Inertia sensor

Abstract

To provide an inertia sensor having high bonding strength between a substrate and a lid body and excellent in reliability.SOLUTION: An inertia sensor, which is an electrostatic capacitance change type inertia sensor, includes: a substrate; a lid body; a function element provided between the substrate and the lid body; a metal eutectic layer that bonds between the substrate and the lid body in a junction area located around the function element; a plurality of interconnections that is connected to the function element through the junction area; and a dummy pattern provided so as to overlap with the metal eutectic layer at the same height as the interconnections in the junction area.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an inertial sensor.

Background Art

[0002] Conventionally, a sensor device including a substrate having a cavity, a sensor element suspended in the cavity, and a lid for sealing the cavity has been known. The substrate and the lid were joined via a bonding material. The bonding material was required to have high bonding strength and high long-term reliability of sealing.

[0003] For example, Patent Document 1 discloses using an AlGe eutectic as the bonding material. According to the document, the concentration of Ge in the AlGe eutectic is uniform or a function of the distance from the lid or the substrate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technology of Patent Document 1, there was a risk that the bonding strength by the bonding material would decrease. Specifically, if the concentration of Ge decreased according to the distance from the lid, AlGe eutectic formation could not be achieved on the substrate side and only the Al layer remained, which could lead to a decrease in bonding strength. Also, in the case of eutectic bonding, it was difficult to provide a eutectic bonding portion directly above the wiring due to the unevenness caused by the lead wiring from the sensor element, and there was a risk that the bonding material would protrude from the bonding region and affect the sensor element. That is, there has been a demand for an inertial sensor with high bonding strength between the substrate and the lid and excellent reliability.

Means for Solving the Problems

[0006] An inertial sensor according to one aspect of the present application is a capacitance change type inertial sensor, comprising a substrate, a lid, a functional element provided between the substrate and the lid, a metal eutectic layer that joins the substrate and the lid in a bonding region located around the functional element, a plurality of wirings that pass through the bonding region and are connected to the functional element, and a dummy pattern provided at the same height as the wiring and overlapping the metal eutectic layer in the bonding region.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

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Modes for Carrying Out the Invention

[0008] Embodiment 1 ***Configuration of the Inertial Sensor*** FIG. 1 is a plan view of the inertial sensor according to Embodiment 1. FIG. 2 is a cross-sectional view of the inertial sensor along the center line 60 of FIG. 1. The configuration of the inertial sensor 100 according to this embodiment will be described with reference to FIGS. 1 and 2.

[0009] The inertial sensor 100 is, for example, an acceleration sensor that detects acceleration in the vertical direction. In each figure, the X-axis, Y-axis, and Z-axis, which are three mutually orthogonal axes, are illustrated. In this embodiment, the Z-axis direction is defined as the vertical direction, but it is not limited thereto. The direction along the X-axis is referred to as the "X direction", the direction along the Y-axis is referred to as the "Y direction", and the direction along the Z-axis is referred to as the "Z direction". Also, the tip side of the arrow in each axis direction is also referred to as the "plus side", and the base side of the arrow is also referred to as the "minus side". For example, the Y direction refers to both the Y direction plus side and the Y direction minus side. Also, the Z direction plus side is also referred to as "up", and the Z direction minus side is also referred to as "down". Also, in the following figures, for the sake of clarity of explanation, there may be cases where the dimensions and scales are described differently from the actual ones.

[0010] The inertial sensor 100 is a uniaxial acceleration sensor composed of a MEMS (Micro Electro Mechanical Systems) device. Note that it is not limited to an acceleration sensor, and any capacitive change type inertial sensor may be used, for example, an angular velocity sensor may also be used. As shown in FIG. 2, the inertial sensor 100 includes a base 10, a sensor element 80 disposed on the base 10, a lid 30 covering the sensor element 80, and the like. The base 10 is an SOI (Silicon On Insulator) substrate, and the substrate 1, the insulating layer 2, and the semiconductor layer 3 are laminated in this order along the Z direction. The substrate 1 is a single crystal silicon substrate, and an insulating layer 2 is provided on its upper surface. The insulating layer 2 is a buried insulating layer made of SiO2.

[0011] The substrate 1 is provided with a recess 5 dug from the peripheral portion. The recess 5 is a cavity and is a part that forms a storage space S for storing the sensor element 80. Due to the recess 5, the movable body 55 (FIG. 1) of the sensor element 80 is configured to be swingable. In FIG. 2, an insulating layer 2 is provided on the bottom surface of the recess 5, but it may not be provided. The semiconductor layer 3 is, for example, a conductive silicon substrate doped with impurities such as phosphorus (P), boron (B), and arsenic (As). In a preferred example, the semiconductor layer 3 and the insulating layer 2 are joined by an Si - SiO2 fusion bond.

[0012] The sensor element 80 is a functional element and is formed by etching and patterning the semiconductor layer 3. In a preferred example, a deep etching technique using a Bosch process is used. The sensor element 80 is fixed to the substrate 1 at the fixing portion 65 (FIG. 1). The lid 30 uses a silicon substrate as a preferred example. The lid 30 is provided with a recess 35 dug from the peripheral portion. The recess 35 is a part that forms a storage space S for housing the sensor element 80. The recess 35 is provided with a stopper portion 31 which is a convex portion for restricting the over - swing of the movable body 55 of the sensor element 80. As shown in FIG. 2, the base body 10 and the lid 30 are joined by a metal eutectic layer 20 at their peripheral portions. Details of the metal eutectic layer 20 will be described later. The storage space S is, in a preferred example, filled with an inert gas such as nitrogen, helium, or argon and is hermetically sealed. It is preferably at approximately atmospheric pressure in a use temperature environment of about - 40°C to 120°C.

[0013] ***Configuration of Sensor Element*** As shown in FIG. 1, the sensor element 80 as a functional element is an acceleration sensor that detects acceleration in the Z direction, and adopts a so - called single - sided seesaw structure in which the movable body 55 swings about the swing axis 61. The sensor element 80 includes a fixing portion 65, a movable body 55 that can swing around a swing axis 61 along the Y - axis passing through the center of the fixing portion 65, a first rotational spring 54a, a second rotational spring 54b, etc. that connect the fixing portion 65 and the movable body 55. The fixing portion 65 is fixed to a pedestal portion (not shown) protruding from the substrate 1 (FIG. 2). The periphery of the pedestal portion is a recess 5 (FIG. 2), and the movable body 55 can swing. In FIG. 1, a line segment that is orthogonal to the swing axis 61 and passes through the center of the sensor element 80 along the X - axis is defined as the center line 60.

[0014] The movable body 55 includes a first bar 52a extending in the X plus direction from the first rotational spring 54a, a second bar 52b extending in the X plus direction from the second rotational spring 54b, and a third bar 53 connecting the first bar 52a and the second bar 52b. Four comb-shaped movable electrode groups 73a to 73d are provided on the third bar 53. The movable electrode group 73a is composed of six movable electrodes 71c extending in the X plus direction from the third bar 53 on the Y minus side of the center line 60. The movable electrode group 73b is composed of six movable electrodes 71c extending in the X minus direction from the third bar 53 on the Y minus side of the center line 60. Note that the number is not limited to six, and any plural number of movable electrodes 71c may be used. The movable electrode groups 73c and 73d are provided at positions that are line-symmetrical to the movable electrode groups 73a and 73b on the Y plus side with the center line 60 as the axis of symmetry.

[0015] On the substrate 1 (Figure 2) side, fixed electrode groups 74a to 74d facing the movable electrode groups 73a to 73d are provided. The fixed electrode group 74a is composed of a support portion 75a fixed to the substrate 1 and seven fixed electrodes 72 extending in the X minus direction from the support portion 75a. The fixed electrode group 74b is composed of a support portion 75b fixed to the substrate 1 and seven fixed electrodes 72 extending in the X plus direction from the support portion 75b. Note that the number is not limited to seven, and any number corresponding to the number of movable electrodes 71c may be used. The fixed electrode groups 74c and 74d are provided at positions that are line-symmetrical to the fixed electrode groups 74a and 74b on the Y plus side with the center line 60 as the axis of symmetry.

[0016] The detection units formed by the fixed electrode group 74a and the movable electrode group 73a, and the detection units formed by the fixed electrode group 74b and the movable electrode group 73b are combined and referred to as the N-type detection unit 76n. In the N-type detection unit 76n, a parallel-plate capacitor is formed by the fixedly disposed fixed electrode 72 and the movable electrode 71c which are arranged opposite to each other. This capacitor changes in accordance with the change in the overlapping area between the fixed electrode 72 and the movable electrode 71c as the displacement of the movable electrode 71c due to acceleration occurs. Similarly, the detection units formed by the fixed electrode group 74c and the movable electrode group 73c, and the detection units formed by the fixed electrode group 74d and the movable electrode group 73d are combined to form the P-type detection unit 76p. In the P-type detection unit 76p, a parallel-plate capacitor is formed by the fixedly disposed fixed electrode 72c and the movable electrode 71 which are arranged opposite to each other. This capacitor changes in accordance with the change in the overlapping area between the fixed electrode 72c and the movable electrode 71 as the displacement of the movable electrode 71 due to acceleration occurs.

[0017] The movable electrode 71c of the N-type detection unit 76n is thinner in the Z direction than the movable electrode 71 of the P-type detection unit 76p. Specifically, the movable electrode 71c is thinner due to being notched stepwise in the middle of the extending direction from the same thickness as the base third bar 53. As a result, in all 12 movable electrodes 71c, the thickness on the Z plus side is thinner at the portion facing the fixed electrode 72. The fixed electrode 72c of the P-type detection unit 76p is thinner in the Z direction than the fixed electrode 72 of the N-type detection unit 76n. Specifically, the fixed electrode 72c is thinner due to being notched stepwise in the middle of the extending direction from the thickness at the base on the support part 75c, 75d side. As a result, in all 14 fixed electrodes 72c, the thickness on the Z plus side is thinner at the portion facing the movable electrode 71.

[0018] With such a configuration, when acceleration occurs in the Z plus direction, the overlapping area decreases in the N-type detection unit 76n, and the overlapping area is maintained in the P-type detection unit 76p. Also, when acceleration occurs in the Z minus direction, the overlapping area is maintained in the N-type detection unit 76n, and the overlapping area decreases in the P-type detection unit 76p. Based on such a correlation, in the sensor element 80, by differentially detecting the change in the overlapping area in the N-type detection unit 76n and the P-type detection unit 76p as a capacitance change, the acceleration in the Z plus / minus direction can be detected.

[0019] ***Configuration of the bonding region*** As shown in FIG. 1, the base body 10 has a substantially rectangular shape, and the short side in the minus X direction is an overhanging portion 11 that protrudes from the short side of the lid body 30. Terminals 91 to 94 for external connection are provided on the overhanging portion 11. The terminal 91 is a movable electrode terminal and is electrically connected to all the movable electrodes 71 and 71c by the wiring 81. The terminal 92 is an N-type fixed electrode terminal and is electrically connected to all the fixed electrodes 72 of the N-type detection unit 76n by the wiring 82. The terminal 93 is a P-type fixed electrode terminal and is electrically connected to all the fixed electrodes 72c of the P-type detection unit 76p by the wiring 83. The terminal 94 is a GND terminal and is electrically connected to the metal eutectic layer 20 by the wiring 84. The details of the connection form between the terminal 94 and the metal eutectic layer 20 will be described later.

[0020] The base body 10 and the lid body 30 are joined in a square annular bonding region 20a that surrounds the periphery of the sensor element 80. The bonding region 20a is a square annular region that is slightly smaller than the outer peripheral edge of the lid body 30. A metal eutectic layer 20 is formed in the bonding region 20a. Further, the metal eutectic layer 20 is formed so as to intersect the wirings 81 to 83 in a plan view. In other words, the capacitance change type inertial sensor 100 includes a base body 10, a lid body 30, a sensor element 80 as a functional element provided between the base body 10 and the lid body 30, and a metal eutectic layer 20 that joins the base body 10 and the lid body 30 around the sensor element 80.

[0021] A first dummy pattern 40 is provided below the metal eutectic layer 20. The first dummy pattern 40 is a wiring layer formed by the same process as the wirings 81 to 84, and is provided in a square annular shape along the bonding region 20a. Among the bonding regions 20a, the portions through which the wirings 81 to 83 pass are separated, and the first dummy pattern 40 and each wiring are electrically insulated from each other. The first dummy pattern 40 is formed as an island pattern at the portion where the wiring is separated. For example, between the wiring 81 and the wiring 82, an island-shaped first dummy pattern 40a is provided. Similarly, between the wiring 82 and the wiring 83, an island-shaped first dummy pattern 40b is provided. In other words, the first dummy pattern 40 is insulated from the plurality of wirings 81 to 83, and the first dummy pattern 40 is provided between the plurality of wirings 81 to 83 in a planar manner. Further, the plurality of wirings 81 to 83 pass through the bonding region 20a and are connected to the sensor element 80. When not distinguishing the island patterns, the first dummy pattern 40 including the first dummy patterns 40a and 40b is referred to as the first dummy pattern 40.

[0022] Also, on the inner peripheral side of the first dummy pattern 40, a second dummy pattern 41 having a square annular shape that is slightly smaller than the first dummy pattern 40 is provided. Similar to the first dummy pattern 40, the second dummy pattern 41 is a wiring layer formed by the same process as the wirings 81 to 84. The portions through which the wirings 81 to 83 pass are separated, and the second dummy pattern 41 and each wiring are electrically insulated from each other. An island-shaped second dummy pattern 41a is provided between the wiring 81 and the wiring 82, and an island-shaped second dummy pattern 41b is provided between the wiring 82 and the wiring 83. When not distinguishing the island patterns, the second dummy pattern 41 including the second dummy patterns 41a and 41b is referred to as the second dummy pattern 41. Note that a similar square annular dummy pattern may also be provided on the outer peripheral side of the first dummy pattern 40. In other words, the first dummy pattern 40 may further include an nth dummy pattern different from the first dummy pattern 40 on the inner peripheral side, or the outer peripheral side, or both sides thereof.

[0023] FIG. 3 is a cross-sectional view of the main parts of the base body and the lid before bonding, and corresponds to FIG. 2. As shown in FIG. 3, before the formation of the metal eutectic layer 20, a first joint portion 15 is provided on the base body 10, and a second joint portion 16 is provided on the lid 30. The first joint portion 15 is an AlCu layer as the first metal layer. The first joint portion 15 is formed, for example, by film formation using a DC sputtering method and then patterning. Note that the first joint portion 15 is also referred to as the first metal layer 15. Cu in the AlCu layer is mixed for the purpose of preventing electromigration and the content rate is low. Therefore, the main component of the first joint portion 15 is Al.

[0024] The second joint portion 16 is a Ge layer as the second metal. In the present embodiment, the second joint portion 16 made of Ge is directly formed on the silicon substrate constituting the lid body 30. In a preferred example, after forming a Ge layer using a DC sputtering method, patterning is performed to form the second joint portion 16. The second joint portion 16 is also referred to as the second metal layer 16. In other words, the main component of the first metal layer is Al, and the main component of the second metal layer is Ge.

[0025] The first joint portion 15 and the second joint portion 16 are joined by a heating process and a pressing process. Specifically, a laminate in which the base body 10 and the lid body 30 are overlapped is heated to a temperature equal to or higher than the eutectic temperature of the first metal layer 15 and the second metal layer 16, and further, eutectic bonding is performed by applying pressure in the heated state. Note that the eutectic temperature of AlGe is about 420°C. In a preferred example, with the base body 10 at the bottom, the laminate is set on the stage of a heating jig, and when the laminate reaches a predetermined temperature, a load is applied from the lid body 30 side by a pressing jig for a predetermined time. At this time, the pressing jig is also heated. Eutectic generally refers to an alloy formed by solidification from a liquid phase state in which two or more kinds of metals are mixed.

[0026] FIG. 4 is an enlarged view of part b in FIG. 2 and shows the state of the metal eutectic layer 20 after joining. When joining the first joint portion 15 and the second joint portion 16, the joining material softens and melts due to the application of heating and pressure, and a part of it is crushed and oozes out. Figure 4 shows this state. Although the end of the metal eutectic layer 20 on the sensor element 80 side protrudes, it can be seen that the second dummy pattern 41b serves as a dike and fits into the recess 19. The recess 19 is a groove-shaped depression formed in the upper insulating layer 8 between the first dummy pattern 40b and the second dummy pattern 41b. The recess 19 is formed in a square ring shape between the first dummy pattern 40 and the second dummy pattern 41 in a planar view. In this way, the second dummy pattern 41b functions as a dike to prevent the protrusion of the metal eutectic layer 20 and prevent it from entering the sensor element 80 side.

[0027] Figure 5 is a cross-sectional view taken along the c-c section of Figure 1. Figure 5 is a cross-sectional view of the terminal 94 which is a GND terminal and its wiring 84, corresponding to Figure 4. As shown in Figure 1, the terminal 94 is connected to the first dummy pattern 40 by the wiring 84. And as shown in Figure 5, a contact portion 18 is provided in a part of the insulating layer 8 above the first dummy pattern 40. The contact portion 18 is a contact hole. When joining, a part of the metal eutectic layer 20 is filled into the contact portion 18 which is an opening, so that the first dummy pattern 40 and the metal eutectic layer 20 are electrically connected. In other words, the GND potential is applied to the first dummy pattern 40 as the first potential. The first dummy pattern 40 is electrically connected to the metal eutectic layer 20, and the first potential is applied to the lid 30 via the metal eutectic layer 20.

[0028] Figure 6 is a cross-sectional view taken along the d-d section of Figure 1. Figure 6 is a cross-sectional view in the extending direction in the Y direction of the bonding region 20a, and the wiring 82 is observed between the first dummy pattern 40a and the first dummy pattern 40b. Here, although there are slight depressions between the insulating layer 8 on the wiring 82 and the first dummy pattern 40a and between the insulating layer 8 and the first dummy pattern 40b, the distance between the wiring 82 and the first dummy patterns 40a and 40b is narrow, and the thicknesses of the three are the same. Therefore, overall, it is substantially flat and there is no problem in forming the metal eutectic layer 20. In other words, the first dummy pattern 40 as a dummy pattern is provided on the metal eutectic layer 20 at the same height as the wirings 81 to 84 in the bonding region 20a.

[0029] ***Configuration of Metal Eutectic Layer*** FIG. 7 is a cross-sectional view showing the cross-section of FIG. 4 in terms of layer configuration. As shown in FIG. 7, on the substrate 10, an insulating layer 6, a wiring layer 7 including a first dummy pattern 40, an insulating layer 8, a metal eutectic layer 20, and a lid 30 are laminated in this order.

[0030] The insulating layer 6 is an interlayer insulating layer, and in a preferred example, it is a SiO2 layer. Note that the insulating layer 6 may be a SiN layer. The wiring layer 7 is formed of a plurality of layers. For example, it has a four-layer structure laminated in the order of Ti, TiN, AlCu, and TiN from the bottom, or a two-layer structure laminated in the order of TiN and AiCu. Note that the first dummy pattern 40, the second dummy pattern 41, and the wirings 81 to 84 are also included in the wiring layer 7, and these are formed in the same process. The insulating layer 8 is an insulating layer, and in a preferred example, it is a SiO2 layer. Note that the insulating layer 8 may be a SiN layer. In other words, in the bonding region 20a, the insulating layer 8 is provided on the plurality of wirings 81 to 84, the first dummy pattern 40, and the second dummy pattern 41.

[0031] The metal eutectic layer 20 shown in FIG. 7 is a faithful trace of the microscopic photograph of the eutectic layer. As a result of elemental analysis, as shown in FIG. 7, the metal eutectic layer 20 is formed in a state where a first region 21 mainly composed of AlCu, which is the first metal, and a second region 22 mainly composed of Ge, which is the second metal, are adjacent to each other. The content ratio of the first metal in the first region 21 is higher than the content of the first metal in the second region 22. The content ratio of the second metal in the second region 22 is higher than the content of the second metal in the first region 21. The second region 22 extends widely along the lid body 30, but a part of it reaches the boundary with the base body 10. For example, in FIG. 6, the extending portions 22a and 22b reach the base body 10. The boundary between the first region 21 and the second region 22 has a lot of entry and exit and is complicatedly intertwined. Also, in the portion where the second region 22 extends, the second region 22 is more than the first region 21.

[0032] The distribution of Ge in the metal eutectic layer 20 is not uniform, and it exists relatively more in the second region 22, and is uniform and has no concentration gradient within that region. However, Ge also exists uniformly in the first region 21 although in a small amount. The first region 21 and the second region 22 are in contact with each other without gaps, and the contact area is larger than the planar area of the bonding region 20a. That is, the first region 21 and the second region 22 are randomly interlocked, and the bonding strength is very high. In other words, the contact area between the first region 21 and the second region 22 is larger than the area of the bonding region 20a where the base body 10 and the lid body 30 are bonded by the metal eutectic layer 20.

[0033] Generally, it is known that Ge has a diamond structure and Al has a face-centered cubic lattice structure. If Ge is more as the main component of the eutectic layer, a solid solution of the diamond structure is formed, and if Al is more, a solid solution of the face-centered cubic lattice structure is formed. A solid solution refers to a substance in which two elements are melted together and the whole becomes a solid phase with a relatively uniform concentration. However, each solid solution has a different component ratio within the solid solubility limit. That is, in the second region 22 with a high Ge content, a solid solution of a diamond structure is realized, and in the first region 21 with a high Al content, a solid solution of a face-centered cubic lattice structure is realized. When cutting the crystal to cut out the surface, the surface energy serves as a guide. When comparing Ge and Al in terms of the surface energy per unit area, it is known that Ge is higher in any plane orientation. In other words, the metal eutectic layer 20 has a plurality of first regions 21 mainly composed of the first metal and having a face-centered cubic lattice structure, and second regions 22 mainly composed of the second metal and having a diamond structure, and they are adjacent to each other.

[0034] As shown in FIG. 7, a part of the second region 22 reaches the boundary with the substrate 10. And the second region 22 extends from the lid body 30 to the substrate 10. In other words, the second region 22 reaches the boundary with the substrate 10. That is, the second region 22 reaches the substrate 10 regardless of the distance from the lid body 30. At the same time, the second region 22 with a high Ge content contains Al within a range not exceeding the solid solubility limit for Ge. And the component ratio of Ge and Al in the second region 22 is relatively uniform and does not depend on the distance from the lid body 30. From the perspective of surface energy, it is better that the second region 22 with a high Ge content reaches the boundary with the substrate 10 in terms of joint strength. More preferably, it is better that there are more portions where the second region 22 with a high Ge content extends from the lid body 30 to the substrate 10. On the other hand, at the boundary between the lid body 30 and the metal eutectic layer 20 in FIG. 7, since the second joint portion 16 made of Ge is directly formed on the lid body 30 (FIG. 3), Ge diffuses into the silicon which is the lid body 30. That is, the second region 22 mainly composed of Ge forms a fine uneven shape at the boundary portion with the lid body 30 (the dotted line in FIG. 7), increasing the contact area and thus increasing the joint strength.

[0035] Also, in the above description, the sensor element 80 was described as a Z-direction acceleration sensor, but it is not limited to this, and any electronic component that requires an airtight environment is acceptable. For example, it can also be a MEMS device such as an angular velocity sensor, or a timing device such as a crystal oscillator or a ceramic oscillator.

[0036] As described above, according to the inertial sensor 100 of the present embodiment, the following effects can be obtained. The inertial sensor 100 is a capacitance change type inertial sensor, and includes a base body 10, a lid body 30, a sensor element 80 as a functional element provided between the base body 10 and the lid body 30, a metal eutectic layer 20 that joins the base body 10 and the lid body 30 around the sensor element 80, a plurality of wirings 81 to 83 that connect to the sensor element 80 through a joining region 20a, and a first dummy pattern 40 that is provided to overlap the metal eutectic layer 20 at the same height as the wirings 81 to 83 in the joining region 20a.

[0037] According to this, the metal eutectic layer 20 is formed on the first dummy pattern 40 and the wirings 81 to 83. Since the first dummy pattern 40 has the same height as the wirings 81 to 83, the unevenness caused by the plurality of wirings is alleviated, and the height of the joining region 20a becomes substantially constant, making it easier to form the metal eutectic layer 20. And since the base body 10 and the lid body 30 are joined by the metal eutectic layer 20 in which the first region 21 having a face-centered cubic lattice structure and the second region 22 having a diamond structure are randomly interlocked, a high joining strength can be obtained. Therefore, it is possible to provide an inertial sensor 100 having a high joining strength between the base body 10 and the lid body 30 and excellent long-term reliability.

[0038] Further, the first dummy pattern 40 is insulated from the plurality of wirings 81 to 83, and the first dummy pattern 40 is provided planar between the plurality of wirings 81 to 83. According to this, while ensuring necessary electrical connections, the height of the joining region 20a where the metal eutectic layer 20 is formed can be made substantially uniform.

[0039] Also, in the joining region 20a, an insulating layer 8 is provided on the plurality of wirings 81 to 84, and the first dummy pattern 40 and the second dummy pattern 41. According to this, since the insulating layer 8 covers the gaps between the first dummy pattern 40, the second dummy pattern 41 and each wiring to fill the gap portions, the unevenness is alleviated and the height of the bonding region 20a can be made more uniform.

[0040] Further, the first dummy pattern 40 may further include an nth dummy pattern different from the first dummy pattern 40 on the inner peripheral side, the outer peripheral side, or both of them. According to this, for example, when the second dummy pattern 41 is provided on the inner peripheral side of the first dummy pattern 40, the second dummy pattern 41b functions as a dike to prevent the overhang of the metal eutectic layer 20 and can prevent the intrusion into the sensor element 80 side. Therefore, the intended performance can be obtained without inhibiting the operation of the sensor element 80, and the reliability can be ensured.

[0041] Further, a GND potential is applied to the first dummy pattern 40 as a first potential, the first dummy pattern 40 is electrically connected to the metal eutectic layer 20, and the first potential is applied to the lid 30 via the metal eutectic layer 20. According to this, since the lid 30 becomes a power supply potential and is electrically stabilized, it is less likely to be affected by noise, the operation of the sensor element 80 can be stabilized, and the reliability can be ensured.

[0042] Further, the metal eutectic layer 20 includes a plurality of first regions 21 mainly composed of a first metal and having a face-centered cubic lattice structure and second regions 22 mainly composed of a second metal and having a diamond structure, and they are adjacent to each other.

[0043] According to this, since the base body 10 and the lid 30 are joined by the metal eutectic layer 20 in which the first region 21 having a face-centered cubic lattice structure and the second region 22 having a diamond structure are randomly interlocked, a high bonding strength can be obtained. Further, since AlGe eutectification is performed throughout the bonding region 20a, it has excellent reliability. Therefore, it is possible to provide an inertial sensor 100 having a high bonding strength between the base body 10 and the lid 30 and excellent reliability.

[0044] Also, the second region 22 has reached the boundary with the substrate 10. According to this, since the second region 22 with a large amount of Ge has reached the boundary with the substrate 10, the bonding strength in the bonding region 20a is increased.

[0045] Also, the second region 22 extends from the lid 30 to the substrate 10. According to this, the bonding strength in the bonding region 20a is further increased.

[0046] Also, in the portion where the second region 22 extends, the second region 22 has more than the first region 21. According to this, since there are many extending portions of the second region 22 with a large amount of Ge, the bonding strength in the bonding region 20a is increased.

[0047] Also, the contact area between the first region 21 and the second region 22 is larger than the area of the bonding region 20a where the substrate 10 and the lid 30 are bonded by the metal eutectic layer 20. According to this, since the first region 21 and the second region 22 are engaged randomly with a wide contact area, their bonding strength is very high.

[0048] Also, the first metal is Al and the second metal is Ge. According to this, a metal eutectic layer 20 with high bonding strength can be formed.

[0049] Embodiment 2 *** Different aspects of the inertial sensor ***

[0050] FIG. 8 is a plan view of the inertial sensor according to Embodiment 2, corresponding to FIG. 1. In the above embodiment, the inertial sensor 100 has been described as housing one sensor element 80, but it is not limited to this, and it may also house a plurality of sensor elements. Hereinafter, the same parts as those in the above embodiment are given the same reference numerals, and redundant explanations are omitted.

[0051] As shown in FIG. 8, in addition to the sensor element 80 described above, the inertial sensor 110 of the present embodiment includes a sensor element 85 and a sensor element 86. The sensor element 85 is a capacitance change type acceleration sensor that detects acceleration in the Y direction. The sensor element 86 is a capacitance change type acceleration sensor that detects acceleration in the X direction. That is, the inertial sensor 110 is a three-axis acceleration sensor capable of detecting acceleration in three axes of the XYZ directions. Similar to the inertial sensor 100, the inertial sensor 110 has a configuration in which the base 10 and the lid 30 are joined by the metal eutectic layer 20 in the joining region 20a, and has an accommodation space S inside. In the accommodation space S, three sensor elements 80, 85, and 86 are accommodated in a state where they can detect oscillations.

[0052] External connection terminals 42 to 49 are provided on the overhanging portion 11 of the base 10. The terminal 42 is a movable electrode terminal and is electrically connected to the movable electrodes of all the sensor elements 80, 85, and 86 by the wiring 142. Note that illustration of the wiring mode of the wiring 142 in the accommodation space S is omitted. The same applies to the other wirings 144 to 149. The terminal 43 is a GND terminal and is electrically connected to the metal eutectic layer 20 by the wiring 143 and the contact portion 18. The terminal 44 is the first fixed electrode terminal of the sensor element 86 and is electrically connected to the first fixed electrode of the sensor element 86 by the wiring 144. The terminal 45 is the second fixed electrode terminal of the sensor element 86 and is electrically connected to the second fixed electrode of the sensor element 86 by the wiring 145.

[0053] The terminal 46 is the first fixed electrode terminal of the sensor element 85 and is electrically connected to the first fixed electrode of the sensor element 85 by the wiring 146. The terminal 47 is the second fixed electrode terminal of the sensor element 85 and is electrically connected to the second fixed electrode of the sensor element 85 by the wiring 147. Terminal 48 is the first fixed electrode terminal of the sensor element 80 and is electrically connected to the first fixed electrode of the sensor element 80 by wiring 148. Terminal 49 is the second fixed electrode terminal of the sensor element 80 and is electrically connected to the second fixed electrode of the sensor element 80 by wiring 149.

[0054] The first dummy pattern 40 includes first dummy pattern islands 40c to 40h which are a plurality of island-shaped parts. Similarly, the second dummy pattern 41 includes second dummy pattern islands 41c to 41g which are a plurality of island-shaped parts. The wirings 144 to 149 pass between these island-shaped parts in a crank shape and enter the storage space S. The wiring 142 extends in the X plus direction, then bends in the Y plus direction, extends along the first dummy pattern 40, then bends in the X plus direction and enters the storage space S. Here, the portion extending along the first dummy pattern 40 can exhibit a dike effect similar to that of the second dummy pattern 41.

[0055] The wiring 144 extends in the X plus direction, then bends in the Y minus direction, extends along the first dummy pattern 40, then bends in the X plus direction and enters the storage space S. Similarly, the wirings 145 to 147 also extend in the X plus direction, then bend in the Y minus direction, extend along the first dummy pattern 40, then bend in the X plus direction and enter the storage space S. The wiring 148 extends in the X plus direction, then bends in the Y plus direction, extends along the first dummy pattern 40, then bends in the X plus direction and enters the storage space S. The wiring 149 extends in the X plus direction, then bends in the Y minus direction, extends along the first dummy pattern 40, then bends in the X plus direction and enters the storage space S.

[0056] Thus, the wiring 142, wirings 144 to 149 each have a bent portion bent in a crank shape and an extending portion extending along the first dummy pattern 40, and this extending portion functions as a dike that prevents the metal eutectic layer 20 from protruding into the storage space S. In other words, the wiring 142, wirings 144 to 149 have a bent portion and an extending portion extending along the first dummy pattern 40.

[0057] FIG. 9 is a partially enlarged view of the plan view of FIG. 8 and is an enlarged view of the peripheral portion of the terminal 43. As shown in FIG. 9, an extension portion 142b branched in the +Y direction and an extension portion 142c branched in the -Y direction are provided in the extending portion of the wiring 142. Thereby, the extending portion of the wiring 142 along the first dummy pattern 40 becomes longer by the added lengths of the extension portions 142b and 142c. Similarly, an extension portion 144c branched in the -Y direction is provided in the extending portion of the wiring 144. Thereby, the extending portion of the wiring 144 along the first dummy pattern 40 becomes longer by the added length of the extension portion 144c.

[0058] An extension portion 145b branched in the +Y direction and an extension portion 145c branched in the -Y direction are provided in the extending portion of the wiring 145. Thereby, the extending portion of the wiring 145 along the first dummy pattern 40 becomes longer by the added lengths of the extension portions 145b and 145c. Although the wirings 146 to 149 are not shown in FIG. 9, the extending portions are extended in the same manner as the above-described wirings. By adding the extension portions to the extending portions of the wiring in this way, a longer dike wiring along the first dummy pattern 40 is formed, so that the metal eutectic layer 20 can be prevented from protruding into the storage space S.

[0059] Embodiment 3 *** Different aspects of the lid *** FIG. 10 is a cross-sectional view of the main part of the lid according to Embodiment 3 and corresponds to FIG. 3. In the above embodiment, it has been described that the structure for preventing the protrusion of the metal eutectic layer 20 is provided on the substrate 10 side, but the structure for preventing the protrusion of the metal eutectic layer 20 may be provided on the lid body 30 side. Hereinafter, the same parts as those in the above embodiment are given the same reference numerals, and redundant descriptions are omitted.

[0060] FIG. 10 is an enlarged view of the periphery of the bonding region 20a in the lid body 30 before bonding. In the lid body 33 of the present embodiment, a recess 25 is provided along the bonding region 20a. The recess 25 is a groove with a flat bottom surface. Before bonding, as shown in FIG. 10, the second bonding portion 16 is formed in the recess 25. When the second bonding portion 16 is bonded to the first bonding portion 15 to form the metal eutectic layer 20, it functions to absorb the protruding portion of the metal eutectic layer 20 into the recess 25 and prevent the lateral outflow. In other words, the lid body 33 is provided with a recess 25 along the bonding region 20a. The lid body 33 can be applied in place of the lid body 30 of the above-described inertial sensors 100 and 110. By using the lid body 33, the dike effect can be further enhanced.

[0061] Embodiment 4 ***Application to Inertial Measurement Device*** FIG. 11 is an exploded perspective view of the inertial measurement device. FIG. 12 is a perspective view of the substrate. In the inertial measurement device 2000 of the present embodiment shown in FIG. 11, an inertial sensor 110 is mounted. The inertial measurement device 2000 is a rectangular parallelepiped having a substantially square planar shape. The inertial measurement device 2000 is an inertial measurement sensor unit (IMU: Inertial Measurement Unit) that detects the posture and behavior of a mounted object such as an automobile or a robot. The inertial measurement device 2000 functions as a so-called six-axis motion sensor including a three-axis acceleration sensor and a three-axis angular velocity sensor.

[0062] The inertial measurement device 2000 includes an outer case 301, a bonding member 310, and a sensor module 325 on which the inertial sensor 110 is mounted. The outer shape of the outer case 301 is a rectangular parallelepiped with a substantially square planar shape, similar to the overall shape of the inertial measurement device 2000. Thread holes 302 are formed near two vertices located in the diagonal direction of the square. By passing two screws through these two thread holes 302, the inertial measurement device 2000 can be fixed to the mounting surface of a mounted object such as an automobile.

[0063] Also, the outer case 301 is box-shaped, and a sensor module 325 is housed inside it. Specifically, the sensor module 325 is inserted inside the outer case 301 with a joining member 310 interposed therebetween.

[0064] The sensor module 325 has an inner case 320 and a substrate 315. The inner case 320 is a member that supports the substrate 315, and the substrate 315 is joined to the lower surface of the inner case 320 via an adhesive.

[0065] Also, the inner case 320 is shaped to fit inside the outer case 301. Recesses 331 for preventing contact with the substrate 315 and openings 321 for exposing connectors 316 (described later) are formed in the inner case 320. The inner case 320 is joined to the outer case 301 via the joining member 310.

[0066] Next, the substrate 315 on which the inertial sensor 110 is mounted will be described. As shown in FIG. 12, an inertial sensor 110, a connector 316, an angular velocity sensor 317z for detecting the angular velocity about the Z axis, etc. are mounted on the surface of the substrate 315 on the side of the inner case 320, which is the upper surface. Angular velocity sensors 317x for detecting the angular velocity about the X axis and 317y for detecting the angular velocity about the Y axis are mounted on the side surface of the substrate 315. Note that an inertial sensor 100 may be mounted instead of the inertial sensor 110.

[0067] Also, a control IC 319 as a control unit is mounted on the surface of the outer case 301 side, which is the lower surface of the substrate 315. The control IC 319 is an MCU (Micro Controller Unit), which incorporates a storage unit including a non-volatile memory, an A / D converter, etc., and controls each part of the inertial measurement device 2000. The storage unit stores a program that defines the order and content for detecting acceleration and angular velocity, a program that digitizes the detection data and incorporates it into packet data, and accompanying data. In addition, a plurality of other electronic components are mounted on the substrate 315.

[0068] According to such an inertial measurement device 2000, since the inertial sensor 110 is used, it is possible to provide an inertial measurement device 2000 with excellent reliability that enjoys the effects according to the above embodiment.

Description of Reference Numerals

[0069] 1… Substrate, 2… Insulating layer, 3… Semiconductor layer, 5… Recess, 6… Insulating layer, 7… Wiring layer, 8… Insulating layer, 10… Substrate body, 11… Protrusion, 15… First joint (first metal layer), 16… Second joint (second metal layer), 18… Contact portion, 19… Recess, 20… Metal eutectic layer, 20a… Joint region, 21… First region, 22… Second region, 22a… Extension portion, 22b… Extension portion, 25… Recess, 30… Cover, 31… Stopper portion, 33… Cover, 35… Recess, 40… First dummy pattern, 40c~40h… First dummy pattern, 41… Second dummy pattern, 41b,41b… Second dummy pattern, 42~49… Terminals, 52a… First bar, 52b… Second bar, 53… Third bar, 54a… First rotary spring, 54b… Second rotary spring, 55… Movable body, 60… Center line, 61… Oscillation axis, 65… Fixed portion, 71,71c… Movable electrodes, 72,72c… Fixed electrodes, 73a~73d… Movable electrode groups, 74a~74d… Fixed electrode groups, 75a… Support portion, 75b… Support portion, 75c… Support portion, 75a… Support portion, 76n… N-type detection portion, 76p… P-type detection portion, 80… Sensor element, 81~84… Wiring, 85… Sensor element, 86… Sensor element, 91~94… Terminals, 100… Inertial sensor, 110… Inertial sensor, 142… Wiring, 142b… Extension portion, 142c… Extension portion, 143… Wiring, 144… Wiring, 144b… Extension portion, 145… Wiring, 145b… Extension portion, 145c… Extension portion, 146~149… Wiring, 301… Outer case, 302… Screw hole, 310… Joint member, 315… Substrate, 316… Connector, 317x… Angular velocity sensor, 317y… Angular velocity sensor, 317z… Angular velocity sensor, 320… Inner case, 321… Opening, 325… Sensor module, 331… Recess, 2000… Inertial measurement device.

Claims

1. A capacitance change type inertial sensor, comprising: a substrate; a lid; a functional element provided between the substrate and the lid; a metal eutectic layer that joins the substrate and the lid in a bonding region located around the functional element; a plurality of wirings that pass through the bonding region and are connected to the functional element; a dummy pattern provided to overlap the metal eutectic layer at the same height as the wirings in the bonding region;[[ / END]] an inertial sensor.

2. The dummy pattern is insulated from the plurality of wirings, The dummy pattern is provided planar between the plurality of wirings, The inertial sensor according to claim 1.

3. In the bonding region, an insulating layer is provided over the plurality of wirings and the dummy pattern, The inertial sensor according to claim 2.

4. When the dummy pattern is a first dummy pattern, a n-th dummy pattern different from the first dummy pattern is further provided on the inner peripheral side, or the outer peripheral side, or both sides of the first dummy pattern, The inertial sensor according to claim 3.

5. A first potential is applied to the dummy pattern, The dummy pattern is electrically connected to the metal eutectic layer, The first potential is applied to the lid through the metal eutectic layer, The inertial sensor according to claim 3.

6. The wiring has a bent portion and an extending portion that extends along the dummy pattern, The inertial sensor according to claim 3.

7. A recess is provided in the lid along the bonding region, The inertial sensor according to claim 5.

8. The metal eutectic layer has a plurality of first regions mainly composed of a first metal and having a face-centered cubic lattice structure, and a plurality of second regions mainly composed of a second metal and having a diamond structure, and the first regions and the second regions are adjacent to each other, The inertial sensor according to claim 4.

9. The second region reaches the boundary with the substrate, The inertial sensor according to claim 8.

10. The second region extends from the lid to the substrate, The inertial sensor according to claim 9.

11. In the portion where the second region extends, there is more of the second region than the first region, The inertial sensor according to claim 10.

12. The contact area between the first region and the second region is larger than the area of the bonding region where the substrate and the lid are joined by the metal eutectic layer, The inertial sensor according to claim 11.

13. wherein the first metal is Al and the second metal is Ge, The inertial sensor according to claim 12.

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