JP4151898B2 - Capacitive pressure sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diaphragm pressure sensor that detects a change in pressure to be measured as a change in capacitance, and more particularly to a capacitance pressure sensor suitable for use in a semiconductor etching process or the like.
[0002]
[Prior art]
Conventionally, various electrostatic pressure sensors used for pressure gauges and the like have been known (see, for example, 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
It should be noted that the applicant has not found any prior art documents closely related to the present invention by the time of filing other than 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 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 the change in the pressure to be measured from the atmosphere and evacuates the inside, and is usually configured as shown in FIG. Briefly describing this, the absolute pressure sensor 1 includes a silicon substrate 2 and a glass substrate 3 which are laminated and anodically bonded (electrostatic bonded), and a sealed space formed between the two substrates is a capacity chamber (vacuum chamber). Four. In the silicon substrate 2, the thick outer peripheral edge portion forms a joined portion 2 </ b> A with the glass substrate 3, and the central portion is the pressure P to be measured.₁ The diaphragm is configured by forming a thin strain-generating portion 2B that is elastically deformed when it is received. A movable electrode 5 is provided on the outer surface side of the strain generating portion 2B, and this movable electrode 5 is electrically connected to a capacitance detecting IC chip 6 provided on the outer surface of the glass substrate 3 via a lead wire 7. ing. On the other hand, a fixed electrode 8 is provided on the back surface of the glass substrate 3 facing the diaphragm so as to face the movable electrode 5 in the vicinity.
[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 is elastically deformed according to the pressure, and the minute gap G between the movable electrode 5 and the fixed electrode 8 is changed. For this reason, the electrostatic capacitance of the capacitor formed by the movable electrode 5 and the fixed electrode 8 changes.₁ Can be detected.
[0006]
When pressure measurement is performed by using such a conventional absolute pressure sensor 1 in, for example, an etching process of a semiconductor manufacturing apparatus, a film forming process by CVD, etc., a minute substance contained in a measurement medium, for example, reactivity Gas plasma is generated to generate Si, Si_ThreeN_FourWhen etching of Al, etc. is performed, since the etching gas contains minute substances such as gasified materials and reaction products, these minute substances are contaminated and the strain generating portion of the diaphragm 2 Deposit 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 (especially the thermal expansion coefficient) of the fine substance attached to and deposited on the strain generating part 2B are different from those of the strain generating part 2B, when the temperature changes due to the so-called bimetallic effect with the deposit, It will cause deflection. Since the amount of deflection depends on the type and amount of deposit, the temperature compensation performed at the start of sensor use becomes invalid. In addition, since the compliance (= volume change / pressure change) of the strain generating portion 2B is also reduced, there is a problem that a minute pressure change cannot be measured with high accuracy.
[0007]
Therefore, in order to solve such a problem, a pressure sensor in which a minute substance contained in a measurement medium is captured by a filter so that the minute substance does not adhere to and accumulate on the strain generating portion has been conventionally used. (See, for example, Patent Document 4).
[0008]
[Patent Document 4]
US Pat. No. 5,811,865
[0009]
[Problems to be solved by the invention]
However, the conventional pressure sensor described in the above-mentioned U.S. Pat. No. 5,811,865 uses a filter with a large mesh size (fine mesh) in order to reduce adhesion and accumulation of minute substances contained in the measurement medium. If it is used, it becomes difficult for the measurement medium to pass through, so that a change in pressure cannot be quickly transmitted to the diaphragm, and the pressure responsiveness of the sensor decreases. On the other hand, when trying to increase the pressure responsiveness using a filter with a small mesh size (coarse mesh), minute substances contained in the measurement medium easily pass and adhere to and accumulate on the strain-generating portion. Since the amount increases, there is a problem that the temperature characteristic of the sensor changes and the measurement error increases. Therefore, conventionally, as long as a filter is used, it has not been possible to design and manufacture a sensor that can simultaneously satisfy both measurement accuracy and pressure response.
[0010]
The present invention has been made in order to solve the above-described conventional problems, and the object of the present invention is to cause a minute substance contained in the measurement medium to cause distortion of the diaphragm even when a coarse filter is used. It is an object of the present invention to provide a capacitance type pressure sensor that can reduce the amount of adhesion and deposition on the part and improve both temperature characteristics and pressure responsiveness at the same time.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, the first invention provides:Pressure change of the medium to be measured provided with a minute gap to prevent entry of minute substances contained in the medium to be measuredIn a capacitive pressure sensor having a diaphragm structure that detects a change in capacitance as a change in capacitance, the substrate has a fixed electrode, a bonding portion, and a strain generating portion, and the bonding portion is bonded to the substrate. A diaphragm having a capacitive chamber formed with the substrate and a movable electrode corresponding to the fixed electrode is provided on the strain generating portion, and the strain generating portion is covered with the strain generating portion by covering the strain generating portion of the diaphragm with a measured pressure. A movable body that is integrally displaced, and a joint fixing portion that is joined to the center of the outer surface of the strain generating portion of the diaphragm, and a strain fixing portion of the diaphragm that is integrally formed with the joint fixing portion. Consists of a cover andThe minute gap isFormed between the cover and the strain generating partThe pressure change of the medium to be measured is received by the cover portion of the movable body, and the diaphragm is elastically deformed through the joint fixing portion.Is.
[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 the distance between the fixed electrode and the movable electrode is changed. Since the cover of the movable body covers the strain generating portion of the diaphragm with a minute gap, minute substances contained in the measurement medium enter the gap and adhere to and accumulate on the strain generating portion. To prevent.
The part that mainly determines the pressure sensitivity of the diaphragm is the strain generating part. If the joint fixing part of the movable body is regarded as a rigid body, the central part of the strain generating part to which the joint fixing part of the movable body is joined cannot be elastically deformed, and the strain generating part outside the central part is elastic. Deform. Even if a minute substance contained in the measurement medium adheres and accumulates on the joint fixed part of the movable body made of a rigid body and the cover part connected to the strain generating part via the rigid body, the pressure sensitivity of the diaphragm is reduced. Has almost no influence, so that the measurement accuracy can be kept stable over a long period of time. In addition, as described in the embodiment of the present invention, the output response to a transient change in pressure is good with this structure.
[0013]
According to a second invention, in the first invention, 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 invention, 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 bonding using a bonding material, the inter-electrode distance varies due to variations in the thickness of the bonding material itself after bonding. Direct bonding, on the other hand, is a method in which the bonding surfaces of the bonding members are mirror-finished and bonded to each other, so there is no need to use any bonding material. Therefore, variations in the distance between electrodes due to variations in the thickness of the bonding material Can be obtained, and a highly accurate inter-electrode distance can be obtained.
In the direct joining, basically, it is only necessary to mirror-finish the joining surfaces of the two joining members and laminate them together. However, in order to obtain a more reliable joining, an appropriate pressure and temperature (for example, 200 to 1300 °). It is preferable to pressurize and heat at about 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 the difference in thermal expansion coefficient.
[0015]
  The third invention isPressure change of the medium to be measured provided with a minute gap to prevent entry of minute substances contained in the medium to be measuredIn a capacitive pressure sensor with a diaphragm structure that detects a change in capacitance,Having a recess, and in the recessA first substrate provided with a fixed electrode; a joint portion; and a strain generating portion;Side surface of the concave portion of the first substrateAnd a diaphragm having a movable electrode corresponding to the fixed electrode in the strain generating portion, and the diaphragm bonded to the joint portion of the diaphragm. A second substrate that surrounds the strain generating portion; and a movable body that is located within the second substrate and is displaced integrally with the diaphragm by the pressure to be measured.The minute gap is formed between the outer peripheral surface of the cover of the movable body and the inner wall surface of the second substrate, the pressure change of the medium to be measured is received by the cover of the movable body, and the bonding is fixed. The diaphragm is elastically deformed through a portionIs.
[0016]
In the third invention, the amount of the minute substance contained in the measurement medium that has entered the second substrate through the minute gap is small, and it is prevented from adhering to and accumulating on the strain generating portion of the diaphragm. To do.
[0017]
  According to a fourth invention, in the third invention,FirstThe inner edge of the bonded portion of the diaphragm to be bonded to the substrate is positioned on the inner side of the inner wall surface of the second substrate by substantially the minute gap.
[0018]
In the fourth invention, a part of the surface of the joint portion of the diaphragm to be joined to the first substrate is located on the inner side of the inner wall surface of the second substrate and faces a minute gap. The minute substance contained in the measurement medium that has penetrated into the second substrate through the surface adheres and accumulates mainly on the portion of the joint that faces the gap, and adheres and accumulates on the strain-generating portion. The amount is small.
[0019]
  The fifth invention is the above-mentioned3In the invention ofThe inner diameter of the recess of the first substrate is R ₁ , The inner diameter of the second substrate is R ₂ The outer diameter of the cover of the movable body is R _Three R ₁ ≦ R _Three <R ₂ Meets the requirements ofIs.
  According to a sixth aspect of the present invention, in the third aspect, when the width of the gap between the cover of the movable body and the second substrate is W and the thickness of the cover of the movable body is L, the thickness The ratio of L to width W is 20 or more.
According to a seventh invention, in any one of the third to sixth inventions, the first substrate, the diaphragm, the second substrate, and the movable body are respectively formed of the same material, and these are directly bonded. They are joined together.
[0020]
In the fifth invention, a sensor having a desired interelectrode 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 the difference in thermal expansion coefficient.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
1 is an external perspective view showing a first embodiment of a capacitive pressure sensor according to the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, and FIG. 3 is a plan view of a first substrate, FIG. 4 is a bottom view of the diaphragm. This embodiment shows an example used for pressure measurement of a semiconductor manufacturing apparatus that physically and chemically dry etches a silicon wafer. In the drawings shown below, the dimensions in the thickness direction are extremely exaggerated for convenience of explanation.
[0022]
In these drawings, an absolute pressure sensor generally indicated by reference numeral 20 is composed of a sensor element S and a package PK that houses the sensor element S, and is disposed in an etching chamber of a semiconductor manufacturing apparatus.
[0023]
The semiconductor manufacturing apparatus has an internal vacuum degree of about several Pa, and a filter F is disposed 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, thereby facilitating the passage of the measurement medium (etching gas) 34.
[0024]
Further, the constituent elements of the sensor element S will be described in detail. The sensor element S includes the first substrate 21, the diaphragm 22, the second substrate 23, the movable body 24, the fixed electrode 25, the movable electrode 26, and the reference. The electrodes 27 and 28 and four electrode extraction pins 29a to 29d are formed. 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 (Al₂O_Three) Or a quartz substrate, which are sequentially laminated with their centers aligned, and are integrally joined by direct joining.
[0025]
Direct bonding is a method of bonding by using only the physicochemical bonding force between bonding members without using any bonding material or the like, and is a method of bonding by bonding the bonding surfaces of two bonding members to a mirror finish and bringing them into close contact with each other It is. In joining, it is not necessary to apply pressure in particular, and it is only necessary to superimpose them. However, it is preferable that heating is performed at about 200 to 1300 ° C. to obtain more reliable joining.
[0026]
The bonding method of the first substrate 21, the diaphragm 22, the second substrate 23, and the movable body 24 is not limited to direct bonding, and when a silicon single crystal substrate is used as a substrate material for these members, diffusion bonding is used. What is necessary is just to join. Further, when silicon and glass are used as the substrate material, anodic bonding may be performed. In any of these bonding methods, as in the direct bonding described above, bonding is performed without interposing a bonding material at the interface between the substrates.
[0027]
A sealed 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, an internal space of the second substrate 23, in other words, a 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 annular minute gap 33 communicates with the inside of the semiconductor manufacturing apparatus, and the measurement medium 34 is guided through the filter F.
[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 hundreds μm, and is formed at the center of a surface (referred to as a diaphragm bonding surface or a bonding surface) to which a diaphragm is bonded. A recess 35 is formed to form the capacity chamber 31. As shown in FIG. 3, the recess 35 is a rectangular recess that is slightly smaller than the first substrate 21, and the fixed electrode 25 and one reference electrode 27 are formed on the bottom surface. Further, pin holes 36a to 36d through which the electrode take-out pins 29a to 29d pass and protective walls 37 are respectively formed at the four corners of the bottom surface of the recessed portion 35, and further to the one side, a vacuum exhaust hole is formed. 38 is formed.
[0030]
The fixed electrode 25 is formed in the center of the bottom surface of the recessed portion 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 an open portion, 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 the molten metal material (platinum or the like) from being scattered 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 recessed portion 35. The evacuation hole 38 is formed in an open portion 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 formed in a thin film shape with a thickness of about several tens of μm, and an outer peripheral edge portion is directly bonded to a bonding surface of the first substrate 21 to form a bonding portion 22A. The inner portion of the joint 22A is the pressure P to be measured.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 central portion of the outer surface (surface on the movable body side). In this case, since the movable body 24 is regarded as a rigid body, the elastically deformable strain-generating portions in the diaphragm 22 after becoming an actual product are the central portion to which the movable body 24 is joined and the joint portion 22A. An annular portion between.
[0032]
In FIG. 4, the movable electrode 26 and the other reference electrode 28 are connected to the fixed electrode 25 and the one reference electrode 27 on the back surface side of the strain-generating portion 22 </ b> B of the diaphragm 22 joined to the first substrate 21. Correspondingly formed. 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 generating portion 22B, thereby maintaining a predetermined distance (approximately several μm) between the fixed electrode 25 and the fixed electrode 25. Are connected to the electrode extraction pad 42a by the 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 periphery of the movable electrode 26, and is connected to the electrode extraction pad 42b by a conductive film 41b. Yes. Needless to say, the reference electrode 28 also faces the reference electrode 27 with a predetermined inter-electrode distance (approximately several μm). 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-like body having a thickness of about 1 mm, an outer shape is a square having the same size as the first substrate 21 and the diaphragm 22, and an inner shape is a circle. By being joined directly on the outer surface of the joining portion 22A of the diaphragm 22, the strain generating portion 22B and the movable body 24 are surrounded.
[0034]
The movable body 24 includes a joint fixing portion 24A that is joined to the center of the outer surface of the strain generating portion 22B of the diaphragm 22, and a cover portion that is integrally formed at the distal end of the joint fixing portion 24A and covers the upper side of the strain generating portion 22B. 24B constitutes a rigid body and is located in the second substrate 23. The joint fixing portion 24 </ b> A is formed in a disk shape having substantially the same diameter as the fixed electrode 25 and the movable electrode 26. Similarly, the cover portion 24 </ b> B has a disk shape substantially the same diameter as the strain-generating portion 22 </ b> B 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 R₁ , The inner diameter of the second substrate 23 is R₂ The outer diameter of the cover 24B of the movable body 24 is R_Three Then R₁ ≦ R_Three <R₂ As shown in FIG. 2, the inner edge a of the joint portion 22A of the diaphragm 22 is positioned at least the width W of the gap 33 from 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 is difficult to pass through and the measurement medium 34 is easy to pass through and does not affect the pressure responsiveness of the absolute pressure sensor 20. Width, preferably the ratio of length L to width W20It is set to about or more.
[0036]
Each of the electrode extraction pins 29a to 29d passes through the electrode holes 36a to 36d formed in the first substrate 21 and protrudes to the back surface side, and is 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 P₁ Thus, the movable body 24 is pushed down to elastically deform the strain generating portion 22B of the diaphragm 22. For this reason, the distance between the fixed electrode 25 and the movable electrode 26 is changed, and the capacitance of the capacitor formed by these two electrodes is changed.₁ Can be detected.
[0038]
The pressure of the measurement medium 34 guided to the absolute pressure sensor 20 is P₁ To P₂ When the pressure changes to P₂ After the measurement medium 34 passes through the filter F, it enters the second substrate 23 through the minute gap 33 and the pressure in the internal space 32 is changed to P.₁ To P₂ Since the replacement requires a required time, the pressure P in the internal space 32 is transiently changed.₁ 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 (| P₁ -P₂|) Occurs. However, in this structure, the movable electrode 26 is displaced by the pressure P₂ (The pressure in the internal space acts in the reverse direction so as to cancel the displacement of the movable electrode 26 part on the cover part 24B facing the strain generating part 22B). Therefore, the small gap 33 formed between the second substrate 23 and the movable body 24 does not reduce the pressure response of the sensor.
[0039]
  Further, 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 the entry of minute substances contained in the measurement medium 34, Moreover, even if it passes through the gap 33, the above-mentioned R₁ ≦R_Three <R₂ Under these conditions, the liquid drops and adheres and accumulates mainly on the surface of the joint portion 22A of the diaphragm 22 positioned directly below the condition, so that the amount of adhesion and deposition on the strain generating portion 22B can be reduced. Therefore, measurement errors due to temperature changes are small, and the temperature characteristics of the sensor can be improved.
[0040]
In addition, if 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 portion during the manufacture is made as compared with the case of manufacturing with different materials. Can be reduced. The secular change of the residual stress becomes an error factor of pressure measurement, so it is desirable to reduce it as much as possible. Further, 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]
Further, 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. In other words, when bonding using a bonding material, the distance between the electrodes varies due to variations in the thickness of the bonding material, but in the case of direct bonding, since no bonding material is used, there is a variation due to the thickness of the bonding material. The distance between the electrodes is determined only by the dry etching amount of the recessed portion 35 of the first substrate 21 and the thicknesses of the fixed electrode 25 and the movable electrode 26. Therefore, it is possible to obtain a distance between the electrodes that is substantially equal to the design value, and an absolute pressure sensor that can perform highly accurate and reliable pressure measurement is obtained.
[0042]
Further, when each constituent member of the sensor element S is formed of a sapphire substrate, since sapphire is a single crystal and there are no grain boundaries such as alumina and ceramics, it has high corrosion resistance, and an alkaline or acidic liquid. Even a highly corrosive measuring medium can be directly contacted to measure the pressure. Therefore, it is not necessary to isolate the surface of the sensor element S from the measurement medium 34 by covering the surface with the sealing liquid, and the sensor can be downsized.
[0043]
In addition, the sapphire substrate uses a manufacturing process similar to the batch process used in semiconductor manufacturing, so that there is little variation between sensor elements such as electrode spacing, making it possible to manufacture a large number of sensor elements with the same characteristics. Yes, and excellent in mass productivity.
[0044]
Next, a method for manufacturing the absolute pressure sensor described above will be schematically described with reference to FIGS.
The absolute pressure sensor 20 described above has a three-layer structure in which three plates are stacked, for example, a large number of sensor elements are manufactured on a 4-inch square sapphire substrate having a thickness of about 1.5 mm, and then individually separated by dicing. This is manufactured by cutting and separating the sensor element and storing it in a package. For convenience of explanation, the 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 process of forming the second substrate and the movable body.
First, a plate material 100 made of a square sapphire substrate is prepared. The plate material 100 has the same size and thickness as the second substrate 23, and the joint surface with the diaphragm 22 is mirror-finished by polishing. Further, after the mirror finish, it is heated to about 1500 ° C. to remove strain (melting point of sapphire: about 1800 ° C.).
[0046]
Next, a first groove 101 having a groove width W is formed by ultrasonic processing, laser processing, blast processing, or the like near the outer periphery of the diaphragm joint surface of the mirror-finished plate material 100 (FIG. 5). The first groove 101 is a groove that is a part of a minute gap 33 formed between the second substrate 23 and the cover 24 </ b> B of the movable body 24, and the outer diameter is the inner diameter of the second substrate 23. R₂ And the inner diameter is the outer diameter R of the cover 24B of the movable body 24._Three Is set equal to
[0047]
Next, a predetermined portion of the diaphragm bonding surface of the plate material 100 is masked with a mask 102, and the second groove 103 is formed by dry etching, blasting, or the like (FIG. 6). Of the diaphragm bonding surface of the plate material 100, the portion covered by the mask 102 is a portion that becomes the bonding fixing portion 24A of the movable body 24 outside the first groove 101, a central portion that becomes the bonding fixing portion 24A, and a protection portion. This is the part that becomes the wall 37. The second groove 103 is a portion having the same outer diameter as the first groove 101 and a sufficiently small inner diameter and serving 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 as it is and is positioned below the second groove 103. As a result, the disc portions 104a and 104b having different diameters are formed in two stages in the center of the plate material 100, and the upper small-diameter disc portion 104a is a non-etched portion and This is the part that becomes the joint fixing part 24A. On the other hand, the large-diameter disk portion 104b on the lower side is a portion that becomes the cover portion 24B of the movable body 24, which is the remaining portion of the etching. Further, the frame wall portion 105 outside the first and second grooves 101 and 103 of the plate material 100 is a portion to be the second substrate 23. Note that the mask 102 is removed from the plate material 100 after the second groove 103 is processed.
[0048]
7A and 7B are a plan view and a cross-sectional view for explaining the joining process of the plate material and the diaphragm.
A sapphire substrate is formed in a predetermined thin film shape, and the front and back surfaces thereof are mirror-finished by polishing to produce a diaphragm 22 having a uniform thickness. 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 surfaces of the small-diameter disk portion 104a and the frame wall portion 105, respectively. When the diaphragm 22 and the plate material 100 are directly joined, it is preferable to heat the diaphragm 22 to about 1000 ° C.
[0049]
8A and 8B are a plan view and a cross-sectional view for explaining a process of forming an electrode on the diaphragm.
A conductive thin film is formed on the inner side of the frame wall portion 105 of the plate material 100, which is near the center and outer periphery of the surface of the diaphragm 22, and is patterned by a printing technique, so that the movable electrode 26 having a predetermined shape and the reference are formed. Electrode 28 is formed. The conductive thin film can be formed by CVD, vacuum deposition, sputtering, or the like, which is a dry film formation usually used in a semiconductor process. Further, the conductive films 41a and 41b and the pads 42a to 42db are formed at the same time.
[0050]
FIGS. 9A and 9B are a plan view and a cross-sectional view for explaining a process 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 joint 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 respectively formed at predetermined positions on the first substrate 21 by laser processing. The pin holes 36a to 36d are formed 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 recessed portion serving as a capacity chamber in the first substrate.
A predetermined portion of the surface of the first substrate 21 is covered with a mask 110, and a recessed portion 35 having a predetermined depth is formed by dry etching or blasting. This recessed portion 35 is a portion that becomes a sealed space by joining the diaphragm 22 in a later process and further becomes a capacity chamber 31 by being evacuated. After the recess 35 is formed, 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 conductive thin film is formed on the bottom surface of the recessed portion 35 of the first substrate 21 and patterned by a printing technique to form a fixed electrode 25 and a reference electrode 27 having a predetermined shape. The conductive thin film can be formed by CVD, vacuum deposition, sputtering, or the like, which is a dry film formation usually used in a semiconductor process, like the movable electrode 26 and the reference electrode 28 described above. 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 process of joining the first substrate and the diaphragm.
The diaphragm 22 is positioned and placed 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. Direct bonding of the first substrate 21 and the diaphragm 22 is also preferably performed by heating to about 1000 ° C.
[0054]
FIGS. 13A and 13B are a plan view and a cross-sectional view for explaining a step of forming the second substrate and the movable body by cutting and separating the plate material into the outer side and the inner side.
A ring-shaped third groove 112 is formed by laser processing, dry etching, or the like on the outer periphery of the surface of the plate material 100 opposite to the diaphragm bonding surface, and communicated 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 second 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 a minute gap 33 having a groove width W.
[0055]
Next, a solder stopper layer is formed by thermal spraying of a conductive material on the pads 42 a to 42 d on the diaphragm 22 through the pin holes 36 a to 36 d of the first substrate 21. Thereafter, molten solder is poured into each of the pin holes 36a to 36d and electrically connected to complete 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 bonded to the package PK so as to separate the outer surface of the cover 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 air in the volume chamber 31 surrounded by the first substrate 21 and the diaphragm 22 is exhausted by this vacuum pump, thereby obtaining a predetermined degree of vacuum. The vacuum chamber. Thereafter, the vacuum pressure evacuation hole 38 of the package PK is sealed to complete the manufacture of the absolute pressure sensor 20 shown in FIGS.
[0057]
In the absolute pressure sensor 20 manufactured in this way, a large number of sensor elements S of the same quality can be manufactured in large quantities since a large number of sensor elements S can be manufactured simultaneously in a sapphire substrate as in the 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, the first substrate 21, the diaphragm 22, the second substrate 23, and the movable body 24 constitute a sensor element S, and the cover portion 24 </ b> B of the movable body 24 and the strain-generating portion 22 </ b> B of the diaphragm 22 and the second The substrate 23 is covered, and a minute gap 120 is formed between the surface (upper surface) of the second substrate 23 and the inner surface of the cover 24B. The gap 120 is a gap within a range in which a minute substance is difficult to pass through, the passage of the measurement medium is easy, and the pressure response of the sensor is not affected, 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 in the first embodiment. The manufacturing method is also 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 inner periphery of the cover 24B of the movable body 24, the first embodiment is similar to 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 depositing on the strain-generating portion 22B of the diaphragm 22.
[0060]
Further, the pressure of the measurement medium 34 guided to the absolute pressure sensor 20 is P₁ To P₂ When the pressure changes to P₂ After the measurement medium 34 passes through the filter F, it enters the second substrate 23 through the minute gap 121 and the pressure in the internal space 32 is changed to P.₁ To P₂ Since it takes a certain time to replace with the pressure P, the pressure P in the internal space 32 is transiently changed.₁ 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 (| P₁ -P₂ |) Occurs. However, in this structure, since the part affected by the pressure difference can be limited to the part covering the second substrate 23 of the cover 24B of the movable body 24, the response is hardly deteriorated.
[0061]
FIG. 15 is a cross-sectional view showing a third embodiment of the present invention.
This embodiment corresponds to the invention described in claim 1, and the sensor element S is constituted by three members of the substrate 21, the diaphragm 22 and the movable body 24, and the sensor element S is accommodated in the package PK. The absolute pressure sensor 130 is used. That is, in the present embodiment, the second substrate 23 described above is omitted.
[0062]
The movable body 24 includes a joining fixing portion 24A having a very small height and a cover portion 24B that covers the entire outer surface of the diaphragm 22. The movable body 24 is interposed between the inner surface of the cover portion 24B and the outer surface of the strain portion 22B 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, the sensor element S can be simplified and the manufacturing cost can be reduced.
[0064]
In the above-described embodiment, the case where the absolute pressure sensor has a square shape has been described. However, the present invention is not limited to this, and various types such as a polygon, a circle, and an ellipse are used. It may be of the shape.
Moreover, in order to increase the area of the fixed electrode 25 and the movable electrode 26, the example in which the capacitive chamber 31 and the strain generating portion 22B of the diaphragm 22 are formed in a circular shape has been shown. Also good.
[0065]
Alternatively, the movable electrode 26 may be formed only at the center of the back surface of the diaphragm 22 corresponding to the joint fixing portion 24A of the movable body 24. Further, 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 error effects such as vibration can be reduced.
[0066]
Further, in the above-described embodiments, the examples in which the sapphire substrate or the quartz substrate is used as the material of the first substrate 21, the diaphragm 22, the second substrate 23, and the movable body 24 have been described. A silicon substrate or glass can also be used.
[0067]
Furthermore, although all of the above-described embodiments have shown examples 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 capacitive pressure sensor according to the present invention includes a movable body that is joined to a diaphragm and that is displaced integrally with the diaphragm, and a joined portion in which the movable body is joined to a strain generating portion of the diaphragm, and the diaphragm. Since a small gap is formed between the cover and the strain generating part, a minute substance enters the gap and adheres to the strain generating part and deposits. Can be prevented. Therefore, when a filter is used, it is not necessary to use a finer eye than necessary, and the responsiveness of the sensor can be improved.
[0069]
In addition, if a minute substance does not adhere to and accumulate on the strain generating portion of the diaphragm, the temperature characteristics of the sensor do not change, and stable performance can be maintained over a long period of time.
[0070]
Further, the present invention includes a second substrate surrounding the strain generating portion of the diaphragm and the movable body, and provides a minute gap between the inner wall surface of the substrate and the cover portion of the movable body, and the inside of the joint portion of the diaphragm. Since the edge is positioned approximately inward from 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 minute substance is located immediately below the gap. It is possible to provide a capacitance type pressure sensor that adheres and deposits on the joint portion of the diaphragm and adheres and deposits on the strain generating portion, and has excellent pressure response and temperature characteristics.
[0071]
Furthermore, since the first substrate, diaphragm, second substrate, and movable body are made of the same material, thermal stress does not occur at the joint due to temperature changes, 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 capacitive pressure sensor according to the present invention.
FIG. 2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is a plan view of a first substrate.
FIG. 4 is a bottom view of a diaphragm.
FIGS. 5A and 5B are a plan view and a cross-sectional view for explaining a process of forming a second substrate and a movable body. FIGS.
6A and 6B are a plan view and a cross-sectional view for explaining a process 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 joining process between a plate material and a diaphragm. FIGS.
FIGS. 8A and 8B are a plan view and a cross-sectional view for explaining a process of forming an electrode on a diaphragm. FIGS.
FIGS. 9A and 9B are a plan view and a cross-sectional view for explaining a process of forming a pin hole and a vacuum exhaust hole in the first substrate. FIGS.
FIGS. 10A and 10B are a plan view and a cross-sectional view for explaining a process of forming a capacitor chamber in the first substrate. FIGS.
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. FIGS.
FIGS. 12A and 12B are a plan view and a cross-sectional view for explaining a process of bonding a first substrate and a diaphragm. FIGS.
FIGS. 13A and 13B are a plan view and a cross-sectional view for explaining a process of cutting and separating a plate material to form a second substrate.
FIG. 14 is a cross-sectional view showing a second embodiment of the present invention.
FIG. 15 is a cross-sectional view showing a third embodiment of the present invention.
FIG. 16 is a cross-sectional view of a conventional capacitive pressure sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 20 ... Absolute pressure sensor, 21 ... 1st board | substrate, 22 ... Diaphragm, 22A ... Joint part, 22B ... Strain part, 23 ... 2nd board | substrate, 24 ... Movable body, 24A ... Joint part, 24B ... Cover part, 25 ... fixed electrode, 26 ... movable electrode, 27, 28 ... reference electrode, 31 ... capacity chamber, 32 ... internal space, 33 ... minute gap, F ... filter.

Claims (7)

A capacitance type pressure sensor having a diaphragm structure that detects a change in pressure of the medium to be measured as a change in capacitance , having a minute gap for preventing entry of a minute substance contained in the medium to be measured. In
A substrate provided with a fixed electrode;
The joint portion is joined to the substrate by having a joint portion and a strain generating portion, thereby forming a capacitance chamber together with the substrate, and a movable electrode corresponding to the fixed electrode is provided in the strain generating portion. Diaphragm,
A movable body that covers the strain-generating portion of the diaphragm and displaces integrally with the strain-generating portion due to 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 portion that is integrally formed with the joint fixing portion and covers the strain generating portion of the diaphragm,
Forming the minute gap between the covering portion and the strain generating portion ;
A capacitance type pressure sensor , wherein a pressure change of the medium to be measured is received by a cover portion of the movable body, and the diaphragm is elastically deformed through the joint fixing portion . The capacitive pressure sensor according to claim 1,
A capacitance type pressure sensor characterized in that a substrate, a diaphragm and a movable body are respectively formed of the same material and are integrally joined by direct joining. A capacitance type pressure sensor having a diaphragm structure that detects a change in pressure of the medium to be measured as a change in capacitance , having a minute gap for preventing entry of a minute substance contained in the medium to be measured. In
A first substrate having a recess, and a fixed electrode provided in the recess ;
A bonding chamber and a strain generating portion are provided, and the bonding portion is bonded to the side surface of the concave portion of the first substrate to form a capacitor chamber together with the first substrate, and the fixed electrode is formed on the strain generating portion. A diaphragm provided with a corresponding movable electrode,
A second substrate joined on the joined portion of the diaphragm and surrounding the strain-generating portion;
A movable body located within the second substrate and displaced integrally with the diaphragm by the pressure to be measured;
Forming the minute gap between the outer peripheral surface of the cover of the movable body and the inner wall surface of the second substrate;
A capacitance type pressure sensor , wherein a pressure change of the medium to be measured is received by a cover portion of the movable body, and the diaphragm is elastically deformed through the joint fixing portion . The capacitive pressure sensor according to claim 3,
A capacitive pressure sensor, wherein an inner edge of a joint portion of a diaphragm to be joined to the first substrate is located substantially inside the minute gap from an inner wall surface of the second substrate. The capacitive pressure sensor according to claim 3,
The inner diameter of the concave portion of the first substrate is R _1. , The inner diameter of the second substrate is R ₂ , The outer diameter of the cover of the movable body is R ₃ R ₁ ≦ R ₃ <R ₂ Capacitance type pressure sensor characterized by satisfying the following conditions . The capacitive pressure sensor according to claim 3,
  When the width of the gap between the cover of the movable body and the second substrate is W and the thickness of the cover of the movable body is L, the ratio of the thickness L to the width W is 20 or more. Capacitance type pressure sensor. The capacitive pressure sensor according to any one of claims 3 to 6,
  A capacitance type pressure sensor, wherein a first substrate, a diaphragm, a second substrate, and a movable body are formed of the same material, and are integrally joined by direct joining.

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