Transducer

Abstract

The invention provides a transducer which can be reliably bonded in a bonding region and has high reliability. The transducer includes: a first substrate; a second substrate disposed so as to overlap the first substrate and having an insulating layer provided on the surface thereof; the functional element is arranged between the first substrate and the second substrate; and a metal eutectic layer that bonds the first substrate and the second substrate in a bonding region located around the functional element, in which a recess is provided in a first surface of the second substrate on the first substrate side, the recess being configured from a second surface serving as a bottom and a side wall connecting the first surface and the second surface, the insulating layer includes a first portion provided on the first surface, second portions provided on the side walls, and a third portion provided on the second surface, and the bonding region is disposed between the second portions when viewed in plan from a Y-axis direction along the Y-axis.

Description

TECHNICAL FIELD

[0001] The present application relates to a transducer. BACKGROUND

[0002] In the past, a sensor device provided with a base having a cavity, a sensor element suspended in the cavity, and a lid sealing the cavity is known. The base and the lid are joined via a joining material. For the joining material, high joining strength and high long-term reliability of the seal are required.

[0003] For example, in Patent Document 1, an inertial sensor using AlGe eutectic as a joining material is disclosed. According to the document, the concentration of Ge in the AlGe eutectic is uniform, or is a function of the distance from the lid or the base. In particular, it is disclosed that in the case where a long-time heat treatment is performed, the concentration of Ge becomes uniform.

[0004] Patent Document 1: U.S. Patent Application Publication No. 2010 / 0059835

[0005] However, in the technology of Patent Document 1, due to the heat treatment at the time of forming the joining material based on the AlGe eutectic, the joining material can possibly spread from the joining region, or the joining material can fly. In particular, if the AlGe eutectic flies due to the long-time heat treatment, it can possibly cause malfunction of the inertial sensor. The inertial sensor is an example of a transducer.

[0006] That is, a transducer capable of being reliably joined in a joining region and having high reliability is required. SUMMARY

[0007] A transducer of one embodiment of the present application includes a first substrate, a second substrate, a functional element provided between the first substrate and the second substrate, and a metal eutectic layer joining the first substrate and the second substrate in a joining region around the functional element, a recess is provided in a first surface of the second substrate which is opposed to the first substrate, the recess has a second surface as a bottom and a side wall connecting the first surface and the second surface, the transducer includes an insulating layer having a first portion provided in the first surface, a second portion provided in the side wall, and a third portion provided in the second surface, and the insulating layer is provided across the joining region. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a plan view of the transducer of Embodiment 1.

[0009] Figure 2 is a cross-sectional view of the transducer of Embodiment 1 taken along b-b of Figure 1

[0010] ​Figure 3 is an enlarged view of the c portion of Figure 2

[0011] Figure 4 is an enlarged view of the d portion of Figure 2

[0012] Figure 5 is a main portion cross-sectional view of the base and the lid before joining.

[0013] Figure 6 is a perspective view showing a main portion of the electrical wiring structure of the metal eutectic layer.

[0014] Figure 7 is a flowchart showing the flow of the manufacturing method of the lid.

[0015] Figure 8 is a cross-sectional view showing a main portion of one embodiment of the manufacturing process.

[0016] Figure 9 is a cross-sectional view showing a main portion of one embodiment of the manufacturing process.

[0017] Figure 10 is a cross-sectional view showing a main portion of one embodiment of the manufacturing process.

[0018] Figure 11 is a cross-sectional view showing a main portion of one embodiment of the manufacturing process.

[0019] Figure 12 is a cross-sectional view showing a main portion of one embodiment of the manufacturing process.

[0020] Figure 13 is a cross-sectional view showing a main portion of one embodiment of the manufacturing process.

[0021] Figure 14 is a cross-sectional view showing a main portion of one embodiment of the manufacturing process.

[0022] Figure 15 is a cross-sectional view showing a main portion of one embodiment of the manufacturing process.

[0023] Figure 16 is a cross-sectional view showing a main portion of one embodiment of the manufacturing process.

[0024] Figure 17 is a cross-sectional view of the joining region of one embodiment of Embodiment 2.

[0025] Figure 18 is a cross-sectional view of the joining region of a different embodiment.

[0026] Figure 19 ​​This is a comparison table of contact resistance corresponding to the presence or absence of a barrier layer.

[0027] Figure 20 This is a top view of the transducer in embodiment 3.

[0028] Figure 21 This is an exploded three-dimensional view of an inertial measurement unit.

[0029] Figure 22 This is a 3D view of the substrate.

[0030] Figure 23 This is a perspective view of the transducer in embodiment 4.

[0031] Figure 24 This is a top view showing the main parts of the transducer's structure.

[0032] Figure 25 It is along Figure 24 A side sectional view of the dd section. Detailed Implementation

[0033] Implementation Method 1

[0034] ***Transducer Structure***

[0035] Figure 1 This is a top view of the transducer in Embodiment 1. Figure 2 It is the edge of the transducer Figure 1 A sectional view of the bb section.

[0036] use Figure 1 , Figure 2 The structure of the transducer 100 in this embodiment will be described.

[0037] The transducer 100 is, for example, an accelerometer that detects acceleration in the vertical direction. Furthermore, the figures illustrate three mutually orthogonal axes: the X-axis, Y-axis, and Z-axis. In this embodiment, the Z-axis direction is defined as the vertical direction, but it is not limited to this. The direction along the X-axis is referred to as the "X-direction," the direction along the Y-axis as the "Y-direction," and the direction along the Z-axis as the "Z-direction." Additionally, the front end of the arrow in each axis direction is referred to as the "positive side," and the base end of the arrow is referred to as the "negative side." For example, the Y-direction refers to both the positive and negative sides of the Y-direction. The positive side of the Z-direction is referred to as "up," and the negative side of the Z-direction is referred to as "down." Furthermore, in the following figures, for ease of understanding, dimensions and scales may sometimes be used that differ from actual dimensions.

[0038] The transducer 100 is a single-axis accelerometer composed of MEMS (Micro Electro Mechanical Systems) devices. Generally, a transducer refers to a converter that transforms one physical quantity into another, including transducers based on electromechanical conversion, transducers based on acoustic-electric conversion, and transducers based on photoelectric conversion. In this application, any transducer that uses a bonding material to join the substrate and the cover can be used. It can be an inertial sensor that converts acceleration or angular velocity into electrical signals, an oscillator (timer) that excites mechanical vibrations through electrical signals, an ultrasonic sensor that converts ultrasonic signals into electrical signals, an RF filter utilizing the electromechanical coupling coefficient of piezoelectric materials, a piezoelectric mirror, a piezoelectric actuator, a pressure sensor, etc.

[0039] Furthermore, in this embodiment 1, an accelerometer, as an example of a transducer, will be used for explanation. In an accelerometer where a MEMS device element formed in a substrate is sealed by a cover, when an acceleration is applied as an external force, an inertial force acts within the MEMS device element, causing a change in the electrostatic capacitance value within the element. This change in electrostatic capacitance is converted into an electrical signal using a differential detection circuit or the like, and then exported as a sensor signal.

[0040] like Figure 2 As shown, the transducer 100 is composed of a substrate 10 serving as a first substrate, a functional element 80 disposed on the substrate 10, a wiring layer 7 extending from the functional element 80, and a cover 30 serving as a second substrate covering the functional element 80.

[0041] The substrate 10 is constructed by sequentially stacking a substrate 1, an embedded insulating layer 2, an SOI (Silicon On Insulator) substrate composed of a semiconductor layer 3, an interlayer insulating layer 6, a wiring layer 7, and a surface insulating layer 8 along the Z direction. The substrate 1 is a single-crystal silicon substrate, and the embedded insulating layer 2 is disposed on its upper surface. The embedded insulating layer 2 is preferably SiO2 formed by thermal oxidation.

[0042] A substrate recess 5 is provided on the substrate 1, which is cut out from the periphery. The substrate recess 5 is a cavity, which is a part that forms a storage space S for housing the functional element 80. The substrate recess 5 serves as a movable part 55 of the functional element 80. Figure 1 A structure capable of swinging. Additionally, in Figure 2 In this case, an insulating layer 2 is embedded in the bottom surface of the recessed portion 5 of the substrate, but it may not be present.

[0043] 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 embodiment, semiconductor layer 3 and buried insulating layer 2 are bonded together by Si-SiO2 SOI bonding. Bonding via insulating films such as SiO2 is sometimes referred to as direct bonding, fusion bonding, permanent bonding, etc.

[0044] The functional element 80 is an accelerometer sensor element, and is formed by etching and patterning the semiconductor layer 3. In a preferred embodiment, a deep etching technique known as the Bosch process is used. The functional element 80 is secured by the fixing part 65 ( Figure 1 It is fixed on the substrate 1. In this embodiment, the functional element 80 is an acceleration sensor element, but it can also be other sensor elements, a vibration element constituting an oscillator, or a piezoelectric reflector element constituting a piezoelectric reflector.

[0045] As a preferred example, the cover 30 uses a silicon substrate. The surface of the cover 30 facing the functional element 80 is called the inner surface 30b, and the surface opposite to the inner surface 30b is called the outer surface 30a. The inner surface 30b corresponds to the first surface. A cover recess 35, carved out from the periphery, is provided on the inner surface 30b of the cover 30. The cover recess 35 is a cavity, forming a storage space S for housing the functional element 80. That is, the storage space S is formed by the substrate recess 5 and the cover recess 35. A protrusion, namely a limiting portion 29, is provided in the cover recess 35 to limit excessive swaying of the movable body 55 of the functional element 80. The substrate 10 and the cover 30 are bonded together in the bonding region 25 provided at their periphery by means of a metal eutectic layer 20. The details of the bonding method will be described later.

[0046] Additionally, a sealing hole 36 penetrating the cover 30 is provided. The sealing hole 36 serves to connect external gases with the storage space S when the base 10 and the cover 30 are joined. The sealing hole 36 is formed as a recess from the outer surface 30a of the cover 30, and can be sealed, for example, using solder balls 37, after the base 10 and the cover 30 are joined. Alternatively, the cover 30 surrounding the sealing hole 36 can be directly melted by laser to achieve a seal. By providing the sealing hole 36, during the formation of the metal eutectic layer 20, exhaust gases and moisture generated inside the base 10 or the cover 30 can be released to the outside through the sealing hole 36. Afterward, the sealing hole 36 is sealed using a laser, thereby maintaining a clean atmosphere inside the storage space S.

[0047] In a preferred embodiment, the storage space S is sealed with an inert gas such as nitrogen, helium, or argon to achieve an airtight seal. Furthermore, in an operating temperature environment of approximately -50°C to 150°C, a pressure close to atmospheric pressure or a vacuum state is preferred. For example, if the functional element 80 is an accelerometer, the storage space S is preferably at a pressure close to atmospheric pressure; if the functional element 80 is an angular velocity sensor, the storage space S is preferably at a vacuum pressure.

[0048] ***Structure of Functional Components***

[0049] like Figure 1 As shown, the functional element 80 is an acceleration sensor that detects acceleration in the Z direction, and adopts a so-called single-sided lever structure in which the movable body 55 swings about the swing axis 61.

[0050] The functional element 80 comprises a fixed part 65, a movable body 55 capable of oscillating around a swing axis 61 passing through the center of the fixed part 65 and along the Y-axis, a first rotary spring 54a and a second rotary spring 54b connecting the fixed part 65 and the movable body 55, etc. The fixed part 65 is fixed to the substrate 1 ( Figure 2 The protruding pedestal portion (not shown) is surrounded by a substrate recess 5. Figure 2 The movable body 55 becomes a structure capable of swinging. Additionally, in Figure 1 In this context, the line segment perpendicular to the swing axis 61 and passing through the center of the functional element 80 along the X-axis is designated as the center line 60.

[0051] The movable body 55 has a first rod 52a extending from the first rotary spring 54a in the positive X direction, a second rod 52b extending from the second rotary spring 54b in the positive X direction, and a third rod 53 connecting the first rod 52a and the second rod 52b.

[0052] The third rod 53 is equipped with four comb-shaped movable electrode groups 73a to 73d.

[0053] The movable electrode group 73a consists of six movable electrodes 71c extending from the third rod 53 in the positive X direction on the negative Y side of the center line 60.

[0054] The movable electrode assembly 73b consists of six movable electrodes 71c extending from the third rod 53 in the negative X direction on the negative Y side of the center line 60. However, it is not limited to six electrodes; any number of movable electrodes 71c is acceptable.

[0055] Movable electrode groups 73c and 73d are positioned symmetrically to movable electrode groups 73a and 73b on the positive side of Y with the center line 60 as the axis of symmetry.

[0056] Moreover, on substrate 1 ( Figure 2The side is provided with fixed electrode groups 74a to 74d opposite to the movable electrode groups 73a to 73d.

[0057] The fixed electrode assembly 74a consists of a support portion 75a fixed to the substrate 1 and seven fixed electrodes 72 extending from the support portion 75a in the negative X direction.

[0058] The fixed electrode assembly 74b consists of a support portion 75b fixed to the substrate 1 and seven fixed electrodes 72 extending from the support portion 75b in the positive X direction.

[0059] Furthermore, the fixed electrode groups 74a and 74b are not limited to seven electrodes each; any number corresponding to the number of movable electrodes 71c is acceptable. More preferably, the fixed electrode groups 74a and 74b are configured to surround the movable electrode 71c in three directions. This eliminates unwanted electrostatic attraction and enables high-precision detection of acceleration in the desired Z-axis direction.

[0060] Fixed electrode groups 74c and 74d are positioned symmetrically to fixed electrode groups 74a and 74b on the positive side of Y with the center line 60 as the axis of symmetry.

[0061] The detection unit formed by the fixed electrode group 74a and the movable electrode group 73a, and the detection unit formed by the fixed electrode group 74b and the movable electrode group 73b are collectively referred to as the N-type detection unit 76n.

[0062] In the N-type detection unit 76n, a parallel plate-type electrostatic capacitor is formed by a fixed electrode 72 and a movable electrode 71c arranged opposite each other. This electrostatic capacitor changes according to the change in the overlap area between the movable electrode 71c and the fixed electrode 72 as the movable electrode 71c shifts due to acceleration.

[0063] Similarly, the detection section formed by the fixed electrode group 74c and the movable electrode group 73c, and the detection section formed by the fixed electrode group 74d and the movable electrode group 73d are collectively referred to as the P-type detection section 76p. In the P-type detection section 76p, a parallel plate-type electrostatic capacitor is formed by the opposing fixed electrode 72c and the movable electrode 71. This electrostatic capacitor changes with the displacement of the movable electrode 71 caused by acceleration, depending on the change in the overlap area between it and the fixed electrode 72c.

[0064] The thickness of the movable electrode 71c in the Z direction of the N-type detection unit 76n is thinner than the thickness of the movable electrode 71 in the Z direction of the P-type detection unit 76p. Specifically, the movable electrode 71c is thinned in a stepped manner starting from the same thickness as the third rod 53 at the root, halfway along its extension direction. Therefore, the thickness on the Z-side of all 12 movable electrodes 71c opposite the fixed electrode 72 is thinner.

[0065] The thickness of the fixed electrode 72c in the Z direction of the P-type detection unit 76p is thinner than the thickness of the fixed electrode 72 in the Z direction of the N-type detection unit 76n. Specifically, the fixed electrode 72c is thinned in a stepped manner starting from the root thickness on the support portion 75c, 75d side midway along its extension direction. Therefore, the thickness on the positive Z side is thinned at the portions of the 14 fixed electrodes 72c opposite the movable electrode 71.

[0066] With this structure, when acceleration is applied in the positive Z direction, the movable body 55 shifts in the negative Z direction due to inertial force, reducing the overlapping area in the N-type detection section 76n. On the other hand, the overlapping area is maintained in the P-type detection section 76p. Furthermore, when acceleration is applied in the negative Z direction, the movable body 55 shifts in the positive Z direction due to inertial force, maintaining the overlapping area in the N-type detection section 76n, and reducing the overlapping area in the P-type detection section 76p.

[0067] Based on this correlation, in the functional element 80, the change in the overlapping area of ​​the N-type detection unit 76n and the P-type detection unit 76p is differentially detected as a change in electrostatic capacitance, thereby enabling the detection of acceleration in the positive / negative Z directions.

[0068] ***Terminal section and mating area***

[0069] like Figure 1 As shown, the base 10 is generally rectangular in shape, and the short side in the negative X direction becomes a protrusion 11 extending from the short side of the cover 30. Terminals 91 to 94 for external connection are provided in the protrusion 11.

[0070] Terminal 91 is a movable electrode terminal, which is electrically connected to all movable electrodes 71 and 71c via wiring 81.

[0071] Terminal 92 is an N-type fixed electrode terminal, which is electrically connected to all the fixed electrodes 72 of the N-type detection unit 76n via wiring 82.

[0072] Terminal 93 is a P-type fixed electrode terminal, which is electrically connected to all fixed electrodes 72c of the P-type detection unit 76p via wiring 83.

[0073] Terminal 94 is a GND terminal and is electrically connected to the metal eutectic layer 20 via wiring 84. Details regarding the connection method between terminal 94 and the metal eutectic layer 20 will be described later. In other words, wiring 81 to wiring 84 pass through the outer side of the bonding region 25 and are electrically connected to the functional element 80.

[0074] The substrate 10 and the cover 30 are bonded together by means of a metallic eutectic layer 20 in a four-sided annular bonding region 25 surrounding the functional element 80. The bonding region 25 is provided along the recess 34 of the cover 30.Figure 2 As shown, the recess 34 is a groove provided on the inner surface 30b of the cover 30. The recess 34 is a cavity with a rectangular cross-section, and a metal eutectic layer 20 is provided inside the recess 34.

[0075] like Figure 1 As shown, the recess 34, when viewed from above, is configured as a four-sided ring surrounding the functional element 80. The bonding region 25 is the area within the recess 34 where a metal eutectic layer 20 is disposed. The metal eutectic layer 20 intersects with wirings 81 to 83 when viewed from above.

[0076] In other words, the transducer 100 includes a substrate 10 as a first substrate, a cover 30 as a second substrate, a functional element 80 disposed between the substrate 10 and the cover 30, and a metal eutectic layer 20 that bonds the substrate 10 and the cover 30 together in a bonding region 25 located around the functional element 80. A recess 34 is provided on the inner surface 30b of the cover 30, which is the first surface that is in contact with the substrate 10.

[0077] ***Detailed information on metallic eutectic layers***

[0078] Figure 3 yes Figure 2 An enlarged view of part c. Figure 4 yes Figure 2 An enlarged view of part d. Figure 5 This is a cross-sectional view of the main parts of the base and cover before assembly.

[0079] Figure 3 This shows a cross-section of the portion where the metal eutectic layer 20 overlaps with the underlying wiring 82. Wiring 82 is wiring that extends from the terminal 92 toward the functional element 80.

[0080] The substrate 10 is composed of, sequentially stacked from the negative Z direction, a substrate 1, a buried insulating layer 2, a semiconductor layer 3, an interlayer insulating layer 6, a wiring layer 7 containing wiring 82, a surface insulating layer 8, and a barrier layer 12. Figure 3 In this design, the substrate 1 to the barrier layer 12 are designated as substrate 10. Furthermore, a cover 30 is bonded to the substrate via a metal eutectic layer 20.

[0081] In a preferred embodiment, the interlayer insulating layer 6 is a SiO2 layer. In this embodiment 1, a high-temperature oxide layer (HTO) using a high-temperature CVD method is used. Alternatively, the interlayer insulating layer 6 may also be a SiN layer. The surface insulating layer 8 is located above the wiring layer 7, therefore, an insulating film that can be formed at a relatively low temperature is preferred. In this embodiment 1, a P-TEOS (Tetra EthOxySilane) film is used using a plasma CVD (Chemical Vapor Deposition) apparatus.

[0082] The wiring layer 7 is formed by multiple layers, for example, a four-layer structure consisting of Ti, TiN, AlCu, and TiN stacked sequentially from bottom to top. Regarding the thickness of each layer, Ti is 60 nm, TiN is 100 nm, AlCu is 600 nm, and TiN is 100 nm. The main component of AlCu is Al, and the Cu content is 0.1% to 1.0%. The wiring layer 7 only needs to have good conductivity and can also be other metal layers.

[0083] The barrier layer 12 is a two-layer structure of Ti and TiN, selectively disposed in the portion overlapping with the metal eutectic layer 20. The Ti layer in the barrier layer 12 is 60 nm thick, and the TiN layer is 100 nm thick. The Ti layer improves the adhesion to the surface insulating layer 8, while the TiN layer prevents Al diffusion from AlCu. The barrier layer 12 only needs to prevent Al diffusion; it can also be other metal films such as TaN, W, or TiW. If the adhesion to the surface insulating layer 8 is good, the Ti layer can be omitted.

[0084] The metal eutectic layer 20 is achieved by... Figure 5 The first joint 15 and the second joint 16 shown are eutectic layers formed by heating and pressurizing. Eutectic generally refers to an alloy formed from the solidification of two or more metals from a liquid state. Specifically, the laminate formed by overlapping the substrate 10 and the cover 30 is heated to above the eutectic temperature of the two metals contained in the first joint 15 and the second joint 16. A load is applied while the two metals are in a liquid state, and then the laminate is cooled back to a solid state, thereby achieving bonding. In a preferred embodiment, the laminate is placed on the worktable of a heating fixture with the substrate 10 facing down. After the laminate reaches a predetermined temperature, a load is applied from the cover 30 side using a weighted fixture for a predetermined time. At this time, the weighted fixture is also heated. Then, after the two metals form a eutectic layer, the load is removed and the laminate is cooled. In this embodiment, the metal eutectic layer 20 contains a first metal in the first joint 15 and a second metal in the second joint 16. The first metal is Al and the second metal is Ge. In addition, the eutectic temperature of Al and Ge eutectic alloy is approximately 420℃.

[0085] like Figure 5As shown, before forming the metal eutectic layer 20, a first bonding portion 15 is provided on the substrate 10, and a second bonding portion 16 is provided on the cap 30. The first bonding portion 15 is a two-layer structure consisting of a barrier layer 12 and a first metal layer 13. The barrier layer 12 is a two-layer structure consisting of Ti and TiN, and the first metal layer 13 is an AlCu layer with Al as the main component. The second bonding portion 16 is a single layer consisting of a second metal layer, which is a Ge layer. However, the Cu in the AlCu layer is incorporated to prevent electromigration, and its content is low. In this embodiment, the Cu content in AlCu is set to 0.1% to 1.0%. On the other hand, the main component of the second bonding portion 16, which is composed of the second metal layer, is Ge. In other words, the main component of the first bonding portion 15 is aluminum, and the main component of the second bonding portion 16 is germanium, and the metal eutectic layer 20 formed by them contains aluminum and germanium.

[0086] Figure 3 The microscopic photograph of the metallic eutectic layer 20 shown faithfully depicts the eutectic layer. The results of elemental analysis, such as... Figure 3 As shown, the metal eutectic layer 20 is formed by a first region 21 mainly composed of Al as the first metal and a second region 22 mainly composed of Ge as the second metal, in an adjacent state. The content of the first metal in the first region 21 is greater than that in the second region 22. The content of the second metal in the second region 22 is greater than that in the first region 21.

[0087] The second region 22 extends wider along the cover 30, but a portion of it reaches the boundary with the base 10. For example, in Figure 3 In the middle, the extensions 22a and 22b reach the substrate 10. However, the extensions 22a and 22b are prevented from diffusing by the barrier layer 12. This is because the barrier layer 12 has the function of preventing Al diffusion. The boundaries between the first region 21 and the second region 22 are numerous and complex. In addition, regarding the extension of the second region 22, the second region 22 has more extensions than the first region 21.

[0088] The distribution of Ge in the metal eutectic layer 20 is not uniform, with a higher concentration in the second region 22, where it is uniform and there is no concentration gradient. However, a small amount of Ge is also present in the first region 21. The first region 21 and the second region 22 are in seamless contact, and their contact area is larger than the planar area of ​​the bonding region 25. That is, the first region 21 and the second region 22 are randomly interlocked, and their 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 25 formed by the bonding of the substrate 10 and the cap 30 through the metal eutectic layer 20.

[0089] Typically, Ge (Ge) has a diamond structure, and Al (Al) has a face-centered cubic lattice structure. As the main components of the eutectic layer, if Ge is abundant, a diamond-structured solid solution is formed; if Al is abundant, a face-centered cubic lattice solid solution is formed. A solid solution is a substance in which two elements are fused together and the whole is a solid phase with a relatively uniform concentration. However, different solid solutions have different composition ratios within the solid solution limit.

[0090] That is, the second region 22, which is dominated by Ge, realizes a solid solution with a diamond structure, and the first region 21, which is dominated by Al, realizes a solid solution with a face-centered cubic lattice structure. When cutting the crystal to reveal the surface, the target is surface energy; however, regarding surface energy per unit area, it is known that Ge is higher in both face orientations when comparing Ge and Al. In other words, the metallic eutectic layer 20 contains multiple adjacent first regions 21 with a face-centered cubic lattice structure dominated by the first metal and second regions 22 with a diamond structure dominated by the second metal.

[0091] like Figure 3 As shown, a portion of the second region 22 reaches the boundary with the substrate 10. Furthermore, the second region 22 extends from the cap 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 cap 30. Simultaneously, the Ge-rich second region 22 contains Al within a range not exceeding the solid solution limit relative to Ge. Moreover, the Ge to Al composition ratio in the second region 22 is relatively uniform, independent of the distance from the cap 30. From the viewpoint of surface energy, the bonding strength is high when the Ge-rich second region 22 reaches the boundary with the substrate 10. More preferably, a larger portion of the Ge-rich second region 22 extends from the cap 30 to the substrate 10.

[0092] On the other hand, Figure 3 The boundary between the cover 30 and the metal eutectic layer 20 is such that a second junction 16 made of Ge is directly formed on the cover 30. Figure 5 Therefore, Ge diffuses into the silicon interior that serves as the cap 30. That is, the second region 22, dominated by Ge, diffuses into the silicon interior at the boundary with the cap 30. Figure 3 The dotted lines in the diagram form tiny bumps and grooves, increasing the contact area and enhancing the bonding strength.

[0093] ***Recesses and Insulation Layer***

[0094] like Figure 3 As shown, the metal eutectic layer 20 is disposed in the recess 34.

[0095] The recess 34 is a rectangular groove provided on the inner surface 30b of the cover 30, having a bottom surface 38 as the bottom and sidewalls 39 at both ends of the bottom surface 38. The bottom surface 38 is equivalent to a second surface. In other words, the recess 34 has a bottom surface 38 as a second surface and sidewalls 39 connecting the inner surface 30b as a first surface and the bottom surface 38 as a second surface.

[0096] An insulating layer 40 is formed on one sidewall 39 of the recess 34. The insulating layer 40 corresponds to the insulating layer in the claim.

[0097] The cross-section of the insulating layer 40 is crank-shaped along the recess 34, and it is composed of a first portion 31 disposed on the inner surface 30b, a second portion 32 disposed on the sidewall 39, and a third portion 33 disposed on the bottom surface 38. An insulating layer 40 with the same structure is also formed on the other sidewall 39. The two insulating layers 40 are symmetrically disposed on both sides of the metal eutectic layer 20. Furthermore, in Figure 3 In the middle, the first part 31 of the insulating layer 40 is in physical contact with the surface insulating layer 8 on the side of the substrate 10.

[0098] In other words, the insulating layer 40 has a first portion 31 disposed on the inner surface 30b, which is the first surface, a second portion 32 disposed on the sidewall 39, and a third portion 33 disposed on the bottom surface 38, which is the second surface. Moreover, the insulating layer 40 is disposed across the bonding region 25.

[0099] In a preferred embodiment, the insulating layer 40 is a SiO2 film. However, it is not limited to a SiO2 film; any chemically stable insulating material can be used, such as a SiN film, a B2O3 film, or a Bi2O3 film, to form the insulating layer 40.

[0100] In other words, the insulating layer 40 is any one of the following: silicon oxide layer, silicon nitride layer, boron oxide layer, and bismuth oxide layer.

[0101] During the formation of the metal eutectic layer 20, the Al of the first bonding portion 15 and the Ge of the second bonding portion 16 are heat-treated within the recess 34. The eutectic layer of Al and Ge changes to a liquid phase at the eutectic point, which could potentially lead to expansion or dispersion. However, the insulating layer 40 formed on both sides of the recess 34 prevents this expansion or dispersion. Specifically, the insulating layer 40 is composed of a chemically stable material such as a SiO2 film, thus preventing eutectic formation between it and AlGe, and functioning as a barrier layer.

[0102] Therefore, it is possible to prevent the liquid phase of the eutectic layer during the formation of the metal eutectic layer 20 from flying towards the functional element 80, and to reliably bond the substrate 10 and the cover 30 at the bonding region 25 within the recess 34 via the metal eutectic layer 20.

[0103] ***Differences related to whether there is an intersection with the routing layer***

[0104] Figure 4 yes Figure 2 An enlarged view of section d shows a cross-section of the area without wiring layer 7 below. (See diagram below.) Figure 4 As shown, in the portion of the lower layer without wiring layer 7, the height of the surface insulating layer 8 on the substrate 10 side is reduced by the amount of thickness of wiring layer 7 compared to the portion with wiring layer 7. Therefore, the first portion 31 of insulating layer 40 does not make physical contact with the surface insulating layer 8 of substrate 10, and a gap may be generated between them. However, in the design, this gap is narrow, so the eutectic layer of liquid phase will not fly out of the recess 34.

[0105] On the other hand, as the volume of the recess 34, in Figure 4 The lower layer has no wiring layer 7, and the recess 34 has a volume ratio of... Figure 3 The recess 34 of the wiring layer 7 has a large volume.

[0106] Here, if we assume Figure 3 The thickness of the metal eutectic layer 20 in the recess 34 of the portion having wiring layer 7 is height t1 and width is width w1. Figure 4 If the thickness of the metal eutectic layer 20 in the recess 34 without wiring layer 7 is height t2 and the width is width w2, then the relationship t1 < t2 and w1 > w2 holds. This is because the width of the liquid phase eutectic layer during the formation of the metal eutectic layer 20 is automatically adjusted to the optimal width based on the distance between the bottom surface 38 of the recess 34 and the surface insulating layer 8 on the substrate 10 side.

[0107] thus, Figure 1 In the top view, the width of the metal eutectic layer 20 is only the portion that intersects with wiring 81 to wiring 84, which is called the width w1, and the rest is called the width w2.

[0108] In other words, the width of the metal eutectic layer 20 is wider in the part that overlaps with the wiring than in the other part, and the height of the metal eutectic layer 20 is lower in the part that overlaps with the wiring than in the other part.

[0109] return Figure 3 .

[0110] In one example, the width of the recess 34 is 90 μm to 100 μm, and the depth of the recess 34 is 0.1 μm to 0.5 μm. In this case, the width of the metal eutectic layer 20 is less than 60 μm. Furthermore, this is just one example; it can be appropriately set according to the size and specifications of the device.

[0111] Figure 6 This is a perspective view showing the main parts of the electrical wiring structure of the metallic eutectic layer. Figure 1Enlarged 3D view of the area surrounding terminal 94.

[0112] like Figure 6 As shown, the metal eutectic layer 20 passes through the first bonding portion 15 ( Figure 5 The protrusion 15b is electrically connected to the terminal 94, which serves as the GND terminal. The protrusion 15b is a wiring pattern formed together with the first joint 15, extending from the joint area 25 toward the terminal 94. Since there is no second joint 16 in the protrusion 15b... Figure 5 The opposite portion on the side of the metal eutectic layer 20 thus functions as an electrical wiring route led out from the metal eutectic layer 20.

[0113] The protrusion 15b is provided in such a way that it overlaps with the wiring 84 connected to the terminal 94 through the surface insulating layer 8. A conductive contact portion 18 is provided in the portion of the surface insulating layer 8 where the wiring 84 overlaps with the protrusion 15b.

[0114] Thus, terminal 94 is electrically connected to the metal eutectic layer 20 via wiring 84, contact portion 18, and protrusion 15b. Furthermore, the potential is not limited to GND; any electrically stable potential is acceptable, such as a constant potential that includes the power supply potential. In other words, cover 30 is electrically connected to any one of the plurality of electrical wirings disposed on the substrate 10 via the metal eutectic layer 20.

[0115] ***Manufacturing Method of the Cover***

[0116] Figure 7 This is a flowchart illustrating the manufacturing process of the cover. Figures 8-16 It is a cross-sectional view showing the main part of a manufacturing process.

[0117] Here, with Figure 7 With reference to other accompanying drawings as appropriate, the manufacturing method of the cover 30 having a recess 34 including an insulating layer 40 will be described.

[0118] In step S10, a silicon substrate 30s is prepared, and an oxide film is formed on both sides of the silicon substrate 30s. This state is as follows: Figure 8 As shown, at this time, the oxide film 64 on the inner surface 30b side is thicker than the oxide film 63 on the outer surface 30a side. Specifically, after forming oxide films based on thermal oxidation on both surfaces, a P-TEOS film is deposited on the inner surface 30b using a plasma CVD device, making the oxide film 64 thicker, thus achieving a surface-to-backside asymmetric film thickness. Furthermore, in Figures 8-16 In the figure, the inner surface 30b of the cover 30 is shown at the top.

[0119] In step S11, a pattern is formed on the outer surface 30a of the silicon substrate 30s using photolithography, thereby selectively removing the oxide film 63, such as that forming the sealing hole. Next, the silicon is etched using anisotropic etching. This state is as follows... Figure 9 As shown. It should be noted that the composition in the following description refers to the composition using photolithography.

[0120] In step S12, after removing the oxide films 63 and 64 from the two sides of the silicon substrate for 30 seconds, the two sides are oxidized again, as follows: Figure 10 As shown, oxide films 66 and 67 are formed. In a preferred embodiment, a wet oxidation process is performed to ensure that the thickness of the thermal oxide film can withstand subsequent Bosch processes.

[0121] In step S13, a recess 34 is formed on the inner surface 30b side of the silicon substrate 30s. Specifically, the recess 34 is patterned in the oxide film 67, and the oxide film 67 and the silicon surface are etched to form the recess 34. Next, after a P-TEOS film is deposited using a plasma CVD apparatus, patterning is performed, and an insulating layer 40 is selectively formed around the sidewalls of the recess 34. This state is as follows. Figure 11 As shown.

[0122] In step S14, after forming a Ge film on the entire surface of the inner surface 30b of the silicon substrate 30s using sputtering, patterning is performed to form a second bonding portion 16 within the recess 34. This state is as follows: Figure 12 As shown. Furthermore, in a preferred embodiment, a protective film 68 made of P-TEOS film is formed on the entire surface of the inner surface 30b containing the second joint 16. The protective film 68 protects the second joint 16 in a subsequent chamber forming process.

[0123] In step S15, an opening 36a, serving as the starting point of a sealing hole, is formed on the oxide film 67 on the inner surface 30b side. More specifically, as... Figure 13 As shown, an opening 36a is formed on the oxide film 67 using a stepper camera. Then, as... Figure 13 As shown, in the recess 34 and the limiting portion 29 ( Figure 5 The remaining parts, including ) form resist 96.

[0124] In step S16, a deep excavation based on Bosch treatment is performed on the inner surface 30b. This state is as follows: Figure 14 As shown, the sealing hole 36b is machined to a single depth from the opening 36a. Additionally, the oxide film 67 is thinned.

[0125] In step S17, a cover recess 35 is formed, which serves as a chamber for the cover 30. First, as... Figure 15As shown, the oxide film 67 on the inner surface 30b is removed, exposing the silicon substrate 30s surface that forms the cavity. Next, a second deep-cutting process based on the Bosch process is performed. This state is as follows... Figure 16 As shown, a recessed portion 35 is formed in the cover, through which a sealing hole 36 passes. At this time, a protective film 68 remains on the surface of the second joint 16.

[0126] In step S18, all oxide films are removed by wet etching using BHF (Buffered Hydrogen Fluoride). This forms... Figure 5 The cover shown is 30.

[0127] As described above, the transducer 100 according to this embodiment can achieve the following effects.

[0128] The transducer 100 includes a substrate 10 as a first substrate, a cover 30 as a second substrate, a functional element 80 disposed between the substrate 10 and the cover 30, and a metal eutectic layer 20 that bonds the substrate 10 and the cover 30 in a bonding region 25 located around the functional element 80. A recess 34 is provided on the inner surface 30b of the cover 30, which is a first surface that mates with the substrate 10. The recess 34 has a bottom surface 38 as a second surface and a sidewall 39 that connects the inner surface 30b as the first surface and the bottom surface 38 as the second surface. The recess 34 also has an insulating layer 40, which has a first portion 31 disposed on the inner surface 30b as the first surface, a second portion 32 disposed on the sidewall 39, and a third portion 33 disposed on the bottom surface 38 as the second surface. The insulating layer 40 is disposed across the bonding region 25.

[0129] Therefore, the substrate 10 and the cover 30 can be reliably bonded within the bonding region 25 via the metal eutectic layer 20. Specifically, during the formation of the metal eutectic layer 20, the Al of the first bonding portion 15 and the Ge of the second bonding portion 16 are heat-treated within the recess 34. The eutectic layer of Al and Ge changes to a liquid phase at the eutectic point, which could potentially expand or scatter. However, the insulating layer 40 formed on both sides of the recess 34 prevents this expansion or scattering. This is because the insulating layer 40 is composed of a chemically stable material such as a SiO2 film, and therefore does not undergo eutecticization with AlGe, functioning as a barrier layer. Thus, the eutectic layer in liquid phase during the formation of the metal eutectic layer 20 can be prevented from scattering towards the functional element 80, and the substrate 10 and the cover 30 can be reliably bonded within the bonding region 25 within the recess 34 via the metal eutectic layer 20.

[0130] Therefore, reliable engagement is possible within the engagement region 25, enabling the provision of a highly reliable transducer 100.

[0131] In addition, the metal eutectic layer 20 contains aluminum and germanium, and the insulating layer 40 is any one of silicon oxide layer, silicon nitride layer, boron oxide layer, and bismuth oxide layer.

[0132] Therefore, the insulating layer 40 is made of a chemically stable material, so it does not undergo eutectic formation with AlGe and can function as a barrier layer.

[0133] Furthermore, the width of the metal eutectic layer 20 is wider in the portion that overlaps with the wiring than in other portions.

[0134] Therefore, when forming the metal eutectic layer 20, the liquid phase eutectic layer naturally expands and adjusts to the optimal width according to the distance between the bottom surface 38 of the recess 34 and the surface insulating layer 8 on the side of the substrate 10, so that the substrate 10 and the cover 30 can be reliably bonded.

[0135] Furthermore, the height of the metal eutectic layer 20 is lower in the portion that overlaps with the wiring than in other portions.

[0136] Therefore, when forming the metal eutectic layer 20, the liquid phase eutectic layer naturally expands and adjusts to the optimal height according to the distance between the bottom surface 38 of the recess 34 and the surface insulating layer 8 on the side of the substrate 10, so that the substrate 10 and the cover 30 can be reliably bonded.

[0137] Implementation Method 2

[0138] ***Different ways of joining areas***

[0139] Figure 17 This is a cross-sectional view of the joining area in one embodiment of implementation 2, and... Figure 3 correspond. Figure 18 These are cross-sectional views of the joining areas in different ways, and... Figure 4 correspond.

[0140] In the above embodiment, the case where the second joint 16 is directly formed into a film on the cover 30 has been described, but it is not limited to this; a barrier layer 17 may also be provided on the substrate. Hereinafter, the same reference numerals will be used for the same parts as in the above embodiment, and repeated descriptions will be omitted.

[0141] In this embodiment, at the junction of the cover 30 and the second joint 16 ( Figure 5 A barrier layer 17 is provided between them. Apart from this, the structure is the same as that of the above embodiment.

[0142] Barrier layer 17 is the same as barrier layer 12, and is a double-layer structure of Ti and TiN, selectively disposed in the portion overlapping with the metal eutectic layer 20. Barrier layer 17 is formed by sequentially stacking Ti and TiN from the cover body 30 side.

[0143] Figure 17The image shows a cross-section of the portion where the metal eutectic layer 20 overlaps with the underlying wiring 82. Therefore, with... Figure 3 Similarly, the first portion 31 of the insulating layer 40 is in physical contact with the surface insulating layer 8 on the substrate 10 side. On the other hand, in Figure 18 In, with Figure 4 Similarly, the first portion 31 of the insulating layer 40 is not in physical contact with the surface insulating layer 8 on the side of the substrate 10.

[0144] like Figure 17 As shown, the metal eutectic layer 20 is formed by a first region 21, primarily composed of Al as the first metal, and a second region 22, primarily composed of Ge as the second metal, in an adjacent state. The second region 22 extends relatively wide along the cap 30, but a portion of it reaches the boundary with the substrate 10. That is, with... Figure 3 Similarly, the metal eutectic layer 20 achieves a high bonding strength.

[0145] Figure 19 This is a comparison table of contact resistance corresponding to the presence or absence of a barrier layer.

[0146] Furthermore, by providing the barrier layer 17, diffusion of Ge into the cover 30 is prevented, and good electrical contact with the silicon constituting the cover 30 is achieved. That is, ohmic contact between the metal eutectic layer 20 and the cover 30 can be achieved through the barrier layer 17. Figure 19 Table 95 shows the experimental results of the inventors. As in Comparative Example 1 of Table 95, when the second joint 16 is directly formed on the cover 30, although Si and Ge form an ohmic contact, the contact resistance value is a relatively large value of about 38.4 MΩ. In addition, the contact resistance value is the resistance value of a single contact of the same size.

[0147] In contrast, as shown in the embodiments in Table 95, when the Ti / TiN barrier layer 17 is provided, an ohmic contact is achieved, and the contact resistance is as low as approximately 1.9 kΩ. This result demonstrates that by providing the Ti / TiN barrier layer 17 between the cover 30 and the metal eutectic layer 20, better electrical conductivity can be obtained. Furthermore, in Figure 18 The same applies to the unwired portion of the lower layer of the metal eutectic layer 20 shown.

[0148] On the other hand, as shown in Comparative Example 2 in Table 95, when a barrier layer 17 made of TiN is provided, it does not become an ohmic contact, and the contact resistance value is also larger than that of Comparative Example 1.

[0149] Furthermore, in the above description, pure Ge without impurities was used for the Ge in the second joint 16. However, according to the experimental results of the inventors, it was confirmed that even when a Ti / TiN barrier layer 17 is provided, ohmic contact is achieved even when P-type Ge containing impurities such as Ga is used instead of pure Ge, and the contact resistance value becomes as low as approximately 62.3 kΩ. Therefore, it is also possible to use P-type Ge in the second joint 16.

[0150] As described above, the transducer 100 according to this embodiment can achieve the following effects in addition to the effects described in the above embodiment.

[0151] The transducer 100 has a Ti / TiN barrier layer 17 between the cover 30 and the metal eutectic layer 20.

[0152] Therefore, it can effectively supply potential to the cover.

[0153] Therefore, reliable engagement is possible within the engagement region 25, enabling the provision of a more reliable transducer 100.

[0154] Implementation Method 3

[0155] ***Applications in inertial measurement units***

[0156] Figure 20 This is a top view of the transducer in embodiment 3, and... Figure 1 correspond.

[0157] In the above embodiment, the case where the transducer 100 houses one functional element 80 has been described, but it is not limited to this and multiple functional elements may also be housed. Hereinafter, the same reference numerals will be used for the same parts as in the above embodiment, and repeated descriptions will be omitted.

[0158] like Figure 20 As shown, in addition to the functional element 80 described above, the transducer 110 of this embodiment also includes functional elements 85 and 86.

[0159] Functional element 85 is an electrostatic capacitance change type accelerometer that detects acceleration in the X direction. Functional element 86 is an electrostatic capacitance change type accelerometer that detects acceleration in the Y direction. That is, transducer 110 is a triaxial accelerometer capable of detecting acceleration in the X, Y, and Z directions. Figure 1 Similarly, the base 10 is generally rectangular, and its long side in the negative X direction has a protrusion 11 extending from the cover 30. A plurality of terminals for external connection are provided in the protrusion 11.

[0160] Like transducer 100, transducer 110 has a structure in which the substrate 10 and the cover 30 are bonded in the bonding region 25 by a metal eutectic layer 20, and a recess 34 is provided in the cover 30. The bonding region 25 is formed within the recess 34 when viewed from above. The area inside the bonding region 25 is the storage space S.

[0161] Three functional components, 80, 85, and 86, are stored in the storage space S in a manner that detects swaying. Figure 20 In this context, the joining region 25 is a four-sided ring area that is slightly smaller than the outer periphery of the cover 30, but it is not limited to this. The joining region 25 can be enclosed simply by surrounding the functional elements 80, 85, and 86, and can also be polygonal or elliptical. However, it is configured to intersect with lead-out wiring (not shown) when viewed from above.

[0162] As described above, the transducer 110 according to this embodiment can achieve the following effects in addition to the effects described in the above embodiment.

[0163] Similar to transducer 100, substrate 10 and cover 30 are bonded in bonding region 25 by metal eutectic layer 20. When viewed from above, bonding region 25 is formed in recess 34 of cover 30.

[0164] Therefore, reliable bonding is possible within the bonding region 25, enabling the provision of a highly reliable transducer 110.

[0165] Figure 21 This is an exploded three-dimensional view of an inertial measurement unit. Figure 22 This is a 3D view of the substrate.

[0166] exist Figure 21 The inertial measurement device 2000 of this embodiment shown is equipped with a transducer 110. The inertial measurement device 2000 is a cuboid with a generally square planar shape.

[0167] The Inertial Measurement Unit 2000 is an inertial measurement sensor unit (IMU) used to detect the posture and motion of mounted objects such as automobiles and robots. The Inertial Measurement Unit 2000 functions as a so-called six-axis motion sensor, equipped with three-axis accelerometers and three-axis angular velocity sensors.

[0168] The inertial measurement device 2000 has a housing 301, a coupling component 310, and a sensor module 325 on which a transducer 110 is mounted.

[0169] The outer casing 301 has the same overall shape as the inertial measurement device 2000, and is a cuboid with a roughly square planar shape. Threaded holes 302 are formed near two vertices along the diagonal of the square. Two screws can pass through these two threaded holes 302 to fix the inertial measurement device 2000 to the mounting surface of the object such as a car.

[0170] Furthermore, the housing 301 is box-shaped, and the sensor module 325 is housed inside it. Specifically, it has a structure in which the sensor module 325 is inserted into the housing 301 by means of a clamping engagement member 310.

[0171] The sensor module 325 has an inner housing 320 and a substrate 315.

[0172] The inner shell 320 is a component that supports the substrate 315, and the substrate 315 is bonded to the lower surface of the inner shell 320 by an adhesive.

[0173] Furthermore, the inner shell 320 is shaped to be housed inside the outer shell 301. The inner shell 320 has an inner shell recess 331 for preventing contact with the substrate 315 and an opening 321 for exposing the connector 316, which will be described later. The inner shell 320 is engaged with the outer shell 301 via a coupling member 310.

[0174] Next, the substrate 315 on which the transducer 110 is mounted will be described.

[0175] like Figure 22 As shown, a transducer 110, a connector 316, and an angular velocity sensor 317z for detecting the angular velocity around the Z-axis are mounted on the upper surface of the substrate 315, i.e., the surface near the inner shell 320. An angular velocity sensor 317x for detecting the angular velocity around the X-axis and an angular velocity sensor 317y for detecting the angular velocity around the Y-axis are mounted on the side of the substrate 315. Alternatively, a transducer 100 can be installed instead of the transducer 110.

[0176] Additionally, a control IC 319, serving as a control unit, is mounted on the lower surface of the substrate 315, specifically on the side closest to the housing 301. The control IC 319 is a Microcontroller Unit (MCU), which integrates a storage unit including non-volatile memory, an A / D converter, etc., to control various parts of the inertial measurement device 2000. The storage unit stores programs specifying the order and content for detecting acceleration and angular velocity, programs for digitizing the detection data and embedding it into grouped data, and other accompanying data. Furthermore, several other electronic components are also mounted on the substrate 315.

[0177] According to such an inertial measurement device 2000, since the transducer 110 is used, it is possible to provide an inertial measurement device 2000 that achieves the effects of the above-described embodiments and has excellent long-term reliability.

[0178] Implementation Method 4

[0179] ***Applied to timer devices***

[0180] Figure 23 This is a perspective view of the transducer in embodiment 4. Figure 24 This is a top view showing the main parts of the transducer's structure. Figure 25 It is along Figure 24 A side sectional view of the dd section.

[0181] In the above embodiments, transducers 100 and 110 have been described, but the invention is not limited thereto. These transducers can also be applied to timers such as oscillators and vibrators. Hereinafter, the same reference numerals will be used for the same parts as in the above embodiments, and repeated descriptions will be omitted.

[0182] Figure 23 The transducer 120 shown in this embodiment is an oscillator. The transducer 120 includes a functional element 78. The functional element 78 is a vibration element composed of a MEMS device. Figure 24 ).

[0183] like Figure 23 As shown, the transducer 120 is a flat cuboid shape and is composed of a first substrate 45, a cover 88, etc. In addition, in each figure, the stacking direction of the cover 88 relative to the first substrate 45 is set as the positive Z direction.

[0184] The first substrate 45 is a base substrate made of an SOI substrate. For example... Figure 24 As shown, a functional element 78 integrally formed with the first substrate 45 is disposed approximately at the center of the first substrate 45. The functional element 78 is configured to include a base 19 supported by the first substrate 45 and a movable portion 14 extending from the base 19. A pair of excitation electrodes (not shown) are formed on the functional element 78. Figure 24 In this embodiment, the movable part 14 has three parts, but is not limited to this. Thus, the functional element 78 in this embodiment is a silicon vibrating element. In addition, the functional element 78 is not limited to a silicon vibrating element, and can also be a quartz vibrating element, a ceramic vibrating element, or other vibrating elements.

[0185] like Figure 23 As shown, the cover 88 is roughly square when viewed from above, and is composed of a second substrate 46, a circuit layer 47, an interlayer insulating layer 48, and an external electrode 49.

[0186] The second substrate 46 is made of a silicon substrate and has a circuit layer 47, an interlayer insulating layer 48, and an external electrode 49 sequentially in its Z positive direction.

[0187] Circuit layer 47 is a circuit layer formed on one side of the second substrate 46 using semiconductor technology, and an oscillation circuit 59 is formed in this layer. Figure 25 The oscillation circuit 59 is composed of an integrated circuit containing active components such as transistors and passive components such as capacitors or resistors. The oscillation circuit 59 is an oscillation circuit that causes the functional element 78 to oscillate to generate an output signal of a predetermined frequency. In this embodiment, the transducer 120 is an oscillator equipped with an oscillation circuit, but it is not limited to this; the transducer 120 may also not have an oscillation circuit. Therefore, the transducer 120 may also be an oscillator or other timing device.

[0188] In a preferred embodiment, the interlayer insulating layer 48 is a SiO2 layer.

[0189] The external electrodes 49 are rectangular mounting terminals, and a pair are provided at opposite corners of the cover 88. That is, when mounting the transducer 120, the cover 88 is oriented towards the mounting surface of the substrate or the like for surface mounting.

[0190] like Figure 24 As shown, transducer 120 is the same as transducer 100, and has a structure in which the first substrate 45 and the second substrate 46 (cover 88) are bonded in the bonding region 25 through a metal eutectic layer 20. A recess 34 is provided in the second substrate 46. The recess 34 is provided in a four-sided ring shape at the periphery of the second substrate 46. The bonding region 25 is formed in the recess 34 when viewed from above. A storage space S is provided inside the bonding region 25.

[0191] like Figure 25 As shown, the storage space S is a space formed by the overlap of the chamber of the first substrate 45 and the chamber of the second substrate 46, and the functional element 78 is arranged in a manner that allows it to swing within the storage space S.

[0192] A through electrode 9 is provided between the bonding area 25 and the storage space S. The through electrode 9 is a through electrode provided in the contact hole that penetrates the second substrate 46, and electrically connects the excitation electrode of the functional element 78 and the oscillation circuit 59. In this embodiment, a pair of through electrodes 9 are provided at the position where they overlap with the external electrode 49.

[0193] One end of the through electrode 9 is electrically connected to the oscillation circuit 59, and the other end is electrically connected to the connection terminal 79 of the second substrate 46. The connection terminal 79 is electrically connected to one excitation electrode of the functional element 78 via wiring (not shown). Similarly, the other excitation electrode of the functional element 78 is also electrically connected to the oscillation circuit 59 via the corresponding through electrode 9.

[0194] The oscillation circuit 59 is electrically connected to an external electrode 49 via a contact electrode 69. The other external electrode 49 is also electrically connected to the oscillation circuit 59 via a contact electrode 69.

[0195] The structure of the recess 34, including the insulating layer 40, and the metal eutectic layer 20 is the same as described in the above embodiment. Furthermore, Figure 24 There are no wirings that intersect with the metal eutectic layer 20, but they can also have intersecting wirings in the same way as in the above embodiment.

[0196] As described above, the transducer 120 according to this embodiment can achieve the following effects in addition to the effects described in the above embodiment.

[0197] Similar to transducer 100, the first substrate 45 and the second substrate 46 are bonded in the bonding region 25 by a metal eutectic layer 20. When viewed from above, the bonding region 25 is formed in the recess 34 of the cover 88.

[0198] Therefore, reliable engagement is possible within the engagement region 25, enabling the provision of a highly reliable transducer 120.

Claims

1. A transducer, wherein, when three axes orthogonal to each other are set as an X axis, a Y axis, and a Z axis, the transducer includes: a first substrate; a second substrate configured to overlap the first substrate in a Z axis direction along the Z axis, and provided with an insulating layer on a surface; a functional element provided between the first substrate and the second substrate; and a metal eutectic layer joining the first substrate and the second substrate in a joining region located around the functional element, a recess is provided on a first surface of the second substrate on the first substrate side, the recess is composed of a second surface as a bottom and a side wall connecting the first surface and the second surface, the insulating layer includes: a first portion provided on the first surface; a second portion provided on the side wall; and a third portion provided on the second surface, the joining region is disposed between the second portions when viewed in a Y axis direction along the Y axis.

2. The transducer according to claim 1, wherein, the metal eutectic layer contains a first metal and a second metal, the insulating layer is any one of a silicon oxide layer, a silicon nitride layer, a boron oxide layer, and a bismuth oxide layer.

3. The transducer according to claim 2, wherein, when viewed in the Z axis direction, the transducer includes a wiring extending from an outer side of the second substrate, crossing the joining region, and electrically connected to the functional element, when a width of a portion of the metal eutectic layer overlapping the wiring is w1, and a width of a portion of the metal eutectic layer not overlapping the wiring is w2, w1 > w2 is satisfied.

4. The transducer according to claim 3, wherein, when a height of the portion of the metal eutectic layer overlapping the wiring is t1, and a height of the portion of the metal eutectic layer not overlapping the wiring is t2, t1 < t2 is satisfied.

5. The transducer according to claim 2, wherein, the first metal has aluminum as a main component, the second metal has germanium as a main component.

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