JP6555238B2 - Mechanical quantity sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a mechanical quantity sensor that detects a mechanical quantity using a change in capacitance and a method for manufacturing the same.

  2. Description of the Related Art Conventionally, a mechanical quantity sensor that has two electrodes facing each other and detects a mechanical quantity using a change in capacitance between two electrodes due to displacement of one of the two electrodes has been proposed. ing.

  For example, Patent Document 1 proposes an acceleration sensor in which a fixed electrode formed by deposition or sputtering on the surface of a substrate and a movable electrode supported by a hinge element disposed on the surface of the substrate are opposed to each other. Has been. This acceleration sensor detects acceleration by using displacement of a movable electrode due to inertial force and change in capacitance between the electrodes due to the displacement.

Special table 2010-517014

  However, in the acceleration sensor described in Patent Document 1, the fixed electrode is formed on the surface of the substrate using deposition or sputtering. For this reason, a large variation occurs in the distance between the fixed electrode and the movable electrode due to the variation in the film thickness. As a result, the detection accuracy varies, and the reliability of the acceleration sensor decreases.

  An object of this invention is to provide a highly reliable mechanical quantity sensor and its manufacturing method in view of the said point.

  In order to achieve the above object, the invention according to claim 1 has two electrodes facing each other, and the capacitance between the two electrodes changes due to displacement of one of the two electrodes. A mechanical quantity sensor that detects a mechanical quantity by using a first substrate (100) that is partially movable in the thickness direction as a movable electrode (105), a sacrificial layer (202), and a sacrificial layer. A frame-shaped recess (204) formed in the active layer, having a support layer (203) and an active layer (201) sandwiched from both sides, and having a fixed electrode (205) constituted by a part of the active layer And the second substrate (200) disposed such that the fixed electrode and the active layer are electrically insulated from a portion different from the fixed electrode, and the fixed electrode faces the movable electrode.

  As described above, when a part of the active layer is a fixed electrode, the surface of the fixed electrode that faces the movable electrode is constituted by the surface of the active layer. Therefore, the distance between the fixed electrode and the movable electrode is less likely to vary, and the reliability of the mechanical quantity sensor can be improved.

  Further, the invention according to claim 17 has two electrodes facing each other, and uses the fact that the capacitance between the two electrodes changes due to the displacement of one of the two electrodes. A method of manufacturing a mechanical quantity sensor for detecting a quantity, comprising: preparing a first substrate (100); forming a movable electrode (105) on the first substrate; and a portion of the first substrate different from the movable electrode Making the movable electrode displaceable, and preparing a second substrate (200) having a sacrificial layer (202), a support layer (203) and an active layer (201) sandwiching the sacrificial layer from both sides, Forming a frame-shaped recess (204) in the active layer, so that the portion of the active layer located inside the recess becomes a fixed electrode (205) electrically insulated from the portion located outside. The fixed electrode is arranged to face the movable electrode. Provided with that, a.

  As described above, when a part of the active layer is a fixed electrode, the surface of the fixed electrode that faces the movable electrode is constituted by the surface of the active layer. Therefore, the distance between the fixed electrode and the movable electrode is less likely to vary, and the reliability of the mechanical quantity sensor can be improved.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows an example of a corresponding relationship with the specific means as described in embodiment mentioned later.

It is sectional drawing of the mechanical quantity sensor concerning 1st Embodiment, Comprising: It is II sectional drawing of FIG. It is a top view of the mechanical quantity sensor concerning 1st Embodiment. It is sectional drawing which shows the manufacturing method of a mechanical quantity sensor. It is sectional drawing which shows the manufacturing method of a mechanical quantity sensor. It is sectional drawing which shows the manufacturing method of a mechanical quantity sensor. It is sectional drawing which shows the manufacturing method of a mechanical quantity sensor. It is sectional drawing which shows operation | movement of a mechanical quantity sensor. It is sectional drawing which shows operation | movement of a mechanical quantity sensor. It is sectional drawing of the modification of 1st Embodiment. It is sectional drawing of the mechanical quantity sensor concerning 2nd Embodiment, Comprising: It is XX sectional drawing of FIG. It is a top view of the mechanical quantity sensor concerning 2nd Embodiment. It is sectional drawing which shows the manufacturing method of a mechanical quantity sensor. It is sectional drawing which shows the manufacturing method of a mechanical quantity sensor. It is sectional drawing which shows the manufacturing method of a mechanical quantity sensor. It is a top view of the mechanical quantity sensor concerning 3rd Embodiment. It is XVI-XVI sectional drawing of FIG. It is XVII-XVII sectional drawing of FIG. It is XVIII-XVIII sectional drawing of FIG. It is sectional drawing which shows the manufacturing method of a mechanical quantity sensor. It is a top view of the mechanical quantity sensor concerning 4th Embodiment. It is a top view of the modification of 4th Embodiment. It is sectional drawing of the mechanical quantity sensor concerning other embodiment. It is sectional drawing of the mechanical quantity sensor concerning other embodiment. It is sectional drawing of the mechanical quantity sensor concerning other embodiment. It is a top view of the mechanical quantity sensor concerning other embodiment. It is sectional drawing of the mechanical quantity sensor concerning other embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

(First embodiment)
A first embodiment of the present invention will be described. As shown in FIG. 1, the mechanical quantity sensor 1 according to the present embodiment includes a substrate 100, a substrate 200, and a joint portion 300. The mechanical quantity sensor 1 is a MEMS (Micro Electro Mechanical Systems) device manufactured by processing the substrate 100 and the substrate 200, and is a sensor that detects acceleration in the thickness direction of the substrate 100.

The substrate 100 is an SOI (Silicon on Insulator) wafer in which an active layer 101, a sacrificial layer 102, and a support layer 103 are sequentially stacked, and a movable electrode 105 (to be described later) is formed by patterning the active layer 101. . In this embodiment, the active layer 101 and the support layer 103 are made of single crystal silicon, and the sacrificial layer 102 is made of SiO ₂ . The substrate 100 corresponds to the first substrate.

  The active layer 101, the sacrificial layer 102, and the support layer 103 are partially removed, whereby the concave portion 104 and the movable electrode 105 are formed. As shown in FIGS. 1 and 2, the movable electrode 105 includes a fixed portion 106, a beam portion 107, and two weight portions 108 each formed of a part of the active layer 101. The fixed portion 106 has a rectangular top surface, and the sacrificial layer 102 and the support layer 103 are left on the back surface of the fixed portion 106 without being removed.

  The beam portion 107 is supported by the fixing portion 106 and extends on both sides in one direction (up and down direction in FIG. 2) parallel to the surface of the active layer 101 with the fixing portion 106 as the center. The two weight portions 108 each have a U-shaped upper surface, are disposed opposite to each other on both sides of the fixed portion 106, and are connected to the beam portion 107 at both ends.

  The sacrificial layer 102 and a part of the support layer 103 are removed from the back surface of the beam portion 107 and the weight portion 108, and the beam portion 107 and the weight portion 108 are released from the support layer 103. Thereby, the weight part 108 can be displaced in the thickness direction. The two weight portions 108 are connected to a portion of the active layer 101 different from the movable electrode 105 through the beam portion 107, the fixed portion 106, the sacrificial layer 102, and the support layer 103. One weight 108 has a larger width and a larger mass in the left-right direction in FIG. 2 than the other weight 108.

  In this embodiment in which the active layer 101, the sacrificial layer 102, and the support layer 103 have such shapes, the two weight portions 108 are displaced in the thickness direction of the substrate 100 when the beam portion 107 is twisted. Specifically, when the beam portion 107 is twisted, one weight portion 108 is displaced to one side in the thickness direction of the substrate 100, and the other weight portion 108 is displaced to the other side in the thickness direction of the substrate 100. In this way, an insulator structure with the fixed portion 106 as a fulcrum is configured.

The substrate 200 is an SOI wafer in which an active layer 201, a sacrificial layer 202, and a support layer 203 are stacked in this order, and a fixed electrode 205 (to be described later) is formed by patterning the active layer 201. In this embodiment, the active layer 201 and the support layer 203 are made of single crystal silicon, and the sacrificial layer 202 is made of SiO ₂ . The substrate 200 corresponds to a second substrate.

  As shown in FIGS. 1 and 2, the substrate 200 is formed with a frame-shaped recess 204. Thereby, the part located inside the recessed part 204 among the active layers 201 is electrically insulated from the part located outside the recessed part 204. A portion of the active layer 201 positioned inside the recess 204 is referred to as a fixed electrode 205.

  The substrate 200 is disposed so that the fixed electrode 205 faces the movable electrode 105. In the present embodiment, two fixed electrodes 205 are formed by forming two recesses 204, and the substrate 200 is arranged so that the two fixed electrodes 205 face the two weight portions 108. .

  In the present embodiment, the fixed electrode 205 is disposed above the movable electrode 105 in the gravitational direction, and the mechanical quantity sensor 1 detects acceleration in the gravitational direction. You may arrange | position on the gravity direction lower side. Further, the movable electrode 105 and the fixed electrode 205 may be arranged so that the mechanical quantity sensor 1 detects acceleration in a direction different from the direction of gravity.

  In the substrate 200, a via that is a TSV (Through-Silicon Via) that opens on the surface of the support layer 203 on the side opposite to the sacrificial layer 202, passes through the substrate 200 and the joint portion 300, and is connected to the fixed portion 106. 206 is formed.

  Further, the substrate 200 is formed with a via 207 that is an TSV that opens on the surface of the support layer 203 opposite to the sacrificial layer 202 and passes through the support layer 203 and the sacrificial layer 202 and is connected to the fixed electrode 205. Has been.

  Further, the substrate 200 has an opening on the surface of the support layer 203 on the side opposite to the sacrificial layer 202, and passes through the support layer 203 and the sacrificial layer 202, and a portion of the active layer 201 located outside the fixed electrode 205. A via 208, which is a TSV connected to, is formed.

  Also, the substrate 200 is formed with a via 209 that is a TSV that opens on the surface of the support layer 203 opposite to the sacrificial layer 202 and is connected to the outer peripheral portion of the active layer 101 through the substrate 200. Yes. Note that a portion of the active layer 101 located outside the movable electrode 105 is an outer peripheral portion of the active layer 101.

  An insulating layer 210 is formed so as to cover the inside of the vias 206 to 209 and the surface of the support layer 203 opposite to the sacrificial layer 202. On the surface of the insulating layer 210, a wiring layer 211 for connecting the mechanical quantity sensor 1 to an external circuit is formed.

  A part of the insulating layer 210 is removed at the bottoms of the vias 206 to 209, and the wiring layer 211 passes through the vias 206 to 209, and the fixed part 205 of the fixed part 106, the fixed electrode 205, and the active layer 201. It is connected to the outer portion and the outer peripheral portion of the active layer 101.

  In addition, on the surface of the support layer 203, a part of the insulating layer 210 is removed to form an opening 212, and the wiring layer 211 is connected to the support layer 203 through the opening 212.

  The surfaces of the insulating layer 210 and the wiring layer 211 are covered with a protective film 213. The protective film 213 is for imparting moisture resistance to the mechanical quantity sensor 1, and is made of SiN here. The protective film 213 may be made of PIQ (registered trademark), which is a polyimide resin.

  An opening 214 is formed in a portion of the protective film 213 formed on the upper surface of the wiring layer 211. Thus, the outer peripheral portion of the active layer 101, the movable electrode 105, the fixed electrode 205, and the portion of the active layer 201 located outside the fixed electrode 205 are connected to an external circuit via the wiring layer 211. be able to.

  As will be described later, when acceleration is applied to the mechanical quantity sensor 1, electrostatic capacitance between one weight portion 108 and one fixed electrode 205, and between the other weight portion 108 and the other fixed electrode 205. Changes. In the present embodiment, the mechanical quantity sensor 1 and a control device (not shown) are connected so as to differentially amplify these capacitance changes that occur during acceleration application. For example, when the power supply voltage is 5V, the potential of the weight portion 108 is 5V. The fixed electrode 205 is connected to an input terminal of a control device (not shown) through the wiring layer 211. In addition, the portion of the active layer 201 located outside the fixed electrode 205 and the outer peripheral portion of the active layer 101 are grounded through the vias 208 and 209, and the potential is fixed.

A bonding portion 300 is disposed between the substrate 100 and the substrate 200. The bonding portion 300 serves as a bonding material when bonding the substrate 100 and the substrate 200 in the process shown in FIG. 5A described later. The distance between the substrate 100 and the substrate 200 is determined by the bonding portion. It is defined by a thickness of 300. In the present embodiment, the bonding part 300 is composed of a layer of SiO ₂ formed by thermally oxidizing the surface of the active layer 201.

  The joining part 300 has a part arranged on the surface of the outer peripheral part of the active layer 101 and a part arranged on the surface of the fixing part 106. A portion of the joint portion 300 disposed on the outer peripheral portion of the active layer 101 is formed in a frame shape so as to include the movable electrode 105 inside. The substrate 100 and the substrate 200 are connected to each other through the bonding portion 300, whereby the movable electrode 105 is hermetically sealed.

  A method for manufacturing the mechanical quantity sensor 1 will be described. The mechanical quantity sensor 1 manufactures the substrate 100 in the process shown in FIG. 3, manufactures the substrate 200 in the process shown in FIG. 4, and then bonds the substrate 100 and the substrate 200 in the processes shown in FIGS. 5 and 6. It is manufactured by forming a wiring or the like.

  A method for manufacturing the substrate 100 will be described with reference to FIG. First, a single crystal silicon substrate is prepared and used as a support layer 103. As shown in FIG. 3A, the support layer 103 is thermally oxidized to form a sacrificial layer 102 and an oxide film 109 on the front and back surfaces of the support layer 103. Form.

  Then, as shown in FIG. 3B, the sacrificial layer 102 is removed by etching at a portion corresponding to the movable electrode 105, and a part of the support layer 103 is removed by etching using the sacrificial layer 102 as a mask. By removing, the recess 104 is formed. However, in the portion corresponding to the fixed portion 106, the sacrificial layer 102 and the support layer 103 are left without being removed.

  After the step shown in FIG. 3B, as shown in FIG. 3C, a cavity-SOI step is performed in which the active layer 101 is bonded to the surface of the sacrificial layer 102 by direct bonding. In the step shown in FIG. 3D, the active layer 101 is processed by etching, and the recess 104 is opened on the surface of the active layer 101 to form the movable electrode 105.

  A method for manufacturing the substrate 200 will be described with reference to FIG. First, as shown in FIG. 4A, an SOI wafer in which an active layer 201, a sacrificial layer 202, and a support layer 203 are sequentially laminated is prepared. Then, as shown in FIG. 4B, the active layer 201 and the support layer 203 are thermally oxidized to form the junction 300 and the oxide film 215.

  In the step shown in FIG. 4C, a portion of the joint portion 300 corresponding to the weight portion 108 of the movable electrode 105 is removed by etching, and a part of the active layer 201 is exposed. In the step shown in FIG. 4D, a part of the active layer 201 exposed in the step shown in FIG. 4C is removed by etching to form a frame-shaped recess 204. As a result, the portion of the active layer 201 positioned inside the recess 204 is electrically insulated from the portion positioned outside the recess 204, thereby forming the fixed electrode 205.

  The bonding of the substrate 100 and the substrate 200 manufactured in this way and the steps after the bonding will be described with reference to FIGS. In the process shown in FIG. 5A, the substrate 100 and the bonding portion 300 formed on the surface of the substrate 200 are bonded together by direct bonding. Thereby, the movable electrode 105 is hermetically sealed.

  5B, a part of the oxide film 215 corresponding to the outer peripheral portion of the fixed portion 106, the fixed electrode 205, and the active layer 201 is removed. In the step shown in FIG. 5C, a part of the support layer 203 is removed by etching using the oxide film 215 as a mask to form vias 206 to 208 and the sacrificial layer 202 is exposed. Thereafter, the oxide film 215 is removed.

  In the step shown in FIG. 5D, an opening is formed in a portion corresponding to the via 206, and an opening is not formed in the portions corresponding to the vias 207 and 208, and sacrifice is performed by etching using a mask (not shown). A via 206 is formed so as to penetrate the layer 202 and the active layer 201 to expose the junction 300.

  In the step shown in FIG. 6A, the surfaces of the support layer 203 and the vias 206 to 208 are thermally oxidized to form the insulating layer 210. Then, a part of the insulating layer 210 formed at the bottom of the via 206 and a part of the bonding part 300 are removed by etching, and the fixing part 106 is exposed. Further, a part of the insulating layer 210 formed at the bottoms of the vias 207 and 208 is removed by etching, and the outer peripheral portions of the fixed electrode 205 and the active layer 201 are exposed. Further, a part of the insulating layer 210 formed on the surface of the support layer 203 is removed to form an opening 212 that exposes the support layer 203.

  In the step shown in FIG. 6B, the wiring layer 211 is formed inside the vias 206 to 208, inside the opening 212, and on the surface of the insulating layer 210. In the step shown in FIG. 6C, a protective film 213 is formed on the surfaces of the insulating layer 210 and the wiring layer 211 by a CVD (Chemical Vapor Deposition) method or a coating method. Further, an opening 214 is formed in the protective film 213 using etching, and a part of the wiring layer 211 is exposed. As a result, the fixed portion 106, the fixed electrode 205, and the active layer 201 can be connected to an external circuit.

  Although not shown in FIGS. 5 and 6, a via 209 is formed in a portion corresponding to the outer peripheral portion of the active layer 101 similarly to the via 206. Then, an insulating layer 210 is formed on the surface of the via 209, and after a part of the insulating layer 210 formed on the bottom of the via 209 and a part of the joint portion 300 are removed, a wiring layer is formed inside the via 209. 211 is formed, and the outer periphery of the active layer 101 can be connected to an external circuit.

  The operation of the mechanical quantity sensor 1 will be described. When the mechanical quantity sensor 1 is accelerated in the thickness direction of the substrate 100 and the substrate 200, the movable electrode 105 is displaced as shown in FIG. That is, one weight portion 108 is displaced to one side in the thickness direction of the substrate 100, and the other weight portion 108 is displaced to the other side in the thickness direction of the substrate 100. Then, the distance between the fixed electrode 205 and the weight portion 108 changes, and the capacitance changes.

For example, if the distance between the electrodes when the mechanical quantity sensor 1 is stationary is d ₀ and the displacement amount of the weight portion 108 is Δd, the distance between one weight portion 108 and one fixed electrode 205 is d ₀ + Δd, and the distance between the other weight 108 and the other fixed electrode 205 is d ₀ −Δd.

  The mechanical quantity sensor 1 obtains a change in capacitance between the fixed electrode 205 and the weight portion 108 when the weight portion 108 is displaced from a change in potential of the fixed electrode 205, and uses the obtained change in capacitance. To detect acceleration.

  In the manufacturing of the conventional mechanical quantity sensor, the positions of the two fixed electrodes 205 change as shown by the broken line in FIG. 7 due to variations in the position of the electrode material and the thickness of the bonding material, and the movable electrode 105 and the fixed electrode 205 are changed. There may be variations in the distance between the two.

  When the distance between the electrodes varies, the initial capacitance and the detection accuracy vary. Therefore, in order to improve the reliability of the mechanical quantity sensor that detects the acceleration using the change in capacitance between the electrodes, it is necessary to reduce the variation in the distance between the electrodes.

  In the present embodiment, the fixed electrode 205 is configured by a part of the active layer 201, and the surface of the fixed electrode 205 that faces the movable electrode 105 is configured by the surface of the active layer 201. Therefore, for example, the distance between the movable electrode 105 and the fixed electrode 205 is less likely to vary than when the fixed electrode 205 is formed on the surface of the active layer 201 by sputtering or the like. Therefore, the reliability of the mechanical quantity sensor can be improved.

  In the present embodiment, since the bonding portion 300 is formed by thermally oxidizing the surface of the active layer 201, an oxide film is formed on the surface of the active layer 201 using, for example, CVD, and this oxide film is bonded. The variation in the thickness of the bonding material is small compared to the case of using it as a material. Therefore, the variation in the distance between the electrodes can be further reduced, and the detection accuracy and reliability of the mechanical quantity sensor 1 can be further improved.

  In addition, in a mechanical quantity sensor including two electrodes, the inclination of the substrate 200 with respect to the substrate 100 may change due to the deformation of the substrate due to a temperature change. When the inclination of the substrate 200 with respect to the substrate 100 changes, for example, the position of one fixed electrode 205 changes as shown by the broken line in FIG. 8, and the distance between the movable electrode 105 and the fixed electrode 205 and the electrostatic capacitance are changed. Fluctuates and the detection accuracy decreases.

  In order to suppress the deformation of the substrate due to the temperature change and suppress the decrease in detection accuracy, it is preferable to configure the substrate 100 and the substrate 200 with a material having a small linear expansion coefficient. In addition, the substrate 100 and the substrate 200 are preferably formed using a material having high rigidity. In order to reduce the change in the inclination of the substrate 200 with respect to the substrate 100, it is preferable that the substrate 100 and the substrate 200 are made of a material having a small difference in linear expansion coefficient. Further, it is preferable that a different material such as a eutectic metal is not interposed between the substrate 100 and the substrate 200.

In this embodiment, SOI wafers made of the same material are used for the substrate 100 and the substrate 200, and single crystal silicon used for the SOI wafer has high rigidity and a small linear expansion coefficient. In addition, the bonding portion 300 that connects the substrate 100 and the substrate 200 is made of SiO ₂ , and no dissimilar material such as a eutectic metal is interposed between the substrate 100 and the substrate 200. Thereby, it can suppress that the distance between electrodes fluctuates and can improve detection accuracy further.

In a mechanical quantity sensor having a movable electrode, it is also important to maintain the internal pressure and operate the movable electrode in a constant atmosphere. In the present embodiment, the substrate 100 and the bonding portion 300 formed on the surface of the substrate 200 are bonded together, and thereby the movable electrode 105 is hermetically sealed. Therefore, it is possible to suppress the pressure in the space in which the movable electrode 105 is displaced from changing due to the environment, and to improve the detection accuracy. In particular, in this embodiment, since the substrate 100 and the substrate 200 are bonded together by Si direct bonding via the bonding portion 300 made of SiO ₂ , the sealing has the same reliability as that of a normal SOI wafer. can get.

  In order to suppress the generation of parasitic / floating capacitance between the active layer 201 and the movable electrode 105 and to secure the movable range of the weight portion 108, as shown in FIG. Of these, it is preferable that the movable electrode 105 is formed so as to reach the outside of the portion facing the movable electrode 105, and the movable range of the weight portion 108 is defined by the fixed electrode 205.

(Second Embodiment)
A second embodiment of the present invention will be described. In the present embodiment, the bonding method of the substrate 100 and the substrate 200 is changed with respect to the first embodiment, and the other aspects are the same as those in the first embodiment. Therefore, only the portions different from the first embodiment are described. explain.

  As shown in FIGS. 10 and 11, in this embodiment, vias 110, 111, and 112 are formed in the substrate 100. The via 110 is a TSV that is opened on the surface of the support layer 103 opposite to the sacrificial layer 102 and is connected to the fixed portion 106 through the support layer 103.

  The via 111 opens on the surface of the support layer 103 opposite to the sacrificial layer 102, penetrates the support layer 103, and is connected to a portion corresponding to the fixed electrode 205 in the outer peripheral portion of the active layer 101. It is. The via 112 opens on the surface of the support layer 103 opposite to the sacrificial layer 102, penetrates the support layer 103, and connects to a portion corresponding to the outer peripheral portion of the active layer 201 among the outer peripheral portion of the active layer 101. TSV.

  An insulating layer 113 is formed so as to cover the inside of the vias 110 to 112 and the surface of the support layer 103 opposite to the sacrificial layer 102. On the surface of the insulating layer 113, a wiring layer 114 for connecting the mechanical quantity sensor 1 to an external circuit is formed.

  The insulating layer 113 and the sacrificial layer 102 are removed at the bottom of the vias 110 to 112, and the wiring layer 114 is connected to the fixed portion 106 and the outer peripheral portion of the active layer 101 through the vias 110 to 112. Yes. Further, on the surface of the support layer 103, a part of the insulating layer 113 is removed to form an opening 115, and the wiring layer 114 is connected to the support layer 103 through the opening 115.

  The surfaces of the insulating layer 113 and the wiring layer 114 are covered with a protective film 116. The protective film 116 is for imparting moisture resistance to the mechanical quantity sensor 1, and is made of SiN here. The protective film 116 may be made of PIQ or the like that is a polyimide resin.

  An opening 117 is formed in a portion of the protective film 116 formed on the upper surface of the wiring layer 114. Thereby, the fixed part 106, the outer peripheral part of the active layer 101, and the support layer 103 can be connected to an external circuit through the wiring layer 114.

  In the present embodiment, the outer periphery of the active layer 101 is connected to the fixed electrode 205 and the outer periphery of the active layer 201 via metal layers 301 and 302 described later. In addition, a portion of the active layer 101 connected to the fixed electrode 205 is electrically insulated from other portions. The fixed electrode 205 is connected to an external circuit via the wiring layer 114 formed inside the via 111, the active layer 101, and the metal layers 301 and 302. The outer peripheral portion of the active layer 201 is connected to an external circuit through the wiring layer 114 formed inside the via 112, the active layer 101, and the metal layers 301 and 302.

  The joint portion 300 of this embodiment includes metal layers 301 and 302 and a spacer 303. The metal layer 301 is formed in a frame shape on the outer periphery of the active layer 101 so as to include the movable electrode 105 and the fixed electrode 205 therein. The metal layer 301 is also formed on the surface of the fixed portion 106. Further, the metal layer 301 is also formed on a portion corresponding to the fixed electrode 205 in the outer peripheral portion of the active layer 101.

  The metal layer 302 is formed on the surface of the active layer 201 so as to face the metal layer 301. In the present embodiment, the metal layers 301 and 302 are made of Al (aluminum).

The spacer 303 is disposed between the substrate 100 and the substrate 200 and is formed in a frame shape so as to include the metal layers 301 and 302 therein. The spacer 303 is made of SiO ₂ and corresponds to a thermal oxide film.

  A method for manufacturing the mechanical quantity sensor of this embodiment will be described. In this embodiment, after the step shown in FIG. 3, as shown in FIG. 12, the surface of the active layer 101 is thermally oxidized to form a spacer 303. Further, the metal layer 301 is formed on the outer periphery of the fixed portion 106 and the active layer 101.

  In addition, as shown in FIG. 13, an SOI wafer in which an active layer 201, a sacrificial layer 202, and a support layer 203 are sequentially stacked is prepared, and after the active layer 201 is patterned to form a fixed electrode 205, A metal layer 302 is formed on the surface. Then, as illustrated in FIG. 14A, the substrate 100 and the substrate 200 are connected by metal bonding between the metal layer 301 and the metal layer 302.

  In the step shown in FIG. 14B, the substrate 100 is thinned and the oxide film 109 is removed. In addition, the vias 110 to 112 that penetrate the support layer 103 are formed by etching, and the support layer 103 is thermally oxidized to form the insulating layer 113. Then, the insulating layer 113 formed on the bottoms of the vias 110 to 112 and a part of the sacrificial layer 102 are removed by etching to expose the outer peripheral portion of the active layer 101 and the fixing portion 106. Further, a part of the insulating layer 113 formed on the surface of the support layer 103 is removed to form an opening 115 to expose the support layer 103.

  In the step shown in FIG. 14C, the wiring layer 114 is formed on the surface of the insulating layer 113, inside the vias 110 to 112, and inside the opening 115. In addition, after the protective film 116 is formed on the surfaces of the insulating layer 113 and the wiring layer 114 using CVD, a part of the protective film 116 is removed, and an opening 117 is formed. As a result, the outer peripheral portion of the active layer 101, the support layer 103, the fixed portion 106, the fixed electrode 205, and the outer peripheral portion of the active layer 201 can be connected to an external circuit.

In the present embodiment, Al constituting the metal layers 301 and 302 of the joint portion 300 has a small difference in linear expansion coefficient from Si and SiO ₂ constituting the substrate 100, the substrate 200, and the spacer 303. Therefore, the generated thermal stress can be reduced, and the change in the capacitance between the electrodes due to a temperature change can be suppressed as in the first embodiment.

(Third embodiment)
A third embodiment of the present invention will be described. In this embodiment, the configuration of the fixed electrode 205 is changed with respect to the first embodiment, and the other parts are the same as those in the first embodiment. Therefore, only the parts different from the first embodiment will be described.

  As shown in FIG. 15, in the present embodiment, a plurality of etching holes 216 are formed in a portion of the fixed electrode 205 facing the movable electrode 105. The etching hole 216 is for introducing an etching medium in a process shown in FIG.

  In the present embodiment, the plurality of etching holes 216 are arranged at equal intervals. Specifically, the etching holes 216 are arranged so as to be positioned at the vertices of a plurality of equilateral triangles spread without gaps. In FIG. 15, only a part of the plurality of etching holes 216 arranged in this way is illustrated.

  Further, as shown in FIG. 16, a recess 217 that exposes the surface of the fixed electrode 205 on the support layer 203 side is formed at the bottom of the recess 204. The recesses 204 and 217 correspond to a first recess and a second recess, respectively.

  As shown in FIG. 17, the fixed electrode 205 is supported by the sacrificial layer 202 and the substrate 100 at one end of both ends in one direction in the plane of the active layer 201. In the present embodiment, the fixed electrode 205 is supported by the sacrificial layer 202 or the like at one end in the longitudinal direction.

  Further, as shown in FIGS. 16 and 18, the sacrificial layer 202 is removed by the formation of the recess 217 at the portion facing the movable electrode 105 and at the other end, and the fixed electrode 205 is supported by the support layer 203. Has been released from. Of the fixed electrode 205, a portion supported by the sacrificial layer 202 or the like is referred to as a fixed portion 218, and a portion released from the support layer 203 is referred to as a release portion 219.

  In the present embodiment, in the step shown in FIG. 4C of the first embodiment, in the joint portion 300, in addition to the portion corresponding to the weight portion 108 of the movable electrode 105, the portion corresponding to the release portion 219 is etched. To remove a portion of the active layer 201.

  Then, as shown in FIG. 19A, a part of the active layer 201 exposed by removing the bonding portion 300 is removed by etching to form a recess 204 and an etching hole 216.

  Thereafter, etching is performed using the active layer 201 as a mask. At this time, the etching medium is introduced from the etching hole 216, and the sacrificial layer 202 is removed at the lower portion of the fixed electrode 205 as shown in FIG. As described above, the etching holes 216 are arranged at equal intervals, and the sacrificial layer 202 is formed on the portion of the fixed electrode 205 facing the movable electrode 105 by appropriately setting the distance between the two adjacent etching holes 216. It is suppressed that it remains.

  As a result, the surface of the fixed electrode 205 on the support layer 203 side is exposed, and the release portion 219 is formed. A portion of the fixed electrode 205 left without removing the sacrificial layer 202 becomes a fixed portion 218.

  In the present embodiment in which the fixed electrode 205 is configured as described above, it is possible to suppress the distortion of the substrate 200 due to a temperature change or the like from being transmitted to a portion of the fixed electrode 205 facing the movable electrode 105. . Therefore, the acceleration detection accuracy can be further improved.

  In the present embodiment, the fixed electrode 205 is supported only at one end of both ends. However, the sacrificial layer 202 is removed only at a portion of the fixed electrode 205 facing the movable electrode 105, and the fixed portion 218 is removed. It may be formed at both ends of the fixed electrode 205, and the fixed electrode 205 may be supported at both ends. Thereby, the deflection of the fixed electrode 205 can be suppressed.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. In the present embodiment, the shape of the fixed electrode 205 is changed with respect to the third embodiment, and the other aspects are the same as those of the third embodiment. Therefore, only the parts different from the third embodiment will be described.

  As shown in FIG. 20, in this embodiment, a slit 220 that reduces the width of the release portion 219 is formed. Specifically, a slit 220 is formed at the end of the release part 219 on the fixed part 218 side. By forming the slit 220, the width in the short direction of the fixed electrode 205, that is, the direction perpendicular to the longitudinal direction of the fixed electrode 205 in the plane of the active layer 201 is made smaller than the other portions.

  The slit 220 reduces the width of the portion of the fixed electrode 205 that connects the portion facing the movable electrode 105 and the fixed portion 218 supported by the sacrificial layer 202. Therefore, the distortion of the substrate 200 can be further suppressed from being transmitted to the portion of the fixed electrode 205 facing the movable electrode 105, and the acceleration detection accuracy can be further improved.

  Note that this embodiment may be applied to a modification of the third embodiment, and slits 220 may be formed at both ends of the release portion 219, as shown in FIG.

(Other embodiments)
In addition, this invention is not limited to above-described embodiment, In the range described in the claim, it can change suitably.

  For example, the movable electrode 105 may not be hermetically sealed. Further, the substrate 100 may be composed of an Si substrate instead of an SOI wafer. Further, the fixed electrode 205 may be disposed on both sides of the movable electrode 105.

  Further, the active layer 101, the support layer 103, the active layer 201, and the support layer 203 may be made of polycrystalline silicon. When these layers are made of polycrystalline silicon, the manufacture of the mechanical quantity sensor 1 becomes easy.

  In the first embodiment, the bonding portion 300 is formed by thermally oxidizing the active layer 201 of the substrate 200. However, the bonding portion 300 may be formed by thermally oxidizing the active layer 101 of the substrate 100. .

  In the first and second embodiments, the mechanical quantity sensor 1 has an insulator structure in which the weights 108 are arranged on both sides of the fixed part 106. However, the mechanical quantity sensor 1 has another structure. It may be. For example, the weight portion 108 may have a rectangular plate shape, and may be supported at both ends by the beam portion 107 as shown in FIG. 22, and may be displaced in the thickness direction of the substrate 100 when the beam portion 107 bends. In this case, the substrate 100 is made of, for example, a Si substrate instead of an SOI wafer, and the substrate 200 is disposed on both sides in the thickness direction of the substrate 100. As shown in FIG. It is preferable to have a configuration facing 205. Further, the weight portion 108 may be formed in a rectangular plate shape, cantilevered by the beam portion 107 as shown in FIG. 23, and may be displaced in the thickness direction of the substrate 100 when the beam portion 107 is bent. In this case, as shown in FIG. 23, it is preferable that the weight portion 108 is opposed to the two fixed electrodes 205 on both sides in the thickness direction.

  Further, the movable electrode 105 may be formed so as to detect acceleration in a direction different from the thickness direction of the substrate 100. For example, the weight portion 108 has a rectangular plate shape, the beam portion 107 is formed thinner than the weight portion 108, the movable electrode 105 is configured so that the beam portion 107 supports the weight portion 108 at both ends, and the weight portion 108 is the beam. The both sides of the portion 107 may be opposed to the fixed electrode 205. In such a configuration, when the beam portion 107 is twisted, the weight portion 108 swings about the axis of the beam portion 107 as indicated by an arrow A1 in FIG. Then, using this change in capacitance between the electrodes, acceleration in the direction indicated by the arrow A2 in FIG. 24, that is, the direction parallel to the surface of the substrate 100 and perpendicular to the axis of the beam portion 107 is detected. Can do.

  Further, the present invention may be applied to a mechanical quantity sensor other than an acceleration sensor, for example, a tilt sensor. Further, the present invention may be applied to a mechanical quantity sensor such as a gyroscope that detects an angular velocity in a state where the movable electrode 105 is vibrated. Such a mechanical quantity sensor includes two movable electrodes 105 as shown in FIGS. Each of the two movable electrodes 105 includes a comb electrode 118, and the comb electrodes 118 are arranged so as to face each other. Further, the movable electrode 105 is supported by a spring portion (not shown), and when the AC voltage is applied to the movable electrode 105, the movable electrode 105 vibrates in the extending direction of the comb electrode 118. When rotation about the thickness direction of the substrate 100 occurs, the movable electrode 105 is displaced in a direction perpendicular to both the extending direction of the comb electrode 118 and the thickness direction of the substrate 100. The mechanical quantity sensor shown in FIG. 25 and FIG. 26 detects the angular velocity by using the change in the capacitance between the two movable electrodes 105 caused thereby. In such a mechanical quantity sensor, the fixed electrode 205 is disposed so as to face each of the two movable electrodes 105, and the AC voltage is applied to the fixed electrode 205, whereby the vibration of the movable electrode 105 can be controlled. In this vibration control, it is preferable that the distance between the movable electrode 105 and the fixed electrode 205 has little variation. By applying the present invention to such a mechanical quantity sensor, variation in the distance between the movable electrode 105 and the fixed electrode 205 can be suppressed, and the reliability of the mechanical quantity sensor can be improved.

DESCRIPTION OF SYMBOLS 100 Substrate 105 Movable electrode 200 Substrate 201 Active layer 202 Sacrificial layer 203 Support layer 204 Concave portion 205 Fixed electrode

Claims (28)

A mechanical quantity sensor that has two electrodes facing each other and detects a mechanical quantity by utilizing a change in capacitance between the two electrodes due to displacement of one of the two electrodes. And
A first substrate (100) partially movable as a movable electrode (105) in the thickness direction;
A sacrificial layer (202), a support layer (203) and an active layer (201) sandwiching the sacrificial layer from both sides, and a fixed electrode (205) constituted by a part of the active layer, the active layer The fixed electrode and a portion of the active layer different from the fixed electrode are electrically insulated by a frame-shaped recess (204) formed in the layer so that the fixed electrode faces the movable electrode. And a second substrate (200) disposed on the mechanical quantity sensor. A frame-shaped joint (300) disposed between the first substrate and the second substrate so as to include the movable electrode inside;
The first substrate is connected to the second substrate through the bonding portion,
The movable electrode is hermetically sealed by the first substrate, the second substrate, and the bonding portion,
The mechanical quantity sensor according to claim 1, wherein a distance between the first substrate and the second substrate is defined by a thickness of the joint portion. The mechanical quantity sensor according to claim 2 , wherein the joint portion is formed of a thermal oxide film.   4. The mechanical quantity sensor according to claim 1, wherein the active layer is made of single crystal silicon or polycrystalline silicon. The movable electrode includes a weight portion (108) that is displaced in the thickness direction of the first substrate, and a beam portion (107) that connects the weight portion to a portion different from the movable electrode in the first substrate. Have
5. The mechanical quantity sensor according to claim 1, wherein the weight portion is displaced in a thickness direction when the beam portion is twisted. 6. The movable electrode includes a weight portion (108) that is displaced in the thickness direction of the first substrate, and a beam portion (107) that connects the weight portion to a portion different from the movable electrode in the first substrate. Have
The mechanical quantity sensor according to any one of claims 1 to 4, wherein the weight portion is displaced in a thickness direction when the beam portion is bent.   The second substrate has an opening on a surface of the support layer opposite to the sacrificial layer, and first vias (206, 209) penetrating the second substrate and connected to the first substrate. And a second via (207, 208) that is open on a surface of the support layer opposite to the sacrificial layer and penetrates the support layer and the sacrificial layer and is connected to the active layer. The mechanical quantity sensor according to any one of claims 1 to 6.   The potential of a portion of the first substrate different from the movable electrode and a portion of the active layer located outside the recess are fixed through the first via and the second via, respectively. Item 8. The mechanical quantity sensor according to Item 7.   The mechanical quantity sensor according to any one of claims 1 to 8, wherein a movable range of the movable electrode is defined by the fixed electrode. Two second substrates,
The mechanical quantity sensor according to claim 1, wherein the movable electrode faces the fixed electrode on both sides in the thickness direction. Two movable electrodes facing each other;
Controlling the vibration of the movable electrode by applying an alternating voltage to the fixed electrode;
The mechanical quantity sensor according to any one of claims 1 to 10, wherein the mechanical quantity is detected by utilizing a change in capacitance between the two movable electrodes due to displacement of the two movable electrodes. The recess as a first recess,
The mechanical quantity sensor according to any one of claims 1 to 11, wherein a second recess (217) that exposes a surface of the fixed electrode on the side of the support layer is formed in the first recess.   The mechanical quantity sensor according to claim 12, wherein the fixed electrode is supported by the sacrificial layer at one end in a plane of the active layer.   The mechanical quantity sensor according to claim 12, wherein the fixed electrode is supported by the sacrificial layer at both ends in one direction within a plane of the active layer.   A slit (220) in the fixed electrode where the surface on the side of the support layer is exposed by the second recess, the width in the direction perpendicular to the one direction in the surface of the active layer is smaller than that of the other part. The mechanical quantity sensor according to claim 13 or 14, wherein:   The mechanical quantity sensor according to any one of claims 12 to 15, wherein a plurality of etching holes (216) arranged at equal intervals are formed in the fixed electrode. Manufacture of a mechanical quantity sensor that has two electrodes facing each other and detects a mechanical quantity by using a change in capacitance between the two electrodes due to displacement of one of the two electrodes A method,
Providing a first substrate (100);
Forming a movable electrode (105) on the first substrate, and allowing the movable electrode to be displaced relative to a portion of the first substrate different from the movable electrode;
Providing a second substrate (200) having a sacrificial layer (202) and a support layer (203) and an active layer (201) sandwiching the sacrificial layer from both sides;
By forming a frame-shaped recess (204) in the active layer, a portion of the active layer located inside the recess is used as a fixed electrode (205) that is electrically insulated from a portion located outside. And
Disposing the fixed electrode so as to face the movable electrode, and a method of manufacturing a mechanical quantity sensor. Disposing a frame-shaped joint (300) between the first substrate and the second substrate so as to include the movable electrode inside;
The method of manufacturing a mechanical quantity sensor according to claim 17, further comprising: connecting the first substrate and the second substrate via the joint portion and hermetically sealing the movable electrode. By disposing the bonding portion, the bonding portion is formed on the surface of the first substrate by thermally oxidizing the first substrate, and the bonding portion is formed between the first substrate and the second substrate. Place and
The method of manufacturing a mechanical sensor according to claim 18, wherein the hermetic sealing connects the first substrate and the second substrate by direct bonding between the bonding portion and the second substrate. By disposing the bonding portion, the bonding portion is formed on the surface of the second substrate by thermally oxidizing the second substrate, and the bonding portion is formed between the first substrate and the second substrate. Place and
The method of manufacturing a mechanical sensor according to claim 18, wherein the hermetic sealing connects the first substrate and the second substrate by direct bonding between the bonding portion and the first substrate. By disposing the bonding portion, metal layers (301, 302) are formed on the surfaces of the first substrate and the second substrate, and the first substrate or the second substrate is thermally oxidized to form a thermal oxide film ( 303), the bonding portion including the metal layer and the thermal oxide film is disposed between the first substrate and the second substrate,
In the hermetic sealing, the first substrate and the first substrate are formed by metal bonding between a portion of the metal layer formed on the surface of the first substrate and a portion formed on the surface of the second substrate. The method of manufacturing a mechanical quantity sensor according to claim 18, wherein the two substrates are connected.   The method for manufacturing a mechanical quantity sensor according to any one of claims 17 to 21, wherein the concave portion is formed so that the movable range of the movable electrode is defined by the fixed electrode. By removing a part of the support layer and the sacrificial layer, a plurality of first vias (207, 208) that are open at the surface of the support layer and pass through the support layer and connected to the active layer Forming the vias of
After forming the first via, an opening is formed in the surface of the support layer by etching using a mask in which an opening is formed in a portion corresponding to a via different from the first via among the plurality of vias. The mechanical quantity sensor according to claim 17, further comprising: forming a second via (206, 209) penetrating through the second substrate and connected to the first substrate. Manufacturing method. The recess as a first recess,
The mechanical quantity sensor according to any one of claims 17 to 23, wherein a second recess (217) that exposes a surface of the fixed electrode on the side of the support layer is formed in the first recess. Production method.   25. The mechanics according to claim 24, wherein in forming the second recess, the second recess is formed so that the fixed electrode is supported by the sacrificial layer at one end in a plane of the active layer. Manufacturing method of quantity sensor.   25. The mechanics according to claim 24, wherein in forming the second recess, the second recess is formed so that the fixed electrode is supported by the sacrificial layer at both end portions in one direction in the plane of the active layer. Manufacturing method of quantity sensor.   A slit (220) in a portion of the fixed electrode where the surface on the side of the support layer is exposed by the second recess is made smaller in width in the direction perpendicular to the one direction in the surface of the active layer than the other portion. The method of manufacturing a mechanical quantity sensor according to claim 25 or 26, further comprising: The mechanical quantity according to any one of claims 24 to 27, further comprising forming a plurality of etching holes (216) arranged at equal intervals in the fixed electrode before forming the second recess. Sensor manufacturing method.

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