d of the first substrate 21. After that, the molten solder is poured into each of the pin holes 36a to 36d and electrically connected to each other, thereby completing the sensor element S including the first substrate 21, the diaphragm 22, the second substrate 23, the movable body 24, and the like. The sensor element S is housed in a package PK (FIG. 2). At this time, the sensor element S is sealed and joined to the package PK so as to separate the outer surface of the cover portion 24B of the movable body 24 and the inner space 32 side from the capacity chamber 31 side.
[0056]
Thereafter, the vacuum exhaust hole 38 is connected to a vacuum pump (not shown), and the vacuum pump evacuates the air in the capacity chamber 31 surrounded by the first substrate 21 and the diaphragm 22 to obtain a predetermined vacuum degree. Vacuum chamber. Thereafter, the manufacturing of the absolute pressure sensor 20 shown in FIGS. 1 to 4 is completed by sealing the vacuum evacuation hole 38 of the package PK.
[0057]
In the absolute pressure sensor 20 manufactured in this manner, a large number of sensor elements S of the same quality can be mass-produced because a large number of sensor elements S can be manufactured simultaneously in a substrate made of sapphire, similarly to a semiconductor process. It is possible to reduce the manufacturing cost.
[0058]
FIG. 14 is a sectional view showing a second embodiment of the present invention.
In this embodiment, a sensor element S is constituted by a first substrate 21, a diaphragm 22, a second substrate 23, and a movable body 24, and a strain generating part 22B of the diaphragm 22 and a second And a small gap 120 is formed between the surface (upper surface) of the second substrate 23 and the inner surface of the cover portion 24B. The gap 120 is a gap within a range in which a minute substance does not easily pass and the measurement medium easily passes and does not affect the pressure responsiveness of the sensor, for example, about several μm. Further, a sufficient gap 121 is set between the outer peripheral surface of the cover 24B of the movable body 24 and the inner peripheral surface of the package PK. Other structures are substantially the same as those of the first embodiment. The manufacturing method is substantially the same.
[0059]
Even in such a structure, since the minute gap 120 is formed between the surface of the second substrate 23 and the outer peripheral portion of the inner surface of the cover 24B of the movable body 24, the same as in the above-described embodiment, It is possible to prevent a minute substance contained in the measurement medium from entering the internal space 32 of the second substrate 23 and adhering to and accumulating on the strain generating portion 22B of the diaphragm 22.
[0060]
The pressure of the measurement medium 34 guided to the absolute pressure sensor 20 is P ₁ To P ₂ When the pressure changes to ₂ After passing through the filter F, the measuring medium 34 enters the second substrate 23 through the minute gap 121 and increases the pressure in the internal space 32 to P ₁ To P ₂ It takes a certain time to replace the pressure P with the pressure P in the internal space 32 transiently. ₁ And the pressure P applied to the outer surface of the cover 24B of the movable body 24 (the surface exposed to the outside of the package PK) ₂ Pressure difference (| P ₁ −P ₂ |) Occurs. However, in the present structure, the portion affected by the pressure difference can be limited to the portion of the cover 24B of the movable body 24 that covers the second substrate 23, so that the response is hardly deteriorated.
[0061]
FIG. 15 is a sectional view showing a third embodiment of the present invention.
This embodiment corresponds to the first aspect of the present invention, in which a sensor element S is composed of a substrate 21, a diaphragm 22, and a movable body 24, and the sensor element S is housed in a package PK. This is an absolute pressure sensor 130. That is, in the present embodiment, the above-mentioned second substrate 23 is omitted.
[0062]
The movable body 24 is composed of a joint fixing portion 24A having a minute height and a cover portion 24B covering the entire outer surface of the diaphragm 22. A minute gap 122 is formed. The manufacturing method is substantially the same as in the above embodiment. The gap 122 is set to a gap through which a minute substance passes, for example, about several μm.
[0063]
In such a structure, since the second substrate 23 surrounding the outer periphery of the movable body 24 is not required, simplification of the sensor element S and reduction in manufacturing cost can be achieved.
[0064]
In each of the above-described embodiments, the case where the shape of the absolute pressure sensor is a square has been described. However, the present invention is not limited to this, and various shapes such as a polygon, a circle, and an ellipse may be used. May be used.
Further, the example in which the capacity chamber 31 and the strain-generating portion 22B of the diaphragm 22 are formed in a circular shape in order to increase the area of the fixed electrode 25 and the movable electrode 26 is shown, but the present invention is not limited to this. Is also good.
[0065]
Further, the movable electrode 26 may be formed only at the center of the rear surface of the diaphragm 22 corresponding to the joint fixing portion 24A of the movable body 24. In addition, if an appropriate number of depressions are provided on the surface of the cover 24B of the movable body 24, the weight of the movable body 24 can be reduced, and the influence of errors such as vibration can be reduced.
[0066]
Further, in the above-described embodiment, an example in which a sapphire substrate or a quartz substrate is used as a material of the first substrate 21, the diaphragm 22, the second substrate 23, and the movable body 24 has been described. It is also possible to use a silicon substrate or glass.
[0067]
Furthermore, although the above-described embodiments show examples in which the present invention is applied to an absolute pressure sensor, the present invention is not limited to this, and can be applied to a sensor using atmospheric pressure as a reference pressure. It is.
[0068]
【The invention's effect】
As described above, the capacitance type pressure sensor according to the present invention includes a movable body which is joined to the diaphragm and is displaced integrally therewith, and the movable body is joined to a strain-generating portion of the diaphragm, and a diaphragm is provided. And a cover that covers the upper part of the strain-generating part. A minute gap is formed between the covering part and the strain-generating part. Can be prevented. Therefore, when a filter is used, it is not necessary to use a filter whose eyes are smaller than necessary, and the responsiveness of the sensor can be improved.
[0069]
In addition, unless a minute substance adheres or accumulates on the strain generating portion of the diaphragm, the temperature characteristics of the sensor do not change, and stable performance can be maintained for a long period of time.
[0070]
In addition, the present invention includes a second substrate surrounding the strain generating portion of the diaphragm and the movable body, providing a minute gap between the inner wall surface of the substrate and the covering portion of the movable body, and the inside of the joint portion of the diaphragm. Since the edge is located substantially inside the inner wall surface of the second substrate by the gap, even if a minute substance enters the second substrate through the gap, most of the edge is located immediately below the gap. It is possible to provide an electrostatic capacitance type pressure sensor which has a small amount of adhesion and deposition on the joint of the diaphragm and adheres and accumulates on the strain generating portion, and has excellent pressure response and temperature characteristics.
[0071]
Furthermore, since the first substrate, the diaphragm, the second substrate, and the movable body are made of the same material, thermal stress does not occur at the joint due to temperature change, and the elastic deformation of the diaphragm is not affected. Can be improved.
[Brief description of the drawings]
FIG. 1 is an external perspective view showing a first embodiment of a capacitance type pressure sensor according to the present invention.
FIG. 2 is a sectional view taken along line II-II of FIG.
FIG. 3 is a plan view of a first substrate.
FIG. 4 is a bottom view of the diaphragm.
FIGS. 5A and 5B are a plan view and a cross-sectional view illustrating a step of forming a second substrate and a movable body.
FIGS. 6A and 6B are a plan view and a cross-sectional view illustrating a step of forming a second substrate and a movable body.
FIGS. 7A and 7B are a plan view and a cross-sectional view for explaining a step of joining a plate material and a diaphragm.
FIGS. 8A and 8B are a plan view and a cross-sectional view for explaining a step of forming an electrode on a diaphragm.
FIGS. 9A and 9B are a plan view and a cross-sectional view illustrating a step of forming a pin hole and a vacuum exhaust hole in a first substrate.
FIGS. 10A and 10B are a plan view and a cross-sectional view for explaining a step of forming a capacitance chamber in a first substrate.
FIGS. 11A and 11B are a plan view and a cross-sectional view illustrating a step of forming an electrode on a first substrate.
FIGS. 12A and 12B are a plan view and a cross-sectional view for explaining a step of joining a first substrate and a diaphragm.
FIGS. 13 (a) and 13 (b) are a plan view and a sectional view for explaining a step of cutting and separating a plate material to form a second substrate.
FIG. 14 is a sectional view showing a second embodiment of the present invention.
FIG. 15 is a sectional view showing a third embodiment of the present invention.
FIG. 16 is a sectional view of a conventional capacitance type pressure sensor.
[Explanation of symbols]
Reference Signs List 20: Absolute pressure sensor, 21: First substrate, 22: Diaphragm, 22A: Joint, 22B: Strain-flexing part, 23: Second substrate, 24: Movable body, 24A: Joint, 24B: Covering part, 25: fixed electrode, 26: movable electrode, 27, 28: reference electrode, 31: capacitance chamber, 32: internal space, 33: minute gap, F: filter.

Claims (5)

In a capacitance pressure sensor with a diaphragm structure that detects a change in measured pressure as a change in capacitance,
A substrate provided with a fixed electrode, a joint portion and a strain-generating portion, the joint portion being joined to the substrate to form a capacitance chamber together with the substrate, A diaphragm provided with a corresponding movable electrode, and a movable body that covers the strain-generating portion of the diaphragm and is displaced integrally with the strain-generating portion by a measured pressure,
The movable body is composed of a joint fixing portion joined to the center of the outer surface of the strain generating portion of the diaphragm, and a cover formed integrally with the joint fixing portion and covering the strain generating portion of the diaphragm. A minute gap is formed between the pressure sensor and the strain generating portion. The capacitance type pressure sensor according to claim 1,
A capacitance type pressure sensor, wherein a substrate, a diaphragm and a movable body are respectively formed of the same material, and these are integrally joined by direct joining. In a capacitance pressure sensor with a diaphragm structure that detects a change in measured pressure as a change in capacitance,
A first substrate provided with a fixed electrode, a joint portion and a strain generating portion, the joint portion being joined to the substrate to form a capacitance chamber together with the substrate, A diaphragm provided with a movable electrode corresponding to the fixed electrode, a second substrate joined on the joining portion of the diaphragm and surrounding the strain-generating portion, and A movable body that is displaced integrally with the diaphragm,
The movable body is composed of a joint fixing portion joined to the center of the outer surface of the strain generating portion of the diaphragm, and a cover formed integrally with the joint fixing portion and covering the strain generating portion of the diaphragm. A minute gap is formed between the capacitance type pressure sensor and the second substrate. The capacitance type pressure sensor according to claim 3,
The minute gap is formed between the inner wall surface of the second substrate and the outer peripheral surface of the cover of the movable body, and the inner edge of the joint of the diaphragm joined to the first substrate is formed by the second substrate. A capacitance type pressure sensor which is located substantially inside the minute gap from the inner wall surface of the pressure sensor. The capacitance type pressure sensor according to claim 3 or 4,
A capacitance type pressure sensor, wherein a first substrate, a diaphragm, a second substrate, and a movable body are respectively formed of the same material, and these are integrally joined by direct joining.

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