JP2007232650A - Capacitance type pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance type pressure sensor having sufficient junction strength between substrates, and capable of exhibiting a sufficient sensor characteristic, even when an extraction electrode exists in a junction area between the substrates. <P>SOLUTION: In this capacitance type pressure sensor of the present invention, contact resistance between the contact layer 15 and the silicon substrate 13 is stabilized by interposing a gold-silicon eutectic layer 16' between the contact layer 15 and the silicon substrate 13, that is, by connecting the contact layer 15 electrically to the silicon substrate 13, using a gold-silicon eutectic reaction, when anodic-joining the silicon substrate 13 to a glass substrate 20, and a Q-value of the sensor is thereby stabilized to exhibit the sufficient sensor characteristic. The sufficient junction strength is also provided between the contact layer 15 and the silicon substrate 13, because connected by the gold-silicon eutectic reaction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a capacitance-type pressure sensor that detects pressure using capacitance.

  The capacitive pressure sensor joins a substrate having a pressure-sensitive diaphragm, which is a movable electrode, and a substrate having a fixed electrode so as to have a predetermined interval (cavity) between the pressure-sensitive diaphragm and the fixed electrode. It is constituted by. In this capacitance-type pressure sensor, when pressure is applied to the pressure-sensitive diaphragm, the pressure-sensitive diaphragm is deformed, thereby changing the distance between the pressure-sensitive diaphragm and the fixed electrode. The capacitance between the pressure-sensitive diaphragm and the fixed electrode changes due to the change in the interval, and the change in pressure is detected using the change in capacitance.

In the capacitance type pressure sensor, for example, as shown in FIG. 5, a glass substrate 102 having a fixed electrode 103 is disposed on a support substrate 101, and a silicon substrate 104 having a diaphragm 104a is formed on the glass substrate 102. It is constructed by joining. In such a capacitive pressure sensor, the extraction electrode 105 for the fixed electrode 103 and the extraction electrode 106 for the movable electrode (diaphragm 104a) are patterned on the glass substrate 102. It is provided in a bonding region between the substrate 104 and the substrate 104.
JP-A-8-75582

  However, in such a structure, the extraction electrodes 105 and 106 exist in the junction region between the glass substrate 102 and the silicon substrate 104. For this reason, if the glass substrate 102 and the silicon substrate 104 are not satisfactorily bonded to the extraction electrodes 105 and 106, the airtightness of the cavity between the glass substrate 102 and the silicon substrate 104 is not sufficient, and the diaphragm 104a serves as a movable electrode. There is a problem that it does not function and as a result, it does not work as a sensor. In addition, if the glass substrate 102 and the silicon substrate 104 are not satisfactorily bonded at the extraction electrodes 105 and 106, there is a problem that the contact resistance becomes unstable and the Q value of the sensor varies.

  The present invention has been made in view of such a point, and even when a lead electrode is present in a bonding region between substrates, the capacitance has sufficient bonding strength between the substrates and can exhibit sufficient sensor characteristics. An object of the present invention is to provide a mold pressure sensor.

  The capacitance type pressure sensor of the present invention is a capacitance type pressure sensor formed by bonding a glass substrate having a fixed electrode and a silicon substrate having a movable electrode, and the glass substrate is a drawer for the movable electrode. A contact layer extending from a junction region between the glass substrate and the silicon substrate to the lead electrode formation region, and in the junction region, the contact layer, and the silicon substrate; And a gold-silicon eutectic layer provided therebetween.

  According to this configuration, the gold-silicon eutectic layer is interposed between the contact layer and the silicon substrate, that is, the gold-silicon eutectic reaction is used to join the silicon substrate and the glass substrate. By electrically connecting the silicon substrate, the contact resistance between the contact layer and the silicon substrate is stabilized, whereby the Q value of the sensor is stabilized and sufficient sensor characteristics can be exhibited. Further, since the contact layer and the silicon substrate are bonded by a gold-silicon eutectic reaction, the bonding layer has a sufficient bonding strength.

  In the capacitive pressure sensor of the present invention, it is preferable that the bonding region has a recess, and the contact layer is formed in the recess. According to this configuration, the thickness due to the contact layer can be absorbed on the glass substrate side, so that the bonding between the silicon substrate and the glass substrate can be more reliably performed.

  In the capacitive pressure sensor of the present invention, the depth of the recess is set so that the glass substrate and the contact layer are substantially flush with each other when the contact layer is formed in the recess. It is preferable. According to this configuration, the space between the glass substrate and the contact layer can be flattened in the bonding region, and only the gold layer contributing to the gold-silicon eutectic reaction can be protruded. A silicon eutectic reaction can be performed. As a result, the bonding strength between the silicon substrate and the glass substrate can be further increased.

  In the capacitive pressure sensor of the present invention, it is preferable that a gold layer is formed on the lead electrode forming region of the contact layer in a state separated from the gold-silicon eutectic layer. According to this configuration, it is possible to prevent the gold layer from being affected by the gold-silicon eutectic reaction in the junction region.

  According to the capacitance type pressure sensor of the present invention, the capacitance type pressure sensor is formed by bonding a glass substrate having a fixed electrode and a silicon substrate having a movable electrode, and the silicon substrate is used for the movable electrode. A contact layer extending from a junction region between the glass substrate and the silicon substrate to the lead electrode formation region, the contact layer, and the silicon in the junction region And a gold-silicon eutectic layer provided between the substrates, so that even if a lead electrode is present in the bonding region between the substrates, the substrate has sufficient bonding strength and sufficient sensor. The characteristic can be exhibited.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
(Embodiment 1)
1A and 1B are diagrams of a capacitive pressure sensor according to an embodiment of the present invention, in which FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line Ib-Ib in FIG. .

  A capacitive pressure sensor 1 shown in FIG. 1A is configured by bonding a glass substrate 20 having a fixed electrode 11 and a silicon substrate 13 having a diaphragm which is a movable electrode. Between the glass substrate 20 and the silicon substrate 13, a cavity 12 which is a movable region of the diaphragm is formed.

  Outside the cavity 12 region, an electrode pad 17 that is a lead electrode for the movable electrode and an electrode pad 19 that is a lead electrode for the fixed electrode 11 are formed. The electrode pad 17 for the movable electrode is electrically connected to the silicon substrate 13 having the movable electrode via the contact layer 15, and the electrode pad 19 for the fixed electrode is fixed to the fixed electrode via the contact pins 14 and 18. 11 is electrically connected.

  FIG. 1B is a diagram for explaining a connection state between the silicon substrate 13 having the movable electrode and the electrode pad 17 for the movable electrode. As can be seen from FIG. 1B, the glass substrate 20 has an electrode formation region 20 a for forming the electrode pad 17 and a bonding region 20 b for bonding to the silicon substrate 13. Here, a step is provided on the glass substrate 20, the bonding region 20b is provided at a high position, and the electrode formation region 20a is provided at a low position. However, the present invention is not limited to this configuration.

  On the glass substrate 20, the contact layer 15 extends from the electrode formation region 20a to the bonding region 20b. Therefore, the contact layer 15 is bonded to the silicon substrate 13 in the bonding region 20b, and the electrode pad 17 is formed in the upper portion in the electrode formation region 20a. For this reason, the silicon substrate 13 having the movable electrode is electrically connected to the electrode pad 17 through the contact layer 15. Examples of the contact layer 15 include metals that have good adhesion to glass such as Ti, Cu, and Cr and diffuse into silicon. Further, the thickness of the contact layer 15 is preferably about 100 nm to about 300 nm in consideration of electrical conductivity, gold-silicon eutectic reaction, anodic bonding property, and the like.

  A gold-silicon eutectic layer 16 ′ is formed on the contact layer 15 in the bonding region 20 b, that is, on the contact layer 15 interposed between the silicon substrate 13 and the glass substrate 20. The gold-silicon eutectic layer 16 ′ is formed by bonding the gold of the gold seed layer 16 formed on the contact layer 15 and the silicon of the silicon substrate 13 when the silicon substrate 13 and the glass substrate 20 are bonded, for example, anodic bonded. Obtained by eutectic reaction. The gold-silicon eutectic layer 16 ′ also serves to prevent the surface of the contact layer 15 from being oxidized.

  Thus, the gold-silicon eutectic layer 16 ′ is interposed between the contact layer 15 and the silicon substrate 13, that is, the gold-silicon eutectic reaction is used at the time of anodic bonding of the silicon substrate 13 and the glass substrate 20. By electrically connecting the contact layer 15 and the silicon substrate 13 to each other, the contact resistance between the contact layer 15 and the silicon substrate 13 is stabilized, whereby the Q value of the sensor is stabilized and sufficient sensor characteristics are obtained. Can be demonstrated. Further, since the contact layer 15 and the silicon substrate 13 are bonded by a gold-silicon eutectic reaction, the bonding layer 15 has a sufficient bonding strength.

  A gold seed layer 16 is formed on the contact layer 15 in the electrode formation region 20a. This gold seed layer 16 is formed separately from the gold-silicon eutectic layer 16 '. The gold seed layer 16 and the gold-silicon eutectic layer 16 'are preferably separated by a sufficient distance W so that the gold seed layer 16 does not affect the gold-silicon eutectic reaction in the junction region 20b. For example, the distance W is about 10 μm to about 200 μm. This can prevent the gold seed layer 16 from being affected by the gold-silicon eutectic reaction in the junction region 20b. The gold seed layer 16 functions as a plating seed layer. In addition, the material which comprises a seed layer can be suitably changed according to the material which comprises the electrode pad formed on it, considering contact resistance etc.

  An electrode pad 17 is formed on the gold seed layer 16. The electrode pad 17 is electrically connected to an external circuit by connection means such as wire bonding. The material composing the electrode pad 17 is appropriately determined according to the material composing the seed layer. The structure in the electrode formation region is not limited to this and can be variously changed.

  The interface between the silicon substrate 13 and the glass substrate 20 preferably has high adhesion. When bonding the silicon substrate 13 to the glass substrate 20, the silicon substrate 13 is mounted on the bonding surface of the glass substrate 20, and an anodic bonding process is performed to increase the adhesion between the substrates 13 and 20. it can. Thus, by exhibiting high adhesiveness at the interface between the glass substrate 20 and the silicon substrate 13, the airtightness in the cavity 12 can be kept high.

  Here, the anodic bonding treatment is performed by applying a predetermined voltage (for example, 300 V to 1 kV) at a predetermined temperature (for example, 400 ° C. or lower), thereby generating a large electrostatic attraction between silicon and glass, This refers to a treatment in which a chemical bond via oxygen is formed at the glass-silicon interface in contact, or a covalent bond is formed by releasing oxygen. The covalent bond at this interface is a Si—Si bond or a Si—O bond between the Si atom of silicon and the Si atom contained in the glass. Therefore, silicon and glass are firmly bonded by this Si—Si bond or Si—O bond, and very high adhesion is exhibited at the interface between the two. In order to perform such anodic bonding efficiently, the glass material of the glass substrate 20 is preferably a glass material containing an alkali metal such as sodium (for example, Pyrex (registered trademark) glass).

  The capacitance type pressure sensor having such a configuration has a predetermined capacitance between the diaphragm, which is a movable electrode, and the fixed electrode 11. When pressure is applied to the pressure sensor, the diaphragm moves according to the pressure. As a result, the diaphragm is displaced. At this time, the capacitance between the diaphragm and the fixed electrode 11 changes. Therefore, the change can be a pressure change using the capacitance as a parameter.

  Next, a manufacturing method of the capacitive pressure sensor according to the first embodiment will be described. 2 (a) to 2 (c) are cross-sectional views for explaining a method for manufacturing the capacitive pressure sensor according to the first embodiment of the present invention.

  When manufacturing the capacitive pressure sensor according to the present embodiment, for example, an embedded substrate in which a silicon conductive portion is embedded in a glass substrate is manufactured, a cavity recess is formed in the embedded substrate, and a fixed electrode is formed. To do. Specifically, one main surface of the low-resistance silicon substrate is etched to form a protrusion, a glass substrate is placed on the protrusion, and the silicon substrate and the glass substrate are heated under vacuum, The silicon substrate is pressed against the glass substrate, and the protruding portion is pushed into the glass substrate to bond the silicon substrate and the glass substrate. Thereafter, the glass substrate and the silicon substrate are polished to expose the protruding portions on both surfaces of the glass substrate, thereby manufacturing an embedded substrate in which the conductive portion is embedded in the glass substrate. Thereafter, a cavity recess is formed in the embedded substrate, and a fixed electrode is formed.

  Next, as shown in FIG. 2A, the contact layer 15 is formed along the step from the electrode formation region 20a of the glass substrate 20 to the bonding region 20b. In this case, a resist film is formed on the glass substrate 20, the resist film is patterned so as to open the contact layer formation region, the material constituting the contact layer 15 is formed by sputtering or the like, and then the resist film is removed. (Lift off).

  Next, as shown in FIG. 2B, a gold seed layer 16 is formed on the contact layer 15 in a separated state. In this case, a resist film is formed in a region including the contact layer 15, the resist film is patterned so as to open the gold seed layer forming region, and a material (gold) constituting the gold seed layer 16 is formed by sputtering or the like. Then, the resist film is removed (lifted off). As a result, the electrode pad 17 can be formed on the gold seed layer 16 by plating.

  Next, as shown in FIG. 2C, an electrode pad 17 is formed on the gold seed layer 16. In this case, a mask is provided in a region other than the electrode pad formation region, and the electrode pad 17 is formed by plating only the electrode pad formation region. The plating conditions vary depending on the material, but are usually used. Next, a resist film is formed over the entire surface, and the resist film is patterned (photolithography) so that the resist film remains in the electrode pad peripheral region, and the gold seed layer 16 and the contact layer 15 are etched using the resist film as a mask. Thereafter, the remaining resist film is removed.

  Next, the silicon substrate 13 formed in advance to a predetermined thickness of about several tens of μm by etching, polishing, or the like is placed on the glass substrate 20 so that the diaphragm as the movable electrode is positioned at a predetermined interval from the fixed electrode 11. Join on top. At this time, an anodic bonding process is performed by applying a voltage of about 500 V to the silicon substrate 13 and the glass substrate 20 under heating at about 400 ° C. or lower. Thereby, the adhesiveness in the interface between the silicon substrate 13 and the glass substrate 20 becomes higher, and the airtightness of the cavity 12 can be improved. At this time, in the gold seed layer 16 between the contact layer 15 and the silicon substrate 13 in the junction region 20b, the gold in the gold seed layer 16 causes a gold-silicon eutectic reaction with the silicon in the silicon substrate 13, and thus the gold-silicon. It becomes the eutectic layer 16 '. In this way, a capacitive pressure sensor is obtained.

  In the capacitive pressure sensor thus obtained, the fixed electrode 11 is electrically connected to the electrode pad 19 via the contact pins 14 and 18, and the diaphragm is electrically connected to the electrode pad 17 via the contact layer 15. Connected. Therefore, the capacitance change signal detected between the diaphragm and the fixed electrode 11 can be acquired from the electrode pads 17 and 19. The measured pressure can be calculated based on this signal.

  In this capacitive pressure sensor, the gold-silicon eutectic layer 16 ′ is interposed between the contact layer 15 and the silicon substrate 13, that is, when the silicon substrate 13 and the glass substrate 20 are anodic bonded. -The contact resistance between the contact layer 15 and the silicon substrate 13 is stabilized by electrically connecting the contact layer 15 and the silicon substrate 13 using a silicon eutectic reaction, thereby stabilizing the Q value of the sensor. Thus, sufficient sensor characteristics can be exhibited. Further, since the contact layer 15 and the silicon substrate 13 are bonded by a gold-silicon eutectic reaction, the bonding layer 15 has a sufficient bonding strength. Furthermore, since there is no extraction electrode between the silicon substrate 13 having the diaphragm and the bonding region 20b, the reliability of bonding between the diaphragm and the glass substrate 20 is improved, and the airtightness of the cavity 12 is improved. It becomes possible.

  The capacitance-type pressure sensor thus obtained was subjected to a two-week accelerated test (pressure cooker test) under the conditions of 100% RH, 2 atm, and 121 ° C., and as a result, contact resistance in the bonding region was determined. Was several Ω and was sufficiently low.

(Embodiment 2)
FIG. 3 is a cross-sectional view showing a schematic configuration of the capacitive pressure sensor according to Embodiment 2 of the present invention. 3, the same parts as those in FIG. 1B are denoted by the same reference numerals as those in FIG. 1B, and detailed description thereof is omitted.

  In the capacitive pressure sensor shown in FIG. 3, the bonding region 20b has a recess 20c, and the contact layer 15 is formed in the recess 20c. By adopting such a configuration, the thickness due to the contact layer 15 can be allowed on the glass substrate 20 side, so that the bonding between the silicon substrate 13 and the glass substrate 20 can be performed more reliably. In particular, the depth D of the recess 20c is set so that the glass substrate 20 and the contact layer 15 are substantially flush with each other when the contact layer 15 is formed in the recess 20c. Since the space between the contact layer 15 can be flattened and only the gold seed layer 16 contributing to the gold-silicon eutectic reaction can protrude, the gold-silicon eutectic reaction can be performed more reliably. it can. As a result, the bonding strength between the silicon substrate 13 and the glass substrate 20 can be further increased.

  Next, a manufacturing method of the capacitive pressure sensor according to the second embodiment will be described. 4 (a) to 4 (d) are cross-sectional views for explaining a method for manufacturing a capacitive pressure sensor according to Embodiment 2 of the present invention.

  When manufacturing the capacitive pressure sensor according to the present embodiment, an embedded substrate is manufactured in the same manner as in the first embodiment, a cavity recess is formed in the embedded substrate, and a fixed electrode is formed.

  Next, as shown in FIG. 4A, a recess 20 c for the contact layer 15 is formed in the bonding region 20 b of the glass substrate 20. In this case, a resist film is formed on the glass substrate 20, the resist film is patterned so that the resist film remains in a region other than the recess formation region, and the glass substrate 20 is milled using the resist film as a mask. Thereafter, the remaining resist film is removed.

  Next, as shown in FIG. 4B, the contact layer 15 is formed along the step from the electrode formation region 20a of the glass substrate 20 to the recess 20c of the bonding region 20b. In this case, a resist film is formed on the glass substrate 20, the resist film is patterned so as to open the contact layer formation region, the material constituting the contact layer 15 is formed by sputtering or the like, and then the resist film is removed. (Lift off).

  Next, as shown in FIG. 4C, a gold seed layer 16 is formed on the contact layer 15 in a separated state. In this case, a resist film is formed in a region including the contact layer 15, the resist film is patterned so as to open the gold seed layer forming region, and a material (gold) constituting the gold seed layer 16 is formed by sputtering or the like. Then, the resist film is removed (lifted off). As a result, the electrode pad 17 can be formed on the gold seed layer 16 by plating.

  Next, as shown in FIG. 4D, an electrode pad 17 is formed on the gold seed layer 16. In this case, a mask is provided in a region other than the electrode pad formation region, and the electrode pad 17 is formed by plating only the electrode pad formation region. The plating conditions vary depending on the material, but are usually used. Next, a resist film is formed over the entire surface, and the resist film is patterned (photolithography) so that the resist film remains in the electrode pad peripheral region, and the gold seed layer 16 and the contact layer 15 are etched using the resist film as a mask. Thereafter, the remaining resist film is removed.

  Next, the silicon substrate 13 formed in advance to a predetermined thickness of about several tens of μm by etching, polishing, or the like is placed on the glass substrate 20 so that the diaphragm as the movable electrode is positioned at a predetermined interval from the fixed electrode 11. Join on top. At this time, an anodic bonding process is performed by applying a voltage of about 500 V to the silicon substrate 13 and the glass substrate 20 under heating at about 400 ° C. or lower. Thereby, the adhesiveness in the interface between the silicon substrate 13 and the glass substrate 20 becomes higher, and the airtightness of the cavity 12 can be improved. At this time, in the gold seed layer 16 between the contact layer 15 and the silicon substrate 13 in the junction region 20b, the gold in the gold seed layer 16 causes a gold-silicon eutectic reaction with the silicon in the silicon substrate 13, and thus the gold-silicon. It becomes the eutectic layer 16 '. In this way, a capacitive pressure sensor is obtained.

  In the capacitive pressure sensor thus obtained, the fixed electrode 11 is electrically connected to the electrode pad 19 via the contact pins 14 and 18, and the diaphragm is electrically connected to the electrode pad 17 via the contact layer 15. Connected. Therefore, the capacitance change signal detected between the diaphragm and the fixed electrode 11 can be acquired from the electrode pads 17 and 19. The measured pressure can be calculated based on this signal.

  In this capacitive pressure sensor, the gold-silicon eutectic layer 16 ′ is interposed between the contact layer 15 and the silicon substrate 13, that is, when the silicon substrate 13 and the glass substrate 20 are anodic bonded. -The contact resistance between the contact layer 15 and the silicon substrate 13 is stabilized by electrically connecting the contact layer 15 and the silicon substrate 13 using a silicon eutectic reaction, thereby stabilizing the Q value of the sensor. Thus, sufficient sensor characteristics can be exhibited. Further, since the contact layer 15 and the silicon substrate 13 are bonded by a gold-silicon eutectic reaction, the bonding layer 15 has a sufficient bonding strength. In particular, since the thickness of the contact layer 15 is allowed by the recess 20c of the glass substrate 20, the bonding between the silicon substrate 13 and the glass substrate 20 can be performed more reliably. Furthermore, since there is no extraction electrode between the silicon substrate 13 having the diaphragm and the bonding region 20b, the reliability of bonding between the diaphragm and the glass substrate 20 is improved, and the airtightness of the cavity 12 is improved. It becomes possible.

  The present invention is not limited to Embodiments 1 and 2 above, and can be implemented with various modifications. For example, the structure and shape of the capacitive pressure sensor is not particularly limited as long as it is formed by joining a glass substrate having a fixed electrode and a silicon substrate having a movable electrode. Moreover, there is no restriction | limiting in particular about the numerical value and material which were demonstrated in the said Embodiment 1,2. In addition, the etching and milling processes in the first and second embodiments are performed under conditions normally used. In addition, the processes described in the first and second embodiments are not limited to this, and the processes may be performed by changing the order as appropriate. Other modifications may be made as appropriate without departing from the scope of the object of the present invention.

  The present invention can be applied to, for example, a barometer that monitors atmospheric pressure or a capacitance-type pressure sensor that monitors gas pressure.

It is a figure which shows schematic structure of the electrostatic capacitance type pressure sensor which concerns on Embodiment 1 of this invention, (a) is a top view, (b) is sectional drawing which follows the Ib-Ib line | wire in (a). is there. (A)-(c) is sectional drawing for demonstrating the manufacturing method of the electrostatic capacitance type pressure sensor which concerns on Embodiment 1 of this invention. It is sectional drawing which shows schematic structure of the capacitive pressure sensor which concerns on Embodiment 2 of this invention. (A)-(d) is sectional drawing for demonstrating the manufacturing method of the electrostatic capacitance type pressure sensor which concerns on Embodiment 2 of this invention. It is sectional drawing which shows the conventional electrostatic capacitance type pressure sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitance type pressure sensor 11 Fixed electrode 12 Cavity 13 Silicon substrate 14, 18 Contact pin 15 Contact layer 16 Gold seed layer 16 'Gold-silicon eutectic layer 17, 19 Electrode pad 20 Glass substrate 20a Electrode formation area 20b Bonding area 20c recess

Claims (4)

  A capacitance type pressure sensor formed by bonding a glass substrate having a fixed electrode and a silicon substrate having a movable electrode, wherein the glass substrate has a lead electrode forming region for the movable electrode, and the glass A contact layer extending from a junction region between the substrate and the silicon substrate to the lead electrode formation region; and a gold-silicon eutectic provided in the junction region between the contact layer and the silicon substrate. And a capacitive pressure sensor.   The capacitive pressure sensor according to claim 1, wherein the bonding region has a recess, and the contact layer is formed in the recess.   3. The electrostatic discharge according to claim 2, wherein the depth of the recess is set so that the glass substrate and the contact layer are substantially flush with each other when the contact layer is formed in the recess. Capacitive pressure sensor.   4. The static layer according to claim 1, wherein a gold layer is formed on the lead electrode forming region of the contact layer in a state separated from the gold-silicon eutectic layer. 5. Capacitive pressure sensor.

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