JP4548771B2 - Manufacturing method of capacitive pressure sensor - Google Patents

Description

The present invention relates, for example, for the production how the capacitive pressure sensor having a diaphragm structure for detecting the capacitance corresponding to the measured pressure as the pressure.

  Conventionally, a capacitive pressure sensor having a diaphragm structure that detects a change in pressure to be measured as a change in capacitance is widely known. As an example of such a capacitive pressure sensor, a sensor pedestal having a movable electrode formed in a strain-generating region of a diaphragm and having a recessed portion in part and a fixed electrode formed on the bottom surface of the recessed portion is disposed around the strain-generating region. There is a pressure sensor that detects a change in capacitance between a movable electrode of a diaphragm and a fixed electrode of a sensor base as a change in pressure by joining and applying pressure to the diaphragm surface.

  In order to avoid adverse effects on the sensor characteristics in areas where calibration is impossible, when such a differential pressure, vacuum, and pressure in the vicinity thereof are measured with high accuracy using such a capacitive pressure sensor. In addition, it is necessary to manage the structure of the sensor itself with high accuracy in terms of dimensions, such as strictly managing the distance between the sensor diaphragm on which the movable electrode is formed and the sensor base on which the fixed electrode is formed. For this reason, the bonding between the sensor diaphragm constituting the sensor chip and the sensor pedestal is directly bonded without any intervening interface (for example, see Patent Document 1).

  Hereinafter, the structure of the capacitance-type pressure sensor described in Patent Document 1 will be described. As shown in FIG. 5, the capacitance type pressure sensor 200 includes a first sapphire substrate 201, a second sapphire substrate 202, and a third sapphire in which each peripheral joint portion is closely fixed by direct bonding of sapphires. A substrate 203 is included. The first sapphire substrate 201 has a shallow recess 201a on the lower surface side, and a fixed electrode 201b made of a conductive film is disposed on the bottom of the recess 201a. Further, the second sapphire substrate 202 is directly bonded to the lower surface side of the recessed portion of the first sapphire substrate 201 so as to close the recessed portion 201a. A movable electrode 202b and an extraction terminal 202c of the movable electrode 202b are formed on the upper surface side of the second sapphire substrate 202 facing the fixed electrode 201b. Note that the second sapphire substrate 202 is formed to be thinner than the first sapphire substrate 201 and has a movable diaphragm structure. In addition, a measurement pressure application recess 203a having a shallow depth is formed on the lower side surface of the second sapphire substrate 202, and a measurement pressure introduction through hole 203b communicating with the outside air of the recess 203a is formed. The third sapphire substrate 203 is directly bonded. Further, on the lower surface side of the third sapphire substrate 203, a pedestal 204 having an opening 204b communicating with the through hole 203b is disposed.

Japanese Patent No. 2852593 (page 3, FIG. 4)

In order to form the through hole 203b in the third sapphire substrate 203 of such a capacitive pressure sensor, laser processing such as CO ₂ laser and excimer laser, and mechanical processing such as ultrasonic processing are performed. A burr having a height of about several μm is formed near the periphery of the hole opening, and debris that is a deposit of processing powder generated during processing of the through hole is formed.

  Hereinafter, inconveniences caused by directly joining the constituent elements of the capacitance type pressure sensor while burrs and debris are generated in the opening of such a through hole (measurement pressure introduction hole) are based on FIG. 6 and FIG. I will explain. FIG. 6 is a cross-sectional configuration diagram of a capacitive pressure sensor formed by directly joining the sensor diaphragm 20 and the sensor base 30 to the spacer 11. When the measurement pressure introduction hole is formed in the spacer 11, a burr 11A and a debris 11B (only the burr 11A is shown in FIG. 6) are generated in the opening. In the case where the sensor diaphragm 20 is a sensor diaphragm used for measuring a slight differential pressure, it is particularly easy to bend. Therefore, when the sensor diaphragm 20 is directly joined to the spacer 11 in a state where such burrs 11A and debris 11B are formed, as shown in FIG. 6A, the sensor pedestal 30 is attached to the sensor diaphragm 20 in this state. If it joins directly, as shown in FIG.6 (b), the sensor diaphragm 20 will warp toward the recessed part 30a of the sensor base 30 (refer with the dashed-two dotted line of FIG. 6 (a), (b) comparison). If the burr 11A is large, the sensor diaphragm 20 cannot be joined to the spacer 11.

  On the other hand, in order to prevent such warpage of the sensor diaphragm 20, the burr 11A and the debris 11B are also removed by mirror-polishing the burr and debris formation region of the spacer 11 after that. However, at this time, a shape defect called so-called sagging occurs in which the vicinity of the periphery of the through hole opening gradually falls into the through hole as it goes toward the opening. This becomes more pronounced as the surface roughness is reduced by mirror polishing. If the sensor diaphragm 20 is directly joined to the spacer 11 in this state, the sensor diaphragm 20 is joined directly with the central portion hanging along the sag 11C as shown in FIG. When 30 is directly joined to the sensor diaphragm 20, as shown in FIG. 7B, the sensor diaphragm 20 warps on the side opposite to the concave portion 30a of the sensor base 30 (two-dot chain lines in FIGS. 7A and 7B). And comparison).

  When the sensor diaphragm 20 is warped by the burr 11A, the debris 11B, or the sag 11C, the distance between the movable electrodes 21 and 22 formed on the sensor diaphragm 20 and the fixed electrodes 31 and 32 formed on the sensor pedestal 30 is shown. Cannot be controlled to the prescribed dimensions, resulting in abnormal sensor characteristics due to abnormal shape of the sensor diaphragm 20.

An object of the present invention is to solve the problems as described above, to provide a method for manufacturing a pressure sensor that can of doing precisely pressure measurement in differential refinement pressure range.

To solve the problems described above, the manufacturing method of such a capacitive pressure sensor in claim 1 of the present invention, comprising: a spacer, a diaphragm is joined to the spacer, and a sensor base which is bonded to the diaphragm In the method of manufacturing a capacitive pressure sensor, the spacer is formed by processing a through-hole in a plate body made of a single crystal of aluminum oxide, and a burr and a debris formation region around the edge of the through-hole opening of the spacer are polished. In this way, the burrs and debris are removed and a recess is formed by etching around the entire periphery of the opening on the diaphragm joint side of the through hole, and a plane around the recess of the spacer is formed from a single crystal of aluminum oxide. A sensor diaphragm in which the outer diameter of the strain-generating region of the sensor diaphragm is substantially equal to the diameter of the through hole. A sensor in which a diaphragm is directly joined, a movable electrode is formed at a predetermined position of the sensor diaphragm, is made of a single crystal of aluminum oxide, and a fixed electrode is formed in part, and forms a capacitance measuring chamber together with the sensor diaphragm The pedestal is directly joined to the sensor diaphragm.

  When the sensor diaphragm is directly joined to the spacer, the sensor diaphragm can be prevented from warping toward the sensor base due to burrs or debris formed when the through hole of the spacer is formed. Further, when the spacer is polished to remove such burrs and debris, sagging occurs on the polished surface toward the through hole. By forming a recess including the polished surface in the vicinity of the periphery of the opening of the through hole, the sensor diaphragm is formed. Can be prevented from warping to the opposite side of the sensor base along the sagging. As a result, the distance between the region of the sensor diaphragm with the movable electrode and the region of the sensor base with the fixed electrode can be strictly managed, and the pressure can be measured with high accuracy.

According to a second aspect of the present invention, there is provided a method of manufacturing a capacitive pressure sensor according to the first aspect of the present invention, in which the deburring portion of the spacer is formed by etching instead of etching. It is characterized by forming by.

By forming a recess in the vicinity of the periphery of the opening of the through hole by deburring machining, i.e., finishing chamfering , the sensor diaphragm is prevented from sticking to the bottom surface of the stepped portion by the unevenness portion for preventing adhesion. The distance between the sensor diaphragm with the movable electrode and the bottom surface of the sensor pedestal with the fixed electrode can be strictly managed together with the function of the recess, and the pressure can be measured accurately .

According to a third aspect of the present invention, there is provided a method of manufacturing a capacitive pressure sensor according to the first or second aspect of the present invention, wherein the plate is made of a single crystal of aluminum oxide. Instead of using the sensor diaphragm and the sensor base, a plate body made of quartz, a sensor diaphragm, and a sensor base are used.

  Even if these components are made of quartz instead of a single crystal of aluminum oxide, the same effect can be exhibited.

  According to the method for manufacturing a capacitive pressure sensor of the present invention, a stable shape without warping can be realized even in a sensor diaphragm which is easily bent, and in particular, a capacitive pressure sensor capable of measuring a fine differential pressure with high accuracy can be obtained.

Hereinafter, a capacitive pressure sensor manufactured in a method for manufacturing a capacitive pressure sensor according to an embodiment of the present invention will be described. In describing the structure of such a capacitive pressure sensor, a manufacturing method thereof will be described with reference to the drawings in order to facilitate understanding. The manufacturing method of such a capacitive pressure sensor includes the following procedure. In each drawing showing a cross section, a part of the solid line is omitted for easy understanding of the description.

First, a plate body 10 having a rectangular shape in plan view made of sapphire, which is a single crystal of aluminum oxide, is prepared (see FIG. 1A), and this plate body 10 is subjected to CO ₂ laser, excimer laser, ultrasonic processing, or the like. The spacer 11 is formed by processing the through hole 10a (see FIG. 1B).

  Here, when a through-hole is processed in a hard material such as sapphire, a burr 11A having a height of, for example, about several μm is generated at the periphery of the opening of the through-hole. In addition, when the through hole is processed, processing waste is scattered and accumulated in the vicinity of the periphery of the through hole opening, so-called debris 11B is generated. In the present embodiment, for ease of explanation, it is assumed that burrs 11A and debris 11B are formed on the sensor diaphragm joint surface side of the spacer 11 in the drawing.

  Next, the burrs and debris formation regions at the periphery of the through-hole opening of the spacer are polished to remove the burrs 11A and debris 11B formed in these regions (see FIG. 1C).

  It should be noted that sagging 11C is generated in the polishing region from which the burr 11A and the debris 11B are removed by such post-polishing. The sag 11C is generated around the opening edge of the through hole 10a, and refers to a depressed area that gradually falls toward the through hole 10a.

  Then, in the polished region and at least one region of the spacer 11, more specifically, at least the region where the sensor diaphragm 20 is directly joined thereafter, the above-described sagging around the entire periphery of the opening of the through hole 10a. A recess 11a having an opening including a region 11C is formed by etching (see FIG. 1D). In addition, the recessed part 11a has the dimension whose depth D is 2 micrometers and width W is about 250 micrometers as an example. The method for forming the recess 11a is preferably dry etching, but may be formed by wet etching. Further, the recess 11a may be polygonal or circular when viewed from above.

  Next, a sensor diaphragm 20 made of sapphire, which is a single crystal of aluminum oxide, is directly joined to one side of the spacer 11 and a plane around the recess (see FIG. 2A). . It should be noted that the outer diameter of the strain generating region of the sensor diaphragm 20 (the region excluding the direct joint portion with the sensor pedestal 30 and changing in response to the application of pressure) and the hole diameter of the through hole 10a of the spacer 10 are substantially equal. Yes.

  Next, movable electrodes 21 and 22 made of gold or platinum are formed at predetermined positions of the sensor diaphragm 20 (see FIG. 2B).

  Next, the sensor base 30 is prepared (see FIG. 2B). The sensor pedestal 30 is made of sapphire, which is a single crystal of aluminum oxide. The sensor pedestal 30 has a recess 30a in a part thereof, and fixed electrodes 31 and 32 are formed on the bottom surface of the recess 30a. A capacity chamber for measurement is formed. Further, detection signal extraction electrode pads 35 and 36 are formed on the upper surface of the sensor base 30.

  Next, the sensor base 30 is directly joined to the sensor diaphragm 20 (see FIG. 2C).

  In the sensor chip 1 configured as described above, the sensor diaphragm 20 does not warp to the bottom surface side of the recessed portion of the sensor base 30 due to the burr 11A or the debris 11B of the spacer 11 (FIGS. 2C and 6B). See comparison)). Further, the sensor diaphragm 20 is not directly joined along the sag 11C generated by the post-polishing for removing the burrs 11A and debris 11B of the spacer 11, and the sensor diaphragm 20 is opposite to the bottom surface of the recess of the sensor base 30. (Refer to FIG. 2 (c) and FIG. 7 (b) for comparison). That is, the movable electrodes 21 and 22 of the sensor diaphragm 20 and the fixed electrodes 31 and 32 of the sensor pedestal 30 are opposed to each other with a predetermined dimensional interval. As a result, the capacitance value between the electrodes becomes an appropriate capacitance value, and a capacitive pressure gauge such as a micro differential pressure gauge or a vacuum gauge that enables accurate pressure measurement when the sensor chip 1 is accommodated in a package as will be described later. realizable.

  Subsequently, a capacitive pressure gauge 100 in which the sensor chip 1 is accommodated in a package will be described.

  As shown in FIG. 3, the capacity-type pressure gauge 100 includes a package 110 composed of an upper housing 111 and a lower housing 112, and a pedestal plate 120 composed of an upper pedestal plate 121 and a lower pedestal plate 122 housed in the package. The sensor chip 1 is housed in a package and joined to a pedestal plate 120, and electrode lead portions (not shown) that are directly attached to the package 110 and are electrically connected to the inside and outside of the package. The pedestal plate 120 is spaced from the package 110 and is supported by the package 110 only through the support diaphragm 150.

  On the other hand, a pressure introduction portion (not shown) is formed in the lower housing 112, and a corrosive process gas that is a fluid to be measured applies pressure to the sensor diaphragm 20 through the pressure introduction portion. The sensor chip 1 is a capacitive pressure sensor manufactured by the above-described manufacturing method.

  Although not shown in detail in FIG. 3, the upper housing 111, the support diaphragm 150, the upper pedestal plate 121, and the sensor chip 1 cooperate to define a sealed space that is vacuum inside and independent of the process gas. is doing. In addition, a gas adsorbing material called a getter (not shown) is provided in the sealed space, and the degree of vacuum is maintained.

  On the other hand, the support diaphragm 150 is formed of a polygonal or circular metal thin plate that matches the shape of the casing 110, and the peripheral edge is sandwiched between the edges of the upper housing 111 and the lower housing 112 and joined by welding or the like. ing. Further, a pressure introduction hole 150 a for guiding pressure to the sensor chip 1 is formed in the central portion of the support diaphragm 150.

  A thin ring-shaped upper pedestal plate 121 made of sapphire, which is a single crystal of aluminum oxide, and a lower pedestal are provided on both surfaces of the support diaphragm 150 at a certain distance from the joint between the support diaphragm 150 and the casing 110 over the entire circumferential direction. The plate 122 is joined.

  Further, the upper pedestal plate 121 of the support diaphragm 150 is bonded to the sensor chip 1 manufactured in the above-described process, which becomes a post-bonding aluminum oxide-based bonding material called glass bonding or solid-liquid bonding (see Japanese Patent Application Laid-Open No. 2002-111011). ) Etc. are joined by a relatively inexpensive joining method.

  As described above, the sensor chip 1 includes the spacer 11 in which the through hole 10a is formed in the plate body 10 and the recess 11a is formed, and the sensor diaphragm 20 that is directly bonded to the spacer 11 and generates a strain in response to the application of pressure. In the case of this embodiment, the sensor base 30 is formed which is directly joined to the sensor diaphragm 20 to form a vacuum capacity chamber.

  Further, the electrodes 21, 22, 31, and 32 formed on the sensor diaphragm 20 and the sensor base 30 are led out to the vacuum chamber side in the package through the electrode pads 35 and 36, and the outside of the vacuum chamber of the package 110 is electrically connected. An electrical signal is transmitted to the outside by a lead wire (not shown here).

  As described above, the capacitive pressure gauge 100 shown in FIG. 3 uses the sensor chip 1 manufactured by the manufacturing method of this embodiment. According to the manufacturing method of the sensor chip 1, when the sensor diaphragm 20 is directly joined to the spacer 11, the sensor diaphragm 20 warps toward the bottom surface of the concave portion of the sensor base 30 by the burr 11 </ b> A and the debris 11 </ b> B formed when the through hole of the spacer 11 is formed. Can be prevented. Further, when the spacer 11 is polished to remove such burrs 11A and debris 11B, a sag 11C is generated toward the through hole on the polished surface, but by forming a recess 11a in the vicinity of the periphery of the opening of the through hole 10a. It is possible to prevent the sensor diaphragm 20 from warping on the opposite side of the bottom surface of the recess of the sensor base 30. As a result, the distance between the sensor diaphragm 20 provided with the movable electrodes 21 and 22 and the recess 30a of the sensor base 30 provided with the fixed electrodes 31 and 32 can be strictly managed, and the pressure can be measured with high accuracy.

  Further, in this embodiment, the sensor chip 1 having high measurement accuracy is accommodated in the package via the support diaphragm 150 and the pedestal plate 120 as described above, and the whole is configured as the capacitive pressure gauge 100. By adopting such a structure, the end face when the sensor chip is divided by the dicing of the sensor chip 1 is prevented from coming into direct contact with the process gas, and particles, impurities, etc. remaining on the end face when the sensor chip is cut are caused by distortion of the sensor diaphragm 20. Prevents accumulation in the area. Moreover, since the periphery of the direct joint portion between the sensor diaphragm 20 and the sensor base 30 does not directly contact the process gas, the durability of the pressure sensor itself is enhanced.

  Moreover, since the lead wire of the electrode can be taken out to the vacuum chamber side isolated from the space filled with the process gas, the durability of the electrode lead portion can be ensured. Furthermore, since the sensor diaphragm 20 and the sensor pedestal 30 are joined to the upper pedestal plate 121 of the support diaphragm 150 via the spacer 11, the thermal stress transmitted from the support diaphragm 150 is not easily transmitted to the sensor chip 1.

  Therefore, as described in the above manufacturing method, the capacitive pressure according to the present embodiment is based on the point that the spacer 11 of the sensor chip 1 is devised and the sensor chip 1 is housed in the package with the structure as described above. The meter 100 has excellent durability and enables highly accurate pressure measurement.

  In the above-described embodiment, the recess 11a formed at the periphery of the through hole opening of the spacer 11 forms a stepped portion 11b (see FIG. 4) in cooperation with the through hole. As shown in FIG. 4 (a), the concave portion 11a is formed by dry etching so that a convex portion (concave portion for preventing adhesion) 11c for preventing the sensor diaphragm 20 from adhering to the bottom surface of the stepped portion 11b is formed. It may be formed.

  Further, as shown in FIG. 4B, a thin film (concave portion for preventing adhesion) having fine uneven portions 11d on the surface may be formed on the bottom surface of the step portion 11b.

  By providing such an additional configuration, these unevenness portions for preventing adhesion prevent the sensor diaphragm 20 from adhering to the bottom surface of the stepped portion 11b, so that the movable electrodes 21 and 22 can be combined with the function of the recessed portion 11a. The distance between the sensor diaphragm 20 provided and the bottom surface of the sensor pedestal 30 provided with the fixed electrodes 31 and 32 can be strictly managed, and the pressure can be measured with higher accuracy.

  In addition, as shown in FIG. 4C, the recess formed in the periphery of the through hole opening of the spacer 11 is tapered from the predetermined position of the through hole 10a toward the through hole opening. You may form so that it may consist of the part 11t. An edge is formed between the taper surface of the taper portion 11t and the diaphragm joint surface of the spacer 11, and the taper portion 11t is formed when the diaphragm 20 is directly joined to the spacer 11. An inclination angle that does not follow the tapered surface is formed with respect to the diaphragm joint surface of the spacer 11. Even if such a tapered portion 11t is provided on the periphery of the through-hole opening, the same effect as described above can be exhibited.

  Further, although not shown here, when burrs and debris are removed by post-polishing on the base plate joining side of the spacer 11, sagging may be removed by etching or deburring machining as in this embodiment. The spacer 11 and the upper pedestal plate 121 are joined by so-called solid-liquid joining, and the spacer itself does not have such a thin thickness that warpage is generated due to subtle unevenness of the joined portion unlike the sensor diaphragm 20. Therefore, the influence by burrs, debris, etc. is less than in the case where the spacer 11 and the sensor diaphragm 20 are directly joined. However, by removing the burrs and debris in this portion by etching or deburring machining, the dimensional relationship between the base plate 122 and the spacer 11 can be managed more strictly, and the sensor characteristics can be further improved. Can do.

  In the capacitive pressure sensor according to the above-described embodiment, the plate body 10, the sensor diaphragm 20, and the sensor base 30 are made of sapphire, which is a single crystal body of aluminum oxide. Even if it is made of another aluminum oxide single crystal such as ruby or made of quartz, the same action can be exhibited.

  In the above-described embodiment, the recessed portion 30a is formed on the sensor diaphragm side. However, the capacitive chamber may be formed by providing the recessed portion on the sensor diaphragm side.

  Moreover, although the above-mentioned capacity-type pressure gauge 100 was described as a vacuum gauge for measuring in a vacuum region, it goes without saying that a sufficient effect is exhibited even when the present invention is applied to a capacity-type pressure gauge as a differential pressure gauge. .

It is process drawing which showed the manufacturing method of the capacity | capacitance type pressure sensor (sensor chip) concerning one Embodiment of this invention in the cross section in order of Fig.1 (a) thru | or FIG.1 (d). FIG. 3 is a process diagram illustrating a method of manufacturing a capacitive pressure sensor (sensor chip) subsequent to FIG. 1 in the order of FIGS. 2 (a) to 2 (c). It is sectional drawing shown in the state which accommodated the capacitive pressure sensor (sensor chip) manufactured by the manufacturing method of the capacitive pressure sensor concerning one Embodiment of this invention in the package. Sectional drawing (Fig.4 (a)) which showed the 1st modification of the manufacturing method of the capacitive pressure sensor concerning one Embodiment of this invention, and sectional drawing (FIG.4 (b)) which showed the 2nd modification And FIG. 4C is a sectional view showing a third modification (FIG. 4C). It is sectional drawing which shows an example of the conventional capacitive pressure sensor. It is sectional drawing (FIG. 6 (a)) which shows partially an example of the capacity | capacitance type pressure sensor (sensor chip) manufactured not based on this embodiment, and sectional drawing (FIG.6 (b)) shown entirely. . It is sectional drawing (FIG. 7 (a)) which shows partially another example of the capacitive pressure sensor manufactured without being based on this embodiment, and sectional drawing (FIG.7 (b)) shown entirely.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor chip 10 Plate body 10a Through-hole 10b Opening part 11 Spacer 11a Recessed part 11b Step part 11c Adhesion prevention convex part 11d Uneven part 11t Taper part 11A Burr 11B Debris 11C Sag 20 Sensor diaphragm 21, 22 Movable electrode 30 Sensor base 30a Recess 31, 32 Fixed electrode 35, 36 Electrode pad 100 Capacity type pressure gauge 110 Package 111 Upper housing 112 Lower housing 120 Base plate 121 Upper base plate 122 Lower base plate 150 Support diaphragm 150a Pressure introducing hole 200 Capacitive pressure sensor 201 First sapphire substrate 201a Recessed portion 201b Fixed electrode 202 Second sapphire substrate 202b Movable electrode 202c Extraction terminal 203 Third sapphire substrate 03a measured pressure applying recessed portion 203b through hole 204 base 204b opening

Claims (3)

In a method of manufacturing a capacitive pressure sensor comprising a spacer, a diaphragm joined to the spacer, and a sensor base joined to the diaphragm,
Forming the spacer by processing a through hole in a plate body made of a single crystal of aluminum oxide,
By removing the burr and debris formation area around the edge of the through hole opening of the spacer, the burr and debris are removed,
Forming a recess by etching over the entire circumference of the through-hole diaphragm joint side opening in the polished region,
A sensor diaphragm made of a single crystal of aluminum oxide is directly bonded to a plane around the recess of the spacer, and the outer diameter of the strain-generating region of the sensor diaphragm is directly equal to the hole diameter of the through hole.
Forming a movable electrode at a predetermined position of the sensor diaphragm;
Fixed electrodes and formed in a and part of a single crystal of aluminum oxide, capacitive pressure sensors pedestal to form a capacitance chamber for pressure measurement with the sensor diaphragm, characterized that you joined directly to the sensor diaphragm A method for manufacturing a sensor. The method of manufacturing a capacitive pressure sensor according to claim 1, wherein the recessed portion of the spacer, characterized that you formed by machining deburring instead be formed by etching, the production method of the capacitive pressure sensor. The method of manufacturing a capacitive pressure sensor according to claim 1 or claim 2, the plate body made of single crystal of acid aluminum, the sensor diaphragm, and a plate member made of quartz instead of using a sensor base, a sensor diaphragm, and characterized by Rukoto using the sensor base, the manufacturing method of the capacitive pressure sensor.

Images