JP2007064919A - Electrostatic capacity type mechanical quantity sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic capacity type mechanical quantity sensor which is capable of preventing reductions in sensor performance due to the presence of gases in a closed space between a substrate and a movable electrode and avoiding large-size formation due to a gas-trap function and which keeps a pressure sensor integrated with an acceleration sensor. <P>SOLUTION: A fixed electrode 14a for the pressure sensor and a fixed electrode 14b for the acceleration sensor are formed on a principal surface 11a of a first glass substrate 11. A silicon substrate 16 is joined onto the first glass substrate 11 in such a way that a pressure-sensitive diaphragm 16a may be arranged above the fixed electrode 14a and that a rocking member 16b may be arranged above the fixed electrode 14b. A second glass substrate 18 is joined onto the silicon substrate 16 in such a way as to envelop the rocking member 16b. A cavity 17a on the side of the pressure sensor communicates with cavities 17b and 17d on the side of the acceleration sensor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a capacitance-type mechanical quantity sensor that detects a mechanical quantity such as pressure or acceleration using an electrostatic capacity.

  Examples of the mechanical quantity sensor include a pressure sensor and an acceleration sensor. Such a mechanical quantity sensor includes a capacitive mechanical quantity sensor that detects an electrostatic capacity between a movable electrode and a fixed electrode. The capacitance type pressure sensor is configured by joining 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 between the pressure-sensitive diaphragm and the fixed electrode. Has been. 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.

Further, in the capacitance type acceleration sensor, a substrate having a swing member that is a movable electrode and a substrate having a fixed electrode are joined so as to have a predetermined interval between the swing member and the fixed electrode. It is comprised by. In this capacitance type acceleration sensor, when acceleration is applied to the swing member, the swing member swings, thereby changing the interval between the swing member and the fixed electrode. The capacitance between the oscillating member and the fixed electrode changes due to the change in the interval, and the change in acceleration is detected using the change in capacitance.
In addition, with the aim of reducing the size and cost of the sensor, a capacitive mechanical quantity sensor in which a capacitive pressure sensor and a capacitive acceleration sensor are integrated has been developed (Patent Documents 1 and 2). .

When the above-described capacitance type mechanical quantity sensor is configured using glass and silicon, it is known that the residual gas generated during the manufacturing process is a big problem affecting the performance. For example, in a capacitive pressure sensor, when a glass substrate and a silicon substrate having a pressure sensitive diaphragm are anodically bonded, a gas mainly composed of oxygen is generated at the bonded portion, and the gas remains in the space. . Such a gas causes a decrease in sensing performance. Conventionally, in order to adsorb such a gas, a technique has been proposed in which a getter chamber connected to the space and provided with a getter material is provided separately from the sealed space between the substrate and the pressure-sensitive diaphragm ( Patent Document 3). Note that this document describes an example in which the same structure as the pressure sensor is used as an electrostatic actuator.
JP-A-8-160072 JP 2004-191128 A JP 20042455753 A

  However, when the above-described technology is applied to a pressure sensor, a getter chamber is provided separately from the sealed space between the substrate and the pressure-sensitive diaphragm. There is a problem that the capacitive pressure sensor is increased in size.

  The present invention has been made in view of the above points, and can prevent deterioration in the performance of the sensor due to the presence of gas in a sealed space between the substrate and the movable electrode, and further increase the size by the gas trap function. An object of the present invention is to provide a capacitance type mechanical quantity sensor that can be avoided.

  The capacitance-type mechanical quantity sensor of the present invention is a capacitance-type dynamic quantity sensor in which a pressure sensor that detects pressure by capacitance and an acceleration sensor that detects acceleration by capacitance are arranged in parallel. A first substrate having a pair of main surfaces facing away from each other and having a first fixed electrode for the pressure sensor and a second fixed electrode for the acceleration sensor formed on one of the main surfaces; The first conductive movable part for the pressure sensor disposed opposite to the first fixed electrode with a predetermined distance and the second fixed electrode disposed opposite to the second fixed electrode. A second substrate having a second conductive movable part for an acceleration sensor; and a third substrate disposed on at least the second substrate so as to enclose the second conductive movable part. The first and second substrates contain the first and second fixed electrodes; Serial and first cavity is formed which communicates with the region of the pressure sensor and the area of the acceleration sensor, the first cavity is characterized in that it is joined to be sealed.

  In the capacitance type mechanical quantity sensor of the present invention, the second substrate has a through hole in a region of the acceleration sensor, and the second and third substrates are on the second conductive movable part. It is preferable that the second cavities formed in the first and second cavities are joined so as to be sealed, and the first and second cavities communicate with each other through the through holes.

  The capacitance type mechanical quantity sensor of the present invention is a capacitance type mechanical quantity sensor formed by stacking a pressure sensor for detecting pressure by capacitance and an acceleration sensor for detecting acceleration by capacitance. The first fixed electrode for the pressure sensor formed on one main surface of the pair of main surfaces facing each other and the acceleration sensor for the acceleration sensor formed on the other main surface of the pair of main surfaces A first substrate having a second fixed electrode and a through hole; a second substrate having a first conductive movable portion for the pressure sensor disposed at a predetermined interval from the first fixed electrode; And a fourth substrate having a second conductive movable part for the acceleration sensor arranged at a predetermined interval from the two fixed electrodes, and the first and second substrates are arranged on the first fixed electrode. Are joined to form a third cavity. And the fourth substrate are joined so that a fourth cavity is formed on the second fixed electrode, and the third and fourth cavities communicate with each other through the through hole of the first substrate. And sealed by the joint portion of the first and second substrates and the joint portion of the first and fourth substrates.

  According to these configurations, since the cavity of the pressure sensor region communicates with the cavity of the acceleration sensor region, in this capacitance type mechanical quantity sensor, the volume is much larger than the cavity volume of the pressure sensor alone. The cavity can be secured. As a result, even if gas is generated in a sealed space between the first substrate and the second substrate, the gas can be diffused into a cavity having a relatively large volume. Thereby, the performance degradation of the sensor due to the presence of gas can be prevented. Further, according to this capacitance type mechanical quantity sensor, since no getter chamber or the like is provided, it is possible to avoid an increase in size due to the gas trap function.

  In the capacitive mechanical quantity sensor of the present invention, the first and third substrates are glass substrates, the second substrate is a silicon substrate, or the first substrate is a glass substrate, The second and fourth substrates are preferably silicon substrates.

  In the capacitance type mechanical quantity sensor of the present invention, the first substrate electrically connects an electrode formed on the one main surface and an electrode formed on the other main surface. It is preferable to further include a conductive portion.

  According to this configuration, since an electrode serving as an extraction portion to the outside can be formed on one surface, a device suitable for surface mounting can be obtained.

  In the capacitance-type mechanical quantity sensor of the present invention, the conductive portion is preferably a silicon member embedded in the glass substrate. In this case, it is preferable to have a Si—Si bond or a Si—O bond at the interface between the glass substrate and the silicon member. According to this configuration, since the Si-Si bond or the Si-O bond is present at the interface between the glass substrate and the silicon member, the glass substrate and the silicon member are firmly bonded, and the adhesion between the two is improved. In addition, the airtightness of the cavity is improved.

  In the capacitance-type mechanical quantity sensor of the present invention, the first conductive movable part is a pressure-sensitive diaphragm that is displaced by a pressure to be measured, the pressure is detected using the pressure-sensitive diaphragm, and the second conductive Preferably, the movable part is a rocking member that rocks according to the acceleration to be measured, and the acceleration is detected using the rocking member.

  According to the capacitance type mechanical quantity sensor of the present invention, the cavity on the pressure sensor area side and the cavity on the acceleration sensor area side communicate with each other, so that a mechanical quantity sensor in which the pressure sensor and the acceleration sensor are integrated is configured. In this case, the cavities of both sensors can be communicated to reduce the influence of residual gas to a negligible level even without a getter chamber. For this reason, it is possible to prevent deterioration in the performance of the sensor due to the presence of gas in the sealed space between the substrate and the movable electrode, and it is possible to avoid an increase in size due to the gas trap function.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
(Embodiment 1)
In the present embodiment, the capacitance type mechanical quantity sensor includes a capacitance type dynamic quantity sensor in which a pressure sensor that detects pressure by capacitance and an acceleration sensor that detects acceleration by capacitance are arranged in parallel. A case of a quantity sensor (horizontal type) will be described. 1A and 1B are schematic views of a capacitive mechanical quantity sensor according to Embodiment 1 of the present invention, where FIG. 1A is a plan view and FIG. 1B is a cross-sectional view.

  In the figure, 11 indicates a first glass substrate. The first glass substrate 11 has a pair of main surfaces 11a and 11b facing each other. A pressure sensor and an acceleration sensor are arranged in parallel on the first glass substrate 11. In the first glass substrate 11, islands (silicon members) 12a to 12d made of silicon are embedded. The islands 12a to 12d are conductive members that electrically connect the electrodes formed on the main surface 11a and the electrodes formed on the main surface 11b. The islands 12a and 12b are conductive members on the pressure sensor side, and the islands 12c and 12d are conductive members on the acceleration sensor side. The islands 12a to 12d are exposed on both main surfaces of the first glass substrate 11, respectively. The formation of the islands 12a to 12d will be described later.

  In the pressure sensor region A on the main surface 11a of the first glass substrate 11, an electrode 13a is formed so as to be electrically connected to one exposed portion of the island 12a, and one of the islands 12b is formed. A fixed electrode 14a is formed so as to be electrically connected to the exposed portion. This fixed electrode 14a is a fixed electrode for a pressure sensor. A fixed electrode 14b is formed in the acceleration sensor region B on the main surface 11a of the first glass substrate 11 so as to be electrically connected to one exposed portion of the island 12c. An electrode 13b is formed so as to be electrically connected to one exposed portion of 12d. This fixed electrode 14b is a fixed electrode for an acceleration sensor.

  In the pressure sensor region A on the main surface 11b of the first glass substrate 11, an electrode 15a is formed so as to be electrically connected to the other exposed portion of the island 12a, and the other of the island 12b is formed. An electrode 15b is formed so as to be electrically connected to the exposed portion. Further, in the acceleration sensor region B on the main surface 11b of the first glass substrate 11, an electrode 15c is formed so as to be electrically connected to the other exposed portion of the island 12c, and the island 12d. An electrode 15d is formed so as to be electrically connected to the other exposed portion. As described above, since the electrodes 15a to 15d are provided on the same main surface 11b, connection to an external device is facilitated.

  On the main surface 11a of the first glass substrate 11, a pressure-sensitive diaphragm 16a (movable electrode) that is a conductive movable part on the pressure sensor side and a swing member 16b that is a conductive movable part on the acceleration sensor side are provided. A silicon substrate 16 is bonded. In this silicon substrate 16, a pressure sensitive diaphragm 16 a that is movable by a measured pressure as a conductive movable portion is provided in the pressure sensor region A, and a vibration is measured by a measured acceleration as a conductive movable portion in the acceleration sensor region B. A swinging member 16b that moves and a cantilever 16c that supports the swinging member 16b are provided. In addition, between the pressure sensor region A and the acceleration sensor region B on the silicon substrate 16, and at the end of the pressure sensor region A (left end toward the paper surface) and the end of the acceleration sensor region B (right end toward the paper surface) A first joint portion 16d that joins a second glass substrate described later is provided. Further, the end of the pressure sensor region A of the silicon substrate 16 (left end toward the paper surface) and the end of the acceleration sensor region B (right end toward the paper surface) are joined to the main surface 11a of the first glass substrate 11. Two joint portions 16e are provided. Further, in the silicon substrate 16, a recess 16f is formed above the lead-out portions (islands 12b, 12c) of the fixed electrodes 14a, 14b. By forming the recess 16f in this manner, parasitic capacitance in a region other than the sensing region can be reduced.

  The first glass substrate 11 and the silicon substrate 16 are arranged such that the pressure sensitive diaphragm 16a is disposed at a predetermined interval from the fixed electrode 14a, and the swing member 16b is disposed at a predetermined interval from the fixed electrode 14b. In the state of being aligned with each other, the second joint 16e is joined. Further, the first glass substrate 11 and the silicon substrate 16 are joined so that cavities 17a and 17b are formed on the fixed electrodes 14a and 14b. That is, the cavity 17a is provided on the fixed electrode 14a in the pressure sensor region A, and the cavity 17b is provided on the fixed electrode 14b in the acceleration sensor region B. The cavities 17 a and 17 b communicate between the pressure sensor region A and the acceleration sensor region B. That is, as shown in FIG. 1A, the cavity 17a in the pressure sensor region A and the cavity 17b in the acceleration sensor region B are communicated with each other by the communication portion 17c.

  A second glass substrate 18 is disposed on the silicon substrate 16. The second glass substrate 18 is bonded at the first bonding portion 16 d of the silicon substrate 16. The second glass substrate 18 is provided with a hole 18a through which outside air enters. The pressure-sensitive diaphragm 16a is moved by the pressure of the outside air that has entered through the hole 18a. As a method of forming the hole 18a in the second glass substrate 18, a sandblasting process or the like can be used. The acceleration sensor region B is configured such that the swing member 16b swings in a space formed by the first and second glass substrates 11 and 18 and the silicon substrate 16. Further, in the acceleration sensor region B of the silicon substrate 16, a through hole 16h is formed in one cantilever 16c that supports the swing member 16b. Accordingly, the cavity 17d configured between the swinging member 16b and the second glass substrate 18 in the acceleration sensor region B communicates with the cavity 17b through the through hole 16h. Thereby, a cavity with a large volume can be provided. Since the silicon substrate 16 and the second glass substrate 18 are bonded by the first bonding portion 16d, the pressure-sensitive diaphragm 16a is thereby sealed in the cavity.

  The pressure-sensitive diaphragm 16a and the swing member 16b in the silicon substrate 16 are provided by forming recesses from both sides of the silicon substrate 16 by etching or the like. Further, when the cantilever 16c and the swing member 16b are formed on the silicon substrate 16, for example, etching is performed by applying a micromachining machine technique. The concave portion on the glass substrate bonding surface side of the silicon substrate 16 has a size that can accommodate at least the fixed electrodes 14a and 14b. By bonding the silicon substrate 16 to the first glass substrate 11, the cavity 17a, 17b is constituted. Thereby, an electrostatic capacity is generated between the pressure-sensitive diaphragm 16a and the fixed electrode 14a, and an electrostatic capacity is generated between the swinging member 16b and the fixed electrode 14b.

  It is preferable that the interface between the first glass substrate 11 and the islands 12a to 12d has high adhesion. As will be described later, these interfaces are formed by pushing the islands 12a to 12d into the first glass substrate 11 under heating. Although high adhesion can be exhibited even at the interface obtained by such a method, adhesion is further enhanced by applying anodic bonding treatment after the islands 12a to 12d are pushed into the first glass substrate 11. be able to. Anodic bonding treatment is applied at a predetermined temperature (for example, 400 ° C. or lower) at a predetermined voltage (for example, 300 V to 1 kV), thereby generating a large electrostatic attraction between silicon and glass and sharing at the interface. A process that causes a bond to occur. 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 first glass substrate 11 is preferably a glass material containing an alkali metal such as sodium (for example, Pyrex (registered trademark) glass).

  The same applies to the interface between the main surface 11 a of the first glass substrate 11 and the silicon substrate 16 and the interface between the silicon substrate and the second glass substrate 18. That is, the adhesion can be enhanced by mounting the silicon substrate 16 on the main surface 11a of the first glass substrate 11 and performing an anodic bonding process. Thus, the interface between the first glass substrate 11 and the islands 12a to 12d, the interface between the first glass substrate 11 and the silicon substrate 16, and the interface between the second glass substrate 18 and the silicon substrate 16 By exhibiting high adhesiveness, the cavity 17a formed between the pressure-sensitive diaphragm 16a and the main surface 11a of the first glass substrate 11, the swing member 16b, and the main surface 11a of the first glass substrate 11 It is possible to maintain high airtightness in the cavity 17b formed between the oscillating member 16b and the cavity 17d formed between the swinging member 16b and the second glass substrate 18.

  In the pressure sensor region A of the capacitive mechanical quantity sensor having such a configuration, a predetermined capacitance is provided between the pressure-sensitive diaphragm 16 a and the fixed electrode 14 a on the first glass substrate 11. When pressure is applied to the pressure sensor, the pressure-sensitive diaphragm 16a moves according to the pressure. As a result, the pressure sensitive diaphragm 16a is displaced. At this time, the electrostatic capacitance between the pressure-sensitive diaphragm 16a and the fixed electrode 14a on the first glass substrate 11 changes. Therefore, the change can be a pressure change using the capacitance as a parameter.

  On the other hand, in the acceleration sensor region B of the capacitance type mechanical quantity sensor, the swing member 16b is measured acceleration in a space formed by the first and second glass substrates 11 and 18 and the silicon substrate 16. Oscillates. Since the oscillating member 16b is a conductor, the capacitance between the oscillating member 16b and the fixed electrode 14b changes when the oscillating member 16b oscillates. By detecting this change, acceleration can be measured.

  In this capacitance type mechanical quantity sensor, since the cavity 17a in the pressure sensor region A communicates with the cavities 17b and 17d in the acceleration sensor region B, the cavity 17a and the cavities 17b and 17d constitute a cavity. Become. Therefore, in this capacitance type mechanical quantity sensor, it is possible to secure a cavity having a very large volume compared to the volume of the cavity in the pressure sensor alone. As a result, even if gas is generated in a sealed space between the glass substrate and the silicon substrate, the gas can be diffused into a cavity having a relatively large volume. Thereby, the performance degradation of the sensor due to the presence of gas can be prevented. Further, according to this capacitance type mechanical quantity sensor, since no getter chamber or the like is provided, it is possible to avoid an increase in size due to the gas trap function.

  Next, a manufacturing method of the capacitive pressure sensor of the present embodiment will be described. 2 (a) to (c), FIGS. 3 (a) to (c), and FIGS. 4 (a) to 4 (e) are diagrams illustrating a method of manufacturing a capacitive mechanical quantity sensor according to Embodiment 1 of the present invention. It is sectional drawing for demonstrating.

  First, a silicon substrate 16 having a low resistance by doping impurities is prepared. The impurity may be an n-type impurity or a p-type impurity. The concentration is, for example, about 0.01 Ω · cm. One main surface of the silicon substrate 16 is etched to form a recess 16g for the cavity 17a for controlling the distance between the pressure sensitive diaphragm 16a and the fixed electrode 14a, as shown in FIG. In this case, the silicon substrate 16 is thermally oxidized to form a silicon oxide film. Then, a resist film is formed on the silicon oxide film, and the resist film is patterned (photolithography) so that the resist film remains outside the region where the recess 16g is formed, and the silicon oxide film is etched using the resist film as a mask, Thereafter, the remaining resist film is removed. The silicon substrate 16 is etched using the silicon oxide film having the opening formed in this way as a mask to provide a recess 16g. Etching may be dry etching or wet etching. However, in the case of wet etching, it is preferable to perform anisotropic etching by defining the crystal plane of the surface of the silicon substrate 16 so that the etching rate is different.

  Next, as shown in FIG. 2B, in the recess 16g, a recess 16f is formed in a region corresponding to the upper portion of the lead electrodes 14a and 14b (islands 12b and 12c). The recess 16f is formed by the same method as that for forming the recess 16g. Next, the other main surface of the silicon substrate 16 is etched to form a pressure sensitive diaphragm 16a and a swing member 16b as shown in FIG. The pressure-sensitive diaphragm 16a and the swing member 16b are formed by the same method as the method of forming the recess 16g. When forming the pressure-sensitive diaphragm 16a and the swinging member 16b, the penetrating portion 16h can be formed by etching from one main surface side of the silicon substrate 16, that is, the cavity 17 forming side.

  Next, as shown in FIG. 3A, the first glass substrate 11 in which the islands 12a to 12d are embedded is produced. The first glass substrate 11 can be manufactured by the steps shown in FIGS. 4A to 4E, the islands 12a and 12b are shown for the sake of clarity. That is, first, a silicon substrate 12 having a low resistance by doping impurities is prepared. The silicon substrate 12 is etched to form islands 12a to 12d as shown in FIG.

  Next, as shown in FIG. 4B, the first glass substrate 11 is placed on the silicon substrate 12 on which the islands 12a and 12b are formed. Further, the silicon substrate 12 and the first glass substrate 11 are heated under vacuum, and the silicon substrate 12 is pressed against the first glass substrate 11 as shown in FIG. 12b is pushed into the main surface 11b of the first glass substrate 11 to bond the silicon substrate 12 and the first glass substrate 11 together. The temperature at this time is not higher than the melting point of silicon and is preferably a temperature at which the glass can be deformed (for example, not higher than the softening point temperature of the glass). For example, the heating temperature is about 600 ° C.

  Further, in order to further improve the adhesion at the interface 11c between the islands 12a, 12b of the silicon substrate 12 and the first glass substrate 11, it is preferable to perform an anodic bonding treatment. In this case, an electrode is attached to each of the silicon substrate 12 and the first glass substrate 11 and a voltage of about 300 V to 1 kV is applied under heating at about 400 ° C. or lower. Thereby, the adhesiveness at the interface 11c becomes higher, and the airtightness of the cavities 17a and 17b of the capacitance type mechanical quantity sensor can be improved.

  Next, as shown in FIG. 4D, the islands 12a and 12b are partially exposed at the main surface 11a by polishing the main surface 11a side of the first glass substrate 11. As a result, the islands 12a and 12b are embedded in the first glass substrate 11. Further, as shown in FIG. 4E, the islands 12 a and 12 b are partially exposed from both surfaces of the first glass substrate 11 by polishing the silicon substrate 12. In this way, the first glass substrate 11 in which the silicon member is embedded is manufactured.

  Next, as illustrated in FIG. 3B, electrodes 15 a to 15 d are formed on the main surface 11 b of the first glass substrate 11 so as to be electrically connected to the islands 12 a to 12 d, respectively. In this case, first, an electrode material is deposited on the main surface 11b of the first glass substrate 11, a resist film is formed thereon, and the resist film is patterned so that the resist film remains in the electrode formation region ( Photolithography), the electrode material is etched using the resist film as a mask, and then the remaining resist film is removed.

  Next, as shown in FIG. 3C, electrodes 13a and 13b are formed on the main surface 11a of the first glass substrate 11 so as to be electrically connected to the islands 12a and 12d, respectively. Fixed electrodes 14a and 14b are formed so as to be electrically connected to the bodies 12b and 12c, respectively. In this case, first, an electrode material is deposited on the main surface 11a of the first glass substrate 11, a resist film is formed thereon, and the resist film is left so that the resist film remains in the electrode and fixed electrode formation region. Is patterned (photolithography), the electrode material is etched using the resist film as a mask, and then the remaining resist film is removed.

  Next, the silicon substrate 16 having the pressure-sensitive diaphragm 16a that is displaced by the measured pressure and the swinging member 16b that is swung by the measured acceleration is positioned so that the pressure-sensitive diaphragm 16a is positioned at a predetermined interval from the fixed electrode 14a. In addition, the swing member 16b is joined to the main surface 11a of the first glass substrate 11 so as to be positioned at a predetermined distance from the fixed electrode 14b. That is, the main surface 11a of the first glass substrate 11 and the second bonding portion 16e of the silicon substrate 16 are bonded. At this time, an anodic bonding process is performed by applying a voltage of about 500 V to the silicon substrate 16 and the first glass substrate 11 under heating at about 400 ° C. or lower. Thereby, the adhesiveness in the interface between the silicon substrate 16 and the 1st glass substrate 11 becomes higher, and the airtightness of the cavities 17a and 17b can be improved.

  Next, the second glass substrate 18 is subjected to sand blasting to form holes 18a. The second glass substrate 18 is bonded to the silicon substrate 16. That is, the second glass substrate 18 and the first bonding portion 16d of the silicon substrate 16 are bonded. At this time, an anodic bonding process is performed by applying a voltage of about 500 V to the silicon substrate 16 and the second glass substrate 18 under heating at about 400 ° C. or lower. Thereby, the adhesiveness at the interface between the silicon substrate 16 and the second glass substrate 18 becomes higher, and the airtightness of the cavity 17d can be improved.

  In the capacitive mechanical quantity sensor thus obtained, on the pressure sensor side, the fixed electrode 14a is electrically connected to the electrode 15b via the island 12b, and the electrode 13a via the island 12a. Are electrically connected to the electrode 15a. Therefore, the capacitance change signal detected between the pressure-sensitive diaphragm 16a and the fixed electrode 14a can be acquired from the electrodes 15a and 15b via the islands 12a and 12b. The measured pressure can be calculated based on this signal. On the acceleration sensor side, the fixed electrode 14b is electrically connected to the electrode 15c via the island-shaped body 12c, and the electrode 13b is electrically connected to the electrode 15d via the island-shaped body 12d. Therefore, the capacitance change signal detected between the swing member 16b and the fixed electrode 14b can be obtained from the electrodes 15c and 15d via the islands 12c and 12d. The measured acceleration can be calculated based on this signal.

In the capacitance type mechanical quantity sensor, when gas is generated in the cavity between the fixed electrode and the movable electrode, the internal pressure is increased and the temperature characteristic change is increased. Therefore, the relationship between the cavity volume and temperature characteristics was examined. In FIG. 5, the vertical axis indicates the rate of change in capacitance at full scale when the temperature is changed to 90 ° C. with respect to room temperature, and the horizontal axis indicates the volume of the cavity that is hermetically sealed. As can be seen from FIG. 5, when the volume of the cavity is about 2 × 10 ⁻³ cm ³ to about 6 × 10 ⁻³ cm ^{3, the} capacitance change rate (temperature characteristic) decreases, and then gradually decreases. Thus, the volume of the cavity becomes almost zero at about 8 × 10 ⁻³ cm ³ . Thus, it can be seen that as the volume of the cavity increases, the rate of change in capacitance (temperature characteristic change) decreases, and the gas in the cavity does not affect the sensor characteristics. In the capacitance type mechanical quantity sensor according to the present invention shown in FIG. 1, since the cavity volume (cavities 17a, 17b, 17d) is about 1 × 10 ⁻² cm ³ or more, gas exists in the cavity. Does not affect the sensor characteristics.

  According to the capacitance type mechanical quantity sensor according to the present embodiment, the cavity 17a on the pressure sensor region A side and the cavities 17b and 17d on the acceleration sensor region B side communicate with each other, and the cavity volume increases. Therefore, it is possible to prevent the sensor performance from being deteriorated due to the presence of the gas in the sealed space between the first glass substrate 11 and the pressure sensitive diaphragm 16a. Further, according to the capacitance type mechanical quantity sensor according to the present embodiment, the acceleration sensor and the pressure sensor can be manufactured in the same process, so that the process cost can be reduced. In addition, since no getter chamber or the like is provided, an increase in size due to the gas trap function can be avoided. Furthermore, according to the capacitance-type mechanical quantity sensor according to the present embodiment, the oscillating member 16b of the acceleration sensor can also be disposed in a vacuum, so that the oscillating member 16b is not affected by particles or convection. , Can accurately detect acceleration.

  In the present embodiment, a through hole 16h is provided in the silicon substrate 16, and the cavity 17a on the fixed electrode 14a in the pressure sensor region A, the cavity 17b on the fixed electrode 14b in the acceleration sensor region B, and the acceleration sensor region B However, in the present invention, the through hole 16h is not provided in the silicon substrate 16 and the fixed electrode 14a in the pressure sensor region A is provided. The cavity 17a may be configured to communicate with the cavity 17b on the fixed electrode 14b in the acceleration sensor region B.

(Embodiment 2)
In the present embodiment, the capacitance type mechanical quantity sensor is a capacitance type dynamic quantity formed by stacking a pressure sensor that detects pressure by capacitance and an acceleration sensor that detects acceleration by capacitance. A case of a sensor (vertical type) will be described. FIG. 6 is a cross-sectional view showing a schematic configuration of a capacitive mechanical quantity sensor according to Embodiment 2 of the present invention.

  In the figure, reference numeral 21 denotes a first glass substrate. The first glass substrate 21 has a pair of main surfaces 21a and 21b facing each other. A pressure sensor is provided on the main surface 21a side of the first glass substrate 21, and an acceleration sensor is provided on the main surface 21b side. The first glass substrate 21 is provided with a through hole 21c penetrating from the main surface 21a to the main surface 21b. The through hole 21c can be formed by performing a sandblasting process on the first glass substrate 21. Further, an island-like body (silicon member) 22 made of silicon is embedded in the first glass substrate 21. The island 22 is a conductive member that electrically connects the electrode formed on the main surface 21a and the electrode formed on the main surface 21b. The islands 22 are exposed on both main surfaces of the first glass substrate 11. The formation of the islands 22 is the same as in the first embodiment.

  A fixed electrode 23 is formed in the pressure sensor region A on the main surface 11 a side of the first glass substrate 11 so as to be electrically connected to one exposed portion of the island-shaped body 22. This fixed electrode 23 is a fixed electrode for a pressure sensor. Further, a fixed electrode 24 is formed in the acceleration sensor region B on the main surface 11b side of the first glass substrate 11 so as to be electrically connected to the other exposed portion of the island-like body 22. The fixed electrode 24 is a fixed electrode for the acceleration sensor.

  On the main surface 21a of the first glass substrate 21, a first silicon substrate 25 having a pressure-sensitive diaphragm 25a (movable electrode) which is a conductive movable portion on the pressure sensor side is bonded. This pressure-sensitive diaphragm 25a is movable as a conductive movable part by a pressure to be measured. On the main surface 21b of the first glass substrate 21, a second silicon substrate 26 having a swing member 26a that is a conductive movable part on the acceleration sensor side and a cantilever 26b that supports the swing member 26a is joined. Has been. The swing member 26a swings at a measured acceleration as a conductive movable part. The first silicon substrate 25 is bonded to the main surface 21a of the first glass substrate 21 by the first bonding portion 25b. The second silicon substrate 26 is bonded to the main surface 21b of the first glass substrate 21 by the second bonding portion 26c.

  The first glass substrate 21 and the first silicon substrate 25 are bonded at the first bonding portion 25b in a state where the pressure-sensitive diaphragm 25a is aligned with the fixed electrode 23 so as to be disposed at a predetermined interval. The The first glass substrate 21 and the second silicon substrate 26 are joined by the second joining portion 26c in a state where the swing member 26a is aligned with the fixed electrode 24 so as to be arranged at a predetermined interval. The Further, the first glass substrate 21 and the first silicon substrate 25 are joined so that a cavity 27 a is formed on the fixed electrode 23. The first glass substrate 21 and the second silicon substrate 26 are joined so that a cavity 27 b is formed on the fixed electrode 24. The cavities 27a and 27b communicate with each other between the pressure sensor region A and the acceleration sensor region B through a through hole 21c. Thereby, a cavity with a large volume can be provided.

  A second glass substrate 28 is disposed on the second silicon substrate 26. The second glass substrate 28 is bonded at the third bonding portion 26 d of the second silicon substrate 26. The acceleration sensor region B is configured such that the swing member 26 a swings in a space formed by the second glass substrate 28 and the second silicon substrate 26. Since the first and second silicon substrates 25 and 26 and the first glass substrate 11 are bonded by the first and second bonding portions 25b and 26c, the pressure-sensitive diaphragm 25a is thereby Sealed in the cavity.

  The pressure-sensitive diaphragm 25a in the first silicon substrate 25 and the swing member 26a in the second silicon substrate 26 are provided by forming recesses from both sides of the first and second silicon substrates 25 and 26 by etching or the like. It has been. Further, when the cantilever 26b and the swing member 26a are formed on the second silicon substrate 26, for example, etching is performed by applying a micromachining machine technique. The recesses on the first glass substrate bonding surface side of the first and second silicon substrates 25 and 26 have a size that can accommodate at least the fixed electrodes 23 and 24, respectively. The cavity 27 a is configured by bonding to one glass substrate 21, and the cavity 27 b is configured by bonding the second silicon substrate 26 to the first glass substrate 21. As a result, a capacitance is generated between the pressure-sensitive diaphragm 25 a and the fixed electrode 23, and a capacitance is generated between the swing member 26 a and the fixed electrode 24.

  The interface between the first glass substrate 21 and the island 22, the interface between the main surface 21 a of the first glass substrate 21 and the first bonding portion 25 b of the first silicon substrate 25, and the main of the first glass substrate 21 The interface between the surface 21b and the second bonding portion 26c of the second silicon substrate 26 and the interface between the second glass substrate 28 and the third bonding portion 26d of the second silicon substrate 25 may have high adhesion. preferable. The adhesiveness of these interfaces can be further increased by performing anodic bonding treatment in the same manner as in the first embodiment. Thereby, it comprises in the cavity 27a comprised between the pressure sensitive diaphragm 25a and the main surface 21a of the 1st glass substrate 21, and between the rocking | fluctuation member 26a and the main surface 21a of the 1st glass substrate 21. FIG. The airtightness in the cavity 27b can be kept high.

  In the pressure sensor region A of the capacitance type mechanical quantity sensor having such a configuration, a predetermined capacitance is provided between the pressure sensitive diaphragm 25 a and the fixed electrode 23 on the first glass substrate 21. When pressure is applied to the pressure sensor, the pressure-sensitive diaphragm 25a moves according to the pressure. Thereby, the pressure sensitive diaphragm 25a is displaced. At this time, the electrostatic capacitance between the pressure sensitive diaphragm 25a and the fixed electrode 23 on the first glass substrate 21 changes. Therefore, the change can be a pressure change using the capacitance as a parameter.

  On the other hand, in the acceleration sensor region B of the capacitance type mechanical quantity sensor, the swing member 26a is located in the space formed by the first and second glass substrates 21 and 28 and the second silicon substrate 26. It swings with the measured acceleration. Since the oscillating member 26a is a conductor, the capacitance with the fixed electrode 24 changes when the oscillating member 26a oscillates. By detecting this change, acceleration can be measured.

  In this capacitance type mechanical quantity sensor, the cavity 27a in the pressure sensor region A communicates with the cavity 27b in the acceleration sensor region B, so that the cavity 27a and the cavity 27b constitute a cavity. Therefore, in this capacitance type mechanical quantity sensor, it is possible to secure a cavity having a very large volume compared to the volume of the cavity in the pressure sensor alone. As a result, even if gas is generated in a sealed space between the glass substrate and the silicon substrate, the gas can be diffused into a cavity having a relatively large volume. Thereby, the performance degradation of the sensor due to the presence of gas can be prevented. Further, according to this capacitance type mechanical quantity sensor, since no getter chamber or the like is provided, it is possible to avoid an increase in size due to the gas trap function.

  Next, a manufacturing method of the capacitive pressure sensor of the present embodiment will be described. 7 (a), (b), FIGS. 8 (a) to (c), and FIGS. 9 (a) to 9 (c) show a method of manufacturing a capacitive mechanical quantity sensor according to Embodiment 2 of the present invention. It is sectional drawing for demonstrating.

  First, a first silicon substrate 25 doped with impurities to reduce resistance is prepared. The impurity may be an n-type impurity or a p-type impurity. The concentration is, for example, about 0.01 Ω · cm. One main surface of the first silicon substrate 25 is etched to form a recess 25c for the cavity 27a for controlling the distance between the pressure-sensitive diaphragm 25a and the fixed electrode 23 as shown in FIG. Form. In this case, the first silicon substrate 25 is thermally oxidized to form a silicon oxide film. Then, a resist film is formed on the silicon oxide film, and the resist film is patterned (photolithography) so that the resist film remains outside the region where the recess 25c is formed, and the silicon oxide film is etched using the resist film as a mask, Thereafter, the remaining resist film is removed. The first silicon substrate 25 is etched using the silicon oxide film having the opening formed in this way as a mask to provide a recess 25c. Etching may be dry etching or wet etching.

  Next, the other main surface of the first silicon substrate 25 is etched to form a pressure-sensitive diaphragm 25a as shown in FIG. 7B. The pressure-sensitive diaphragm 25a is formed by the same method as the method of forming the recess 25c.

  Next, a second silicon substrate 26 having a low resistance by doping impurities is prepared in the same manner as described above. As shown in FIG. 8A, a recess 26e for the cavity 27b for controlling the distance between the swing member 26a and the fixed electrode 24 is formed by etching one main surface of the second silicon substrate 26. Form. In this case, the second silicon substrate 26 is thermally oxidized to form a silicon oxide film. Then, a resist film is formed on the silicon oxide film, and the resist film is patterned (photolithography) so that the resist film remains outside the region where the recess 26e is formed, and the silicon oxide film is etched using the resist film as a mask, Thereafter, the remaining resist film is removed. The second silicon substrate 26 is etched using the silicon oxide film having the opening formed as described above as a mask to provide a recess 26e. Etching may be dry etching or wet etching.

  Next, the other main surface of the second silicon substrate 26 is etched, and as shown in FIG. 8B, a recess 26f for controlling the distance between the swing member 26a and the second glass substrate 28. Form. Further, the other main surface of the second silicon substrate 26 is etched to form a recess 26g for forming the cantilever 26b in the recess 26f as shown in FIG. 8C. The recesses 26f and 26g are formed by a method similar to the method of forming the recess 26e.

  Subsequently, the 1st glass substrate 21 which embedded the island-shaped body 22 is produced. The method of embedding the islands 22 in the first glass substrate 21 is the same as the process shown in FIG. 4 in the first embodiment. Next, as shown in FIG. 9A, a through hole 21c is formed in the first glass substrate 21 by sandblasting or the like. Next, the fixed electrode 23 is formed on the main surface 21 a of the first glass substrate 21 so as to be electrically connected to the island-like body 22. In this case, first, an electrode material is deposited on the main surface 21a of the first glass substrate 21, a resist film is formed thereon, and the resist film is patterned so that the resist film remains in the electrode formation region ( Photolithography), the electrode material is etched using the resist film as a mask, and then the remaining resist film is removed.

  Next, as shown in FIG. 9C, the fixed electrode 24 is formed on the main surface 21 b of the first glass substrate 21 so as to be electrically connected to the island-like body 2. In this case, first, an electrode material is deposited on the main surface 21b of the first glass substrate 21, a resist film is formed thereon, and the resist film is patterned so that the resist film remains in the fixed electrode formation region. (Photolithography), the electrode material is etched using the resist film as a mask, and then the remaining resist film is removed.

  Next, the first silicon substrate 25 having the pressure-sensitive diaphragm 25a that is displaced by the measured pressure and the silicon substrate 16 having the swinging member 16b that is swung by the measured acceleration are used. The pressure-sensitive diaphragm 25a is connected to the fixed electrode 23. It joins on the main surface 21a of the 1st glass substrate 21 so that it may be located in predetermined intervals. Further, the swinging member 26 a that swings due to the acceleration to be measured is joined to the main surface 21 b of the first glass substrate 21 so as to be positioned at a predetermined distance from the fixed electrode 24. That is, the main surface 21 a of the first glass substrate 21 and the first bonding portion 25 b of the first silicon substrate 25 are bonded, and the main surface 21 b of the first glass substrate 21 and the second of the second silicon substrate 26 are second. The joint portion 26c is joined. At this time, an anodic bonding process is performed by applying a voltage of about 500 V to the first and second silicon substrates 25 and 26 and the first glass substrate 21 under heating at about 400 ° C. or less. Thereby, the adhesiveness in the interface between the 1st and 2nd silicon substrates 25 and 26 and the 1st glass substrate 21 becomes higher, and the airtightness of the cavities 27a and 27b can be improved.

  Next, the second glass substrate 28 is bonded to the second silicon substrate 26. That is, the second glass substrate 28 and the third bonding portion 26d of the second silicon substrate 26 are bonded. At this time, an anodic bonding process is performed by applying a voltage of about 500 V to the second silicon substrate 26 and the second glass substrate 28 under heating at about 400 ° C. or lower. As a result, the adhesion at the interface between the second silicon substrate 26 and the second glass substrate 218 becomes higher, and the airtightness of the space between the swing member 26a and the second glass substrate 28 is improved. Can be made.

  In the capacitive mechanical quantity sensor thus obtained, the fixed electrode 23 is electrically connected to an electrode (not shown) through the island 22 on the pressure sensor side. Therefore, the change signal of the capacitance detected between the pressure sensitive diaphragm 25 a and the fixed electrode 23 can be acquired from the electrode via the island 22. The measured pressure can be calculated based on this signal. On the acceleration sensor side, the fixed electrode 24 is electrically connected to an electrode (not shown) via the island-like body 22. Therefore, the change signal of the capacitance detected between the swing member 26 a and the fixed electrode 24 can be acquired from the electrode via the island 22. The measured acceleration can be calculated based on this signal.

  According to the capacitance type mechanical quantity sensor according to the present embodiment, the cavity 27a on the pressure sensor region A side and the cavity 27b on the acceleration sensor region B side communicate with each other, and the cavity volume increases. Further, it is possible to prevent the sensor performance from being deteriorated due to the presence of gas in the sealed space between the first glass substrate 21 and the pressure sensitive diaphragm 25a. Further, according to the capacitance type mechanical quantity sensor according to the present embodiment, since no getter chamber or the like is provided, an increase in size due to the gas trap function can be avoided. Furthermore, according to the capacitance-type mechanical quantity sensor according to the present embodiment, the oscillating member 26a of the acceleration sensor can also be arranged in a vacuum, so that the oscillating member 26a is not affected by particles or convection. , Can accurately detect acceleration.

  The present invention is not limited to Embodiments 1 and 2 above, and can be implemented with various modifications. For example, the numerical values and materials described in the first and second embodiments are not particularly limited. 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 capacitive mechanical quantity sensor that monitors pressure only when a tire rotates in a TPMS (Tire Pressure Monitoring System) with a battery.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows schematic structure of the electrostatic capacitance type mechanical quantity sensor which concerns on Embodiment 1 of this invention, (a) is a top view, (b) is sectional drawing. (A)-(c) is sectional drawing for demonstrating the manufacturing method of the electrostatic capacitance type mechanical quantity sensor which concerns on Embodiment 1 of this invention. (A)-(c) is sectional drawing for demonstrating the manufacturing method of the electrostatic capacitance type mechanical quantity sensor which concerns on Embodiment 1 of this invention. (A)-(e) is sectional drawing for demonstrating the manufacturing method of the electrostatic capacitance type mechanical quantity sensor which concerns on Embodiment 1 of this invention. It is a characteristic view which shows the relationship between the cavity volume and temperature characteristic in an electrostatic capacitance type mechanical quantity sensor. It is sectional drawing which shows schematic structure of the electrostatic capacitance type mechanical quantity sensor which concerns on Embodiment 2 of this invention. (A), (b) is sectional drawing for demonstrating the manufacturing method of the electrostatic capacitance type mechanical quantity sensor which concerns on Embodiment 2 of this invention. (A)-(c) is sectional drawing for demonstrating the manufacturing method of the electrostatic capacitance type mechanical quantity sensor which concerns on Embodiment 2 of this invention. (A)-(c) is sectional drawing for demonstrating the manufacturing method of the electrostatic capacitance type mechanical quantity sensor which concerns on Embodiment 2 of this invention.

Explanation of symbols

A Pressure sensor area B Acceleration sensor area 11, 18, 21, 28 Glass substrate 11a, 11b, 21a, 21b Main surface 12, 16, 25, 26 Silicon substrate 12a-12d, 22 Island-like body 13a, 13b, 15a-15d Electrodes 14a, 14b, 23, 24 Fixed electrodes 16a, 25a Pressure sensitive diaphragms 16b, 26a Oscillating members 16c, 26b Cantilevers 16d, 16e, 25b, 26c, 26d Joints

Claims (9)

  A capacitance type mechanical quantity sensor in which a pressure sensor for detecting pressure by capacitance and an acceleration sensor for detecting acceleration by capacitance are arranged side by side, and a pair of principal surfaces facing each other are provided. A first substrate having a first fixed electrode for the pressure sensor and a second fixed electrode for the acceleration sensor formed on one of the main surfaces, and a predetermined distance from the first fixed electrode. The pressure sensor has a first conductive movable part for the pressure sensor and a second conductive movable part for the acceleration sensor arranged to face the second fixed electrode at a predetermined interval. A second substrate and at least a third substrate disposed on the second substrate so as to enclose the second conductive movable part, wherein the first and second substrates are the first and second substrates. 2 including a fixed electrode, the area of the pressure sensor and the acceleration sensor Capacitive dynamic quantity sensor first cavity is formed, the first cavity is characterized in that it is joined to be sealed communicating with the service area.   The second substrate has a through hole in the area of the acceleration sensor, and the second and third substrates are sealed with a second cavity formed on the second conductive movable part. The capacitive mechanical quantity sensor according to claim 1, wherein the first and second cavities communicate with each other through the through hole.   A capacitance type mechanical quantity sensor formed by stacking a pressure sensor for detecting pressure by capacitance and an acceleration sensor for detecting acceleration by capacitance, and one of a pair of principal surfaces facing each other A first fixed electrode for the pressure sensor formed on the main surface of the first sensor, a second fixed electrode for the acceleration sensor formed on the other main surface of the pair of main surfaces, and a first hole having a through hole. A substrate, a second substrate having a first conductive movable part for the pressure sensor arranged at a predetermined interval from the first fixed electrode, and a predetermined interval from the second fixed electrode. And a fourth substrate having a second conductive movable part for the acceleration sensor, wherein the first and second substrates are joined so that a third cavity is formed on the first fixed electrode. The first and fourth substrates are the second fixed electrodes. Are joined to form a fourth cavity, and the third and fourth cavities communicate with each other through the through hole of the first substrate, and a joint portion between the first and second substrates. In addition, the capacitive mechanical quantity sensor is sealed by a joint portion of the first and fourth substrates.   3. The capacitive mechanical quantity sensor according to claim 1, wherein the first and third substrates are glass substrates, and the second substrate is a silicon substrate.   4. The capacitive mechanical quantity sensor according to claim 3, wherein the first substrate is a glass substrate, and the second and fourth substrates are silicon substrates.   The said 1st board | substrate is further equipped with the electroconductive part which electrically connects the electrode formed on said one main surface, and the electrode formed on said other main surface, It is characterized by the above-mentioned. The capacitive mechanical quantity sensor according to any one of claims 1 to 5.   The capacitive mechanical quantity sensor according to claim 6, wherein the conductive portion is a silicon member embedded in the glass substrate.   The capacitive mechanical quantity sensor according to claim 7, wherein the sensor has an Si—Si bond or an Si—O bond at an interface between the glass substrate and the silicon member.   The first conductive movable part is a pressure-sensitive diaphragm that is displaced by a measured pressure, and a swing member that detects pressure using the pressure-sensitive diaphragm and swings the second conductive movable part by a measured acceleration. The capacitance type mechanical quantity sensor according to claim 1, wherein acceleration is detected using the swing member.

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