JP2007101222A - Pressure sensor - Google Patents

Pressure sensor Download PDF

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JP2007101222A
JP2007101222A JP2005288044A JP2005288044A JP2007101222A JP 2007101222 A JP2007101222 A JP 2007101222A JP 2005288044 A JP2005288044 A JP 2005288044A JP 2005288044 A JP2005288044 A JP 2005288044A JP 2007101222 A JP2007101222 A JP 2007101222A
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electrode
dielectric film
pressure
diaphragm
pressure sensor
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Jun Watanabe
潤 渡辺
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Seiko Epson Corp
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Seiko Epson Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance type pressure sensor having high measurement accuracy. <P>SOLUTION: The pressure sensor 1 includes a capacitor constituted of the first electrode 5 formed on a lower side substrate 2 and the second electrode 10 formed on the under surface of a diaphragm 9 on an upper side substrate 3, and a vacuum cavity 18 is demarcated between the first and second electrodes. A dielectric film 8 having a section shape inclined moderately upward from a center part 8a toward the outside and furthermore inclined moderately downward toward the outside over a top part 8b is laminated on the second electrode 10. Though the contact area between the second electrode and the dielectric film is proportional to the square of the distance (radius) from the center part to the fringe of the contact face, since the film thickness of the dielectric film is increased moderately from the center part toward the top part and then decreased moderately over the top part, linearity of a capacitance of the capacitor with respect to an external pressure can be secured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、圧力によるダイヤフラムの撓み量に対応した静電容量の変化を利用して圧力を測定する静電容量型圧力センサに関する。   The present invention relates to a capacitance-type pressure sensor that measures pressure by using a change in capacitance corresponding to the amount of diaphragm deflection caused by pressure.

従来から、印加の圧力により変形するダイヤフラムと固定された電極とを間隙をもって対向配置し、ダイヤフラムと電極間の静電容量の変化から圧力を測定する静電容量型の圧力センサが知られている。特に、タッチモード式と呼ばれる静電容量型圧力センサは、印加圧力に関する静電容量の出力特性における優れた直線性、及び高い耐圧性を発揮することから、自動車タイヤの空気圧センサなど、様々な用途への利用が提案されている。   2. Description of the Related Art Conventionally, a capacitance type pressure sensor is known in which a diaphragm deformed by an applied pressure and a fixed electrode are opposed to each other with a gap, and a pressure is measured from a change in capacitance between the diaphragm and the electrode. . In particular, the capacitive pressure sensor called the touch mode type exhibits excellent linearity in the output characteristics of the capacitance with respect to the applied pressure and high pressure resistance. Use for is proposed.

一般にタッチモード式圧力センサは、シリコン基板にダイヤフラムを形成しかつこれにボロンなどの不純物をドーピングして可動電極とし、これに対向する固定電極をガラス基板上に形成しかつその上に誘電体膜を形成し、ダイヤフラムと誘電体膜間の隙間を真空に封止して構成される(例えば、特許文献1,2を参照)。図7は、従来のタッチモード式圧力センサにおける、印加圧力に対する静電容量の変化を示している。ダイヤフラムが誘電体膜に接触する前の未接触領域Aでは、静電容量がほとんど変化しない。圧力P0 でダイヤフラムが誘電体膜との接触を開始する接触初期領域Bでは、静電容量が急激に上昇する。その後、圧力P1 P2 間の領域Cにおいて、静電容量が圧力に関して概ね直線的に変化する。圧力P2 を超えると、静電容量は飽和してそれ以上増加しなくなる。一般に、直線的な領域Cを測定可能な圧力範囲として使用している。出力特性の直線性は、ダイヤフラムの形状と関係があり、ダイヤフラムの厚さと隙間の幅を最適化する必要があるとされている(例えば、非特許文献1を参照)。   Generally, a touch mode type pressure sensor is formed by forming a diaphragm on a silicon substrate and doping it with impurities such as boron to form a movable electrode, and forming a fixed electrode on the glass substrate on the glass substrate, and a dielectric film thereon And the gap between the diaphragm and the dielectric film is sealed in a vacuum (see, for example, Patent Documents 1 and 2). FIG. 7 shows changes in capacitance with applied pressure in a conventional touch mode type pressure sensor. In the non-contact area A before the diaphragm contacts the dielectric film, the capacitance hardly changes. In the initial contact region B where the diaphragm starts to contact the dielectric film at the pressure P0, the capacitance increases rapidly. Thereafter, in the region C between the pressures P1 and P2, the capacitance changes approximately linearly with respect to the pressure. When the pressure P2 is exceeded, the capacitance saturates and does not increase any further. In general, the linear region C is used as a measurable pressure range. The linearity of the output characteristics is related to the shape of the diaphragm, and it is said that the thickness of the diaphragm and the width of the gap need to be optimized (see, for example, Non-Patent Document 1).

また、圧力に対する静電容量の直線領域を広げて、測定範囲を広げるために、ガラス基板に形成される電極をその長手方向寸法が幅方向中心から幅方向に向けて漸次増加する形状とし、ダイヤフラムが電極と接触する面積の増加率を圧力増加に対して一定にした圧力センサが提案されている(例えば、特許文献3を参照)。更に、電極のダイヤフラムの初期接触領域と対向した部分に切欠き部を設け、測定に寄与しない浮遊容量を低減し、低容量で高感度を実現する圧力センサ(例えば、特許文献4を参照)や、ダイヤフラムと対向する電極に分割領域を設けてコンデンサの電極面積を変化させ、センサ出力を調整できるようにした圧力センサ(例えば、特許文献5を参照)が知られている。   In addition, in order to widen the linear region of the capacitance with respect to pressure and widen the measurement range, the electrode formed on the glass substrate has a shape in which the longitudinal dimension gradually increases from the center in the width direction to the width direction, and the diaphragm There has been proposed a pressure sensor in which the rate of increase of the area in contact with the electrode is constant with respect to the pressure increase (see, for example, Patent Document 3). In addition, a pressure sensor (see, for example, Patent Document 4) that realizes high sensitivity with low capacitance by providing a notch in the portion of the electrode facing the initial contact region of the diaphragm to reduce stray capacitance that does not contribute to measurement. A pressure sensor (see, for example, Patent Document 5) is known in which a divided region is provided in an electrode facing a diaphragm to change the electrode area of a capacitor so that the sensor output can be adjusted.

また、測定精度の長期安定性を保証するために、ガラス基板に溝を形成しかつこれに導電性材料を埋めて、下部電極をガラス基板表面と同じ高さに形成し、シリコン基板とガラス基板とを隙間無く陽極接合できるようにした圧力センサが知られている(例えば、特許文献6を参照)。   In addition, in order to guarantee the long-term stability of the measurement accuracy, a groove is formed in the glass substrate and a conductive material is buried in this, and the lower electrode is formed at the same height as the surface of the glass substrate. There is known a pressure sensor that can perform anodic bonding with no gap (see, for example, Patent Document 6).

更に、導電性の金属材からなる基台の表面に、その中心から外方に向けてダイヤフラムとの空隙が縮まるような窪み部を形成し、該窪み部上に電極部と絶縁層とを形成することにより、ダイヤフラムが撓む際に電極部との空隙が一定の変化率で安定に変化し、それにより静電容量も一定に安定して変化するようにし、電極の接触面積を工夫することなく、飽和領域をなくし、ダイナミックレンジを広げることができる圧力センサが開発されている(例えば、特許文献7を参照)。   Furthermore, a recess is formed on the surface of the base made of a conductive metal material so that the gap with the diaphragm is reduced outward from the center, and an electrode portion and an insulating layer are formed on the recess. As a result, when the diaphragm bends, the gap between the electrode and the electrode section will change stably at a constant rate of change, so that the capacitance will also change stably and stably, and the electrode contact area will be devised. However, pressure sensors that can eliminate the saturation region and widen the dynamic range have been developed (see, for example, Patent Document 7).

また、固定電極を覆う絶縁層上に、ダイヤフラムに向けた突出部を形成して、ダイヤフラムの絶縁層と接触する部分と固定電極間の距離を増加させ、又は固定電極の中央部に切欠き部を形成して、ダイヤフラムと対向する固定電極の対向面積を少なくして、測定開始圧に対する静電容量を低くし、測定範囲内での変化量を増やした圧力センサが提案されている(例えば、特許文献8を参照)。   In addition, a projecting portion toward the diaphragm is formed on the insulating layer covering the fixed electrode to increase the distance between the fixed electrode and the portion in contact with the insulating layer of the diaphragm, or a notch in the central portion of the fixed electrode A pressure sensor has been proposed in which the opposed area of the fixed electrode facing the diaphragm is reduced, the capacitance with respect to the measurement start pressure is lowered, and the amount of change within the measurement range is increased (for example, (See Patent Document 8).

山本敏外、「タッチモード容量型圧力センサ」、フジクラ技法、2001年10月、第101号、p.71〜74Toshigai Yamamoto, “Touch mode capacitive pressure sensor”, Fujikura technique, October 2001, No. 101, p. 71-74 特表平10−509241号公報Japanese National Patent Publication No. 10-509241 特開2002−214058号公報Japanese Patent Laid-Open No. 2002-214058 特開2002−195903号公報JP 2002-195903 A 特開2002−221460号公報JP 2002-221460 A 特開2002−221461号公報JP 2002-221461 A 特開2004−191137号公報JP 2004-191137 A 特開2005−83801号公報Japanese Patent Laying-Open No. 2005-83801 特開2005−233877号公報JP 2005-233877 A

しかしながら、上述した従来のタッチモード式静電容量型圧力センサには、次のような問題点がある。よく知られているように、ダイヤフラム側の可動電極とガラス基板側の固定電極間の静電容量Cは、誘電体膜の膜厚をd、その誘電率をε、可動電極と誘電体膜との接触面積をSとしたとき、C=ε・S/dで表される。誘電体膜の膜厚dは一定であるが、接触面積Sが下向き凸に撓むダイヤフラムの中心部から接触面の外縁まで距離(半径)の2乗に比例する。そのため、上記特許文献1などに記載される圧力センサは、図7の領域Cにおける静電容量の変化が完全な直線ではなく、むしろ上向き凸の放物線を描くように変化するので、高い測定精度を確保することが困難である。これを解消するためには、圧力センサの出力に補償回路を接続するなど、何らかの工夫をする必要がある。   However, the above-described conventional touch mode capacitive pressure sensor has the following problems. As is well known, the capacitance C between the movable electrode on the diaphragm side and the fixed electrode on the glass substrate side is such that the film thickness of the dielectric film is d, the dielectric constant is ε, the movable electrode and the dielectric film are When the contact area of S is S, it is expressed by C = ε · S / d. Although the film thickness d of the dielectric film is constant, the contact area S is proportional to the square of the distance (radius) from the center of the diaphragm that bends downward to the outer edge of the contact surface. For this reason, the pressure sensor described in Patent Document 1 and the like has a high measurement accuracy because the change in capacitance in the region C of FIG. 7 is not a complete straight line, but rather changes to draw an upwardly convex parabola. It is difficult to secure. In order to solve this problem, it is necessary to devise some means such as connecting a compensation circuit to the output of the pressure sensor.

また、上記特許文献3などに記載されるように、固定側の電極を異形形状にした場合、ダイヤフラムの撓み位置と電極位置とを整合させることが困難である。そのため、測定精度にばらつきが生じたり、歩留まりを低下させる虞がある。   Further, as described in Patent Document 3 and the like, when the fixed-side electrode is formed in a deformed shape, it is difficult to align the bending position of the diaphragm and the electrode position. For this reason, the measurement accuracy may vary, and the yield may be reduced.

上記特許文献7に記載される圧力センサは、基台自体が固定電極であるため、ダイヤフラムとの電気的絶縁性を確保することが困難であり、そのために複雑な構造が要求される虞がある。また、高圧側において飽和領域を無くして測定圧力範囲を広げることはできるが、低圧側の測定圧力範囲を広げることはできない。低圧側では、接触初期状態における絶縁層の厚さが厚いため、むしろ測定感度が低下する虞がある。上記特許文献8に記載される圧力センサも同様に、低圧側での静電容量変化を少なくしているので、低圧側の測定圧力範囲を広げることは困難である。   In the pressure sensor described in Patent Document 7, since the base itself is a fixed electrode, it is difficult to ensure electrical insulation from the diaphragm, and thus a complicated structure may be required. . Further, the measurement pressure range can be expanded by eliminating the saturation region on the high pressure side, but the measurement pressure range on the low pressure side cannot be expanded. On the low pressure side, the thickness of the insulating layer in the initial contact state is thick, so there is a possibility that the measurement sensitivity is rather lowered. Similarly, since the pressure sensor described in Patent Document 8 reduces the capacitance change on the low pressure side, it is difficult to widen the measurement pressure range on the low pressure side.

また、ダイヤフラム自体が可動電極となる従来の圧力センサでは、ガラス基板の表面に配線される電極膜とシリコン基板との接合部分に電気的絶縁性を確保する必要がある。そのため、ガラス基板とシリコン基板とを完全に気密に接合することが困難で、上記特許文献6に記載されるような構造上の工夫が必要である。そのために、工数が増加しかつ工程が複雑になり、生産性が低下して製造コストを増大させる虞がある。   Further, in the conventional pressure sensor in which the diaphragm itself is a movable electrode, it is necessary to ensure electrical insulation at the joint between the electrode film wired on the surface of the glass substrate and the silicon substrate. Therefore, it is difficult to completely and airtightly join the glass substrate and the silicon substrate, and a structural device as described in Patent Document 6 is required. For this reason, the number of man-hours increases, the process becomes complicated, and the productivity may be reduced to increase the manufacturing cost.

そこで本発明は、上述した従来の問題点に鑑みてなされたものであり、その目的は、圧力に関する静電容量の出力特性における直線性を改善し、より高い測定精度を可能にするタッチモード式静電容量型圧力センサを提供することにある。特に本発明は、低圧側における静電容量の直線性を向上させ、測定可能な圧力範囲をより広く設定できるようにすることを目的とする。   Therefore, the present invention has been made in view of the above-described conventional problems, and its object is to improve the linearity in the output characteristics of the capacitance related to pressure and to enable higher measurement accuracy. The object is to provide a capacitive pressure sensor. In particular, it is an object of the present invention to improve the linearity of capacitance on the low-pressure side and to set a wider pressure range that can be measured.

また、本発明は、構造や工程を複雑にし又は工数を増やすことなく、ダイヤフラムと誘電体膜間に画定されるチャンバを確実に真空に封止することができ、安定した測定精度を確保し得るタッチモード式静電容量型圧力センサを提供することにある。   In addition, the present invention can reliably seal the chamber defined between the diaphragm and the dielectric film in a vacuum without complicating the structure or process or increasing the number of steps, and can ensure stable measurement accuracy. It is to provide a touch mode type capacitive pressure sensor.

本発明によれば、上記目的を達成するために、第1電極及びその上に積層した誘電体膜とを上面に有する絶縁材料の下側基板と、ダイヤフラム及びその下面に形成した第2電極を有する絶縁材料の上側基板とを備え、誘電体膜と第2電極とが僅かな間隙をもって対向配置され、かつそれらの間に画定されるチャンバを真空に封止するように、下側基板と上側基板とが一体にかつ気密に接合され、ダイヤフラムが圧力を受けて撓むことにより誘電体膜に接触する第2電極と第1電極との間の静電容量を測定することによって、ダイヤフラムに印加した圧力を測定する圧力センサであって、誘電体膜が、ダイヤフラムの撓みの中心位置に対応する中心部から外側へ漸次上向きに傾斜し、頂点部を越えて更に外側へ漸次下向きに傾斜する断面形状を有する圧力センサが提供される。   According to the present invention, in order to achieve the above object, the lower substrate of the insulating material having the first electrode and the dielectric film laminated thereon on the upper surface, the diaphragm and the second electrode formed on the lower surface thereof are provided. A lower substrate and an upper substrate so that the dielectric film and the second electrode are opposed to each other with a slight gap and the chamber defined therebetween is sealed in a vacuum. Applied to the diaphragm by measuring the electrostatic capacity between the second electrode and the first electrode that are in contact with the dielectric film when the substrate is integrally and airtightly bonded and the diaphragm is bent under pressure. A cross section in which the dielectric film is gradually inclined upward from the center corresponding to the center position of the diaphragm deflection, and gradually inclined downward further beyond the apex. Shape A pressure sensor for are provided.

このように誘電体膜の膜厚が中心部から接触面の外縁まで距離(半径)に関して緩やかに増加しかつ頂点部を越えて緩やかに減少することによって、第2電極と誘電体膜との接触面積は、誘電体膜の中心部から接触面の外縁まで距離(半径)の2乗に比例するが、放物線を描く従来の出力特性に対して、圧力の増加に対する静電容量の増加を効果的に抑制し、直線性の高い出力特性に調整することができる。   As described above, the film thickness of the dielectric film gradually increases with respect to the distance (radius) from the center portion to the outer edge of the contact surface and gradually decreases beyond the apex portion, whereby the contact between the second electrode and the dielectric film is achieved. The area is proportional to the square of the distance (radius) from the center of the dielectric film to the outer edge of the contact surface, but it is effective to increase the capacitance with increasing pressure, compared to the conventional output characteristics that draw a parabola. And can be adjusted to output characteristics with high linearity.

或る実施例では、下側基板及び上側基板が水晶で形成され、かつこれら両基板が全周縁に沿って、例えば陽極接合や金属接合などを用いて、金属接合部により一体にかつ気密に接合されている。従来のように下側及び上側基板間で絶縁膜を設ける必要が無く、簡単な構造で確実にダイヤフラムと誘電体膜間のチャンバを真空に封止できるので、安定して高い測定精度を維持することができる。   In one embodiment, the lower substrate and the upper substrate are formed of quartz, and the two substrates are joined together integrally and in an airtight manner along the entire periphery, for example using anodic bonding or metal bonding. Has been. There is no need to provide an insulating film between the lower and upper substrates as in the prior art, and the chamber between the diaphragm and the dielectric film can be surely sealed in a vacuum with a simple structure, so that high measurement accuracy is stably maintained. be able to.

以下に、本発明の好適実施例について添付図面を参照しつつ詳細に説明する。
図1(A)(B)は、本発明による圧力センサの好適な実施例の構成を概略的に示している。本実施例の圧力センサ1は、それぞれ矩形の水晶薄板からなる下側基板2と上側基板3とを備える。下側基板2は、図2に示すように、上側基板3との対向面に概ね正方形の浅い凹所4が、例えばウエットエッチング又は機械加工により形成されている。凹所4の平坦な底部には、概ね正方形の第1電極5が形成され、該凹所の中央側の側辺から引き出したリード6を介して、下側基板2上面の取出電極7に接続されている。第1電極5の上には、後述する断面形状の誘電体膜8が積層されている。
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1A and 1B schematically show the configuration of a preferred embodiment of a pressure sensor according to the present invention. The pressure sensor 1 of the present embodiment includes a lower substrate 2 and an upper substrate 3 each made of a rectangular quartz thin plate. As shown in FIG. 2, the lower substrate 2 has a substantially square shallow recess 4 formed on the surface facing the upper substrate 3 by, for example, wet etching or machining. A substantially square first electrode 5 is formed on the flat bottom of the recess 4 and is connected to the extraction electrode 7 on the upper surface of the lower substrate 2 through a lead 6 drawn out from the side on the center side of the recess. Has been. On the first electrode 5, a dielectric film 8 having a cross-sectional shape to be described later is laminated.

上側基板3は、図1(A)(B)に示すように、その上面を例えばエッチング又は機械加工などして凹部を形成することにより薄肉化したダイヤフラム9を有する。ダイヤフラム9は、要求される圧力感度に応じて薄く又は厚く形成することができ、本実施例の水晶の場合には、例えば10μm以下の厚さまで薄くすることができる。ダイヤフラム9の下面には、図3に示すように、概ね正方形をなす第2電極10が形成されている。第2電極10と第1電極5とは、誘電体膜8を挟んで互いに対応する対向位置に配置され、コンデンサを構成する。第2電極10は、上側基板3下面を長手方向に反対側の端部に向けて引き出されたリード11を介して、取出電極12に接続されている。   As shown in FIGS. 1A and 1B, the upper substrate 3 has a diaphragm 9 whose upper surface is thinned by forming a recess by etching or machining, for example. The diaphragm 9 can be formed thin or thick according to the required pressure sensitivity. In the case of the crystal of this embodiment, the diaphragm 9 can be thinned to a thickness of 10 μm or less, for example. As shown in FIG. 3, a second electrode 10 having a substantially square shape is formed on the lower surface of the diaphragm 9. The second electrode 10 and the first electrode 5 are disposed at opposing positions corresponding to each other with the dielectric film 8 interposed therebetween, and constitute a capacitor. The second electrode 10 is connected to the extraction electrode 12 via a lead 11 that is drawn with the lower surface of the upper substrate 3 directed toward the opposite end in the longitudinal direction.

第1電極5及び第2電極10は、それぞれ例えばAl膜やAl合金などの導電性金属材料を蒸着やスパッタリングなどで成膜しかつこれをパターニングすることにより形成される。リード6,11及び取出電極7,12は、例えばCr/Au膜またはCr/Ni/Au膜で形成され、同様にこれらの導電性金属材料を蒸着やスパッタリングなどで成膜しかつこれをパターニングすることにより形成される。   The first electrode 5 and the second electrode 10 are formed by depositing and patterning a conductive metal material such as an Al film or an Al alloy, for example, by vapor deposition or sputtering. The leads 6 and 11 and the extraction electrodes 7 and 12 are formed of, for example, a Cr / Au film or a Cr / Ni / Au film. Similarly, these conductive metal materials are formed by vapor deposition or sputtering and patterned. Is formed.

更に上側基板3には、該上側基板の第2電極10の取出電極12に対応する位置、及び下側基板2の第1電極5の取出電極7に対応する位置に、それぞれ貫通孔13,14が設けられている。本実施例の貫通孔13,14は、水晶からなる上側基板3をウエットエッチングで加工することにより、上面及び下面からそれぞれ奥に向けてテーパ状に形成されている。上側基板3上面には、各貫通孔13,14の開口周縁にそれぞれ外部電極15,16が形成されている。   Further, the upper substrate 3 has through holes 13 and 14 at positions corresponding to the extraction electrode 12 of the second electrode 10 of the upper substrate and positions corresponding to the extraction electrode 7 of the first electrode 5 of the lower substrate 2, respectively. Is provided. The through holes 13 and 14 of this embodiment are formed in a tapered shape from the upper surface and the lower surface toward the back by processing the upper substrate 3 made of crystal by wet etching. On the upper surface of the upper substrate 3, external electrodes 15 and 16 are formed on the peripheral edges of the through holes 13 and 14, respectively.

誘電体膜8は、図4に示すように、ダイヤフラム9の中心位置に対応する中心部8aから外側に向けて漸次上向きに傾斜し、頂点部8bを越えて更に外側へ漸次下向きに傾斜する断面形状を有する。中心部8aは下向き凸に緩やかに湾曲し、かつ頂点部8bは上向き凸に緩やかに湾曲している。従って、誘電体膜8の膜厚は、中心部8aから頂点部8bに向けて緩やかに増加しかつ頂点部8bを越えて緩やかに減少する。誘電体膜8は、例えばガラス材料をスパッタリングすることにより形成することができる。前記誘電体膜には、ガラス以外に、例えばSiO やセラミックスなどの絶縁材料を用いることができる。 As shown in FIG. 4, the dielectric film 8 has a cross section that gradually inclines outward from the center 8a corresponding to the center position of the diaphragm 9 and gradually inclines further outward beyond the apex 8b. Has a shape. The central portion 8a is gently curved downward and the apex portion 8b is gently curved upward. Accordingly, the film thickness of the dielectric film 8 gradually increases from the central portion 8a toward the vertex portion 8b and gradually decreases beyond the vertex portion 8b. The dielectric film 8 can be formed, for example, by sputtering a glass material. In addition to glass, for example, an insulating material such as SiO 2 or ceramics can be used for the dielectric film.

下側基板2と上側基板3とは、その全周縁に沿って金属接合部17により一体にかつ気密に接合されている。前記下側基板及び上側基板の対向面にそれぞれ全周縁に沿って所定幅の金属接合部を設け、かつそれらを熱圧着又は共晶接合することにより、容易に一体にかつ気密に接合することができる。これにより、圧力センサ1の内部には、ダイヤフラム9と下側基板2の凹所4との間にキャビティ18が画定される。   The lower substrate 2 and the upper substrate 3 are integrally and airtightly bonded by the metal bonding portion 17 along the entire periphery. By providing metal joints with a predetermined width along the entire periphery on the opposing surfaces of the lower substrate and the upper substrate, and by thermocompression bonding or eutectic bonding, they can be easily and integrally joined together. it can. As a result, a cavity 18 is defined inside the pressure sensor 1 between the diaphragm 9 and the recess 4 of the lower substrate 2.

各貫通孔13,14には、それぞれ導電材料からなる封止材19,20が充填されている。前記封止材は、下側基板2と上側基板3との接合後に、真空雰囲気内で前記貫通孔を気密に封止するように充填する。これにより、キャビティ18が真空に封止される。それと同時に、封止材19,20により取出電極7,12即ち第1及び第2電極5,10と対応する外部電極15,16とがそれぞれ互いに電気的に接続される。前記封止材には、例えばAuSn、AuGe、はんだ材料、高温はんだなどを用いることができる。また、前記各貫通孔の内周面が金属膜で予め被覆されていると、封止材の導入が容易になるので有利である。   The through holes 13 and 14 are filled with sealing materials 19 and 20 made of a conductive material, respectively. The sealing material is filled so that the through hole is hermetically sealed in a vacuum atmosphere after the lower substrate 2 and the upper substrate 3 are joined. Thereby, the cavity 18 is sealed in a vacuum. At the same time, the extraction electrodes 7, 12, that is, the first and second electrodes 5, 10 and the corresponding external electrodes 15, 16 are electrically connected to each other by the sealing materials 19, 20. As the sealing material, for example, AuSn, AuGe, a solder material, high-temperature solder, or the like can be used. Further, it is advantageous that the inner peripheral surface of each through-hole is previously coated with a metal film because the introduction of the sealing material is facilitated.

図5(A)〜(C)は、圧力センサ1の使用時において、ダイヤフラム9の撓みに対応して第2電極10と誘電体膜8との接触面が広がる様子を段階的に示している。図5(A)は、ダイヤフラム9が外部圧力により撓み、第2電極10が誘電体膜8と接触し始めた初期状態である。誘電体膜8が上述したように頂点部8bから中心部8aに向けて凹んだ形状をなすので、この接触初期状態における第2電極10と誘電体膜8との接触面積は、従来技術の平坦で膜厚一定の誘電体膜の場合よりも大きい。   5A to 5C show, in a stepwise manner, when the pressure sensor 1 is used, the contact surface between the second electrode 10 and the dielectric film 8 expands in response to the deflection of the diaphragm 9. . FIG. 5A shows an initial state in which the diaphragm 9 is bent by the external pressure and the second electrode 10 starts to contact the dielectric film 8. Since the dielectric film 8 has a concave shape from the apex portion 8b toward the center portion 8a as described above, the contact area between the second electrode 10 and the dielectric film 8 in this initial contact state is flat as in the prior art. And larger than the case of a dielectric film having a constant film thickness.

外部圧力が増加してダイヤフラム9が更に撓むと、図5(B)に示すように、中心部8aから頂点部8bへの上向き傾斜面に沿って第2電極10と誘電体膜8との接触面積が増加する。頂点部8bが上向き凸に湾曲しているので、その近傍に近付くと、前記接触面積の増加は低下する。図5(C)に示すように、更にダイヤフラム9が頂点部8bを越えて撓むと、誘電体膜8が外側へ下向きに傾斜しているので、前記接触面積の増加は更に抑制され、限界に達する。   When the external pressure is increased and the diaphragm 9 is further bent, the contact between the second electrode 10 and the dielectric film 8 along the upward inclined surface from the central portion 8a to the apex portion 8b as shown in FIG. 5B. Increases area. Since the apex portion 8b is curved upward, the increase in the contact area decreases when approaching the vicinity thereof. As shown in FIG. 5C, when the diaphragm 9 is further bent beyond the apex portion 8b, the dielectric film 8 is inclined downward to the outside, so that the increase in the contact area is further suppressed, and the limit is reached. Reach.

図6は、本実施例による圧力センサ1における圧力と静電容量との関係を実線で示している。同図には、比較のために、従来技術の平坦で膜厚一定の誘電体膜を有する圧力センサにおける圧力と静電容量との関係を破線で示している。従来技術に関連して上述した図7と同様に、図6において、圧力P0 は第2電極10が誘電体膜8に接触し始めたときの圧力であり、圧力P1 は接触初期状態から直線的関係を開始する圧力であり、圧力P2 は直線的関係が終了して飽和状態が開始する圧力である。圧力P0 P1 間の領域Bが接触初期状態であり、圧力P1 P2 間の領域Cが従来技術の直線的関係に対応する領域であり、圧力P2 以上の領域Dが飽和領域である。   FIG. 6 shows the relationship between the pressure and the capacitance in the pressure sensor 1 according to this embodiment with a solid line. In the figure, for comparison, the relationship between pressure and capacitance in a pressure sensor having a dielectric film with a flat and constant film thickness according to the prior art is indicated by a broken line. Similar to FIG. 7 described above in connection with the prior art, in FIG. 6, the pressure P0 is the pressure when the second electrode 10 starts to contact the dielectric film 8, and the pressure P1 is linear from the initial contact state. The pressure at which the relationship starts is the pressure P2 is the pressure at which the linear relationship ends and the saturation state begins. A region B between the pressures P0 P1 is an initial contact state, a region C between the pressures P1 P2 is a region corresponding to the linear relationship of the prior art, and a region D above the pressure P2 is a saturation region.

第1電極5と第2電極10とにより構成されるコンデンサの静電容量Cは、誘電体膜8の膜厚をd、誘電体膜8の誘電率をε、第2電極10と誘電体膜8との接触面積をSとしたとき、C=ε・S/dで表される。接触面積Sは、中心部8aから接触面の外縁まで距離(半径)の2乗に比例するが、誘電体膜8の膜厚dは、中心部8aから接触面の外縁まで距離(半径)に関して緩やかに増加し、かつ頂点部8bを越えて緩やかに減少する。その結果、図6の領域Cでは、破線で示すように放物線を描く従来の出力特性から、圧力の増加に対する静電容量の増加を抑制し、実線で示すように直線性の高い出力特性に調整することができる。例えば、ダイヤフラム9の撓み量が圧力の増加に関して一定の割合で増加し、かつそれに対応して第2電極10と誘電体膜8との接触面積が一定の割合で増加すると仮定した場合、静電容量の変化量ΔC=ε・ΔS/Δdが一定となるように、誘電体膜8の膜厚dを決定すればよい。   The capacitance C of the capacitor formed by the first electrode 5 and the second electrode 10 is such that the film thickness of the dielectric film 8 is d, the dielectric constant of the dielectric film 8 is ε, and the second electrode 10 and the dielectric film. When the contact area with 8 is S, C = ε · S / d. The contact area S is proportional to the square of the distance (radius) from the central portion 8a to the outer edge of the contact surface, but the film thickness d of the dielectric film 8 is related to the distance (radius) from the central portion 8a to the outer edge of the contact surface. It gradually increases and gradually decreases beyond the apex 8b. As a result, in the region C of FIG. 6, the increase in the capacitance with respect to the increase in pressure is suppressed from the conventional output characteristic in which the parabola is drawn as shown by the broken line, and the output characteristic is adjusted to have high linearity as shown by the solid line. can do. For example, if it is assumed that the amount of deflection of the diaphragm 9 increases at a constant rate with respect to an increase in pressure, and the contact area between the second electrode 10 and the dielectric film 8 increases at a constant rate accordingly, The film thickness d of the dielectric film 8 may be determined so that the capacitance change amount ΔC = ε · ΔS / Δd is constant.

更に本実施例では、接触初期領域Bにおける第2電極10と誘電体膜8との接触面積が従来よりも大きくなる。従って、接触初期領域Bにおける静電容量、特に圧力P0 における静電容量を従来よりも増加させることができる。その結果、接触初期領域Bを領域Cに連続する直線状に調整することができ、高精度に測定可能な圧力範囲を低圧力側に拡大することができる。   Furthermore, in the present embodiment, the contact area between the second electrode 10 and the dielectric film 8 in the initial contact region B is larger than that in the prior art. Therefore, the capacitance in the initial contact region B, particularly the capacitance at the pressure P0 can be increased as compared with the conventional case. As a result, the contact initial region B can be adjusted to a linear shape continuous to the region C, and the pressure range that can be measured with high accuracy can be expanded to the low pressure side.

以上、本発明の好適な実施例について詳細に説明したが、本発明は上記実施例に様々な変形・変更を加えて実施することができる。例えば、上記実施例の上側及び下側基板は、その双方又は一方を、水晶以外にパイレックスガラスやソーダガラスなどのガラス材料、セラミックス材料、その他様々な公知の絶縁材料で形成することができる。また、上側基板と下側基板とを異なる材料で形成する場合には、それらの熱膨張率が互いに同等又は近似するように選択することが好ましい。   Although the preferred embodiments of the present invention have been described in detail above, the present invention can be implemented by adding various modifications and changes to the above embodiments. For example, both or one of the upper and lower substrates of the above embodiment can be formed of glass materials such as Pyrex glass and soda glass, ceramic materials, and various other known insulating materials in addition to quartz. Moreover, when forming an upper board | substrate and a lower board | substrate with a different material, it is preferable to select so that those thermal expansion coefficients may mutually be equivalent or approximate.

(A)図は本発明による圧力センサの実施例を示す平面図、(B)図はそのI−I線における断面図。(A) The figure is a top view which shows the Example of the pressure sensor by this invention, (B) The figure is sectional drawing in the II line | wire. 図1の圧力センサの下側基板を示す平面図。The top view which shows the lower board | substrate of the pressure sensor of FIG. 図1の圧力センサの上側基板を示す下面図。The bottom view which shows the upper side board | substrate of the pressure sensor of FIG. 下側基板の固定電極及び誘電体膜を示す断面図。Sectional drawing which shows the fixed electrode and dielectric material film of a lower board | substrate. 本実施例の圧力センサの作動状態について、(A)図は接触初期状態、(B)図は接触面積が増加した状態、(C)図は飽和状態をそれぞれ示す断面図。As for the operating state of the pressure sensor of this embodiment, (A) is an initial contact state, (B) is a state where the contact area is increased, and (C) is a cross-sectional view showing a saturated state. 本実施例の圧力センサにおける圧力と静電容量との関係を示す線図。The diagram which shows the relationship between the pressure in the pressure sensor of a present Example, and an electrostatic capacitance. 従来の静電容量型圧力センサにおける圧力と静電容量との関係を示す線図。The diagram which shows the relationship between the pressure and the electrostatic capacitance in the conventional electrostatic capacitance type pressure sensor.

符号の説明Explanation of symbols

1…圧力センサ、2…下側基板、3…上側基板、4…凹所、5…第1電極、6,11…リード、7,12…取出電極、8…誘電体膜、8a…中心部、8b…頂点部、9…ダイヤフラム、10…第2電極、13,14…貫通孔、15,16…外部電極、17…金属接合部、18…チャンバ、19,20…封止材。
DESCRIPTION OF SYMBOLS 1 ... Pressure sensor, 2 ... Lower side board, 3 ... Upper side board, 4 ... Recessed part, 5 ... 1st electrode, 6, 11 ... Lead, 7, 12 ... Extraction electrode, 8 ... Dielectric film, 8a ... Center part 8b ... apex, 9 ... diaphragm, 10 ... second electrode, 13, 14 ... through-hole, 15, 16 ... external electrode, 17 ... metal joint, 18 ... chamber, 19, 20 ... sealing material.

Claims (2)

第1電極及びその上に積層した誘電体膜とを上面に有する絶縁材料の下側基板と、ダイヤフラム及びその下面に形成した第2電極を有する絶縁材料の上側基板とを備え、前記誘電体膜と前記第2電極とが僅かな間隙をもって対向配置され、かつそれらの間に画定されるチャンバを真空に封止するように、前記下側基板と前記上側基板とが一体にかつ気密に接合され、前記ダイヤフラムが圧力を受けて撓むことにより前記誘電体膜に接触する前記第2電極と第1電極との間の静電容量を測定して、前記圧力を測定するための圧力センサであって、
前記誘電体膜が、前記ダイヤフラムの撓みの中心位置に対応する中心部から外側へ漸次上向きに傾斜し、頂点部を越えて更に外側へ漸次下向きに傾斜する断面形状を有することを特徴とする圧力センサ。
A dielectric substrate comprising: a lower substrate of an insulating material having a first electrode and a dielectric film laminated thereon; and an upper substrate of an insulating material having a diaphragm and a second electrode formed on the lower surface thereof. And the second electrode are opposed to each other with a slight gap, and the lower substrate and the upper substrate are integrally and hermetically bonded so that a chamber defined between them is sealed in a vacuum. A pressure sensor for measuring the pressure by measuring a capacitance between the second electrode and the first electrode contacting the dielectric film when the diaphragm is bent under pressure. And
The pressure is characterized in that the dielectric film has a cross-sectional shape that gradually inclines outward from the center corresponding to the center position of the diaphragm deflection, and gradually inclines outward further beyond the apex. Sensor.
前記下側基板及び前記上側基板が水晶で形成され、前記両基板が全周縁に沿って金属接合部により一体にかつ気密に接合されていることを特徴とする請求項1に記載の圧力センサ。   2. The pressure sensor according to claim 1, wherein the lower substrate and the upper substrate are formed of quartz, and the two substrates are integrally and airtightly bonded together by a metal bonding portion along the entire periphery.
JP2005288044A 2005-09-30 2005-09-30 Pressure sensor Pending JP2007101222A (en)

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JP2009038732A (en) * 2007-08-03 2009-02-19 Panasonic Corp Electronic component and manufacturing method thereof, and electronic device provided with electronic component
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JP2009038732A (en) * 2007-08-03 2009-02-19 Panasonic Corp Electronic component and manufacturing method thereof, and electronic device provided with electronic component
CN101776502B (en) * 2008-12-24 2012-01-04 佳能安内华股份有限公司 Capacitance diaphragm gauge and vaccum apparatus
WO2013073506A1 (en) * 2011-11-14 2013-05-23 オムロン株式会社 Capacitance type pressure sensor, method for manufacturing same, and input device
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CN103765179A (en) * 2011-11-14 2014-04-30 欧姆龙株式会社 Capacitance type pressure sensor, method for manufacturing same, and input device
KR20130087426A (en) * 2012-01-27 2013-08-06 가부시키가이샤 와코무 Capacitive pressure sensing semiconductor device
JP2013156066A (en) * 2012-01-27 2013-08-15 Wacom Co Ltd Electrical capacitance pressure sensing semiconductor device
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US9702778B2 (en) 2012-02-06 2017-07-11 Wacom Co., Ltd. Position indicator
US9778123B2 (en) 2012-02-06 2017-10-03 Wacom Co., Ltd. Position indicator
US10101228B2 (en) 2012-02-06 2018-10-16 Wacom Co., Ltd. Position indicator
KR101818315B1 (en) * 2013-03-11 2018-01-12 오므론 가부시키가이샤 Capacitive pressure sensor and input device

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