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WO2009090851A1 - Pressure sensor and method of manufacturing the same - Google Patents

Pressure sensor and method of manufacturing the same Download PDF

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Publication number
WO2009090851A1
WO2009090851A1 PCT/JP2008/073871 JP2008073871W WO2009090851A1 WO 2009090851 A1 WO2009090851 A1 WO 2009090851A1 JP 2008073871 W JP2008073871 W JP 2008073871W WO 2009090851 A1 WO2009090851 A1 WO 2009090851A1
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WIPO (PCT)
Prior art keywords
silicon substrate
cavity
pressure sensor
pressure
substrate
Prior art date
Application number
PCT/JP2008/073871
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French (fr)
Japanese (ja)
Inventor
Masahiro Kubo
Katsuya Kikuiri
Tetsuya Fukuda
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Alps Electric Co., Ltd.
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Application filed by Alps Electric Co., Ltd. filed Critical Alps Electric Co., Ltd.
Publication of WO2009090851A1 publication Critical patent/WO2009090851A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
    • G01L9/0051—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance
    • G01L9/0052—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance of piezoresistive elements
    • G01L9/0054—Transmitting or indicating the displacement of flexible diaphragms using variations in ohmic resistance of piezoresistive elements integral with a semiconducting diaphragm
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L19/00—Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges
    • G01L19/06—Means for preventing overload or deleterious influence of the measured medium on the measuring device or vice versa
    • G01L19/0627—Protection against aggressive medium in general
    • G01L19/0654—Protection against aggressive medium in general against moisture or humidity

Definitions

  • the present invention relates to a pressure sensor capable of preventing water and dust from entering the cavity, and a method of manufacturing the same.
  • Patent Document 1 discloses a pressure sensor for gauge pressure detection formed using a silicon substrate.
  • Patent Document 1 a cavity (void space) and an introduction hole are formed in a first silicon single crystal substrate, and a diaphragm is formed in a second silicon single crystal substrate.
  • a strain detection sensor that detects strain of the diaphragm is provided.
  • the pressure sensor of the invention described in Patent Document 2 is a capacitance type, and an electrode provided at a position opposed to the diaphragm is formed to extend from the introduction hole to the surface of the substrate (insulator 2, 2 '). ing. Furthermore, in Patent Document 3, the exposed surface of the substrate (insulators 2 and 2 ') is subjected to water repelling treatment.
  • the present invention is intended to solve the above-described conventional problems, and in particular, it is an object of the present invention to provide a pressure sensor capable of preventing water or dust from entering the cavity and a method of manufacturing the same.
  • the pressure sensor in the present invention is A cavity formed on the back surface side of a silicon substrate, a diaphragm formed on the silicon substrate above the cavity, and a base substrate located on the lower side facing the diaphragm via the cavity and joined to the silicon substrate And a pressure introducing hole formed in the base substrate,
  • the maximum opening width of the pressure introducing hole is smaller than the height dimension of the cavity, and a water repellent film is formed only on the side wall surface of the pressure introducing hole with respect to the base substrate. is there. This makes it possible to prevent water and dust from entering the cavity and stabilize the pressure characteristics, as compared with the prior art.
  • a plurality of the pressure introducing holes are formed. It is possible to suppress pressure characteristic change due to clogging.
  • an upper silicon substrate, a lower silicon substrate, and an SiO 2 film located between the upper silicon substrate and the lower silicon substrate are provided.
  • the cavity is formed in the lower silicon substrate, and the diaphragm is formed by the upper silicon substrate and the SiO 2 film located above the cavity.
  • the cavity and the diaphragm can be appropriately formed.
  • a piezo element whose resistance value changes according to the distortion of the diaphragm is formed on the upper surface side of the diaphragm.
  • the method of manufacturing a pressure sensor according to the present invention is characterized by having the following steps.
  • the base substrate is formed of silicon, and the pressure introducing hole and the water repellent film are formed by Si deep etching.
  • the pressure introducing hole and the water repellent film can be appropriately formed.
  • the water repellent film can be appropriately formed only on the side wall surface of the pressure introducing hole with respect to the base substrate.
  • the pressure introducing hole is formed in the base substrate, and then the base substrate having the pressure introducing hole formed is bonded to the lower side of the silicon substrate. It can also be done. In such a case, it is possible to appropriately prevent the penetration of the slurry or the like into the cavity even if the back grinding process is performed on the base substrate provided with the pressure introducing hole bonded to the silicon substrate.
  • an SOI substrate comprising an upper silicon substrate, a lower silicon substrate, and a SiO 2 film located between the upper silicon substrate and the lower silicon substrate is used,
  • the cavity is formed in the lower silicon substrate by Si deep etching, and at this time, the SiO 2 film serves as a stopper film for reactive ion etching, and the SiO 2 film located on the cavity and the upper silicon substrate are formed.
  • a diaphragm is formed. Thereby, the diaphragm and the cavity can be appropriately formed.
  • the pressure introducing hole is formed in the base substrate by Si deep etching after bonding the base substrate to the lower silicon substrate, the pressure introducing hole is formed because the SiO 2 film functions as a stopper for reactive ion etching. It is possible to manufacture a pressure sensor having stable pressure characteristics with less variation, since the cavity and diaphragm formed in the SOI substrate are not affected by Si deep etching at the time of etching.
  • the pressure sensor of the present invention it is possible to prevent the entry of water or dust into the cavity and to stabilize the pressure characteristic as compared with the conventional case.
  • FIG. 1 is a plan view of the pressure sensor according to the present embodiment
  • FIG. 2 is a cross-sectional view of the pressure sensor shown in FIG. 1 cut along line AA and viewed from the arrow direction
  • FIG. FIG. 4 is an enlarged sectional view of the pressure introducing hole.
  • FIG. 2 also shows some of the wiring layers and pads that can be seen when the cut surface is viewed in the direction of the arrow.
  • the pressure sensor 1 in the present embodiment is for gauge pressure detection that detects air pressure on the basis of atmospheric pressure.
  • the measurement pressure introduction port is on the upper side of the case (not shown) that houses the pressure sensor 1 on the lower side.
  • An atmospheric pressure introduction port is provided.
  • the pressure sensor 1 shown in FIGS. 1 and 2 includes a base substrate 2 and an SOI substrate 3 bonded on the base substrate 2.
  • the SOI (Silicon on Insulator) substrate 3 has a laminated structure of a lower silicon substrate 4 and an upper silicon substrate 6 and an SiO 2 film 5 located between the lower silicon substrate 4 and the upper silicon substrate 6.
  • a cavity (recess) 7 is formed in the lower silicon substrate 4 at a central portion in plan view.
  • a diaphragm 8 is formed by the SiO 2 film 5 and the upper silicon substrate 6 located above the cavity 7.
  • the shapes of the cavity 7 and the diaphragm 8 in plan view are substantially rectangular.
  • the periphery of the diaphragm 8 is a fixed area 9 in which distortion does not occur even if pressure is applied to the upper silicon substrate 6.
  • Piezo elements B to E are formed substantially at the centers of the edge portions of the four sides of the diaphragm 8. As shown in FIG. 1, the first piezoelectric element B and the second piezoelectric element C are connected in series via the first output pad 11. In addition, the third piezo element D and the fourth piezo element E are connected in series via the second output pad 12.
  • the first piezoelectric element B and the third piezoelectric element D are connected via the input pad 13, and the second piezoelectric element C and the fourth piezoelectric element E are connected via the ground pad 14.
  • Wiring layers 10 connected to the respective piezoelectric elements B to E are formed to extend on the fixed area 9, and the pads 11 to 14 are provided at four corners of the fixed area 9.
  • the wiring layer 10 and the pads 11 to 14 are formed of a good conductor such as Au or Al by sputtering or plating.
  • each of the piezoelectric elements B to E is formed of a P-type semiconductor in which the surface of the diaphragm 8 is doped with boron.
  • the increase / decrease of the resistance value of the second piezoelectric element C and the third piezoelectric element D, and the resistance value of the first piezoelectric element B and the fourth piezoelectric element E Piezo elements B to E are arranged such that the increasing and decreasing tendencies are opposite to each other.
  • the plan view shape of each of the piezoelectric elements B to E is substantially rectangular, but it is possible to form, for example, a meander shape.
  • a protective film of Si 3 N 4 or the like is formed on the upper silicon substrate 6.
  • the pads 11 to 14 are exposed from the protective film, and the pads 11 to 14 and an external circuit with a case not shown are electrically connected by wire bonding or the like.
  • each pressure introducing hole 20 is in communication with the cavity 7.
  • the plan view shape of each pressure introducing hole 20 is a circular shape, but the shape is not particularly limited.
  • the base substrate 2 is preferably made of silicon, and each pressure introducing hole 20 is preferably formed by Si deep etching.
  • Si deep etching mainly, isotropic etching using sulfur hexafluoride (SF 6 ), and a side wall protection process performed using a polytetrafluoroethylene (PTFE) -based gas such as C 4 F 8 Repeat alternately.
  • PTFE polytetrafluoroethylene
  • the water repellent film 21 is formed on the side wall surface 20 a of the pressure introducing hole 20.
  • the water repellent film 21 is a C—F—Si film or a C—F film.
  • the water repellent film 21 is formed only on the side wall surface 20 a of the pressure introducing hole 20 with respect to the base substrate 2.
  • the water repellent film is also formed on the side wall surface of the cavity 7 with respect to the SOI substrate 3.
  • the water repellent effect of the water repellent film 21 is naturally higher than the surfaces of the base substrate 2 and the SOI substrate 3, and the contact angle at the water repellent film 21 is about 95 to 105 °.
  • the side wall surface 20a of the pressure introducing hole 20 is not a clean vertical surface but a curved uneven surface (wave shape), but this is an isotropic etching process and protective film deposition by Si deep etching It is the result of repeating the steps.
  • the maximum opening width T1 of each pressure introducing hole 20 is smaller than the height dimension T2 of the cavity 7.
  • the maximum opening width T1 of the pressure introducing hole 20 is the maximum spacing between the surface (side wall surface 20a) of the water repellent film 21 in the cross section shown in FIG.
  • the maximum diameter is indicated, and in the case of a shape other than a circular shape, the maximum width dimension in a plane orthogonal to the height direction is indicated.
  • the size of the dust is smaller than the height dimension T2 of the cavity 7.
  • the pressure characteristics can be stabilized.
  • the height dimension T2 of the cavity 7 is about 80 to 200 ⁇ m
  • the height dimension of the pressure introducing hole 20 (the thickness dimension of the base substrate 2) T3 is about 100 to 300 ⁇ m
  • the maximum opening width T1 of the pressure introducing hole 20 Is about 10 to 80 ⁇ m
  • the film thickness T 4 of the water repellent film 21 is about 0.01 to 0.3 ⁇ m.
  • the thickness dimension of the SiO 2 film is about 0.3 to 0.5 ⁇ m
  • the thickness dimension of the upper silicon substrate 6 is about 5 to 100 ⁇ m.
  • the water repellent film 21 is formed on the side wall surface 20 a of the pressure introducing hole 20 formed in the base substrate 2. Therefore, the entry of water into the cavity 7 can be appropriately prevented. Not only at the time of change of the use environment but also after the formation of the pressure introducing hole 20, for example, when the cleaning process for the pressure sensor 1 is performed, it is possible to prevent the entry of water.
  • the pressure sensor 1 for detecting the gauge pressure can prevent water and dust from entering the cavity 7 as compared with the related art, and can obtain stable pressure characteristics.
  • the water repellent film 21 is formed only on the side wall surface 20 a of the pressure introducing hole 20 with respect to the base substrate 2, and is not formed on other parts. That is, since the water repellent film 21 is not formed on the surface (corresponding to the back surface in FIG. 2) opposite to the cavity 7 forming surface of the base substrate 2, the pressure sensor 1 is appropriately die-bonded to a predetermined position in the case. It becomes possible.
  • the pressure introduction hole 20 may be one, but if it is one, if the pressure introduction hole 20 is clogged with dust etc, the pressure characteristic changes, and in the worst case, a pressure sensor for gauge pressure detection It can not be used as 1. Therefore, in order to prevent such a defect, even if there is a clogged pressure introduction hole 20, a pressure introduction hole 20 which is not clogged elsewhere is secured to be suitable as a pressure sensor 1 for gauge pressure detection. It is preferable to provide a plurality of (at least three or more is desirable) pressure introducing holes 20 to function.
  • the cavity 7 and the diaphragm 8 are appropriately formed by using the SOI substrate 3. It can.
  • the cavity 7 can be formed by Si deep etching, but the SiO 2 film 5 functions as a stopper film at the time of reactive ion etching and can appropriately prevent over-etching.
  • the SiO 2 film 5 also serves as a stopper film in reactive ion etching. Therefore, the cavity 7 and the diaphragm 8 are not affected by the Si deep etching when forming the pressure introducing hole 20, and the pressure sensor 1 can be provided with a pressure characteristic with small variation and stable.
  • Each process drawing shown in FIGS. 5 to 7 is a cross-sectional view of the same part as that of FIG. 2 in the manufacturing process.
  • FIGS. 5 to 7 show a method of manufacturing the pressure sensor 1 of a single product, it is possible to perform each process in a wafer state in which a large number of pressure sensors 1 are connected in series during the manufacturing process. It is preferable that 1 can be produced.
  • the piezo elements B to E, the wiring layer 10 and the pads 11 to 14 are formed on the upper silicon substrate 6 constituting the SOI substrate 3 (see also FIG. 1).
  • the surface of the lower silicon substrate 6 (corresponding to the back surface side in FIG. 5) is back ground to make the lower silicon substrate 6 a predetermined thickness.
  • a resist layer is formed on the surface of the lower silicon substrate 6 (corresponding to the back surface side in FIG. 5), and an extraction pattern for forming the cavity 7 is formed in the resist layer.
  • the lower silicon substrate 6 exposed from the removal pattern is removed by dry etching to form a cavity 7.
  • Si deep etching can be used to form the cavity 7.
  • fluorine reacts with silicon but does not react with SiO 2.
  • the lower silicon substrate 4 is removed in the reactive etching step, but the exposed SiO 2 film serves as a stopper film to prevent over-etching.
  • the base substrate 2 formed of silicon is bonded under the SOI substrate 3 shown in FIG.
  • the SOI substrate 3 and the base substrate 2 can be bonded at room temperature.
  • the base substrate 2 is back ground to have a predetermined thickness.
  • the pressure sensor 1 shown in FIG. 2 is turned over and the base substrate 2 is on the upper side
  • the layer 30 is applied, and a removal pattern 30 a for forming the pressure introducing hole 20 is formed in the resist layer 30.
  • the base substrate 2 not covered with the resist layer 30 is removed by Si deep etching.
  • Si deep etching mainly, isotropic etching using sulfur hexafluoride (SF 6 ), and a side wall protection process performed using a polytetrafluoroethylene (PTFE) -based gas such as C 4 F 8 Repeat alternately.
  • PTFE polytetrafluoroethylene
  • the water repellent film 21 is formed on the side wall surface 20 a of the pressure introducing hole 20.
  • the water repellent film 21 is a C—F—Si film or a C—F film.
  • the water repellent film 21 is formed only on the side wall surface 20 a of the pressure introducing hole 20 with respect to the base substrate 2. As described above, when the cavity 7 is formed by Si deep etching in the step of FIG. 5, the water repellent film is also formed on the side wall surface of the cavity 7 with respect to the SOI substrate 3.
  • the maximum opening width T1 of the pressure introducing hole 20 is formed smaller than the height dimension T2 of the cavity 7.
  • the water repellent film 21 can be formed only on the side wall surface 20a of the pressure introducing hole 20 with respect to the base substrate 2 by the above-described Si deep etching (see FIG. 4). That is, since the water repellent film 21 is not formed on the surface of the base substrate 2 on the side opposite to the cavity 7 forming surface, the die can be appropriately die-mounted when the pressure sensor 1 is installed in the case after manufacturing the pressure sensor 1. It becomes possible to bond.
  • the cavity 7 and the diaphragm 8 are not easily affected by the presence of the SiO 2 film 5 when forming the pressure introducing hole 20. That is, the side of the SOI substrate 3 is also scraped by Si deep etching when forming the pressure introducing hole 20, and there is no problem that the size of the cavity 7 changes or the thickness of the diaphragm 8 changes. Therefore, even if the pressure introducing hole 20 is formed in a state in which the base substrate 2 is bonded to the SOI substrate 3, the pressure sensor 1 can be manufactured which has stable pressure characteristics with small variation.
  • the resist layer 30 is removed.
  • the pressure sensor 1 capable of preventing the entry of water or dust into the cavity 7 can be manufactured simply and appropriately. In addition, even if a cleaning process or the like is performed after the pressure introducing hole 20 is formed, it is possible to prevent water or dust from entering the cavity. Further, when the pressure introducing hole 20 is formed in advance in the base substrate 2, subsequently, the base substrate 2 in which the pressure introducing hole 20 is formed is bonded to the SOI substrate 3, and then back grinding is performed on the base substrate 2.
  • the slurry or the like easily intrudes into the cavity 7 according to the manufacturing method of this embodiment. And the entry of slurry etc. into the cavity 7 can be appropriately prevented. Therefore, optimization and simplification of the manufacturing process of the pressure sensor 1 can be facilitated as compared with the prior art.
  • FIG. 8 is an electron micrograph of a recess formed in the SOI substrate of the present example
  • FIG. 9 is an electron micrograph of the recess formed in the SOI substrate of the comparative example.
  • the concave portion penetrating to the SiO 2 film is formed on the silicon substrate constituting the SOI substrate by Si deep etching.
  • Si deep etching mainly, an isotropic etching using sulfur hexafluoride (SF 6 ) and a sidewall protection process performed using C 4 F 8 gas were alternately repeated.
  • a water repellent film was formed on the side wall of the recess by this Si deep etching.
  • the size in plan view of the recess was 700 ⁇ m ⁇ 700 ⁇ m.
  • the concave portion penetrating to the SiO 2 film is formed in the silicon substrate of the SOI substrate in the same manner as above by forming the concave portion by Si deep etching and removing the water repellent film with a solvent (hydrofluoroether HFE). And formed a recess without a water repellent film.
  • a solvent hydrofluoroether HFE
  • the samples of the example and the comparative example were immersed in BHF (buffered hydrofluoric acid) capable of etching SiO 2 .
  • a plan view of a pressure sensor in the present embodiment A cross-sectional view of the pressure sensor shown in FIG. 1 taken along line AA and viewed in the direction of the arrow; Partial back view of pressure sensor, Enlarged sectional view of pressure introduction hole, One process drawing (sectional drawing in the same part as FIG. 2 in a manufacturing process) which shows the manufacturing process of the pressure sensor of this embodiment, One process drawing performed next to FIG. 5 (cross-sectional view in the same portion as FIG. 2 in the manufacturing process), One process drawing performed next to FIG. 6 (cross-sectional view in the same portion as FIG. 2 in the manufacturing process), Electron micrograph of Example (with water repellent film on side wall surface of recess) Electron micrograph of comparative example (without water repellent film on side wall surface of recess)

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  • Measuring Fluid Pressure (AREA)
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Abstract

Provided are a pressure sensor having better ability of preventing entry of water and dust into a cavity than conventional products and a method of manufacturing the pressure sensor. The pressure sensor has the cavity (7) formed in a lower silicon substrate (4), a diaphragm (8) formed by an SiO2 film (5) and an upper silicon substrate (6) that are located above the cavity, a base substrate (2) joined to the lower silicon substrate (4), and a pressure introduction hole (20) formed in a base substrate (2). The maximum opening width (T1) of the pressure introduction hole (20) is smaller than the height (T2) of the cavity (7). The base substrate (2) has a water repelling film which is formed only on a side wall surface (20a) of the pressure introduction hole (20).

Description

圧力センサ及びその製造方法Pressure sensor and method of manufacturing the same
　本発明は、特に、キャビティ内に水や塵埃の侵入を防止できる圧力センサ及びその製造方法に関する。 In particular, the present invention relates to a pressure sensor capable of preventing water and dust from entering the cavity, and a method of manufacturing the same.
　下記の特許文献１にはシリコン基板を用いて形成されたゲージ圧検知用の圧力センサが開示されている。 Patent Document 1 below discloses a pressure sensor for gauge pressure detection formed using a silicon substrate.
　特許文献１では、第１のシリコン単結晶基板にキャビティ（空隙室）及び導入孔が形成され、第２のシリコン単結晶基板にダイアフラムが形成される。またダイアフラムの歪みを検知する歪検出センサが設けられている。 In Patent Document 1, a cavity (void space) and an introduction hole are formed in a first silicon single crystal substrate, and a diaphragm is formed in a second silicon single crystal substrate. In addition, a strain detection sensor that detects strain of the diaphragm is provided.
　しかしながら特許文献１の構成では、導入孔の孔径が大きく、キャビティの高さ寸法より厚い塵埃がキャビティ内に入り込みやすい。このため塵埃がダイアフラム変位を阻害し圧力特性が変化しやすい構成となっていた。 However, in the configuration of Patent Document 1, the diameter of the introduction hole is large, and dust that is thicker than the height dimension of the cavity is likely to enter the cavity. For this reason, the dust inhibits the displacement of the diaphragm and the pressure characteristic is easily changed.
　また特許文献１では、水分も導入孔を介してキャビティ内に侵入しやすく、その結果、ダイアフラム変位を阻害したり、キャビティ内を汚染する問題があった。 Moreover, in patent document 1, it is easy for moisture to enter the cavity through the introduction hole, and as a result, there is a problem that the displacement of the diaphragm is inhibited or the inside of the cavity is contaminated.
　特許文献２に記載された発明の圧力センサは、静電容量式であり、ダイアフラムと対向位置に設けられた電極を導入孔から基板（絶縁物２，２´）の表面にまで延出形成している。さらに特許文献３では基板（絶縁物２，２´）の露出面に撥水処理を施している。 The pressure sensor of the invention described in Patent Document 2 is a capacitance type, and an electrode provided at a position opposed to the diaphragm is formed to extend from the introduction hole to the surface of the substrate (insulator 2, 2 '). ing. Furthermore, in Patent Document 3, the exposed surface of the substrate (insulators 2 and 2 ') is subjected to water repelling treatment.
　しかしながら特許文献２に記載された発明では、特許文献１に記載された発明と同様に、キャビティ内への塵埃の侵入を効果的に防止できずダイアフラム変位を阻害する問題が依然として残っている。さらに、基板（絶縁物２，２´）のダイボンディングする表面も全て撥水処理がされているためダイボンディングを適切に施すことができないといった問題があった。 However, in the invention described in Patent Document 2, as in the invention described in Patent Document 1, the problem that dust can not be effectively prevented from entering the cavity and the problem of inhibiting diaphragm displacement still remains. Furthermore, since the surface of the substrate (insulators 2 and 2 ') to be die-bonded is also subjected to the water-repellent treatment, there is a problem that the die bonding can not be properly performed.
　特許文献３には、圧力センサを収納するケースに設けられた圧力導入孔をフッ素樹脂系フィルタで覆う発明が開示されているが、かかる構成ではケース外からケース内部への水分の侵入を防げてもケース内部で生じた水滴のキャビティ内へへの侵入を適切に防止することは出来ない。また、塵埃のキャビティ内への侵入も適切に防ぐことはできない。
特開２０００－２４９６１３号公報 特開平８－１８９８７０号公報 特開平７－１５１６２６号公報 Although the invention which covers the pressure-introduction hole provided in the case which accommodates a pressure sensor in patent document 3 with a fluorine resin filter is disclosed, the penetration | invasion of the water | moisture content from the outside of a case to the inside of a case can be prevented in this structure. Also, it is not possible to properly prevent the intrusion of water droplets generated inside the case into the cavity. In addition, dust can not be properly prevented from entering the cavity.
JP 2000-249613 A JP-A-8-189870 Japanese Patent Application Laid-Open No. 7-151626
　そこで本発明は上記従来の課題を解決するためのものであり、特に、従来に比べて、キャビティ内に水や塵埃の侵入を防止できる圧力センサ及びその製造方法を提供することを目的としている。 Accordingly, the present invention is intended to solve the above-described conventional problems, and in particular, it is an object of the present invention to provide a pressure sensor capable of preventing water or dust from entering the cavity and a method of manufacturing the same.
　本発明における圧力センサは、
　シリコン基板の裏面側に形成されるキャビティと、前記キャビティ上の前記シリコン基板に形成されるダイアフラムと、前記キャビティを介して前記ダイアフラムと対向する下側に位置し前記シリコン基板に接合されるベース基板と、前記ベース基板に形成される圧力導入孔とを有し、
　前記圧力導入孔の最大開口幅は、前記キャビティの高さ寸法よりも小さく、前記ベース基板に対して前記圧力導入孔の側壁面にのみ撥水膜が形成されていることを特徴とするものである。これにより、従来に比べて、キャビティ内に水や塵埃の侵入を防止でき、圧力特性の安定化を図ることが可能になる。 The pressure sensor in the present invention is
A cavity formed on the back surface side of a silicon substrate, a diaphragm formed on the silicon substrate above the cavity, and a base substrate located on the lower side facing the diaphragm via the cavity and joined to the silicon substrate And a pressure introducing hole formed in the base substrate,
The maximum opening width of the pressure introducing hole is smaller than the height dimension of the cavity, and a water repellent film is formed only on the side wall surface of the pressure introducing hole with respect to the base substrate. is there. This makes it possible to prevent water and dust from entering the cavity and stabilize the pressure characteristics, as compared with the prior art.
　本発明では、前記圧力導入孔は複数個形成されていることが好ましい。目詰まりによる圧力特性変化を抑制できる。 In the present invention, preferably, a plurality of the pressure introducing holes are formed. It is possible to suppress pressure characteristic change due to clogging.
　また本発明では、上側シリコン基板と、下側シリコン基板と、前記上側シリコン基板と前記下側シリコン基板との間に位置するＳｉＯ2膜を備え、
　前記下側シリコン基板に前記キャビティが形成され、前記キャビティ上に位置する前記上側シリコン基板及び前記ＳｉＯ2膜により前記ダイアフラムが形成されていることが好ましい。キャビティ及びダイアフラムを適切に形成できる。 In the present invention, an upper silicon substrate, a lower silicon substrate, and an SiO 2 film located between the upper silicon substrate and the lower silicon substrate are provided.
Preferably, the cavity is formed in the lower silicon substrate, and the diaphragm is formed by the upper silicon substrate and the SiO 2 film located above the cavity. The cavity and the diaphragm can be appropriately formed.
　また本発明では、前記ダイアフラムの歪みに応じて抵抗値が変化するピエゾ素子が前記ダイアフラムの上面側に形成されていることが好ましい。 Further, in the present invention, it is preferable that a piezo element whose resistance value changes according to the distortion of the diaphragm is formed on the upper surface side of the diaphragm.
　また本発明における圧力センサの製造方法は、以下の工程を有することを特徴としている。 The method of manufacturing a pressure sensor according to the present invention is characterized by having the following steps.
　シリコン基板の裏面側にキャビティを形成して、前記キャビティ上に位置する前記シリコン基板にダイアフラムを形成する工程、
　前記キャビティを介して前記ダイアフラムと対向する前記シリコン基板の下側にベース基板を接合する工程、
　前記ベース基板に圧力導入孔を形成し、このとき、前記圧力導入孔の最大開口幅を前記キャビティの高さ寸法よりも小さく形成し、さらに前記ベース基板に対して前記圧力導入孔の側壁面にのみ撥水膜を形成する工程。 Forming a cavity on the back side of the silicon substrate to form a diaphragm on the silicon substrate located above the cavity;
Bonding a base substrate to the lower side of the silicon substrate facing the diaphragm via the cavity;
The pressure introducing hole is formed in the base substrate, and at this time, the maximum opening width of the pressure introducing hole is formed smaller than the height dimension of the cavity, and the side wall surface of the pressure introducing hole is further made to the base substrate. Step of forming a water repellent film only.
　これにより、キャビティ内に水や塵埃の侵入を防止できる圧力センサを簡単且つ適切に製造できる。また、圧力導入孔の形成後に洗浄工程等を行っても水や塵埃のキャビティ内への侵入を防ぐことが出来、従来に比べて、製造工程の最適化及び簡略化を図りやすくなる。 This makes it possible to simply and properly manufacture a pressure sensor that can prevent water or dust from entering the cavity. In addition, even if a cleaning process or the like is performed after the formation of the pressure introducing hole, it is possible to prevent water or dust from invading the inside of the cavity, and it becomes easier to optimize and simplify the manufacturing process as compared with the prior art.
　本発明では、前記ベース基板をシリコンで形成し、前記圧力導入孔及び撥水膜の形成をＳｉディープエッチングにより行うことが好ましい。圧力導入孔及び撥水膜を適切に形成できる。特に撥水膜をベース基板に対して圧力導入孔の側壁面にのみ適切に形成できる。 In the present invention, preferably, the base substrate is formed of silicon, and the pressure introducing hole and the water repellent film are formed by Si deep etching. The pressure introducing hole and the water repellent film can be appropriately formed. In particular, the water repellent film can be appropriately formed only on the side wall surface of the pressure introducing hole with respect to the base substrate.
　また本発明では、前記圧力導入孔を複数個形成することが好ましい。
　また本発明では、前記シリコン基板への接合前に、前記ベース基板に前記圧力導入孔を形成し、その後、前記圧力導入孔が形成された前記ベース基板を、前記シリコン基板の下側に接合することも出来る。かかる場合、シリコン基板に接合された圧力導入孔を備えるベース基板に対してバックグラインド工程を施してもスラリー等のキャビティ内への侵入を適切に防ぐことが出来る。 In the present invention, it is preferable to form a plurality of the pressure introducing holes.
Further, in the present invention, before bonding to the silicon substrate, the pressure introducing hole is formed in the base substrate, and then the base substrate having the pressure introducing hole formed is bonded to the lower side of the silicon substrate. It can also be done. In such a case, it is possible to appropriately prevent the penetration of the slurry or the like into the cavity even if the back grinding process is performed on the base substrate provided with the pressure introducing hole bonded to the silicon substrate.
　また本発明では、上側シリコン基板と、下側シリコン基板と、前記上側シリコン基板と前記下側シリコン基板との間に位置するＳｉＯ2膜を備えるＳＯＩ基板を用い、
　前記下側シリコン基板に前記キャビティをＳｉディープエッチングにて形成し、このとき前記ＳｉＯ2膜が反応性イオンエッチングのストッパ膜となり、前記キャビティ上に位
置する前記ＳｉＯ2膜及び前記上側シリコン基板に前記ダイアフラムを形成することが好ましい。これにより、ダイアフラム及びキャビティを適切に形成できる。またベース基板を下側シリコン基板に接合した後に、ベース基板に圧力導入孔をＳｉディープエッチングで形成するとき、ＳｉＯ2膜が反応性イオンエッチングのストッパとして機能しているので、圧力導入孔を形成する際のＳｉディープエッチングの影響を、ＳＯＩ基板に形成されたキャビティ及びダイアフラムが受けず、ばらつきが小さく安定した圧力特性を備える圧力センサを製造できる。 In the present invention, an SOI substrate comprising an upper silicon substrate, a lower silicon substrate, and a SiO 2 film located between the upper silicon substrate and the lower silicon substrate is used,
The cavity is formed in the lower silicon substrate by Si deep etching, and at this time, the SiO 2 film serves as a stopper film for reactive ion etching, and the SiO 2 film located on the cavity and the upper silicon substrate are formed. Preferably, a diaphragm is formed. Thereby, the diaphragm and the cavity can be appropriately formed. In addition, when the pressure introducing hole is formed in the base substrate by Si deep etching after bonding the base substrate to the lower silicon substrate, the pressure introducing hole is formed because the SiO 2 film functions as a stopper for reactive ion etching. It is possible to manufacture a pressure sensor having stable pressure characteristics with less variation, since the cavity and diaphragm formed in the SOI substrate are not affected by Si deep etching at the time of etching.
　本発明の圧力センサによれば、従来に比べて、キャビティ内に水や塵埃の侵入を防止でき、圧力特性の安定化を図ることが可能になる。 According to the pressure sensor of the present invention, it is possible to prevent the entry of water or dust into the cavity and to stabilize the pressure characteristic as compared with the conventional case.
　図１は本実施形態における圧力センサの平面図、図２は、図１に示す圧力センサをＡ－Ａ線に沿って切断し矢印方向から見た断面図、図３は圧力センサの部分裏面図、図４は、圧力導入孔の拡大断面図、である。なお図２には、切断面を矢印方向へ見たときに見える一部の配線層及びパッドも図示してある。 1 is a plan view of the pressure sensor according to the present embodiment, FIG. 2 is a cross-sectional view of the pressure sensor shown in FIG. 1 cut along line AA and viewed from the arrow direction, and FIG. FIG. 4 is an enlarged sectional view of the pressure introducing hole. FIG. 2 also shows some of the wiring layers and pads that can be seen when the cut surface is viewed in the direction of the arrow.
　本実施形態における圧力センサ１は、大気圧を基準として空気圧を検知するゲージ圧検知用であり、例えば、圧力センサ１を収納するケース（図示しない）の上側に測定圧導入ポートが、下側に大気圧導入ポートが設けられている。 The pressure sensor 1 in the present embodiment is for gauge pressure detection that detects air pressure on the basis of atmospheric pressure. For example, the measurement pressure introduction port is on the upper side of the case (not shown) that houses the pressure sensor 1 on the lower side. An atmospheric pressure introduction port is provided.
　図１，図２に示す圧力センサ１は、ベース基板２と、ベース基板２の上に接合されたＳＯＩ基板３とを備えて構成される。ＳＯＩ（Silicon on Insulator）基板３は、下側シリコン基板４と上側シリコン基板６と、下側シリコン基板４と上側シリコン基板６との間に位置するＳｉＯ2膜５との積層構造である。 The pressure sensor 1 shown in FIGS. 1 and 2 includes a base substrate 2 and an SOI substrate 3 bonded on the base substrate 2. The SOI (Silicon on Insulator) substrate 3 has a laminated structure of a lower silicon substrate 4 and an upper silicon substrate 6 and an SiO 2 film 5 located between the lower silicon substrate 4 and the upper silicon substrate 6.
　図２に示すように下側シリコン基板４には平面視中央部分に、キャビティ（凹部）７が形成される。キャビティ７の上側に位置するＳｉＯ2膜５及び上側シリコン基板６によりダイアフラム８が形成されている。キャビティ７及びダイアフラム８の平面視形状は略矩形状である。 As shown in FIG. 2, a cavity (recess) 7 is formed in the lower silicon substrate 4 at a central portion in plan view. A diaphragm 8 is formed by the SiO 2 film 5 and the upper silicon substrate 6 located above the cavity 7. The shapes of the cavity 7 and the diaphragm 8 in plan view are substantially rectangular.
　ダイアフラム８の周囲は上側シリコン基板６に圧力が作用しても歪みが生じない固定領域９である。 The periphery of the diaphragm 8 is a fixed area 9 in which distortion does not occur even if pressure is applied to the upper silicon substrate 6.
　ダイアフラム８の４辺の各縁部の略中央には、ピエゾ素子Ｂ～Ｅが形成される。図１に示すように、第１ピエゾ素子Ｂと第２ピエゾ素子Ｃとが第１の出力パッド１１を介して直列接続される。また、第３ピエゾ素子Ｄと第４ピエゾ素子Ｅとが第２の出力パッド１２を介して直列接続される。 Piezo elements B to E are formed substantially at the centers of the edge portions of the four sides of the diaphragm 8. As shown in FIG. 1, the first piezoelectric element B and the second piezoelectric element C are connected in series via the first output pad 11. In addition, the third piezo element D and the fourth piezo element E are connected in series via the second output pad 12.
　第１ピエゾ素子Ｂと第３ピエゾ素子Ｄは入力パッド１３を介して、及び、第２ピエゾ素子Ｃと第４ピエゾ素子Ｅはグランドパッド１４を介して、夫々接続される。各ピエゾ素子Ｂ～Ｅに接続される配線層１０は固定領域９上に延出形成され、各パッド１１～１４は固定領域９の四隅に設けられている。配線層１０や各パッド１１～１４はスパッタやメッキによりＡｕやＡｌ等の良導体で形成される。 The first piezoelectric element B and the third piezoelectric element D are connected via the input pad 13, and the second piezoelectric element C and the fourth piezoelectric element E are connected via the ground pad 14. Wiring layers 10 connected to the respective piezoelectric elements B to E are formed to extend on the fixed area 9, and the pads 11 to 14 are provided at four corners of the fixed area 9. The wiring layer 10 and the pads 11 to 14 are formed of a good conductor such as Au or Al by sputtering or plating.
　例えば、各ピエゾ素子Ｂ～Ｅはダイアフラム８の表面にホウ素がドープされたＰ型半導体で形成される。 For example, each of the piezoelectric elements B to E is formed of a P-type semiconductor in which the surface of the diaphragm 8 is doped with boron.
　ダイアフラム３が圧力を受けて歪んだときに、前記第２ピエゾ素子Ｃ及び前記第３ピエゾ素子Ｄの抵抗値の増減傾向と、前記第１ピエゾ素子Ｂ及び前記第４ピエゾ素子Ｅの抵抗値の増減傾向とが逆傾向となるように、各ピエゾ素子Ｂ～Ｅが配置されている。図１では各ピエゾ素子Ｂ～Ｅの平面視形状が略矩形状となっているが例えばミアンダ形状で形成することが可能である。 When the diaphragm 3 receives pressure and is distorted, the increase / decrease of the resistance value of the second piezoelectric element C and the third piezoelectric element D, and the resistance value of the first piezoelectric element B and the fourth piezoelectric element E Piezo elements B to E are arranged such that the increasing and decreasing tendencies are opposite to each other. In FIG. 1, the plan view shape of each of the piezoelectric elements B to E is substantially rectangular, but it is possible to form, for example, a meander shape.
　図示しないが上側シリコン基板６上にはＳｉ3Ｎ4等の保護膜が形成されている。各パッド１１～１４は保護膜から露出しており、各パッド１１～１４と、図示しないケースとの外部回路とがワイヤボンディング等で電気的に接続されている。 Although not shown, a protective film of Si 3 N 4 or the like is formed on the upper silicon substrate 6. The pads 11 to 14 are exposed from the protective film, and the pads 11 to 14 and an external circuit with a case not shown are electrically connected by wire bonding or the like.
　図２，図３に示すようにベース基板２には複数個の圧力導入孔２０が形成されている。各圧力導入孔２０はキャビティ７に連通している。例えば図３のように各圧力導入孔２０の平面視形状は円形状であるが形状は特に限定されるものでない。ベース基板２はシリコンで形成され、各圧力導入孔２０はＳｉディープエッチングにより形成されたものであることが好適である。 As shown in FIGS. 2 and 3, a plurality of pressure introducing holes 20 are formed in the base substrate 2. Each pressure introducing hole 20 is in communication with the cavity 7. For example, as shown in FIG. 3, the plan view shape of each pressure introducing hole 20 is a circular shape, but the shape is not particularly limited. The base substrate 2 is preferably made of silicon, and each pressure introducing hole 20 is preferably formed by Si deep etching.
　Ｓｉディープエッチングでは、主に、六フッ化硫黄（ＳＦ6）を用いた等方性エッチングと、Ｃ4Ｆ8等のポリテトラフルオロエチレン(ＰＴＦＥ)系のガスを用いて行われる側壁保護の工程を交互に繰り返して行う。このようなＳｉディープエッチングを用いることで細くて深い（高アスペクト比）孔の形成が可能である。またこのとき図４に示すように圧力導入孔２０の側壁面２０ａには撥水膜２１が形成される。撥水膜２１はＣ－Ｆ－Ｓｉ膜、あるいはＣ－Ｆ膜である。図４に示すように撥水膜２１は、ベース基板２に対して、圧力導入孔２０の側壁面２０ａにのみ形成される。なおＳｉディープエッチングにてキャビティ７を形成した場合、撥水膜はＳＯＩ基板３に対してキャビティ７の側壁面にも形成される。 In Si deep etching, mainly, isotropic etching using sulfur hexafluoride (SF 6 ), and a side wall protection process performed using a polytetrafluoroethylene (PTFE) -based gas such as C 4 F 8 Repeat alternately. By using such Si deep etching, it is possible to form thin and deep (high aspect ratio) holes. At this time, as shown in FIG. 4, the water repellent film 21 is formed on the side wall surface 20 a of the pressure introducing hole 20. The water repellent film 21 is a C—F—Si film or a C—F film. As shown in FIG. 4, the water repellent film 21 is formed only on the side wall surface 20 a of the pressure introducing hole 20 with respect to the base substrate 2. When the cavity 7 is formed by Si deep etching, the water repellent film is also formed on the side wall surface of the cavity 7 with respect to the SOI substrate 3.
　撥水膜２１の撥水効果は、当然に、ベース基板２やＳＯＩ基板３の表面に比べて高く、撥水膜２１での接触角は、９５～１０５°程度である。 The water repellent effect of the water repellent film 21 is naturally higher than the surfaces of the base substrate 2 and the SOI substrate 3, and the contact angle at the water repellent film 21 is about 95 to 105 °.
　図４に示すように圧力導入孔２０の側壁面２０ａはきれいな垂直面でなく湾曲した凹凸面（波形状）となっているが、これはＳｉディープエッチングによる等方性エッチング工程と保護膜成膜工程とを繰り返して行った結果である。 As shown in FIG. 4, the side wall surface 20a of the pressure introducing hole 20 is not a clean vertical surface but a curved uneven surface (wave shape), but this is an isotropic etching process and protective film deposition by Si deep etching It is the result of repeating the steps.
　図２，図４に示すように各圧力導入孔２０の最大開口幅Ｔ１は、キャビティ７の高さ寸法Ｔ２より小さい。ここで圧力導入孔２０の最大開口幅Ｔ１は、図４で示す断面での撥水膜２１の表面（側壁面２０ａ）間の最大間隔であり、圧力導入孔２０の平面視形状が略円形状であれば最大径を指し、また円形状以外の形状であれば、高さ方向と直交する平面内での最大幅寸法を指す。 As shown in FIGS. 2 and 4, the maximum opening width T1 of each pressure introducing hole 20 is smaller than the height dimension T2 of the cavity 7. Here, the maximum opening width T1 of the pressure introducing hole 20 is the maximum spacing between the surface (side wall surface 20a) of the water repellent film 21 in the cross section shown in FIG. In this case, the maximum diameter is indicated, and in the case of a shape other than a circular shape, the maximum width dimension in a plane orthogonal to the height direction is indicated.
　本実施形態の圧力センサ１の構造であれば、たとえ圧力導入孔２０を通ってキャビティ７内に塵埃が侵入しても、塵埃のサイズは、キャビティ７の高さ寸法Ｔ２よりも小さい。このように、ダイアフラム変位を阻害するほどのサイズの塵埃がキャビティ７内へ侵入するのを防ぐことが可能になるので圧力特性の安定化を図ることが可能になる。 With the structure of the pressure sensor 1 of the present embodiment, even if dust intrudes into the cavity 7 through the pressure introducing hole 20, the size of the dust is smaller than the height dimension T2 of the cavity 7. As described above, since it is possible to prevent dust having a size enough to inhibit the displacement of the diaphragm from entering the cavity 7, the pressure characteristics can be stabilized.
　例えば、キャビティ７の高さ寸法Ｔ２は、８０～２００μｍ程度、圧力導入孔２０の高さ寸法（ベース基板２の厚さ寸法）Ｔ３は、１００～３００μｍ程度、圧力導入孔２０の最大開口幅Ｔ１は、１０～８０μｍ程度、撥水膜２１の膜厚Ｔ４は、０．０１～０．３μｍ程度、である。そのほか、ＳｉＯ2膜の厚さ寸法は、０．３～０．５μｍ程度、上側シリコン基板６の厚さ寸法は、５～１００μｍ程度である。 For example, the height dimension T2 of the cavity 7 is about 80 to 200 μm, the height dimension of the pressure introducing hole 20 (the thickness dimension of the base substrate 2) T3 is about 100 to 300 μm, and the maximum opening width T1 of the pressure introducing hole 20 Is about 10 to 80 μm, and the film thickness T 4 of the water repellent film 21 is about 0.01 to 0.3 μm. Besides, the thickness dimension of the SiO 2 film is about 0.3 to 0.5 μm, and the thickness dimension of the upper silicon substrate 6 is about 5 to 100 μm.
　さらに図１～図４に示す本実施形態の圧力センサ１では、ベース基板２に形成された圧力導入孔２０の側壁面２０ａに撥水膜２１が形成されている。このため、キャビティ７内への水の侵入を適切に防ぐことが出来る。使用環境の変化の際のみならず、圧力導入孔２０の形成後にて、例えば圧力センサ１に対する洗浄工程を行ったときでも水の侵入を防ぐことが出来る。 Further, in the pressure sensor 1 of the present embodiment shown in FIGS. 1 to 4, the water repellent film 21 is formed on the side wall surface 20 a of the pressure introducing hole 20 formed in the base substrate 2. Therefore, the entry of water into the cavity 7 can be appropriately prevented. Not only at the time of change of the use environment but also after the formation of the pressure introducing hole 20, for example, when the cleaning process for the pressure sensor 1 is performed, it is possible to prevent the entry of water.
　以上により本実施形態のゲージ圧検知用の圧力センサ１は、従来に比べて、キャビティ７内に水や塵埃の侵入を防止でき、安定した圧力特性を得ることが出来る。 As described above, the pressure sensor 1 for detecting the gauge pressure according to the present embodiment can prevent water and dust from entering the cavity 7 as compared with the related art, and can obtain stable pressure characteristics.
　しかも上記したように撥水膜２１は、ベース基板２に対して圧力導入孔２０の側壁面２０ａにのみ形成されており、その他の部分には形成されていない。すなわちベース基板２のキャビティ７形成面とは逆側の表面（図２では裏面に相当）に撥水膜２１は形成されていないので、圧力センサ１をケース内の所定位置に適切にダイボンディングすることが可能になる。 Moreover, as described above, the water repellent film 21 is formed only on the side wall surface 20 a of the pressure introducing hole 20 with respect to the base substrate 2, and is not formed on other parts. That is, since the water repellent film 21 is not formed on the surface (corresponding to the back surface in FIG. 2) opposite to the cavity 7 forming surface of the base substrate 2, the pressure sensor 1 is appropriately die-bonded to a predetermined position in the case. It becomes possible.
　圧力導入孔２０は、図２、図３に示すように複数個設けられることが好ましい。圧力導入孔２０は１個でもよいが、１個であると、その圧力導入孔２０が塵埃等により目詰りを起こすと圧力特性が変化してしまい、最悪の場合、ゲージ圧検知用の圧力センサ１として使用できなくなる。よってこのような不具合を防ぐため、たとえ、目詰りを起こした圧力導入孔２０があっても他に目詰りを起こしていない圧力導入孔２０を確保してゲージ圧検知用の圧力センサ１として適切に機能するように、複数（最低３個以上が望ましい）の圧力導入孔２０を設けることが好ましい。 It is preferable that a plurality of pressure introducing holes 20 be provided as shown in FIGS. 2 and 3. The pressure introduction hole 20 may be one, but if it is one, if the pressure introduction hole 20 is clogged with dust etc, the pressure characteristic changes, and in the worst case, a pressure sensor for gauge pressure detection It can not be used as 1. Therefore, in order to prevent such a defect, even if there is a clogged pressure introduction hole 20, a pressure introduction hole 20 which is not clogged elsewhere is secured to be suitable as a pressure sensor 1 for gauge pressure detection. It is preferable to provide a plurality of (at least three or more is desirable) pressure introducing holes 20 to function.
　キャビティ７、ダイヤフラム８及びピエゾ素子Ｂ～Ｅを形成するシリコン基板にはＳＯＩ基板３板以外のものを使用してもよいが、ＳＯＩ基板３を使用することでキャビティ７及びダイアフラム８を適切に形成できる。キャビティ７はＳｉディープエッチングにより形成できるが、ＳｉＯ2膜５が反応性イオンエッチングの際のストッパ膜として機能し、オーバーエッチングすることを適切に防止できる。またベース基板２をＳＯＩ基板３に接合した状態でベース基板２に圧力導入孔２０をＳｉディープエッチングで形成する際にもＳｉＯ2膜５が反応性イオンエッチングの際のストッパ膜となる。よって圧力導入孔２０を形成する際のＳｉディープエッチングの影響をキャビティ７及びダイアフラム８が受けず、ばらつきが小さく安定した圧力特性を備える圧力センサ１に出来る。 Although a silicon substrate other than the SOI substrate 3 plate may be used as the silicon substrate for forming the cavity 7, the diaphragm 8 and the piezoelectric elements B to E, the cavity 7 and the diaphragm 8 are appropriately formed by using the SOI substrate 3. it can. The cavity 7 can be formed by Si deep etching, but the SiO 2 film 5 functions as a stopper film at the time of reactive ion etching and can appropriately prevent over-etching. When the pressure introducing hole 20 is formed in the base substrate 2 by Si deep etching in a state where the base substrate 2 is bonded to the SOI substrate 3, the SiO 2 film 5 also serves as a stopper film in reactive ion etching. Therefore, the cavity 7 and the diaphragm 8 are not affected by the Si deep etching when forming the pressure introducing hole 20, and the pressure sensor 1 can be provided with a pressure characteristic with small variation and stable.
　図５ないし図７を用いて本実施形態の圧力センサ１の製造方法を説明する。図５ないし図７に示す各工程図は製造工程中における図２と同じ部分での断面図である。図５～図７では単品の圧力センサ１の製造方法を示しているが、製造工程中の多数の圧力センサ１が連設されたウェハ状態にて各工程を施すことが一度に多数の圧力センサ１を製造できて好適である。 The manufacturing method of the pressure sensor 1 of this embodiment is demonstrated using FIG. 5 thru | or FIG. Each process drawing shown in FIGS. 5 to 7 is a cross-sectional view of the same part as that of FIG. 2 in the manufacturing process. Although FIGS. 5 to 7 show a method of manufacturing the pressure sensor 1 of a single product, it is possible to perform each process in a wafer state in which a large number of pressure sensors 1 are connected in series during the manufacturing process. It is preferable that 1 can be produced.
　図５の工程では、ＳＯＩ基板３を構成する上側シリコン基板６にピエゾ素子Ｂ～Ｅ、配線層１０及び各パッド１１～１４を形成する（図１も参照）。 In the process of FIG. 5, the piezo elements B to E, the wiring layer 10 and the pads 11 to 14 are formed on the upper silicon substrate 6 constituting the SOI substrate 3 (see also FIG. 1).
　次に、下側シリコン基板６の表面（図５では裏面側に相当）をバックグラインド加工して、下側シリコン基板６を所定の厚さにする。 Next, the surface of the lower silicon substrate 6 (corresponding to the back surface side in FIG. 5) is back ground to make the lower silicon substrate 6 a predetermined thickness.
　続いて、下側シリコン基板６の表面（図５では裏面側に相当）にレジスト層を形成し、レジスト層に対してキャビティ７形成のための抜きパターンを形成する。そして抜きパターンから露出する下側シリコン基板６をドライエッチングにて除去しキャビティ７を形成する。キャビティ７の形成にはＳｉディープエッチングを使用できる。このＳｉディープエッチングにおいて、例えば六フッ化硫黄（ＳＦ６）を用いた等方性エッチング（反応性イオンエッチング）のとき、フッ素とシリコンとは反応するがＳｉＯ2とは反応せず、したがってこの等方性エッチング工程にて下側シリコン基板４は除去されるが露出したＳｉＯ2膜はストッパ膜となり、オーバーエッチングが阻止される。 Subsequently, a resist layer is formed on the surface of the lower silicon substrate 6 (corresponding to the back surface side in FIG. 5), and an extraction pattern for forming the cavity 7 is formed in the resist layer. Then, the lower silicon substrate 6 exposed from the removal pattern is removed by dry etching to form a cavity 7. Si deep etching can be used to form the cavity 7. In this Si deep etching, for example, in the case of isotropic etching (reactive ion etching) using sulfur hexafluoride (SF6), fluorine reacts with silicon but does not react with SiO 2. The lower silicon substrate 4 is removed in the reactive etching step, but the exposed SiO 2 film serves as a stopper film to prevent over-etching.
　続いて、図５に示すＳＯＩ基板３の下にシリコンで形成されたベース基板２を接合する。例えばＳＯＩ基板３とベース基板２とを常温接合できる。続いてベース基板２を所定厚とすべくバックグラインド加工する。 Subsequently, the base substrate 2 formed of silicon is bonded under the SOI substrate 3 shown in FIG. For example, the SOI substrate 3 and the base substrate 2 can be bonded at room temperature. Subsequently, the base substrate 2 is back ground to have a predetermined thickness.
　次に図６の工程（図６及び次に説明する図７では図２に示す圧力センサ１を裏返してベース基板２を上側にした状態で示されている）では、ベース基板２の表面にレジスト層３０を塗布し、レジスト層３０に圧力導入孔２０形成のための抜きパターン３０ａを形成する。 Next, in the process of FIG. 6 (shown in FIG. 6 and in FIG. 7 to be described next, the pressure sensor 1 shown in FIG. 2 is turned over and the base substrate 2 is on the upper side) The layer 30 is applied, and a removal pattern 30 a for forming the pressure introducing hole 20 is formed in the resist layer 30.
　そして、図７に示す工程では、レジスト層３０に覆われていないベース基板２をＳｉディープエッチングで除去する。Ｓｉディープエッチングでは、主に、六フッ化硫黄（ＳＦ6）を用いた等方性エッチングと、Ｃ4Ｆ8等のポリテトラフルオロエチレン（ＰＴＦＥ）系のガスを用いて行われる側壁保護の工程を交互に繰り返して行う。このようなＳｉディープエッチングを用いることで細くて深い（高アスペクト比）孔の形成が可能である。またこのとき図４に示すように圧力導入孔２０の側壁面２０ａには撥水膜２１が形成される。撥水膜２１はＣ－Ｆ－Ｓｉ膜、あるいはＣ－Ｆ膜である。図４に示すように撥水膜２１は、ベース基板２に対して、圧力導入孔２０の側壁面２０ａにのみ形成される。なお上記したように図５工程で、Ｓｉディープエッチングにてキャビティ７を形成したとき、撥水膜はＳＯＩ基板３に対してキャビティ７の側壁面にも形成される。 Then, in the step shown in FIG. 7, the base substrate 2 not covered with the resist layer 30 is removed by Si deep etching. In Si deep etching, mainly, isotropic etching using sulfur hexafluoride (SF 6 ), and a side wall protection process performed using a polytetrafluoroethylene (PTFE) -based gas such as C 4 F 8 Repeat alternately. By using such Si deep etching, it is possible to form thin and deep (high aspect ratio) holes. At this time, as shown in FIG. 4, the water repellent film 21 is formed on the side wall surface 20 a of the pressure introducing hole 20. The water repellent film 21 is a C—F—Si film or a C—F film. As shown in FIG. 4, the water repellent film 21 is formed only on the side wall surface 20 a of the pressure introducing hole 20 with respect to the base substrate 2. As described above, when the cavity 7 is formed by Si deep etching in the step of FIG. 5, the water repellent film is also formed on the side wall surface of the cavity 7 with respect to the SOI substrate 3.
　上記した図６，図７工程では、圧力導入孔２０の最大開口幅Ｔ１をキャビティ７の高さ寸法Ｔ２よりも小さく形成する。また上記したＳｉディープエッチングにより、撥水膜２１をベース基板２に対して圧力導入孔２０の側壁面２０ａにのみ形成できる（図４参照）。すなわち、ベース基板２のキャビティ７形成面とは逆側の表面に撥水膜２１は形成されていないので、圧力センサ１を製造した後、圧力センサ１をケース内に設置するとき、適切にダイボンディングすることが可能になる。 6 and 7 described above, the maximum opening width T1 of the pressure introducing hole 20 is formed smaller than the height dimension T2 of the cavity 7. Further, the water repellent film 21 can be formed only on the side wall surface 20a of the pressure introducing hole 20 with respect to the base substrate 2 by the above-described Si deep etching (see FIG. 4). That is, since the water repellent film 21 is not formed on the surface of the base substrate 2 on the side opposite to the cavity 7 forming surface, the die can be appropriately die-mounted when the pressure sensor 1 is installed in the case after manufacturing the pressure sensor 1. It becomes possible to bond.
　また、キャビティ７やダイアフラム８は、圧力導入孔２０形成の際の影響を、ＳｉＯ2膜５の存在により受けにくい。すなわち、圧力導入孔２０形成の際のＳｉディープエッチングにより、ＳＯＩ基板３側も削れて、キャビティ７の大きさが変わったり、ダイアフラム８の厚みが変化するといった問題は生じない。よってベース基板２をＳＯＩ基板３に接合した状態で圧力導入孔２０を形成しても、ばらつきが小さく安定した圧力特性を備える圧力センサ１を製造できる。 Further, the cavity 7 and the diaphragm 8 are not easily affected by the presence of the SiO 2 film 5 when forming the pressure introducing hole 20. That is, the side of the SOI substrate 3 is also scraped by Si deep etching when forming the pressure introducing hole 20, and there is no problem that the size of the cavity 7 changes or the thickness of the diaphragm 8 changes. Therefore, even if the pressure introducing hole 20 is formed in a state in which the base substrate 2 is bonded to the SOI substrate 3, the pressure sensor 1 can be manufactured which has stable pressure characteristics with small variation.
　図７の圧力導入孔２０の形成後、レジスト層３０を除去する。
　上記した製造方法によれば、キャビティ７内に水や塵埃の侵入を防止できる圧力センサ１を簡単且つ適切に製造できる。また、圧力導入孔２０の形成後に洗浄工程等を行っても水や塵埃のキャビティ内への侵入を防ぐことが出来る。また予めベース基板２に圧力導入孔２０を形成し、続いて、圧力導入孔２０が形成されたベース基板２をＳＯＩ基板３に接合し、その後、ベース基板２に対して、バックグラインドを行うと従来のように大きな開口を有し且つ側壁に撥水処理がされていない圧力導入孔を備える圧力センサでは、キャビティ７内にスラリー等が侵入しやすかったが、本実施形態の製造方法によれば、キャビティ７へのスラリー等の侵入を適切に防ぐことが出来る。よって従来に比べて圧力センサ１の製造工程の最適化及び簡略化を図りやすくなる。 After forming the pressure introducing hole 20 of FIG. 7, the resist layer 30 is removed.
According to the above-described manufacturing method, the pressure sensor 1 capable of preventing the entry of water or dust into the cavity 7 can be manufactured simply and appropriately. In addition, even if a cleaning process or the like is performed after the pressure introducing hole 20 is formed, it is possible to prevent water or dust from entering the cavity. Further, when the pressure introducing hole 20 is formed in advance in the base substrate 2, subsequently, the base substrate 2 in which the pressure introducing hole 20 is formed is bonded to the SOI substrate 3, and then back grinding is performed on the base substrate 2. In the pressure sensor having a pressure introducing hole having a large opening as in the prior art and the side wall not subjected to water repellent treatment, the slurry or the like easily intrudes into the cavity 7 according to the manufacturing method of this embodiment. And the entry of slurry etc. into the cavity 7 can be appropriately prevented. Therefore, optimization and simplification of the manufacturing process of the pressure sensor 1 can be facilitated as compared with the prior art.
　図８は、本実施例のＳＯＩ基板に形成した凹部の電子顕微鏡写真、図９は比較例のＳＯＩ基板に形成した凹部の電子顕微鏡写真である。 FIG. 8 is an electron micrograph of a recess formed in the SOI substrate of the present example, and FIG. 9 is an electron micrograph of the recess formed in the SOI substrate of the comparative example.
　実施例では、ＳＯＩ基板を構成するシリコン基板に対してＳｉディープエッチングによりＳｉＯ2膜まで貫く凹部を形成した。Ｓｉディープエッチングでは、主に、六フッ化硫黄（ＳＦ6）を用いた等方性エッチングと、Ｃ4Ｆ8ガスを用いて行われる側壁保護の工程を交互に繰り返して行った。このＳｉディープエッチングにより凹部の側壁には撥水膜が形成された。凹部の平面視形状の大きさは７００μｍ×７００μｍであった。 In the embodiment, the concave portion penetrating to the SiO 2 film is formed on the silicon substrate constituting the SOI substrate by Si deep etching. In Si deep etching, mainly, an isotropic etching using sulfur hexafluoride (SF 6 ) and a sidewall protection process performed using C 4 F 8 gas were alternately repeated. A water repellent film was formed on the side wall of the recess by this Si deep etching. The size in plan view of the recess was 700 μm × 700 μm.
　一方、比較例ではＳｉＯ2膜まで貫く凹部をＳＯＩ基板のシリコン基板に対して前記と同様にＳｉディープエッチングにて凹部を形成し、撥水膜を除去する溶剤（ハイドロフルオロエーテル　ＨＦＥ）にて除去し、撥水膜のない凹部を形成した。 On the other hand, in the comparative example, the concave portion penetrating to the SiO 2 film is formed in the silicon substrate of the SOI substrate in the same manner as above by forming the concave portion by Si deep etching and removing the water repellent film with a solvent (hydrofluoroether HFE). And formed a recess without a water repellent film.
　実験では、実施例及び比較例の試料を、ＳｉＯ2をエッチング可能なＢＨＦ（バッファードフッ酸）に浸漬させた。 In the experiment, the samples of the example and the comparative example were immersed in BHF (buffered hydrofluoric acid) capable of etching SiO 2 .
　図８に示すように、凹部の側壁に撥水膜が形成された実施例では、ＢＨＦの凹部内への侵入がなくＳＯＩ基板を構成するＳｉＯ2膜がエッチングされていないのが確認できた。一方、図９に示すように、凹部の側壁に撥水膜が形成されていない比較例では、ＢＨＦが凹部内へ侵入し、したがってＳｉＯ2膜５がエッチングされているのを確認できた。 As shown in FIG. 8, in the example in which the water repellent film was formed on the side wall of the recess, it was confirmed that there was no penetration of BHF into the recess and that the SiO 2 film constituting the SOI substrate was not etched. On the other hand, as shown in FIG. 9, in the comparative example in which the water repellent film was not formed on the side wall of the recess, it was confirmed that BHF penetrated into the recess and therefore the SiO 2 film 5 was etched.
本実施形態における圧力センサの平面図、A plan view of a pressure sensor in the present embodiment, 図１に示す圧力センサをＡ－Ａ線に沿って切断し矢印方向から見た断面図、A cross-sectional view of the pressure sensor shown in FIG. 1 taken along line AA and viewed in the direction of the arrow; 圧力センサの部分裏面図、Partial back view of pressure sensor, 圧力導入孔の拡大断面図、Enlarged sectional view of pressure introduction hole, 本実施形態の圧力センサの製造工程を示す一工程図（製造工程中における図２と同じ部分での断面図）、One process drawing (sectional drawing in the same part as FIG. 2 in a manufacturing process) which shows the manufacturing process of the pressure sensor of this embodiment, 図５の次に行われる一工程図（製造工程中における図２と同じ部分での断面図）、One process drawing performed next to FIG. 5 (cross-sectional view in the same portion as FIG. 2 in the manufacturing process), 図６の次に行われる一工程図（製造工程中における図２と同じ部分での断面図）、One process drawing performed next to FIG. 6 (cross-sectional view in the same portion as FIG. 2 in the manufacturing process), 実施例（凹部の側壁面に撥水膜あり）の電子顕微鏡写真、Electron micrograph of Example (with water repellent film on side wall surface of recess) 比較例（凹部の側壁面に撥水膜なし）の電子顕微鏡写真、Electron micrograph of comparative example (without water repellent film on side wall surface of recess)
符号の説明Explanation of sign
１　圧力センサ
２　ベース基板
３　ＳＯＩ基板
４　下側シリコン基板
５　ＳｉＯ2膜
６　上側シリコン基板
７　キャビティ
８　ダイアフラム
１０　配線層
１１～１４　パッド
２０　圧力導入孔
２０ａ　（圧力導入孔の）側壁面
２１　撥水膜
３０　レジスト層
３０ａ　抜きパターン
Ｂ～Ｅ　ピエゾ素子 DESCRIPTION OF SYMBOLS 1 pressure sensor 2 base substrate 3 SOI substrate 4 lower silicon substrate 5 SiO 2 film 6 upper silicon substrate 7 cavity 8 diaphragm 10 wiring layer 11 to 14 pad 20 pressure introducing hole 20 a side wall surface 21 (of pressure introducing hole) water repellent film 30 Resist layer 30a Open pattern B to E Piezo element

Claims (9)

  1. 　シリコン基板の裏面側に形成されるキャビティと、前記キャビティ上の前記シリコン基板に形成されるダイアフラムと、前記キャビティを介して前記ダイアフラムと対向する下側に位置し前記シリコン基板に接合されるベース基板と、前記ベース基板に形成される圧力導入孔とを有し、
    　前記圧力導入孔の最大開口幅は、前記キャビティの高さ寸法よりも小さく、前記ベース基板に対して前記圧力導入孔の側壁面にのみ撥水膜が形成されていることを特徴とする圧力センサ。     A cavity formed on the back surface side of a silicon substrate, a diaphragm formed on the silicon substrate above the cavity, and a base substrate located on the lower side facing the diaphragm via the cavity and joined to the silicon substrate And a pressure introducing hole formed in the base substrate,
    A pressure sensor characterized in that the maximum opening width of the pressure introducing hole is smaller than the height dimension of the cavity, and a water repellent film is formed only on the side wall surface of the pressure introducing hole with respect to the base substrate. .
  2. 　前記圧力導入孔は複数個形成されている請求項１記載の圧力センサ。 The pressure sensor according to claim 1, wherein a plurality of the pressure introducing holes are formed.
  3. 　上側シリコン基板と、下側シリコン基板と、前記上側シリコン基板と前記下側シリコン基板との間に位置するＳｉＯ2膜とを備え、
    　前記下側シリコン基板に前記キャビティが形成され、前記キャビティ上に位置する前記上側シリコン基板及び前記ＳｉＯ2膜により前記ダイアフラムが形成されている請求項１又は２に記載の圧力センサ。     An upper silicon substrate, a lower silicon substrate, and an SiO 2 film located between the upper silicon substrate and the lower silicon substrate,
    The pressure sensor according to claim 1, wherein the cavity is formed in the lower silicon substrate, and the diaphragm is formed by the upper silicon substrate and the SiO 2 film located on the cavity.
  4. 　前記ダイアフラムの歪みに応じて抵抗値が変化するピエゾ素子が前記ダイアフラムの上面側に形成されている請求項１ないし３のいずれかに記載の圧力センサ。 The pressure sensor according to any one of claims 1 to 3, wherein a piezo element whose resistance value changes according to the distortion of the diaphragm is formed on the upper surface side of the diaphragm.
  5. 　以下の工程を有することを特徴とする圧力センサの製造方法。
    　シリコン基板の裏面側にキャビティを形成して、前記キャビティ上に位置する前記シリコン基板にダイアフラムを形成する工程、
    　前記キャビティを介して前記ダイアフラムと対向する前記シリコン基板の下側にベース基板を接合する工程、
    　前記ベース基板に圧力導入孔を形成し、このとき、前記圧力導入孔の最大開口幅を前記キャビティの高さ寸法よりも小さく形成し、さらに前記ベース基板に対して前記圧力導入孔の側壁面にのみ撥水膜を形成する工程。     A manufacturing method of a pressure sensor characterized by having the following processes.
    Forming a cavity on the back side of the silicon substrate to form a diaphragm on the silicon substrate located above the cavity;
    Bonding a base substrate to the lower side of the silicon substrate facing the diaphragm via the cavity;
    The pressure introducing hole is formed in the base substrate, and at this time, the maximum opening width of the pressure introducing hole is formed smaller than the height dimension of the cavity, and the side wall surface of the pressure introducing hole is further made to the base substrate. Step of forming a water repellent film only.
  6. 　前記ベース基板をシリコンで形成し、前記圧力導入孔及び撥水膜の形成をＳｉディープエッチングにより行う請求項５記載の圧力センサの製造方法。 The method for manufacturing a pressure sensor according to claim 5, wherein the base substrate is formed of silicon, and the pressure introducing hole and the water repellent film are formed by Si deep etching.
  7. 　前記圧力導入孔を複数個形成する請求項５又は６に記載の圧力センサの製造方法。 The method of manufacturing a pressure sensor according to claim 5 or 6, wherein a plurality of the pressure introducing holes are formed.
  8. 　前記シリコン基板への接合前に、前記ベース基板に前記圧力導入孔を形成し、その後、前記圧力導入孔が形成された前記ベース基板を、前記シリコン基板の下側に接合する請求項５ないし７のいずれかに記載の圧力センサの製造方法。 8. The pressure introducing hole is formed in the base substrate before bonding to the silicon substrate, and then the base substrate having the pressure introducing hole formed is bonded to the lower side of the silicon substrate. The manufacturing method of the pressure sensor in any one of-.
  9. 　上側シリコン基板と、下側シリコン基板と、前記上側シリコン基板と前記下側シリコン基板との間に位置するＳｉＯ2膜を備えるＳＯＩ基板を用い、
    　前記下側シリコン基板に前記キャビティをＳｉディープエッチングにて形成し、このとき前記ＳｉＯ2膜が反応性イオンエッチングのストッパ膜となり、前記キャビティ上に位置する前記ＳｉＯ2膜及び前記上側シリコン基板に前記ダイアフラムを形成する請求項５
    ないし８のいずれかに記載の圧力センサの製造方法。     Using an SOI substrate comprising an upper silicon substrate, a lower silicon substrate, and a SiO 2 film located between the upper silicon substrate and the lower silicon substrate,
    The cavity is formed in the lower silicon substrate by Si deep etching, and at this time, the SiO 2 film serves as a stopper film for reactive ion etching, and the SiO 2 film located on the cavity and the upper silicon substrate are formed. Forming a diaphragm;
    The manufacturing method of the pressure sensor in any one of 8.
PCT/JP2008/073871 2008-01-16 2008-12-27 Pressure sensor and method of manufacturing the same WO2009090851A1 (en)

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JP2013145226A (en) * 2011-12-13 2013-07-25 Denso Corp Pressure sensor
JP2014197026A (en) * 2014-07-08 2014-10-16 横河電機株式会社 Pressure sensor and manufacturing method thereof
JP5843302B1 (en) * 2015-08-19 2016-01-13 株式会社トライフォース・マネジメント Manufacturing method of composite sensor device
JP2016027349A (en) * 2015-10-30 2016-02-18 横河電機株式会社 Pressure sensor
JP2017187446A (en) * 2016-04-08 2017-10-12 アルプス電気株式会社 Sensor device
WO2018047626A1 (en) * 2016-09-06 2018-03-15 株式会社デンソー Pressure sensor

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JPH03181834A (en) * 1989-12-12 1991-08-07 Fuji Electric Co Ltd Semiconductor pressure converter
JPH08136377A (en) * 1994-11-14 1996-05-31 Omron Corp Pressure sensor and pressure sensor unit
JP2005164538A (en) * 2003-12-05 2005-06-23 Nissan Motor Co Ltd Pressure sensor
JP2006030158A (en) * 2004-06-15 2006-02-02 Canon Inc Semiconductor device and its manufacturing method

Cited By (8)

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Publication number Priority date Publication date Assignee Title
JP2013145226A (en) * 2011-12-13 2013-07-25 Denso Corp Pressure sensor
JP2014197026A (en) * 2014-07-08 2014-10-16 横河電機株式会社 Pressure sensor and manufacturing method thereof
JP5843302B1 (en) * 2015-08-19 2016-01-13 株式会社トライフォース・マネジメント Manufacturing method of composite sensor device
JP2016027349A (en) * 2015-10-30 2016-02-18 横河電機株式会社 Pressure sensor
JP2017187446A (en) * 2016-04-08 2017-10-12 アルプス電気株式会社 Sensor device
WO2018047626A1 (en) * 2016-09-06 2018-03-15 株式会社デンソー Pressure sensor
JP2018040638A (en) * 2016-09-06 2018-03-15 株式会社デンソー Pressure sensor
CN109690274A (en) * 2016-09-06 2019-04-26 株式会社电装 Pressure Sensor

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