JP4839466B2 - Inertial force sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to an inertial force sensor and a method for manufacturing the same, and more particularly, to an inertial force sensor for anodic bonding a cap and a frame provided on a substrate so as to cover a mass body and a method for manufacturing the same.

As a conventional inertial force sensor that detects characteristics derived from inertial forces such as acceleration, angular velocity, and angular acceleration, for example, Patent Document 1 discloses a method for manufacturing an acceleration sensor as follows. That is, the acceleration sensor includes a substrate, a sensor element (mass body) formed on the substrate, a polysilicon bonding frame that is formed on the substrate and surrounds the sensor element in plan view, and an end surface. It is formed on the surface of the cap that covers the upper part of the sensor with a predetermined space therebetween by bonding to the upper surface of the polysilicon bonding frame, and a part of the cap that faces the sensor element. Is electrically connected to the sensor element via the first wiring and the first pad formed on the substrate, and is electrically connected to the substrate. And a third pad that is electrically connected to the polysilicon bonding frame via the second wiring and formed on the substrate. In this acceleration sensor, a step of forming a second metal film that electrically connects the first to third pads, and after this step, a voltage is applied between the substrate and the cap, and the cap and the polysilicon are formed. A step of anodic bonding the bonding frame and a step of removing the second metal film after this step are included.
JP 2005-172543 A

  By the way, in the acceleration sensor described in Patent Document 1, in order to prevent the sensor element from sticking to the cap due to electrostatic attraction generated in anodic bonding, a reliable electrical connection between the first metal film and the polysilicon bonding frame is necessary. It is. This electrical connection is realized by physically bringing a part of the polysilicon bonding frame into contact with the first metal film. However, before the anodic bonding, the bonding surface between the polysilicon bonding frame and the cap is not flat due to stress, processing accuracy, and the like, and warpage and unevenness are generated. For example, the first metal film and the polysilicon bonding frame are brought into physical contact with each other at the time of anodic bonding on the entire surface of the wafer on which a large number of sensor elements are formed. It is difficult. If the first metal film and the sensor element are not at the same potential when a voltage for anodic bonding is applied, the sensor element moves to the first metal film by electrostatic attraction and sticks to the first metal film. . This sticking causes breakage of the sensor element and the yield of the acceleration sensor is reduced.

  SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an inertial force sensor capable of improving yield by preventing the mass body from sticking to the cap in anodic bonding, and a method for manufacturing the same.

  In order to solve the above-described problems, an inertial force sensor according to an aspect of the present invention includes a substrate having a main surface, a mass body arranged apart from the substrate, and supporting the mass body on the main surface of the substrate. A rigid first support, a frame provided on the main surface of the substrate, surrounding the mass, a cap anodically bonded to the frame so as to cover the mass, and a mass of the cap A second support part, comprising: a conductive film provided on the opposing main surface; a contact electrode in contact with the conductive film; and a second support part supporting the contact electrode on the main surface of the substrate and having rigidity. The rigidity in the direction from the substrate to the conductive film is lower than the rigidity in the direction from the substrate to the conductive film of the first support portion.

  In order to solve the above-described problems, a method for manufacturing an inertial force sensor according to an aspect of the present invention includes a substrate having a main surface, a mass body spaced apart from the substrate, and the mass body on the main surface of the substrate. A first support portion that is supported and rigid, a frame that is provided on the main surface of the substrate and surrounds the mass body, a cap that is provided with a conductive film on the main surface, a contact electrode, and a contact electrode On the main surface of the substrate, and a second support portion having a rigidity in the direction from the substrate to the conductive film lower than that of the first support portion. A step of electrically connecting the mass body and the contact electrode to make the same potential, and a step of arranging the cap so as to cover the mass body and the contact electrode and the cap and the frame body in contact with each other Between the frame and the cap. By applying a voltage smaller than the first voltage for moving the tact electrode and contacting the conductive film, and then gradually increasing the voltage applied between the frame and the cap to be equal to or higher than the first voltage, Anodizing the frame and the cap.

  According to the present invention, the yield can be improved by more reliably preventing the mass body from sticking to the cap in anodic bonding.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<First Embodiment>
FIG. 1 is a plan view showing the configuration of the inertial force sensor according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the II-II cross section in FIG. 1 of the inertial force sensor according to the first embodiment of the present invention. 3 is a cross-sectional view showing a section taken along the line III-III in FIG. 1 of the inertial force sensor according to the first embodiment of the present invention.

1 to 3, inertial force sensor 101 is, for example, a capacitive acceleration sensor.
The inertial force sensor 101 includes an inertial force detection unit 7, electrode pads 9 to 13, a movable contact electrode 22, a joining frame (frame body) 2, a glass cap 19, a lower layer wiring 8, a silicon substrate 15, Insulating films 16, 17, 18, a metal thin film 21, support beams (second elastic portions) 23, 26, anchors 24, 27, and a signal processing unit 51 are provided. The inertial force detection unit 7 includes an anchor 3, a beam (first elastic portion) 4, a movable mass body 5, and detection electrodes 6a and 6b.

  The anchor 3 is provided on the main surface S1 of the silicon substrate 15, and supports the beam 4 on the main surface S1 of the silicon substrate 15 so that the beam 4 is separated from the silicon substrate 15. The beam 4 supports the movable mass body 5 on the main surface S <b> 1 of the silicon substrate 15 so that the movable mass body 5 is separated from the silicon substrate 15.

  The joining frame 2 is provided on the main surface S1 of the silicon substrate 15 and surrounds the inertial force detection unit 7, the movable contact electrode 22, the support beams 23 and 26, and the anchors 24 and 27.

  The glass cap 19 is anodically bonded to the bonding frame 2 so as to cover the inertial force detection unit 7, the movable contact electrode 22, the support beams 23 and 26, and the anchors 24 and 27. More specifically, the inertial force detection unit 7, the movable contact electrode 22, the support beams 23 and 26, and the anchors 24 and 27 are sealed by the joint frame 2, the glass cap 19, and the silicon substrate 15.

  The metal thin film 21 is provided on the lower surface of the glass cap 19, that is, the main surface S <b> 2 facing the movable mass body 5.

  The movable contact electrode 22 is disposed in a sealed cavity 20 formed by the bonding frame 2, the glass cap 19, and the silicon substrate 15. The movable contact electrode 22 is in contact with the metal thin film 21.

  The anchors 24 and 27 are provided on the main surface S1 of the silicon substrate 15, and support the support beams 23 and 26 on the main surface S1 of the silicon substrate 15 so that the support beams 23 and 26 are separated from the silicon substrate 15. . The support beams 23 and 26 support the movable contact electrode 22 on the main surface S <b> 1 of the silicon substrate 15 so that the movable contact electrode 22 is separated from the silicon substrate 15.

  The out-of-plane rigidity of the movable contact electrode 22 and the out-of-plane rigidity of the support beams 23 and 26 that support the movable contact electrode 22 are greater than the out-of-plane rigidity of the movable mass body 5 and the out-of-plane rigidity of the beam 4 that supports the movable mass body 5. It is set to a low value, for example, 1/2 or less. For this reason, the movable contact electrode 22 is easy to move in the out-of-plane direction as compared with the movable mass body 5. Here, the out-of-plane direction means the direction from the silicon substrate 15 to the metal thin film 21 (upward direction in FIG. 2).

  The electrode pad 11 is electrically connected to the movable mass body 5. The electrode pad 10 is electrically connected to the detection electrode 6a. The electrode pad 13 is electrically connected to the detection electrode 6b. The electrode pad 9 is electrically connected to the movable contact electrode 22. Here, the silicon substrate 15 and the bonding frame 2 are electrically connected. For example, although not shown, the joining frame 2 may be configured to be electrically connected to the silicon substrate 15 by contacting the anchors 24 and 27. That is, the electrode pad 12 is electrically connected to the bonding frame 2 via the silicon substrate 15.

  The lower layer wiring 8 is sandwiched between the insulating film 16 and the insulating film 18 and embedded in the same layer as the insulating film 17. The lower layer wiring 8 passes under the joint frame 2, electrically connects the movable mass body 5 and the electrode pad 11, electrically connects the detection electrode 6a and the electrode pad 10, and detects the detection electrode 6b and the electrode pad. 13 is electrically connected, and the movable contact electrode 22 and the electrode pad 9 are electrically connected. The electrode pad 12 is a pad that determines the potential of the silicon substrate 15.

  The electrode pads 10, 11, and 13 are connected to a signal processing unit 51, which is a signal processing IC (Integrated Circuit), for example, by wires.

  The silicon substrate 15 is electrically insulated from the movable mass body 5 by insulating films 16, 17 and 18.

  The joining frame 2 is joined to the glass cap 19 by anodic joining. Here, the anodic bonding is a method of chemically bonding glass and silicon by applying a high voltage of several hundred to several kilovolts between the glass and the silicon substrate, for example.

  The anchors 24 and 27 connect the movable contact electrode 22 and the silicon substrate 15. The anchor 24 is electrically connected to the electrode pad 9 through the lower layer wiring 8.

  Inertial force detector 7, joint frame 2, movable contact electrode 22, support beams 23 and 26, and anchors 24 and 27 are made of, for example, the same conductive material. This material is, for example, conductive polysilicon doped with impurities, or single crystal silicon. The lower layer wiring 8 is made of polysilicon having conductivity, for example. The insulating films 16 to 18 are made of a thin film insulating material such as a silicon oxide film and a silicon nitride film.

  The movable mass body 5 functions as a movable electrode. The beam 4 is formed integrally with the movable mass body 5, and moves the movable mass body 5 along the direction A by expanding and contracting in the direction A of acceleration to be detected.

  When acceleration is applied in the left-right direction A in FIG. 1, the movable mass body 5 moves. The acceleration is detected based on the change in capacitance between the movable mass body 5 and the detection electrodes 6a and 6b caused by this movement. That is, the signal processing unit 51 detects a change in capacitance between the movable mass body 5 and the detection electrodes 6a and 6b detected via the electrode pads 10, 11, and 13, and accelerates the detected change in capacitance. Convert to

Next, a method for manufacturing the inertial force sensor 101 will be described.
FIG. 4 is a plan view for explaining the method of manufacturing the inertial force sensor according to the first embodiment of the invention. FIG. 4 shows the configuration of the inertial force sensor 101 before the glass cap is joined. FIG. 5 is a cross-sectional view showing a VV cross section shown in FIG. 4.

  Referring to FIGS. 4 and 5, processing of inertial force detector 7 and glass cap 19 on silicon substrate 15 includes thin film deposition, patterning and etching on silicon substrate 15, processing of glass substrate and formation of metal thin film. Implemented by

  More specifically, first, the silicon substrate 15 having the main surface S1, the movable mass body 5 that is spaced apart from the silicon substrate 15, and the movable mass body 5 are supported on the main surface S1 of the silicon substrate 15, And a rigid beam 4, detection electrodes 6a and 6b provided on the main surface S1 of the silicon substrate 15, and a joining frame 2 provided on the main surface S1 of the silicon substrate 15 and surrounding the inertial force detection unit 7. The glass cap 19 provided with the metal thin film 21 on the main surface, the movable contact electrode 22, and the movable contact electrode 22 are supported on the main surface S1 of the silicon substrate 15, and the direction from the silicon substrate 15 to the metal thin film 21 The support beams 23 and 26 whose rigidity is lower than that of the beam 4 are prepared by various processing operations.

  Referring to FIG. 5, a metal thin film 25 that electrically connects electrode pads 9, 10, 11, 12, and 13 to each other is formed. That is, all electrode pads 9, 10, 11, 12, and 13 are short-circuited by the metal thin film 25 before anodic bonding between the glass cap 19 and the bonding frame 2. Thereby, the silicon substrate 15, the joining frame 2, the movable mass 5, the detection electrodes 6a and 6b, and the movable contact electrode 22 are set to the same potential, for example, the ground potential.

  Next, the glass cap 19 and the joining frame 2 are aligned. That is, the glass cap 19 is disposed so as to cover the inertial force detection unit 7, the movable contact electrode 22, and the support beams 23 and 26, and so that the glass cap 19 and the joining frame 2 are in contact with each other.

  Next, the silicon substrate 15 is heated to about 400 ° C. Then, by applying a negative voltage to the glass cap 19, the bonding frame 2 and the glass cap 19 are anodically bonded.

  That is, a voltage lower than the voltage V <b> 1 for moving the movable contact electrode 22 to contact the metal thin film 21 is applied between the bonding frame 2 and the glass cap 19. Thereafter, the voltage applied between the joining frame 2 and the glass cap 19 is gradually increased to be equal to or higher than the voltage V1, whereby the joining frame 2 and the glass cap 19 are anodically joined.

After this anodic bonding process, the metal thin film 25 is removed.
FIG. 6 is a diagram showing the relationship between the time during anodic bonding and the applied voltage in the method of manufacturing the inertial force sensor according to the first embodiment of the invention.

  With reference to FIG. 6, the applied voltage between the joining frame 2 and the glass cap 19 is not suddenly increased, but is gradually increased from 0V to reach the voltage V1, and then larger than the voltage V1. The voltage V2 is reached, and finally the voltage V3 larger than the voltage V2 is reached.

  Here, the voltage V1 is a voltage at which the movable contact electrode 22 moves and sticks to the glass cap 19 due to electrostatic attraction. The voltage V <b> 2 is a voltage at which the movable mass body 5 moves due to electrostatic attraction and sticks to the glass cap 19 when it is assumed that the movable contact electrode 22 and the glass cap 19 do not stick.

  First, the applied voltage is gradually increased from 0 volt to voltage V1. Then, the movable contact electrode 22 sticks to the glass cap 19 by electrostatic attraction. At this time, the inertial force sensor 101 has a cross-sectional structure shown in FIGS.

  The movable contact electrode 22 is bonded and fixed to the glass cap 19 as it is. Here, a part of the movable contact electrode 22 is in contact with the metal thin film 21. Thereby, the metal thin film 21, the movable contact electrode 22, and the movable mass body 5 are at the same potential.

  Here, the metal thin film 21 is formed of a metal such as aluminum or gold that forms an alloy layer together with the movable contact electrode 22 at the temperature of anodic bonding. With such a configuration, since the movable contact electrode 22 is firmly bonded to the glass cap 19, the movable contact electrode 22 and the metal thin film 21 are brought into a good conductive state because the contact resistance is lowered.

  Next, the applied voltage is raised to the voltage V2. Here, since the movable mass body 5 and the metal thin film 21 are at the same potential and no electrostatic attractive force is generated, the movable mass body 5 is not displaced in the direction of the glass cap 19. Since the movable contact electrode 22 is firmly joined to the glass cap 19, no displacement due to inertial force or the like occurs.

  Here, in the manufacturing method of the inertial force sensor 101, when it is assumed that the electrode pads 9 and 11 and the electrode pad 12 are not short-circuited, the movable mass body 5 and the movable contact electrode 22 are electrically separated from the silicon substrate 15. Therefore, the potential is not fixed. In this case, the potential of the metal thin film 21 provided on the main surface of the glass cap 19 facing the movable mass body 5 is not fixed.

  When the potential of the metal thin film 21, the movable contact electrode 22 and the movable mass body 5 is not fixed due to the sticking of the movable contact electrode 22, the movable mass body 5 and the movable contact electrode 22 are pulled toward the glass cap 19 by electrostatic attraction. Stick and stick. That is, the movable mass body 5 is in contact with the metal thin film 21. Depending on the contact state, the movable mass body 5 may remain attached to the metal thin film 21 even after the anodic bonding process, or may be damaged at the time of contact, and the yield of the inertial force sensor 101 is greatly reduced.

  In the technique described in Patent Document 1, in order to prevent the sensor element from sticking to the cap due to electrostatic attraction during anodic bonding, the first metal film and the polysilicon bonding frame are physically brought into contact during anodic bonding. However, before the anodic bonding, the bonding surface between the polysilicon bonding frame and the cap does not become flat due to stress, processing accuracy, etc., and warpage and unevenness are generated. It is difficult to make physical contact with the joining frame reliably.

  However, in the method of manufacturing the inertial force sensor according to the first embodiment of the present invention, first, the silicon substrate 15 having the main surface S1, the movable mass body 5 disposed away from the silicon substrate 15, and the movable A mass 4 that supports the mass body 5 on the main surface S1 of the silicon substrate 15 and has rigidity, a joining frame 2 that is provided on the main surface S1 of the silicon substrate 15 and surrounds the inertial force detection unit 7, and a main surface The glass cap 19 provided with the metal thin film 21, the movable contact electrode 22, the movable contact electrode 22 is supported on the main surface S 1 of the silicon substrate 15, and the rigidity in the direction from the silicon substrate 15 to the metal thin film 21 is Support beams 23 and 26 lower than the beam 4 are prepared by various processing operations. Next, the silicon substrate 15, the joining frame 2, the movable mass 5, the detection electrodes 6a and 6b, and the movable contact electrode 22 are electrically connected to have the same potential, for example, the ground potential. Next, it arrange | positions so that the glass cap 19 and the joining frame 2 may contact | connect so that the glass cap 19 may cover the inertial force detection part 7, the movable contact electrode 22, and the support beams 23 and 26. FIG. Next, a voltage lower than the voltage V <b> 1 for moving the movable contact electrode 22 to contact the metal thin film 21 is applied between the bonding frame 2 and the glass cap 19. Thereafter, the voltage applied between the joining frame 2 and the glass cap 19 is gradually increased to be equal to or higher than the voltage V1, whereby the joining frame 2 and the glass cap 19 are anodically joined.

  That is, by short-circuiting the electrode pads 9, 11, and 12 before anodic bonding, the bonding frame 2, the movable mass body 5, and the movable contact electrode 22 are set to the same potential. Then, by anodic bonding in this state, the movable contact electrode 22 supported by the weak spring structure sticks to the glass cap 19 first, that is, is in electrical contact with the metal thin film 21, so that the potential of the metal thin film 21 is increased. Fixed to ground. Since the potential of the metal thin film 21 is the same as that of the movable mass body 5, the movable mass body 5 is not attracted to the glass cap 19 by electrostatic attraction, so that contact between the movable mass body 5 and the metal thin film 21 is avoided. can do. That is, as in the technique described in Patent Document 1, the metal thin film 21, the movable mass body 5, and the movable contact electrode 22 are reliably made to be the same without physically contacting the first metal film and the polysilicon bonding frame. Since the potential can be set, the yield of the inertial force sensor can be improved.

  In the method of manufacturing the inertial force sensor according to the first embodiment of the present invention, not only the electrode pads 9, 11, 12 but also the electrode pads 10, 13 are all short-circuited and connected to the ground potential. With such a configuration, an electrostatic attractive force is generated between the detection electrodes 6a, 6b of the inertial force sensor 101 and the movable mass body 5 to prevent the detection electrodes 6a, 6b and the movable mass body 5 from sticking to each other. be able to.

  Further, the silicon substrate 15 and the glass cap 19 are not in physical contact before bonding on the entire wafer surface, and there is a possibility that a gap is left. Accordingly, the voltage V1 at which the movable contact electrode 22 sticks to the glass cap 19 and the voltage V2 at which the movable mass body 5 sticks to the glass cap 19 are not the same value but vary over the entire wafer surface.

  Therefore, in the method of manufacturing the inertial force sensor according to the first embodiment of the present invention, voltage is applied in an analog manner instead of stepwise between the joining frame 2 and the glass cap 19. . With such a configuration, the metal thin film 21 and the movable contact electrode 22 can be physically and reliably brought into contact with each other at the time of anodic bonding over the entire wafer surface on which a large number of inertial force detection units 7 are formed. Thus, the movable mass body 5 and the movable contact electrode 22 can be reliably set to the same potential.

  The inertial force sensor according to the first embodiment of the present invention is an acceleration sensor. However, the present invention is not limited to this, and a movable structure (movable mass body) such as an angular velocity sensor is provided in the cavity. In the case of a sensor that has a possibility that the movable structure and the cap stick to each other due to electrostatic attraction in anodic bonding, the effect of improving the yield can be obtained by applying the present invention.

  Next, another embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

<Second Embodiment>
The present embodiment relates to an inertial force sensor configured to include a plurality of movable contact electrodes as compared with the inertial force sensor according to the first embodiment. The contents other than those described below are the same as those of the inertial force sensor according to the first embodiment.

FIG. 7 is a diagram showing a configuration of an inertial force sensor according to the second embodiment of the present invention.
Referring to FIG. 7, inertial force sensor 102 further includes movable contact electrode 35, support beams 31 and 33, and anchors 32 and 34 as compared with the inertial force sensor according to the first embodiment of the present invention. Is provided. The inertial force sensor 102 includes a signal processing unit 52 instead of the signal processing unit 51. The signal processing unit 52 includes a measurement unit 61.

  The joining frame 2 is provided on the main surface S1 of the silicon substrate 15 and surrounds the inertial force detection unit 7, the movable contact electrodes 22, 35, the support beams 23, 26, 31, 33, and the anchors 24, 27, 32, 34. .

  The glass cap 19 is anodically bonded to the bonding frame 2 so as to cover the inertial force detection unit 7, the movable contact electrodes 22, 35, the support beams 23, 26, 31, 33 and the anchors 24, 27, 32, 34. More specifically, the inertial force detection unit 7, the movable contact electrodes 22, 35, the support beams 23, 26, 31, 33, and the anchors 24, 27, 32, 34 are connected to the joint frame 2, the glass cap 19, and the silicon substrate. 15.

  The metal thin film 21 is provided on the lower surface of the glass cap 19, that is, on the main surface S <b> 2 facing the movable mass body 5.

  The movable contact electrodes 22, 35 are arranged in a sealed cab 20 formed by the joining frame 2, the glass cap 19, and the silicon substrate 15. The movable contact electrodes 22 and 35 are in contact with the metal thin film 21.

  The anchors 24 and 27 are provided on the main surface S1 of the silicon substrate 15, and support the support beams 23 and 26 on the main surface S1 of the silicon substrate 15 so that the support beams 23 and 26 are separated from the silicon substrate 15. . The support beams 23 and 26 support the movable contact electrode 22 on the main surface S <b> 1 of the silicon substrate 15 so that the movable contact electrode 22 is separated from the silicon substrate 15.

  The anchors 32 and 34 are provided on the main surface S1 of the silicon substrate 15, and support the support beams 31 and 33 on the main surface S1 of the silicon substrate 15 so that the support beams 31 and 33 are separated from the silicon substrate 15. . The support beams 31 and 33 support the movable contact electrode 35 on the main surface S <b> 1 of the silicon substrate 15 so that the movable contact electrode 35 is separated from the silicon substrate 15.

  The out-of-plane rigidity of the movable contact electrode 22 and the out-of-plane rigidity of the support beams 23 and 26 that support the movable contact electrode 22 are greater than the out-of-plane rigidity of the movable mass body 5 and the out-of-plane rigidity of the beam 4 that supports the movable mass body 5. It is set to a low value, for example, 1/2 or less. The out-of-plane rigidity of the movable contact electrode 35 and the out-of-plane rigidity of the support beams 31 and 33 that support the movable contact electrode 35 are the out-of-plane rigidity of the movable mass body 5 and the out-of-plane rigidity of the beam 4 that supports the movable mass body 5. It is lower than the rigidity, for example, set to 1/2 or less. For this reason, the movable contact electrodes 22 and 35 are easy to move in the out-of-plane direction as compared with the movable mass body 5. Here, the out-of-plane direction means a direction from the silicon substrate 15 to the metal thin film 21.

  The electrode pad 11 is electrically connected to the movable mass body 5. The electrode pad 10 is electrically connected to the detection electrode 6a. The electrode pad 13 is electrically connected to the detection electrode 6b. The electrode pad 9 is electrically connected to the movable contact electrode 22. The electrode pad 14 is electrically connected to the movable contact electrode 35. Here, the silicon substrate 15 and the bonding frame 2 are electrically connected. For example, although not shown, the joining frame 2 may be configured to be electrically connected to the silicon substrate 15 by contacting the anchors 24, 27, 32, and 34. That is, the electrode pad 12 is electrically connected to the bonding frame 2 via the silicon substrate 15.

  The lower layer wiring 8 is sandwiched between the insulating film 16 and the insulating film 18 and embedded in the same layer as the insulating film 17. The lower layer wiring 8 passes under the joint frame 2, electrically connects the movable mass body 5 and the electrode pad 11, electrically connects the detection electrode 6a and the electrode pad 10, and detects the detection electrode 6b and the electrode pad. 13 is electrically connected, the movable contact electrode 22 and the electrode pad 9 are electrically connected, and the movable contact electrode 35 and the electrode pad 14 are electrically connected. The electrode pad 12 is a pad that determines the potential of the silicon substrate 15.

  The electrode pads 10, 11, 13, and 14 are connected to a signal processing unit 51 that is, for example, a signal processing IC (Integrated Circuit) by wires.

  The silicon substrate 15 is electrically insulated from the movable mass body 5 by insulating films 16, 17 and 18.

  The joining frame 2 is joined to the glass cap 19 by anodic joining. Here, the anodic bonding is a method of chemically bonding glass and silicon by applying a high voltage of several hundred to several kilovolts between the glass and the silicon substrate, for example.

  The anchors 24 and 27 connect the movable contact electrode 22 and the silicon substrate 15. The anchor 24 is electrically connected to the electrode pad 9 through the lower layer wiring 8. The anchors 32 and 34 connect the movable contact electrode 35 and the silicon substrate 15. The anchor 32 is electrically connected to the electrode pad 14 through the lower layer wiring 8.

  Inertial force detector 7, joint frame 2, movable contact electrodes 22, 35, support beams 23, 26, 31, 33, and anchors 24, 27, 32, 34 are made of, for example, the same conductive material. This material is, for example, conductive polysilicon doped with impurities, or single crystal silicon. The lower layer wiring 8 is made of polysilicon having conductivity, for example. The insulating films 16 to 18 are made of a thin film insulating material such as a silicon oxide film and a silicon nitride film.

Next, a method for manufacturing the inertial force sensor 102 will be described.
Processing of the inertial force detection unit 7 and the glass cap 19 on the silicon substrate 15 is performed by thin film deposition, patterning and etching on the silicon substrate 15, processing of the glass substrate, and formation of a metal thin film.

  More specifically, first, the silicon substrate 15 having the main surface S1, the movable mass body 5 that is spaced apart from the silicon substrate 15, and the movable mass body 5 are supported on the main surface S1 of the silicon substrate 15, And a rigid beam 4, detection electrodes 6a and 6b provided on the main surface S1 of the silicon substrate 15, and a joining frame 2 provided on the main surface S1 of the silicon substrate 15 and surrounding the inertial force detection unit 7. The glass cap 19 provided with the metal thin film 21 on the main surface, the movable contact electrodes 22 and 35, and the movable contact electrode 22 are supported on the main surface S1 of the silicon substrate 15 and from the silicon substrate 15 to the metal thin film 21. The supporting beams 23 and 26 having a lower rigidity than the beam 4 and the movable contact electrode 35 are supported on the main surface S1 of the silicon substrate 15, and the silicon substrate 15 is connected to the metal thin film 21. The rigidity of the improvement is prepared by various processing operations and a lower support beam 31, 33 from the beam 4.

  Next, a metal thin film 25 that electrically connects the electrode pads 9, 10, 11, 12, 13, and 14 to each other is formed. That is, all electrode pads 9, 10, 11, 12, 13, and 14 are short-circuited by the metal thin film 25 before the anodic bonding between the glass cap 19 and the bonding frame 2. Thereby, the silicon substrate 15, the joining frame 2, the movable mass 5, the detection electrodes 6a and 6b, and the movable contact electrodes 22 and 35 are set to the same potential, for example, the ground potential.

  Next, the glass cap 19 and the joining frame 2 are aligned. That is, the glass cap 19 is arranged so as to cover the inertial force detection unit 7, the movable contact electrodes 22, 35, and the support beams 23, 26, 31, 33 and so that the glass cap 19 and the joining frame 2 are in contact with each other. To do.

  Next, the silicon substrate 15 is heated to about 400 ° C. Then, by applying a negative voltage to the glass cap 19, the bonding frame 2 and the glass cap 19 are anodically bonded.

  That is, a voltage lower than the voltage V 1 for moving the movable contact electrodes 22 and 35 to contact the metal thin film 21 is applied between the bonding frame 2 and the glass cap 19. Thereafter, the voltage applied between the joining frame 2 and the glass cap 19 is gradually increased to be equal to or higher than the voltage V1, whereby the joining frame 2 and the glass cap 19 are anodically joined.

  After this anodic bonding process, the metal thin film 25 is removed. Then, the measurement unit 61 measures whether the movable contact electrodes 22 and 35 are electrically connected.

  In the inertial force sensor manufacturing method according to the second embodiment of the present invention, in the step of preparing the movable contact electrode and the support beam, a plurality of movable contact electrodes and a corresponding plurality of support beams are prepared. . In this way, by using a plurality of movable contact electrodes for contacting the metal thin film 21, the potential of the metal thin film 21 can be reliably fixed in the anodic bonding, so that the yield of the inertial force sensor is improved. Can do.

  Moreover, in the manufacturing method of the inertial force sensor according to the second embodiment of the present invention, whether or not the plurality of movable contact electrodes are conductive after the joining frame 2 and the glass cap 19 are anodically joined. Measure. Thereby, the potential fixed state of the metal thin film 21 can be easily examined on the wafer. That is, it is difficult to see the movable mass 5 due to the presence of the metal thin film 21, but the movable mass body by anodic bonding is confirmed by confirming the conduction state between the movable contact electrodes via the metal thin film 21 by the measurement unit 61. Since the presence or absence of sticking to the glass cap 19 can be easily detected, the reliability of the inertial force sensor can be improved.

  Since other contents are the same as those of the inertial force sensor and the manufacturing method thereof according to the first embodiment, detailed description will not be repeated here. Therefore, in the inertial force sensor and the manufacturing method thereof according to the second embodiment of the present invention, as in the inertial force sensor and the manufacturing method thereof according to the first embodiment, the mass body is attached to the cap in the anodic bonding. The yield can be improved by more reliably preventing sticking.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a top view which shows the structure of the inertial force sensor which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the II-II cross section in FIG. 1 of the inertial force sensor which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the III-III cross section in FIG. 1 of the inertial force sensor which concerns on the 1st Embodiment of this invention. It is a top view for demonstrating the manufacturing method of the inertial force sensor which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the VV cross section shown in FIG. It is a figure which shows the relationship between the time at the time of anodic bonding in the manufacturing method of the inertial force sensor which concerns on the 1st Embodiment of this invention, and an applied voltage. It is a figure which shows the structure of the inertial force sensor which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

  2 joint frame (frame body), 3, 24, 27, 32, 34 anchor, 4 beam (first elastic part), 5 movable mass body, 6a, 6b detection electrode, 7 inertial force detection part, 8 lower layer wiring, 9 to 13 electrode pad, 15 silicon substrate, 16, 17, 18 insulating film, 19 glass cap, 21 metal thin film, 22, 35 movable contact electrode, 23, 26, 31, 33 support beam (second elastic part), 51, 52 Signal processing unit, 61 Measuring unit, 101, 102 Inertial force sensor.

Claims (9)

A substrate having a main surface;
A mass body spaced apart from the substrate;
A first support portion that supports the mass body on the main surface of the substrate and has rigidity;
A frame provided on the main surface of the substrate and surrounding the mass body;
A cap that is anodically bonded to the frame so as to cover the mass body;
A conductive film provided on a main surface of the cap facing the mass body;
A contact electrode in contact with the conductive film;
A second support part that supports the contact electrode on the main surface of the substrate and has rigidity;
The inertial force sensor in which the rigidity of the second support portion in the direction from the substrate to the conductive film is lower than the rigidity of the first support portion in the direction from the substrate to the conductive film. The contact electrode is made of polysilicon or single crystal silicon,
The inertial force sensor according to claim 1, wherein the conductive film is formed of a metal that forms an alloy layer together with the contact electrode at a temperature at the time of the anodic bonding. The inertial force sensor further includes:
A detection electrode provided on the main surface of the substrate;
A first electrode pad electrically connected to the mass body;
A second electrode pad electrically connected to the detection electrode;
A third electrode pad electrically connected to the contact electrode;
The inertial force sensor according to claim 1, further comprising a fourth electrode pad electrically connected to the frame.   The inertial force sensor according to claim 1, wherein the inertial force sensor includes a plurality of the contact electrodes and the corresponding second support portions, and the plurality of contact electrodes are in contact with the conductive film at a plurality of locations. The inertial force sensor further includes:
The inertial force sensor according to claim 4, further comprising a measurement unit that measures whether the plurality of contact electrodes are conductive. A substrate having a main surface, a mass body disposed away from the substrate, a first support portion that supports the mass body on the main surface of the substrate and has rigidity, and a main surface of the substrate A frame surrounding the mass body, a cap provided with a conductive film on the main surface, a contact electrode, and supporting the contact electrode on the main surface of the substrate; A method of manufacturing an inertial force sensor comprising: a second support portion having a rigidity in a direction toward a membrane lower than that of the first support portion;
Making the same potential by electrically connecting the frame, the mass, and the contact electrode;
Disposing the cap so as to cover the mass body and the contact electrode, and contacting the cap and the frame;
A voltage smaller than a first voltage for moving the contact electrode to contact the conductive film is applied between the frame and the cap, and then a voltage applied between the frame and the cap. The method of manufacturing an inertial force sensor includes the step of anodic bonding the frame and the cap by gradually increasing the voltage to the first voltage or higher. The inertial force sensor further includes:
A detection electrode provided on a main surface of the substrate; a first electrode pad electrically connected to the mass; a second electrode pad electrically connected to the detection electrode; and the contact A third electrode pad electrically connected to the electrode, and a fourth electrode pad electrically connected to the frame,
In the step of setting the frame body, the mass body, and the contact electrode to the same potential,
The method of manufacturing an inertial force sensor according to claim 6, wherein the first electrode pad, the second electrode pad, the third electrode pad, and the fourth electrode pad are short-circuited. The method of manufacturing the inertial force sensor further includes:
Forming the contact electrode with polysilicon or single crystal silicon;
The method of manufacturing an inertial force sensor according to claim 6, further comprising: forming the conductive film with a metal that forms an alloy layer together with the contact electrode by the anodic bonding. The inertial force sensor includes a plurality of contact electrodes and a plurality of corresponding second support portions,
The method of manufacturing the inertial force sensor further includes:
The method of manufacturing an inertial force sensor according to claim 6, further comprising a step of measuring whether or not the plurality of contact electrodes are conductive after the frame body and the cap are anodically bonded.

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