Transducer

Abstract

The invention provides a transducer which can be reliably bonded in a bonding region and has high reliability. The transducer includes: a second semiconductor substrate on which a first insulating layer having a first metal layer provided on a surface thereof is disposed; a first semiconductor substrate which is disposed so as to overlap the second semiconductor substrate and on which a second insulating layer having a second metal layer provided on the surface thereof is disposed; a functional element provided between the first semiconductor substrate and the second semiconductor substrate; and a eutectic reaction layer that bonds the first semiconductor substrate and the second semiconductor substrate in a bonding region located around the functional element, the eutectic reaction layer being a bonding layer formed by eutectic bonding of the first metal layer and the second metal layer. At least one of the first insulating layer and the second insulating layer is provided with a recessed portion having a bottom portion wider than the width of the bonding region, and the bonding region is disposed at the bottom portion.

Description

Technical Field

[0001] This invention relates to transducers. Background Technology

[0002] Previously, sensor devices were known to have a substrate with a cavity, a sensor element suspended within the cavity, and a cover that seals the cavity. The substrate and the cover are joined by a bonding material. This bonding material requires high bonding strength and high long-term reliability of the seal.

[0003] For example, Patent Document 1 discloses an inertial sensor using AlGe eutectic as a bonding material. According to this document, the concentration of Ge in the AlGe eutectic is uniform, or a function of distance from the cap or substrate. In particular, it discloses that the concentration of Ge becomes uniform after prolonged heat treatment.

[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 during the formation of the AlGe eutectic bonding material, the bonding material may overflow and expand from the bonding region, or the bonding material may scatter. If the AlGe eutectic scatters, it may cause malfunction of the inertial sensor. Since the inertial sensor is an example of a transducer, a transducer that can reliably bond within the bonding region and has high reliability is required. Summary of the Invention

[0006] The transducer includes: a first semiconductor substrate having a functional element disposed thereon; a second semiconductor substrate, which together with the first semiconductor substrate houses the functional element; a first insulating layer disposed on the second semiconductor substrate; a second insulating layer disposed on the first semiconductor substrate; and a eutectic reaction layer that bonds the first semiconductor substrate and the second semiconductor substrate in a bonding region, wherein at least one of the first insulating layer and the second insulating layer has a recess that, when viewed from above, extends over a range wider than the bonding region. Attached Figure Description

[0007] Figure 1 This is a top view showing the schematic structure of the transducer according to the first embodiment.

[0008] Figure 2 It means to Figure 1 A top view of the general structure after the second semiconductor substrate, which serves as the cover, has been removed.

[0009] Figure 3 yes Figure 1 and Figure 2 A cross-sectional view at line AA in the diagram.

[0010] Figure 4 yes Figure 1 and Figure 2 A sectional view at line BB in the diagram.

[0011] Figure 5 It means Figure 4 A cross-sectional view of the structure before joining.

[0012] Figure 6 yes Figure 1 and Figure 2 A sectional view at the CC line.

[0013] Figure 7 It means as Figure 2 The top view shows a schematic structure of the Y-axis sensor element 21y of the functional element 2 shown.

[0014] Figure 8 It means as Figure 2 The top view of the schematic structure of the Z-axis sensor element 21z of the functional element 2 shown.

[0015] Figure 9 This is a top view showing the schematic structure of the transducer in the second embodiment.

[0016] Figure 10 yes Figure 9 A sectional view at line DD in the diagram.

[0017] Figure 11 It means Figure 10 A cross-sectional view of the structure before joining.

[0018] Figure 12 This is a top view showing the schematic structure of the transducer in the third embodiment.

[0019] Figure 13 yes Figure 12 A cross-sectional view at the EE line.

[0020] Figure 14 This is a top view showing the schematic structure of the transducer in the fourth embodiment.

[0021] Figure 15 It means to Figure 14 A top view of the general structure after the second semiconductor substrate, which serves as the cover, has been removed.

[0022] Figure 16 yes Figure 14 and Figure 15 A sectional view at the FF line.

[0023] Figure 17 yes Figure 14 and Figure 15A cross-sectional view at the GG line. Detailed Implementation

[0024] 1. First Implementation Method

[0025] First, regarding the transducer 1 of the first embodiment, a triaxial accelerometer with sensor elements for detecting acceleration in the X, Y, and Z directions as functional elements 2 is cited as an example. Figures 1 to 6 Please provide an explanation.

[0026] In addition, Figure 2 In order to facilitate the explanation of the internal structure of transducer 1, the diagram shows the state in which the second semiconductor substrate 23, which serves as the cover, has been removed. Furthermore, in... Figures 1 to 6 The diagram omits the wiring that electrically connects the front end of the wiring 30 extending from the connection terminal 29 in the X-axis direction to the movable or fixed electrodes of each functional element 2.

[0027] For clarity, the X-axis, Y-axis, and Z-axis are shown in the figures as three mutually perpendicular axes. The direction along the X-axis is referred to as the "X-axis direction," the direction along the Y-axis as the "Y-axis direction," and the direction along the Z-axis as the "Z-axis direction." The end of the arrow in each axis is called the "positive side," the base side as the "negative side," the positive side of the Z-axis direction as "up," and the negative side of the Z-axis direction as "down." The Z-axis direction is vertical, and the XY plane is horizontal.

[0028] Generally, a transducer refers to a converter that transforms one physical quantity into another. There are transducers based on electromechanical conversion, transducers based on acoustic-electric conversion, and transducers based on photoelectric conversion, etc. One embodiment of the transducer in this application is simply a transducer that bonds the substrate and the cap at the eutectic reaction layer. It can be an inertial sensor that converts acceleration and 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.

[0029] In this embodiment, a triaxial accelerometer, which is one type of inertial sensor, will be used as an example of a transducer. In an accelerometer that seals a MEMS device element formed in a substrate through a cover, when 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 extracted as a sensor signal.

[0030] In this embodiment, functional element 2 is three sensor elements constituting a triaxial accelerometer, but it can also be a sensor element constituting a uniaxial accelerometer, or other sensor elements, or a vibrating element constituting an oscillator, or a piezoelectric reflector element constituting a piezoelectric reflector.

[0031] Figure 1 The transducer 1 shown can be used as a triaxial accelerometer capable of independently detecting acceleration in three directions. For example... Figure 2 , Figure 3 , Figure 4 , Figure 6 as well as Figure 1 As shown, such a transducer 1 includes: a first semiconductor substrate 22 on which a functional element 2 is disposed; a second semiconductor substrate 23 which, together with the first semiconductor substrate 22, houses the functional element 2; a first insulating layer 34 disposed on the second semiconductor substrate 23; a second insulating layer 32 disposed on the first semiconductor substrate 22; and a eutectic reaction layer 24 which bonds the first semiconductor substrate 22 and the second semiconductor substrate 23 in a bonding region 35 located around the functional element 2.

[0032] The first semiconductor substrate 22 is equivalent to the substrate, such as Figure 2 , Figure 3 as well as Figure 4 As shown, a recess 26 is provided that is recessed from the upper surface toward the side opposite to the second semiconductor substrate 23, and a plurality of support portions 11x, 11y, 11z, and 111z protruding upward from the inner bottom surface 27 of the recess 26. Sensor elements 21x, 21y, 21z, and 121z, which are functional elements 2, are fixed on the upper surfaces of the support portions 11x, 11y, 11z, and 111z in such a way that they are housed inside the recess 26 when viewed from above. Furthermore, in this embodiment, since sensor elements 21z and 121z are provided to detect acceleration in both Z-axis directions, the detection accuracy of acceleration in the Z-axis direction can be improved.

[0033] An X-axis sensor element 21x that detects acceleration in the X-axis direction has a fixing part 22x, which is fixed to the upper surface of a support part 11x. A Y-axis sensor element 21y that detects acceleration in the Y-axis direction has a fixing part 22y, which is fixed to the upper surface of a support part 11y. A Z-axis sensor element 21z that detects acceleration in the Z-axis direction has a fixing part 22z, which is fixed to the upper surface of a support part 11z. A Z-axis sensor element 121z that detects acceleration in the Z-axis direction has a fixing part 122z, which is fixed to the upper surface of a support part 111z.

[0034] likeFigure 6 and Figure 1 As shown, a second insulating layer 32 is provided on the first semiconductor substrate 22, and a recess 31 is provided on the second insulating layer 32, which surrounds the recess 26 when viewed from above and is recessed from the upper surface to the side opposite to the second semiconductor substrate 23. The recess 31 has a bottom wider than the width of the bonding region 35, on which the bonding region 35 is disposed. In addition, an insulating layer 20 is provided on the first semiconductor substrate 22 to prevent the wiring 30 from conducting with the first semiconductor substrate 22.

[0035] Furthermore, on the first semiconductor substrate 22, at the end on the negative side in the X-axis direction and at a position that does not overlap with the second semiconductor substrate 23 when viewed from above, a plurality of connection terminals 29 are provided along the Y-axis direction. From each connection terminal 29, wiring 30 extending in the X-axis direction is provided. In addition, the second insulating layer 32 is not formed on the connection terminals 29 and wiring 30 located at positions that do not overlap with the second semiconductor substrate 23 when viewed from above.

[0036] The second semiconductor substrate 23 is equivalent to a cover, such as Figure 3 and Figure 4 As shown, a recess 28 is provided that is recessed from the lower surface to the side opposite to the first semiconductor substrate 22, thereby accommodating the functional element 2 together with the recess 26 of the first semiconductor substrate 22.

[0037] like Figure 6 and Figure 5 As shown, a first insulating layer 34 is provided on the lower surface of the second semiconductor substrate 23. A recess 33 is provided on the first insulating layer 34, which, when viewed from above, surrounds the recess 28 and is recessed from the lower surface to the side opposite to the first semiconductor substrate 22. The recess 33 has a bottom wider than the width of the bonding region 35, on which the bonding region 35 is disposed. The recess 33 on the first insulating layer 34 is positioned at a location that overlaps with the recess 31 on the second insulating layer 32 when viewed from above.

[0038] The first semiconductor substrate 22 and the second semiconductor substrate 23 are bonded in a bonding region 35 between a recess 31 in the second insulating layer 32 of the first semiconductor substrate 22 and a recess 33 in the first insulating layer 34 of the second semiconductor substrate 23, by a eutectic reaction layer 24. The recesses 31 in the second insulating layer 32 and 33 in the first insulating layer 34 have a wider range than the bonding region 35 when viewed from above. That is, the length of the eutectic reaction layer 24 forming the bonding region 35 in the X-axis direction is shorter than the length of the recesses 31 and 33 in the X-axis direction, and the length of the eutectic reaction layer 24 forming the bonding region 35 in the Y-axis direction is shorter than the length of the recesses 31 and 33 in the Y-axis direction. Therefore, it is possible to prevent the bonding region 35 of the eutectic reaction layer 24, which serves as the bonding material, from overflowing from the recesses 31 and 33 or from scattering away.

[0039] Furthermore, although in this embodiment, recesses 31 and 33 with a range wider than the joint area 35 when viewed from above are provided on both the first insulating layer 34 and the second insulating layer 32, it is not limited to this, and recesses 31 and 33 with a range wider than the joint area 35 when viewed from above may also be provided on either the first insulating layer 34 or the second insulating layer 32.

[0040] Figure 4 This is a partial cross-sectional view of the first semiconductor substrate 22 and the second semiconductor substrate 23 before bonding, corresponding to Figure 5 Before joining, such as Figure 7 As shown, a first metal layer 39 is provided in the recess 33 of the first insulating layer 34, and a second metal layer 38 is provided in the recess 31 of the second insulating layer 32.

[0041] The first metal layer 39 is a Ge layer. The second metal layer 38 is an AlCu layer. The Cu in the AlCu layer is incorporated to prevent electromigration and has a low content. Therefore, the main component of the second metal layer 38 is Al.

[0042] The first metal layer 39 and the second metal layer 38 are bonded through a heating process and a pressurizing process. Specifically, the laminate formed by overlapping the first semiconductor substrate 22 and the second semiconductor substrate 23 is heated to above the eutectic temperature of the first metal layer 39 and the second metal layer 38, and then pressurized while heated to achieve eutectic bonding. The eutectic temperature of AlGe is approximately 420°C. In a preferred embodiment, the laminate is placed on the worktable of a heating fixture with the first semiconductor substrate 22 facing downwards. When the laminate reaches a predetermined temperature, a load for a predetermined time is applied from the second semiconductor substrate 23 side through a pressurizing fixture. At this time, the pressurizing fixture is also heated. Eutectic bonding generally refers to an alloy formed by the solidification of two or more metals from a mixed liquid phase.

[0043] Next, refer to Figure 8 and Figure 7 The principle of detecting the acceleration of the Y-axis sensor element 21y, X-axis sensor element 21x, and Z-axis sensor elements 21z and 21z, which are functional elements 2, will be explained.

[0044] like Figure 8 As shown, the Y-axis sensor element 21y has three fixing portions 22y arranged along the X-axis direction and two connecting portions 61 arranged along the Y-axis direction. The three fixing portions 22y are arranged between the two connecting portions 61, and the central fixing portion 22y is connected to the connecting portion 61. In addition, the distance between the connecting portion 61 and the fixing portion 22y on the positive side of the Y-axis direction is longer than the distance between the connecting portion 61 and the fixing portion 22y on the negative side of the Y-axis direction.

[0045] Two connecting portions 61 are connected to movable portions 62 surrounding the two connecting portions 61 and the three fixed portions 22y on the side opposite to the fixed portion 22y. The movable portion 62 has multiple movable electrodes 63 extending in the positive and negative X-axis directions respectively between the connecting portions 61 and the fixed portions 22y located on the positive side of the Y-axis direction. Furthermore, the connecting portions 61 are elastically deformable in the Y-axis direction like springs, thus allowing the movable portion 62 to shift in the Y-axis direction.

[0046] The two fixing portions 22y located in the center have fixing beams 64 extending along the oblique Y-axis direction on the positive and negative sides of the X-axis direction, respectively, and multiple fixing electrodes 65 extending from the fixing beams 64 toward the positive and negative sides of the X-axis direction, respectively. In addition, the multiple fixing electrodes 65 are arranged on the positive or negative side of the movable electrode 63 in the Y-axis direction, and are arranged in a comb-like pattern that is spaced apart and meshes with respect to the corresponding movable electrode 63.

[0047] When such a Y-axis sensor element 21y is subjected to acceleration in the Y-axis direction, the movable part 62 shifts in the Y-axis direction according to the magnitude of the acceleration. Accompanying this shift, the magnitude of the electrostatic capacitance between the movable electrode 63 and the fixed electrode 65 changes, and thus the acceleration can be determined based on the change in electrostatic capacitance.

[0048] X-axis sensor element 21x is an element that detects acceleration in the X-axis direction. Such X-axis sensor element 21x has the same structure as Y-axis sensor element 21y, except that it is configured to be rotated 90° relative to Y-axis sensor element 21y when viewed from above.

[0049] The connecting part 61, which is connected to the fixed part 22x, can elastically deform in the X-axis direction like a spring, so the movable part 62 can be displaced in the X-axis direction. Therefore, acceleration in the X-axis direction can be detected.

[0050] likeFigure 9 As shown, the Z-axis sensor element 21z has a fixed part 22z, a movable part 72, and a pair of support beams 71 that connect the movable part 72 to the fixed part 22z in a swinging manner. The movable part 72 swings relative to the fixed part 22z about the support beams 71 as an axis J1. Such a Z-axis sensor element 21z is formed, for example, from a silicon substrate doped with impurities such as phosphorus and boron.

[0051] The fixed portion 22z is anodically bonded to the upper surface of the support portion 11z, which protrudes upward from the inner bottom surface 27 of the recess 26 of the first semiconductor substrate 22. Furthermore, movable portions 72 are provided on the positive and negative sides of the fixed portion 22z in the Y-axis direction. The movable portion 72 includes: a first movable electrode 73 located on the positive side of the axis J1 in the Y-axis direction; and a second movable electrode 74 and a third movable electrode 75 located on the negative side of the axis J1 in the Y-axis direction. The first movable electrode 73 and the second movable electrode 74 are designed to have different rotational torques when acceleration in the Z-axis direction is applied, resulting in a predetermined tilt in the movable portion 72 according to the acceleration. Therefore, when acceleration in the Z-axis direction is generated, the movable portion 72 oscillates around the axis J1 in a seesaw-like manner.

[0052] Furthermore, a first detection electrode 76 is disposed on the inner bottom surface 27 of the recess 26 opposite to the first movable electrode 73, a second detection electrode 77 is disposed opposite to the second movable electrode 74, and a dummy electrode 78 is disposed opposite to the third movable electrode 75. Therefore, an electrostatic capacitance is formed between the first movable electrode 73 and the first detection electrode 76, and between the second movable electrode 74 and the second detection electrode 77. In addition, the dummy electrode 78 is provided to suppress the charging generated on the inner bottom surface 27 of the recess 26.

[0053] When such a Z-axis sensor element 21z is subjected to acceleration in the Z-axis direction, the movable part 72 swings in a seesaw manner around axis J1. This seesaw-like swinging of the movable part 72 changes the distance between the first movable electrode 73 and the first detection electrode 76, and the distance between the second movable electrode 74 and the second detection electrode 77. Correspondingly, the electrostatic capacitance between them changes, and therefore, the acceleration can be determined based on this change in electrostatic capacitance.

[0054] Z-axis sensor element 121z is an element that detects acceleration in the Z-axis direction. Such Z-axis sensor element 121z has the same structure as Z-axis sensor element 21z, except that it is configured in a state that is rotated 180° relative to Z-axis sensor element 21z when viewed from above.

[0055] Furthermore, although this embodiment describes a transducer 1 with a structure in which the functional element 2 is bonded on the first semiconductor substrate 22 as an example, it is not limited to this. A structure in which the first semiconductor substrate 22 is set as an SOI (Silicon On Insulator) substrate and the functional element 2 is integrated can also be adopted.

[0056] As described above, in the transducer 1 of this embodiment, the recess 31 provided in the second insulating layer 32 and the recess 33 provided in the first insulating layer 34 have a wider range than the bonding region 35 based on the eutectic reaction layer 24 when viewed from above. Therefore, it is possible to prevent the bonding region 35 of the eutectic reaction layer 24, which serves as the bonding material, from overflowing from the recess 31 and the recess 33 or from scattering the eutectic reaction layer 24, which serves as the bonding material.

[0057] 2. Second Implementation Method

[0058] Next, refer to Figure 10 , Figure 11 as well as Figure 9 The transducer 1a of the second embodiment will be described.

[0059] The transducer 1a of this embodiment is the same as the transducer 1 of the first embodiment, except that the structures of the first insulating layer 34a and the second insulating layer 32a are different. Furthermore, the description will focus on the differences from the first embodiment described above, and descriptions of identical items will be omitted.

[0060] like Figure 10 and Figure 11 As shown, the transducer 1a includes: a first semiconductor substrate 22a on which a functional element 2 is disposed; a second semiconductor substrate 23a which, together with the first semiconductor substrate 22a, houses the functional element 2; a first insulating layer 34a disposed on the second semiconductor substrate 23a; a second insulating layer 32a disposed on the first semiconductor substrate 22a; and a eutectic reaction layer 24 which bonds the first semiconductor substrate 22a and the second semiconductor substrate 23a in a bonding region 35. Furthermore, an insulating layer 20 is disposed on the first semiconductor substrate 22a to prevent the wiring 30 from conducting with the first semiconductor substrate 22a.

[0061] The first insulating layer 34a, when viewed from above, has a first through-hole 37 in the region overlapping with the eutectic reaction layer 24 and the recess 33. The eutectic reaction layer 24 fills the first through-hole 37, and the second semiconductor substrate 23a is connected to the eutectic reaction layer 24 through the first through-hole 37. Therefore, the second semiconductor substrate 23a and the eutectic reaction layer 24 can be at the same potential.

[0062] In a top view, the second insulating layer 32a overlaps with the eutectic reaction layer 24 and the recess 31 in the area where it overlaps with the first through-hole 37. A second through-hole 36 is formed at the location where it overlaps with the first through-hole 37. The eutectic reaction layer 24 fills the second through-hole 36. Through the second through-hole 36, a wiring 30 disposed between the first semiconductor substrate 22a and the second insulating layer 32a is connected to the eutectic reaction layer 24. Therefore, the wiring 30 and the eutectic reaction layer 24 can be set to the same potential.

[0063] Before joining, such as Figure 12 As shown, the second semiconductor substrate 23a and the first metal layer 39 are connected via a first through hole 37 disposed in the first insulating layer 34a, and the wiring 30 and the second metal layer 38 are connected via a second through hole 36 disposed in the second insulating layer 32a.

[0064] By configuring it in this way, the eutectic reaction layer 24, the second semiconductor substrate 23a and the wiring 30 can be at the same potential, and the same effect as the transducer 1 of the first embodiment can be obtained.

[0065] 3. Third Implementation Method

[0066] Next, refer to Figure 13 and Figure 12 The transducer 1b of the third embodiment will be described.

[0067] The transducer 1b of this embodiment is the same as the transducer 1 of the first embodiment, except that the structure of the recess 33b in the first insulating layer 34b is different. Furthermore, the description will focus on the differences from the first embodiment described above, and descriptions of identical items will be omitted.

[0068] like Figure 13 and Figures 14 to 17 As shown, the transducer 1b includes: a first semiconductor substrate 22 on which a functional element 2 is disposed; a second semiconductor substrate 23b which, together with the first semiconductor substrate 22, houses the functional element 2; a first insulating layer 34b disposed on the second semiconductor substrate 23b; a second insulating layer 32 disposed on the first semiconductor substrate 22; and a eutectic reaction layer 24 which bonds the first semiconductor substrate 22 and the second semiconductor substrate 23b in a bonding region 35. Furthermore, an insulating layer 20 is disposed on the first semiconductor substrate 22 to prevent the wiring 30 from conducting with the first semiconductor substrate 22.

[0069] The second semiconductor substrate 23b has a recess 28b having a protrusion 41 extending from the end in the Y-axis direction toward the positive side in the Y-axis direction.

[0070] The recess 33b of the first insulating layer 34b disposed on the lower surface of the second semiconductor substrate 23b has a third through-hole 40 at the protrusion 41, and the second semiconductor substrate 23b and the uneutecticized first metal layer 39 are connected through the third through-hole 40. Therefore, the second semiconductor substrate 23b is connected to the eutectic reaction layer 24 through the first metal layer 39, thereby enabling the second semiconductor substrate 23b and the eutectic reaction layer 24 to be at the same potential.

[0071] By configuring the structure in this way, the eutectic reaction layer 24 and the second semiconductor substrate 23b can be at the same potential, and the same effect as the transducer 1 of the first embodiment can be obtained.

[0072] 4. Fourth Implementation Method

[0073] Next, refer to Figures 14 to 17 The transducer 1c of the fourth embodiment will be described.

[0074] The transducer 1c of this embodiment is the same as the transducer 1 of the first embodiment, except that the structure of the functional element 2c is different. Furthermore, the description will focus on the differences from the first embodiment described above, and descriptions of identical items will be omitted.

[0075] like Figure 15 As shown, the transducer 1c is a tripod oscillator and includes: a first semiconductor substrate 22c on which a functional element 2c is disposed; a second semiconductor substrate 23c which, together with the first semiconductor substrate 22c, houses the functional element 2c; a first insulating layer 34 disposed on the second semiconductor substrate 23c; a second insulating layer 32 disposed on the first semiconductor substrate 22c; and a eutectic reaction layer 24 which bonds the first semiconductor substrate 22c and the second semiconductor substrate 23c in a bonding region 35.

[0076] like Figure 16 and Figure 17 As shown, the first semiconductor substrate 22c is provided with a recess 26 that is recessed from the upper surface toward the side opposite to that of the second semiconductor substrate 23c, and has a support portion 11c that protrudes upward from the inner bottom surface 27 of the recess 26. On the upper surface of the support portion 11c, a vibrating element having three vibrating arms 43, which serves as a functional element 2c, is fixed in such a way that it is housed inside the recess 26 when viewed from above.

[0077] The functional element 2c has a fixing part 42 and three vibrating arms 43 extending from the fixing part 42 in a predetermined direction. The fixing part 42 is fixed to the upper surface of the support part 11c.

[0078] like Figure 16As shown, a second insulating layer 32 is provided on the first semiconductor substrate 22c, and a recess 31 is provided on the second insulating layer 32, which surrounds the recess 26 when viewed from above and is recessed from the upper surface to the side opposite to the second semiconductor substrate 23c. In addition, an insulating layer 20 is provided on the first semiconductor substrate 22c to prevent wiring (not shown) from conducting with the first semiconductor substrate 22c.

[0079] like ​ As shown, the second semiconductor substrate 23c is provided with a recess 28 that is recessed from the lower surface to the side opposite to the first semiconductor substrate 22c, and together with the recess 26 of the first semiconductor substrate 22c, it houses the functional element 2c.

[0080] A first insulating layer 34 is provided on the lower surface of the second semiconductor substrate 23c. The first insulating layer 34 has a recess 33 that surrounds the recess 28 when viewed from above and is recessed from the lower surface to the side opposite to the side of the first semiconductor substrate 22c. The recess 33 provided in the first insulating layer 34 is positioned at a position that overlaps with the recess 31 provided in the second insulating layer 32 when viewed from above.

[0081] The first semiconductor substrate 22c and the second semiconductor substrate 23c are bonded together in a bonding region 35 between a recess 31 in the second insulating layer 32 of the first semiconductor substrate 22c and a recess 33 in the first insulating layer 34 of the second semiconductor substrate 23c, by a eutectic reaction layer 24. The recesses 31 in the second insulating layer 32 and 33 in the first insulating layer 34 have a wider range than the bonding region 35 when viewed from above.

[0082] By setting the structure in this way, the same effect as the transducer 1 in the first embodiment can be obtained.

Claims

1. A transducer, wherein, In a case where three axes perpendicular to each other are set as an X axis, a Y axis, and a Z axis, the transducer includes: a second semiconductor substrate provided with a first insulating layer in which a first metal layer is provided on a surface; a first semiconductor substrate provided so as to overlap the second semiconductor substrate in a Z-axis direction along the Z axis and provided with a second insulating layer in which a second metal layer is provided on a surface; a functional element provided between the first semiconductor substrate and the second semiconductor substrate; a eutectic reaction layer joining the first semiconductor substrate and the second semiconductor substrate in a joining region located around the functional element, the eutectic reaction layer being a joining layer based on eutectic bonding of the first metal layer and the second metal layer, at least either one of the first insulating layer and the second insulating layer is provided with a recess having a bottom wider than a width of the joining region, the joining region being provided to the bottom when viewed from the Z-axis direction.

2. The transducer according to claim 1, wherein the first insulating layer is provided with a first through-hole in a region overlapping the eutectic reaction layer and the recess when viewed from the Z-axis direction, the eutectic reaction layer is filled in the first through-hole and joined to the second semiconductor substrate.

3. The transducer according to claim 2, wherein a wiring is provided between the first semiconductor substrate and the second insulating layer, the second insulating layer is provided with a second through-hole in a region overlapping the eutectic reaction layer and the recess when viewed from the Z-axis direction, the eutectic reaction layer is filled in the second through-hole and joined to the wiring.

4. The transducer according to claim 3, wherein the first through-hole overlaps the second through-hole when viewed from the Z-axis direction.

5. The transducer according to claim 1, wherein the first metal layer is a Ge layer, and the second metal layer is a layer in which Al is a main component.

6. The transducer according to claim 5, wherein the second metal layer is an AlCu layer. ​

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