Physical quantity sensor manufacturing method

Abstract

To provide a physical quantity sensor in which cracks are hardly generated in a fused part of a through hole for sealing.SOLUTION: An angular velocity sensor 1 comprises an angular velocity detection element 3, a substrate 2, and a lid 4. The angular velocity detection element 3 is accommodated in a space 6 between the substrate 2 and the lid 4. The space 6 is sealed by a fused part 4c obtained by fusing a through hole 4b provided in the lid 4. The lid 4 and the fused part 4c include silicon. The fused part 4c includes a continuous curved surface 4d including irregularities.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a physical quantity sensor, an inertial measurement unit, and a method for manufacturing a physical quantity sensor. [Background technology]

[0002] Acceleration sensors, angular velocity sensors, etc. are realized using MEMS (Micro Electro Mechanical Systems). In MEMS, the moving body is housed in a sealed space inside a package. The air pressure in the sealed space is set to a level that allows the moving body to function easily.

[0003] A package sealing method is disclosed in Patent Document 1. According to this, the package includes a cap wafer as a silicon lid. The lid has a through-hole, and in the sealing process, a laser beam is irradiated onto the through-hole, melting the area around the through-hole and sealing it. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2013 / 0074596 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the sealing method of Patent Document 1 had the risk of cracks occurring in the through-hole provided in the lid. Specifically, when laser light is irradiated, the temperature rises rapidly around the sealing material and the through-hole, causing the sealing material to melt. When irradiation stops, the sealing material solidifies. However, because the sealing material and the lid have different thermal expansion coefficients, thermal stress remains near the through-hole close to the sealing material. This residual stress generates distortion, which may induce cracks. [Means for solving the problem]

[0006] The physical quantity sensor comprises a movable body, a base body, and a lid body, the movable body being housed in the space between the base body and the lid body, the space being sealed by a molten portion formed by melting a through hole provided in the lid body, the lid body and the molten portion containing silicon, and the molten portion having a continuous curved surface including irregularities.

[0007] The inertial measurement unit includes the physical quantity sensors described above.

[0008] A method for manufacturing a physical quantity sensor includes forming a through hole and a recess in a lid body containing silicon, storing a movable body in the space between the lid body and a base body, and irradiating the through hole and the recess with laser light to melt the through hole and the recess and seal the space. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional side view showing the configuration of an angular velocity sensor according to a first embodiment. [Figure 2] FIG. 2 is a schematic plan view showing an angular velocity detection element. [Figure 3] FIG. 3 is a schematic diagram for explaining the operation of the angular velocity detection element. [Figure 4] FIG. 3 is a schematic diagram for explaining the operation of the angular velocity detection element. [Figure 5] FIG. 3 is a schematic diagram for explaining the operation of the angular velocity detection element. [Figure 6] FIG. 3 is a schematic diagram for explaining the operation of the angular velocity detection element. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] 5A to 5C are schematic diagrams for explaining a method for manufacturing an angular velocity sensor. [Figure 10] 5A to 5C are schematic diagrams for explaining a method for manufacturing an angular velocity sensor. [Figure 11] FIG. 4 is a schematic plan view showing the shape of a second recess. [Figure 12] FIG. 4 is a schematic cross-sectional side view showing the shape of a second recess. [Figure 13]5A to 5C are schematic diagrams for explaining a method for manufacturing an angular velocity sensor. [Figure 14] 5A to 5C are schematic diagrams for explaining a method for manufacturing an angular velocity sensor. [Figure 15] 5A to 5C are schematic diagrams for explaining a method for manufacturing an angular velocity sensor. [Figure 16] 5A to 5C are schematic diagrams for explaining a method for manufacturing an angular velocity sensor. [Figure 17] FIG. 10 is a schematic cross-sectional side view showing the configuration of an acceleration sensor according to a second embodiment. [Figure 18] FIG. 2 is a schematic plan view showing an acceleration detection element. [Figure 19] FIG. [Figure 20] FIG. 10 is a schematic cross-sectional side view showing the configuration of an inertial sensor according to a third embodiment. [Figure 21] 5A to 5C are schematic diagrams for explaining a manufacturing method of the inertial sensor. [Figure 22] 5A to 5C are schematic diagrams for explaining a manufacturing method of the inertial sensor. [Figure 23] 5A to 5C are schematic diagrams for explaining a manufacturing method of the inertial sensor. [Figure 24] 5A to 5C are schematic diagrams for explaining a manufacturing method of the inertial sensor. [Figure 25] FIG. 2 is a block diagram showing the configuration of a laser sealing device. [Figure 26] 5A to 5C are schematic diagrams for explaining a manufacturing method of the inertial sensor. [Figure 27] 5A to 5C are schematic diagrams for explaining a manufacturing method of the inertial sensor. [Figure 28] 5A to 5C are schematic diagrams for explaining a manufacturing method of the inertial sensor. [Figure 29] 5A to 5C are schematic diagrams for explaining a manufacturing method of the inertial sensor. [Figure 30] FIG. 10 is a schematic perspective view showing the configuration of an inertial measurement unit according to a fourth embodiment. [Figure 31] FIG. 2 is a schematic perspective view showing the configuration of a substrate. [Figure 32] FIG. 11 is a schematic plan view of a main part showing the arrangement of through holes and recesses according to a fifth embodiment. [Figure 33]FIG. 4 is a schematic plan view of a main part showing the arrangement of through holes and recesses. DETAILED DESCRIPTION OF THE INVENTION

[0010] First embodiment In this embodiment, an example of a physical quantity sensor and a characteristic method for manufacturing the physical quantity sensor will be described. As shown in Fig. 1, an angular velocity sensor 1 as a physical quantity sensor includes a base body 2. An angular velocity detection element 3 as a movable body is provided on the base body 2. The material of the base body 2 may be silicon, glass, quartz, or the like.

[0011] The lid 4 is placed on the base 2. The material of the lid 4 is silicon. The lid 4 is bonded to the base 2 by a bonding layer 5. However, the lid 4 may also be bonded directly to the base 2. The direction from the base 2 to the lid 4 is the Z direction. When viewed from the Z direction, the planar shape of the base 2 and the lid 4 is a rectangle. The direction in which one side of the planar shape of the base 2 extends is the X direction, and the direction perpendicular to the X and Z directions is the Y direction.

[0012] The lid 4 has a first recess 4a on the base 2 side. The angular velocity detection element 3 is disposed in the first recess 4a. In this way, the angular velocity sensor 1 includes the base 2 and the lid 4 that houses the angular velocity detection element 3. The angular velocity detection element 3 is housed in the space 6 between the base 2 and the lid 4. As long as the angular velocity detection element 3 is housed in the space 6, the first recess 4a does not have to be provided on the base 2 side of the lid, as will be described later. A through hole 4b is provided in the lid 4. The lid 4 has a fused portion 4c formed by melting the through hole 4b. The fused portion 4c seals the space 6 by closing the through hole 4b. The fused portion 4c is part of the lid 4 and contains silicon. An electrode pad 19 that is electrically connected to the angular velocity detection element 3 is disposed on the base 2.

[0013] The through hole 4b is a through hole during the manufacturing process of the angular velocity sensor 1, but after being closed by the molten portion 4c, it becomes a blind hole. The name "through hole 4b" means that it is a through hole that is open halfway through the manufacturing process.

[0014] Next, the angular velocity detecting element 3 will be described. As shown in FIG. 2, the angular velocity detecting element 3 has a vibration system structure 104, a driving fixed electrode 130, a detecting fixed electrode 140, and a fixed portion 150.

[0015] The vibration system structure 104 is integrally formed, for example, by processing a silicon substrate bonded to the base 2. This makes it possible to apply fine processing techniques used in manufacturing silicon semiconductor devices, and the vibration system structure 104 can be made smaller.

[0016] The vibration system structure 104 is supported by a fixed part 150 fixed to the base 2 and is disposed at a distance from the base 2. The vibration system structure 104 has a first vibrating body 106 and a second vibrating body 108. The first vibrating body 106 and the second vibrating body 108 are connected to each other along the X-axis.

[0017] The first vibrating body 106 and the second vibrating body 108 have shapes that are symmetrical with respect to a boundary line B between them. The boundary line B is a straight line along the Y axis. The configuration of the first vibrating body 106 will be described, and a description of the configuration of the second vibrating body 108 will be omitted.

[0018] The first vibrating body 106 has a driving section 110 and a detection section 120. The driving section 110 has a driving support section 112, a driving spring section 114, and a driving movable electrode 116.

[0019] The drive support part 112 has, for example, a frame-like shape, and the detection part 120 is disposed inside the drive support part 112. The drive support part 112 is composed of a first extension part 112a extending along the X-axis and a second extension part 112b extending along the Y-axis.

[0020] The drive spring portion 114 is disposed outside the drive support portion 112. One end of the drive spring portion 114 is connected to the vicinity of a corner of the drive support portion 112. The corner of the drive support portion 112 is the connection portion between the first extension portion 112a and the second extension portion 112b. The other end of the drive spring portion 114 is connected to the fixed portion 150.

[0021] The first vibrating body 106 is provided with four drive spring portions 114. The first vibrating body 106 is supported by four fixing portions 150. Note that the fixing portion 150 on the boundary line B between the first vibrating body 106 and the second vibrating body 108 does not have to be provided. Furthermore, the first vibrating body 106 and the second vibrating body 108 may be directly connected using an elastically deformable connecting portion.

[0022] The drive spring portion 114 has a shape that extends along the X-axis while reciprocating along the Y-axis. The multiple drive spring portions 114 are provided symmetrically with respect to an imaginary line (not shown) that runs along the X-axis and passes through the center of the drive support portion 112, and an imaginary line (not shown) that runs along the Y-axis and passes through the center of the drive support portion 112. By giving the drive spring portion 114 the shape described above, deformation of the drive spring portion 114 in the Y-axis and Z-axis directions is suppressed, and the drive spring portion 114 can be smoothly expanded and contracted in the X-axis direction, which is the vibration direction of the drive portion 110. Then, as the drive spring portion 114 expands and contracts, the drive support portion 112 can be vibrated along the X-axis.

[0023] The movable driving electrode 116 is disposed outside the driving support portion 112 and connected to the driving support portion 112. The movable driving electrode 116 is connected to the first extending portion 112a of the driving support portion 112.

[0024] The driving fixed electrode 130 is disposed outside the driving support portion 112. The driving fixed electrode 130 is fixed on the base 2. A plurality of driving fixed electrodes 130 are provided and disposed opposite the driving movable electrode 116. The driving fixed electrode 130 has a comb-like shape. The driving movable electrode 116 has a protrusion 116a that can be inserted between the comb teeth of the driving fixed electrode 130. By reducing the distance between the driving fixed electrode 130 and the protrusion 116a, the electrostatic force acting between the driving fixed electrode 130 and the driving movable electrode 116 can be increased.

[0025] When a voltage is applied to the driving fixed electrode 130 and the driving movable electrode 116, an electrostatic force can be generated between the driving fixed electrode 130 and the driving movable electrode 116. This causes the driving spring portion 114 to expand and contract along the X-axis, and the driving support portion 112 of the driving portion 110 to vibrate along the X-axis.

[0026] The detection unit 120 is connected to the drive unit 110. In the illustrated example, the detection unit 120 is arranged inside the drive support unit 112. The detection unit 120 can have a detection support unit 122, a detection spring unit 124, and a detection movable electrode 126. Although not illustrated, the detection unit 120 may be arranged outside the drive support unit 112 as long as it is connected to the drive unit 110.

[0027] The detection support portion 122 has, for example, a frame-like shape. In the illustrated example, the detection support portion 122 is configured by a third extension portion 122a extending along the X-axis and a fourth extension portion 122b extending along the Y-axis.

[0028] The detection spring portion 124 is disposed outside the detection support portion 122. The detection spring portion 124 connects the detection support portion 122 and the drive support portion 112. More specifically, one end of the detection spring portion 124 is connected to the vicinity of a corner of the detection support portion 122. The corner of the detection support portion 122 is the connection portion between the third extension portion 122a and the fourth extension portion 122b. The other end of the detection spring portion 124 is connected to the first extension portion 112a of the drive support portion 112.

[0029] The detection spring portion 124 has a shape that reciprocates along the X-axis and extends along the Y-axis. In the illustrated example, four detection spring portions 124 are provided in the first vibrating body 106. The multiple detection spring portions 124 are provided symmetrically with respect to a virtual line (not shown) that passes through the center of the detection support portion 122 along the X-axis and a virtual line (not shown) that passes through the center of the detection support portion 122 along the Y-axis. By providing the detection spring portions 124 with the above-described shape, deformation of the detection spring portions 124 in the X-axis and Z-axis directions is suppressed, and the detection spring portions 124 can smoothly expand and contract in the Y-axis direction, which is the vibration direction of the detection unit 120. Then, as the detection spring portions 124 expand and contract, the detection support portion 122 of the detection unit 120 can be vibrated along the Y-axis. Note that the number of detection spring portions 124 is not particularly limited as long as the detection spring portions 124 can vibrate the detection support portion 122 along the Y-axis.

[0030] The detection movable electrode 126 is arranged inside the detection support portion 122 and connected to the detection support portion 122. In the illustrated example, the detection movable electrode 126 extends along the X-axis and is connected to the two fourth extension portions 122b of the detection support portion 122.

[0031] The detection fixed electrode 140 is disposed inside the detection support portion 122. The detection fixed electrode 140 is fixed on the base 2. In the illustrated example, a plurality of detection fixed electrodes 140 are provided and are disposed opposite each other with the detection movable electrode 126 interposed therebetween.

[0032] The number and shape of the detection movable electrodes 126 and the detection fixed electrodes 140 are not particularly limited as long as a change in the electrostatic capacitance between the detection movable electrodes 126 and the detection fixed electrodes 140 can be detected.

[0033] Next, a description will be given of the operation of the angular velocity detection element 3. Figures 3 to 6 are schematic diagrams for explaining the operation of the angular velocity detection element 3 of the angular velocity sensor 1 according to this embodiment. For convenience, each part of the angular velocity detection element 3 is illustrated in a simplified form in Figures 3 to 6.

[0034] When a voltage is applied to the driving fixed electrode 130 and the driving movable electrode 116, an electrostatic force can be generated between the driving fixed electrode 130 and the driving movable electrode 116. This allows the driving spring portion 114 to expand and contract along the X-axis, and the driving portion 110 to vibrate along the X-axis, as shown in Figures 3 and 4.

[0035] More specifically, a first AC voltage is applied between the movable driving electrode 116 and the fixed driving electrode 130 of the first vibrating body 106, and a second AC voltage 180 degrees out of phase with the first AC voltage is applied between the movable driving electrode 116 and the fixed driving electrode 130 of the second vibrating body 108. This allows the first driving unit 110a of the first vibrating body 106 and the second driving unit 110b of the second vibrating body 108 to vibrate along the X-axis in opposite phases and at a predetermined frequency. That is, the first driving unit 110a and the second driving unit 110b, which are connected to each other along the X-axis, vibrate in opposite phases along the X-axis. This vibration is referred to as a first vibration. For example, as shown in FIG. 3, the first driving unit 110a is displaced in the α1 direction, and the second driving unit 110b is displaced in the α2 direction, which is opposite to the α1 direction. Next, as shown in Figure 4, the first driver 110a is displaced in the α2 direction, and the second driver 110b is displaced in the α1 direction. The first driver 110a and the second driver 110b repeat this operation. In this way, the first driver 110a and the second driver 110b vibrate in opposite phases to each other.

[0036] Since the detection unit 120 is connected to the drive unit 110, the detection unit 120 also vibrates along the X-axis in accordance with the vibration of the drive unit 110. That is, the first vibrating body 106 and the second vibrating body 108 vibrate in opposite phases to each other along the X-axis. This vibration is referred to as the first vibration.

[0037] As shown in FIGS. 5 and 6, when the first driver 110a and the second driver 110b are performing the first vibration and an angular velocity ω about the Z axis is applied to the angular velocity sensor 3, the Coriolis force acts, displacing the detector 120 along the Y axis. That is, the first detector 120a connected to the first driver 110a and the second detector 120b connected to the second driver 110b are displaced in opposite directions along the Y axis due to the first vibration and the Coriolis force. For example, as shown in FIG. 5, the first detector 120a is displaced in the β1 direction, and the second detector 120b is displaced in the β2 direction, which is opposite to the β1 direction. Next, as shown in FIG. 6, the first detector 120a is displaced in the β2 direction, and the second detector 120b is displaced in the β1 direction. The first detector 120a and the second detector 120b repeat this operation while receiving the Coriolis force.

[0038] Displacement of the first detection unit 120a and the second detection unit 120b along the Y-axis changes the distance L between the detection movable electrode 126 and the detection fixed electrode 140. Therefore, the capacitance between the detection movable electrode 126 and the detection fixed electrode 140 changes. In the angular velocity detection element 3, by applying a voltage to the detection movable electrode 126 and the detection fixed electrode 140, the amount of change in the capacitance between the detection movable electrode 126 and the detection fixed electrode 140 can be detected, and the angular velocity ω about the Z-axis can be obtained.

[0039] Next, we will explain the melting portion 4c of the lid 4. As shown in Figures 7 and 8, when viewed from the Z direction, the melting portion 4c has a substantially circular shape and overlaps with the through-hole 4b. The melting portion 4c has a continuous curved surface 4d that includes irregularities.

[0040] According to this configuration, the through-hole 4b is sealed, and the space 6 is therefore sealed by the lid 4. A molten portion 4c is formed by irradiating with laser light. The molten portion 4c is polycrystalline, and the area around the molten portion 4c is single crystalline. The crystalline structure of the molten portion 4c and the area around the molten portion 4c are different. In areas where the crystal structure changes suddenly, the change in residual stress is large and cracks are likely to occur. When the fusion zone 4c has a continuous curved surface 4d with unevenness, the change in crystal structure is gradual. Therefore, the change in residual stress is gradual, which can suppress the occurrence of cracks.

[0041] The lid body 4 is single crystal, and the fused portion 4c is polycrystalline. Specifically, the lid body 4 is single crystal except for the fused portion 4c. With this configuration, the polycrystalline fused portion 4c can be easily formed by irradiating the single crystal lid body 4 with laser light to heat it.

[0042] Although the dimensions of the lid 4 are not particularly limited, in this embodiment, for example, the thickness of the lid 4 is 180 μm. The depth of the first recess 4a is 50 μm. Therefore, the thickness of the lid 4 at the first recess 4a is 130 μm.

[0043] The diameter of the through hole 4b is 10 μm to 30 μm. The molten portion irregularity depth 7, which is the depth of the molten portion 4c, is preferably 10 μm to 50 μm. The molten portion irregularity depth 7 indicates the length from the bottom of the recessed portion of the molten portion 4c to the protruding portion. When the beam focus diameter of the laser light is 200 μm, the molten portion diameter 8, which is the diameter of the molten portion 4c, is 140 μm to 220 μm. In other words, it is 70 to 110% of the beam focus diameter. The length from the second surface 4f to the end face of the through hole 4b is defined as the molten portion depth 17. The molten portion depth 17 is defined as D, and the molten portion diameter 8 is defined as L. The D / L ratio, which is the depth-to-diameter ratio obtained by dividing the molten portion depth 17 by the molten portion diameter 8, is preferably 0.5 to 3.0.

[0044] The angular velocity detection element 3 always vibrates at a constant frequency, and the air pressure in the space 6 is reduced to reduce the resistance during vibration. The air pressure in the space 6 is set to 0.1 Pa to 10 Pa so that the Q value of the vibration is high and the element 3 vibrates stably.

[0045] If a crack occurs in the lid 4, a leak path is created between the space 6 and the outside air. The air pressure in the space 6 becomes atmospheric pressure. At this time, the vibration of the angular velocity detecting element 3 is damped, and the detection sensitivity of the angular velocity detecting element 3 decreases.

[0046] Next, a method for manufacturing the angular velocity sensor 1 will be described. In FIG. 9, a recess 2a is formed in the insulating substrate 2, and metal wiring (not shown) is formed thereon. The substrate 2 may be glass, quartz, or the like. In this embodiment, for example, Tempax (registered trademark) glass is used. When glass is used for the substrate 2, the recess 2a is formed by wet etching with HF. HF stands for hydrogen fluoride. The angular velocity sensing element 3 is formed by anodically bonding a silicon substrate and then vertically processing it using the Bosch process. A good electrical connection can be achieved by alloying the bumps on the metal wiring (not shown) with silicon through heat treatment. A good silicide alloy can be formed by forming the outermost surface of the metal wiring with platinum. The method for forming the angular velocity sensing element 3 is well known, and a detailed description thereof will be omitted.

[0047] As shown in FIG. 10, a substrate that will serve as the material for the lid 4 is prepared. The substrate for the lid 4 has a silicon (100) surface. A first recess 4a of approximately 30 μm to 50 μm is formed on the first surface 4e by the Bosch process. The surface of the lid 4 opposite the first surface 4e is designated as the second surface 4f. A through-hole 4b and a second recess 4g are further formed on the second surface 4f of the lid 4 by the Bosch process. The second recess 4g is also referred to as a dummy pattern. The etching depth of the through-hole 4b and the second recess 4g may be controlled by utilizing the microloading effect or by adjusting the thickness of a mask. Next, a bonding layer 5 is formed on the lid 4. The bonding layer 5 is printed on the entire wafer on the side of the lid 4 using screen printing technology. The bonding layer 5 may also be disposed on the base 2. In this manner, the through-hole 4b and the second recess 4g are formed on the second surface 4f of the silicon-containing lid 4.

[0048] 11, in a plan view seen from the Z direction, the second recess 4g is formed by a first groove 9 and a second groove 10 that are concentric with the through hole 4b. The groove width 11 of the first groove 9 and the second groove 10 is preferably 10 μm or more and 20 μm or less. The groove distance 12 between the first groove 9 and the second groove 10 is preferably 10 μm or more and 20 μm or less.

[0049] 12, the groove depth 13 of the first groove 9 and the second groove 10 is 20 μm or more and 40 μm or less. The through hole 4b and the second recess 4g are formed using the well-known Bosch process, which allows etching with a high aspect ratio.

[0050] The groove depth 13 may be controlled by changing the number of etching times for the through-hole 4b and the second recess 4g. For example, suppose the length of the through hole 4b is 130 μm and the groove depth 13 is 30 μm. The depth dug in one etching cycle is 1 μm. First, the through hole 4b is dug 100 μm by performing 100 etching cycles. Next, the through hole 4b and the second recess 4g are dug in parallel to each other by 30 μm by adding 30 etching cycles. By this method, the through hole 4b is completely formed and the groove depth 13 becomes 30 μm.

[0051] As shown in FIG. 13, the lid 4 and the base 2 are bonded together. The bonding is performed by applying pressure and heat. The pressure is 10 to 1000 kPa, and the heating is performed at a temperature of 250 to 500°C. The atmosphere may be an inert gas such as nitrogen or argon, and the pressure may be vacuum, atmospheric pressure, or positive pressure. The lid 4 is bonded to the base 2 using a glass frit material that forms the bonding layer 5. In this embodiment, frit bonding using glass frit is used, but anodic bonding, direct bonding, metal eutectic bonding, or plasma activated bonding may also be used. The through hole 4b and the second recess 4g may be formed after bonding the bonding layer 5. The angular velocity sensor 3 is accommodated in a space 6 between the base 2 on which the angular velocity sensor 3 is provided and the lid 4.

[0052] As shown in FIG. 14, degassing is performed by vacuum heating. Specifically, heating is performed at a temperature above 300°C and below 100 Pa for several hours. The gas in the space 6 is extracted to the outside through the through-hole 4b. In this embodiment, the pressure inside the vacuum chamber is reduced to, for example, 1 Pa. The chamber is then placed in a reduced-pressure atmosphere. Next, a hydrophobic treatment is performed to prevent moisture from adhering to the space 6. For the hydrophobic treatment, HMDS, a silane coupling agent, is used. HMDS stands for hexamethyldisilazane. This hydrophobic treatment reduces the moisture content of the space 6 to 100 ppm or less. Preventing moisture from entering the space 6 makes it possible to maintain a high vacuum state in the space 6. This allows the angular velocity sensing element 3 to oscillate stably with a high vibration Q value.

[0053] Next, as shown in FIG. 15, laser light 14 is irradiated onto the second recess 4g and the through-hole 4b. The base 2 and the lid 4 are heated, and while the temperature of the lid 4 is elevated, the laser light 14 is simultaneously irradiated onto the through-hole 4b and the second recess 4g. The laser light 14 is emitted from a laser light source 15 and focused by a focusing optical system 16. The diameter of the focused portion 14a where the laser light 14 is focused is 100 μm to 200 μm. The second recess 4g promotes diffraction of the laser light 14, allowing for melting with lower energy. This reduces dross and debris, and cracks are less likely to occur. By raising the temperature of the lid 4, melting can be achieved with even lower energy. The power of the laser light 14 may be 0.5 to 1.0 times the power required to melt the flat second surface 4f. The second recess 4g and the through-hole 4b are irradiated with laser light 14, which melts the second recess 4g and the through-hole 4b and seals the space 6. The irradiation of the laser light 14 is carried out in a reduced pressure atmosphere in a chamber including a window portion that is transparent to the laser light 14. When the laser light 14 is irradiated, the lid body 4 is heated via the base body 2.

[0054] The wavelength of the laser light 14 is 1070 nm to 1100 nm, which is close to the band gap of silicon. Since the material of the lid body 4 is silicon, a laser with a wavelength with a small optical absorption coefficient was selected to prevent ablation during the laser irradiation process. A wavelength with a small optical absorption coefficient is a laser with a wavelength close to the band gap wavelength of silicon or longer than that. If the wavelength is 800 nm or longer, the optical absorption coefficient is 300 cm -1 By selecting a laser with such a wavelength, it is possible to melt silicon by thermal processing. In this embodiment, for example, a YAG laser (Yttrium Aluminum Garnet) is used and the wavelength of the laser light 14 is set to about 1064 nm.

[0055] As shown in Figure 12, the laser beam 14 is diffracted at the second recess 4g, allowing for more efficient laser melting. For example, when the laser irradiation energy required to melt a flat surface is E0, good melting can be achieved with an energy amount of 0.1 to 0.5 x E0. This allows for hole sealing with reduced debris and dross.

[0056] According to this method, a through hole 4b and a second recess 4g are formed in the lid 4. The through hole 4b is irradiated with laser light 14. The lid 4 melts and the through hole 4b is blocked. At the second recess 4g, part of the laser light 14 is diffracted, so the laser light 14 travels in multiple directions around the through hole 4b. The laser light 14 is absorbed by the silicon at a shallow location near the surface of the lid 4. At the through hole 4b, the temperature is high near the surface of the lid 4, and the temperature decreases gradually with increasing distance from the surface. The temperature also decreases gradually with increasing distance from the through hole 4b.

[0057] The fused portion 4c is polycrystalline, while the area around the fused portion 4c is single crystalline. The fused portion 4c and the area around the fused portion 4c have different crystal structures, but their thermal expansion coefficients are approximately the same. In the through-hole 4b, the crystalline structure changes gradually as the distance from the surface of the lid 4 increases. Furthermore, the crystalline structure changes gradually as the distance from the through-hole 4b increases. Therefore, the change in residual stress is gradual, which helps prevent cracks from occurring.

[0058] When the laser beam 14 is irradiated, the angular velocity sensor 1 is placed in a reduced pressure atmosphere in a chamber including a window portion that is transparent to the laser beam 14 , and the lid 4 is heated via the base 2 . According to this method, the through-hole 4b is sealed in a reduced-pressure atmosphere, so the space 6 housing the angular velocity sensing element 3 is hermetically sealed in a reduced-pressure state. In a reduced-pressure atmosphere, the thermal conductivity of the atmospheric gas is low, causing the temperature of the lid 4 to drop. Generally, the thermal conductivity of gas varies significantly at a pressure between 100 and 1,000 Pa. Therefore, since the pressure in the space 6 where the angular velocity sensing element 3 can easily operate is between 0.1 and 10 Pa, heating the lid 4 through the base 2 significantly reduces efficiency. A drop in the temperature of the lid 4 makes it difficult to melt, requiring stronger laser irradiation energy. This can cause debris and dross to form. In this method, the lid 4 is sufficiently heated to 300°C or higher, ensuring that the lid 4 melts and seals the through-hole 4b.

[0059] Next, as shown in FIG. 16, at least one side of the lid 4 is cut off with a dicing blade 18. This makes it possible to expose the electrode pads 19 arranged on the base 2, which means that wire bonding is possible. Furthermore, the base 2 and the bonding layer 5 are not cut at this time. Therefore, the space 6 can maintain good airtightness. Finally, the four sides of the base 2 are separated, and the angular velocity sensor 1 is taken out. The angular velocity sensor 1 is completed through the above steps.

[0060] Second embodiment This embodiment differs from the first embodiment in that an acceleration detection element is installed instead of the angular velocity detection element 3. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted.

[0061] As shown in FIG. 17, an acceleration sensor 21 serving as a physical quantity sensor includes a base body 2. The base body 2 is provided with an acceleration detection element 22 as a movable body.

[0062] A lid 23 is placed on the base 2. The lid 23 is bonded to the base 2 by a bonding layer 5. The lid 23 has a first recess 23a on the base 2 side. The acceleration detection element 22 is disposed in the first recess 23a. In this way, the acceleration sensor 21 includes the base 2 and the lid 23 that houses the acceleration detection element 22. The acceleration detection element 22 is housed in the space 6 between the base 2 and the lid 23. The lid 23 has a through hole 23b. The lid 23 has a fused portion 23c formed by melting the through hole 23b. The fused portion 23c seals the space 6 by closing the through hole 23b. The fused portion 23c has a continuous curved surface 23d that includes irregularities.

[0063] Next, the acceleration detecting element 22 will be described. 18 is an acceleration sensor element that detects acceleration Ax in the X direction. A first mount portion 76 and a second mount portion 77 are provided on the base 2, and support the acceleration detection element 22. The acceleration detection element 22 includes a movable portion 71, a spring portion 72, a fixed portion 73, a first fixed detection electrode 74, and a second fixed detection electrode 75.

[0064] The movable part 71 has a base part 71a extending in the X direction and movable detection electrodes 71b, which are multiple movable electrodes protruding from the base part 71a on both sides in the Y direction. The movable part 71 is connected to fixed parts 73 via spring parts 72 at both ends of the base part 71a. The fixed parts 73 are fixed to a first mount part 76 protruding from the base body 2. This allows the movable part 71 to be displaced in the X direction relative to the fixed part 73. The first fixed detection electrode 74 and the second fixed detection electrode 75, which are fixed electrodes, are fixed to a second mount part 77 protruding from the base body 2, with the movable detection electrode 71b sandwiched between them.

[0065] A first fixed detection electrode 74 and a second fixed detection electrode 75 are disposed between the two movable detection electrodes 71b. When the movable part 71 is displaced in the positive X direction, the movable detection electrode 71b approaches the first fixed detection electrode 74 and moves away from the second fixed detection electrode 75. When the movable part 71 is displaced in the negative X direction, the movable detection electrode 71b approaches the second fixed detection electrode 75 and moves away from the first fixed detection electrode 74.

[0066] The movable detection electrode 71b of the movable part 71 is electrically connected to the first terminal via wiring provided on the base 2 and the contact 68. The first fixed detection electrode 74 is electrically connected to the second terminal via wiring. The second fixed detection electrode 75 is electrically connected to the third terminal via wiring. A predetermined voltage is applied to the movable detection electrode 71b, first fixed detection electrode 74, and second fixed detection electrode 75 of the movable part 7 via the first terminal, second terminal, and third terminal, and electrostatic capacitance is formed between the movable detection electrode 71b and the first fixed detection electrode 74 and second fixed detection electrode 75, respectively. The first terminal, second terminal, and third terminal are each one of the electrode pads 19.

[0067] Such an acceleration detection element 22 can detect acceleration Ax as follows. When acceleration Ax is applied to the acceleration detection element 22, the movable portion 71 is displaced in the X direction based on the magnitude of the acceleration Ax while elastically deforming the spring portion 72. As the movable portion 71 is displaced, the gap between the movable detection electrode 71b and the first fixed detection electrode 74 and the gap between the movable detection electrode 71b and the second fixed detection electrode 75 change, and the capacitance between them changes accordingly. Therefore, the acceleration Ax can be detected based on the amount of change in this capacitance.

[0068] In Figure 17, a through-hole 23b is provided in the lid 23, allowing the atmospheric pressure of the space 6 housing the acceleration detection element 22 to be adjusted. Adjusting the atmospheric pressure of the space 6 provides a damping effect that reduces the amplitude of unwanted vibrations of the acceleration detection element 22. The damping effect must be sufficient throughout the product's lifespan. Specifically, the sealing pressure is preferably set to 10,000 to 150,000 Pa using an inert gas such as nitrogen or argon. After adjusting the pressure in space 6 to a pressure that allows acceleration detection element 22 to easily operate, through-hole 23b is sealed using laser light 14. When the laser irradiation energy that can melt a flat surface is E0, good melting can be achieved with an energy amount of 0.1 to 0.5 × E0.

[0069] The base 2 and lid 23 are also heated by a heater during the sealing process for sealing the acceleration detection element 22. The heating temperature for the lid 23 is preferably lower than that for the angular velocity detection element 3. This temperature is preferably 200°C to 300°C, lower than that of the first embodiment. During the sealing process for the acceleration detection element 22, the pressure in the space 6 is set to 10,000 to 150,000 Pa, higher than that used when sealing the angular velocity detection element 3, as described above. This ensures that the thermal conductivity of the ambient gas is relatively high. Therefore, the through-hole 23b can be melted well even at a temperature lower than that of the angular velocity detection element 3. Furthermore, because the lid 23 reaches a higher temperature due to the laser melting, it is preferable to set the temperature slightly lower. After all laser melting processes are completed, the acceleration sensor 21 is returned to room temperature and then removed from the chamber.

[0070] In the case of the acceleration sensor 21, it is possible to prevent cracks from occurring in the through-hole 23b, as in the case of the angular velocity sensor 1. Therefore, it is possible to manufacture a highly reliable acceleration sensor 21.

[0071] Next, a description will be given of the fusion portion 23c of the lid 23. As shown in Fig. 19, when viewed from the Z direction, the fusion portion 23c has a substantially circular shape and overlaps with the through-hole 23b. The fusion portion 23c has a continuous curved surface 23d including projections and recesses.

[0072] Although the dimensions of the lid 23 are not particularly limited, in this embodiment, for example, the thickness of the lid 23 is 180 μm. The depth of the first recess 23a is 50 μm. Therefore, the thickness of the lid 23 at the first recess 23a is 130 μm.

[0073] The diameter of through hole 23b is preferably 10 μm to 30 μm. Melt portion irregularity depth 7, which is the depth of melt portion 23c, is 10 μm or more and 50 μm or less. Melt portion irregularity depth 7 indicates the length from the bottom of the recessed portion of melt portion 23c to the protruding portion. When the beam focus diameter of the laser light is 200 μm, melt portion diameter 8, which is the diameter of melt portion 23c, is 140 μm to 220 μm. In other words, it is 70 to 110% of the beam focus diameter. The length from second surface 23f to the end face of through hole 23b is defined as melt portion depth 17. Melt portion depth 17 is defined as D, and melt portion diameter 8 is defined as L. The D / L ratio, which is the depth-to-diameter ratio obtained by dividing melt portion depth 17 by melt portion diameter 8, is preferably 0.01 or more and 0.5 or less.

[0074] Third embodiment This embodiment differs from the first and second embodiments in that the physical quantity sensor is provided with an angular velocity detection element 3 and an acceleration detection element 22. Note that the same components as those in the first and second embodiments are denoted by the same reference numerals, and redundant explanations will be omitted.

[0075] As shown in FIG. 20, an inertial sensor 81 serving as a physical quantity sensor includes a base body 82 . The base 82 includes a silicon substrate 82a, a silicon oxide layer 82b, and a polycrystalline silicon layer 82c. The silicon oxide layer 82b is stacked on the silicon substrate 82a. The polycrystalline silicon layer 82c is stacked on the silicon oxide layer 82b. The angular velocity detecting element 3 and the acceleration detecting element 22 are provided on the silicon oxide layer 82b.

[0076] The inertial sensor 81 includes a base 82 and a lid 83 that houses the angular velocity detecting element 3 and the acceleration detecting element 22. The lid 83 is joined to the base 82 via a joining layer 86. The angular velocity detecting element 3 is housed in a first space 84, which is the space between the base 82 and the lid 83. The acceleration detecting element 22 is housed in a second space 85, which is the space between the base 82 and the lid 83. In this case, no recesses are provided on the surface of the lid 83 that faces the angular velocity detecting element 3 and the acceleration detecting element 22.

[0077] The lid 83 is provided with a first through hole 83a and a second through hole 83b. The lid 83 has a first molten portion 83c as a molten portion formed by melting the first through hole 83a. The first molten portion 83c closes the first through hole 83a, thereby sealing the first space 84. The lid 83 has a second molten portion 83d as a molten portion formed by melting the second through hole 83b. The second molten portion 83d closes the second through hole 83b, thereby sealing the second space 85. A partition wall 87 is arranged between the first space 84 and the second space 85.

[0078] The first through hole 83a and the first fusion zone 83c correspond to the through hole 4b and the fusion zone 4c in the first embodiment, respectively. The shape of the first fusion zone 83c is approximately the same as the fusion zone 4c. The first space 84 and the angular velocity detection element 3 are approximately the same as the space 6 and the angular velocity detection element 3 in the first embodiment, respectively. The air pressure in the first space 84 is approximately the same as the air pressure in the space 6 in the first embodiment.

[0079] The second through hole 83b and the second fusion zone 83d correspond to the through hole 23b and the fusion zone 23c in the second embodiment, respectively. The shape of the second fusion zone 83d is approximately the same as the fusion zone 23c. The second space 85 and the acceleration detecting element 22 are approximately the same as the space 6 and the acceleration detecting element 22 in the second embodiment, respectively. The air pressure in the second space 85 is approximately the same as the air pressure in the space 6 in the second embodiment. The depths of the first fusion zone 83c and the second fusion zone 83d are different because the laser irradiation energies are different.

[0080] Next, a method for manufacturing the inertial sensor 81 will be described. In FIG. 21, a silicon substrate 82a is prepared. A silicon oxide layer 82b serving as a sacrificial layer and a polycrystalline silicon layer 82c serving as an element layer are formed on the silicon substrate 82a. A lower electrode layer (not shown) may be formed under the silicon oxide layer 82b. In this case, silicon nitride serving as an etching stop layer is formed on the lower surface. The silicon oxide layer 82b has a thickness of 2 μm or less, and the polycrystalline silicon layer 82c has a thickness of approximately 15 μm to 30 μm. Sputtering, vapor deposition, and CVD are used to form each layer. Patterning is performed using photolithography, and the angular velocity detecting element 3 and the acceleration detecting element 22 are formed using the Bosch method. At this time, the polycrystalline silicon layer 82c fixed to the silicon substrate 82a as part of the partition wall between the elements is left, preventing communication between the first space 84 and the second space 85. The silicon oxide layer 82b is then released using HF vapor. A plurality of physical quantity sensors, such as the angular velocity detecting element 3 and the acceleration detecting element 22, are provided on the base 82.

[0081] In Figure 22, a substrate 83m is prepared as the material for the lid 83. The substrate 83m has a silicon (100) surface. The surface of the substrate 83m opposite the base 82 is designated as a second surface 83f. A first through hole 83a, a second through hole 83b, a third recess 83g, and a fourth recess 83h are formed on the second surface 83f by the Bosch process. The third recess 83g and the fourth recess 83h correspond to the second recess 4g in the first embodiment.

[0082] The etching depth of the first through-hole 83a, the second through-hole 83b, the third recess 83g, and the fourth recess 83h may be controlled by utilizing the microloading effect or by adjusting the thickness of the mask. Next, a bonding layer 86 is formed on the substrate 83m. The bonding layer 86 is printed on the entire wafer on the substrate 83m side using a screen printing technique, but it may also be formed on the polycrystalline silicon layer 82c side of the base 82. The bonding layer 86 may also be a low-melting-point alloy such as AlGe. To separate the sealed atmosphere between the first space 84 and the second space 85, the bonding layer 86 is also formed on the partition wall 87.

[0083] A plurality of first spaces 84 and a plurality of second spaces 85 are provided between the base 82 and the substrate 83m. Each first space 84 is provided corresponding to at least one angular velocity detecting element 3. Each first through hole 83a and each third recess 83g is provided corresponding to one first space 84. Each second space 85 is provided corresponding to at least one acceleration detecting element 22. Each second through hole 83b and each fourth recess 83h is provided corresponding to one second space 85. Therefore, as shown in FIG. 28, a plurality of first through holes 83a are provided in the substrate 83m. Furthermore, as shown in FIG. 28, a plurality of second through holes 83b are provided in the substrate 83m.

[0084] In FIG. 23, the substrate 83m and the base 82 are bonded by applying pressure and heat. The pressure during bonding is 10 kPa to 1000 kPa. The heating during bonding is performed at a temperature in the range of 250 to 500°C. The bonding atmosphere may be an inert gas atmosphere such as nitrogen gas or argon gas, or may be vacuum, atmospheric pressure, or positive pressure. The substrate 83m is bonded to the polycrystalline silicon layer 82c using an AlGe material that forms the bonding layer 86. In this embodiment, metal eutectic bonding using the AlGe material is used, but anodic bonding, direct bonding, glass frit bonding, or plasma activated bonding may also be used. The first through hole 83a, the second through hole 83b, the third recess 83g, and the fourth recess 83h may be formed after bonding the substrate 83m and the base 82. The substrate formed by bonding the base 82 and the substrate 83m is referred to as a bonded substrate 98.

[0085] 24, degassing is performed by vacuum heating. Specifically, heating is performed at a temperature of 250 to 300°C and an atmospheric pressure of 100 Pa or less for several hours. Gas in first space 84 is extracted to the outside through first through-hole 83a. Gas in second space 85 is extracted to the outside through second through-hole 83b.

[0086] Next, the first space 84 and the second space 85 are subjected to a hydrophobic treatment. For the hydrophobic treatment, HMDS, a silane coupling agent, is used. This hydrophobic treatment makes it possible to reduce the moisture content of the first space 84 and the second space 85 to 100 ppm or less. Therefore, the angular velocity detecting element 3 and the acceleration detecting element 22 can operate well without being affected by fluctuations in the atmospheric gas pressure due to moisture.

[0087] A laser sealing apparatus 88 as shown in FIG. 25 is prepared. The laser sealing apparatus 88 includes a chamber 89. The laser sealing apparatus 88 is equipped with a rotary pump 90 and a turbomolecular pump 91 for reducing the pressure inside the chamber 89. An XY stage 93 for moving a workpiece 92 is disposed inside the chamber 89. The XY stage 93 moves the workpiece 92 and serves to properly align the irradiation position of the laser light 14 emitted from the laser light source 15. The laser light source 15 may be moved instead of the XY stage 93. Furthermore, a sheath heater 94 for heating the workpiece 92 is disposed inside the chamber 89. The workpiece 92 corresponds to a bonded substrate 98. The sheath heater 94 heats the substrate 83m via the base 82 in the bonded substrate 98. In this case, the sheath heater only needs to be able to heat the bonded substrate 98, and a halogen heater may be used instead of the sheath heater. Furthermore, since it is only necessary to heat the substrate 83m, the substrate 83m side of the bonded substrate 98 may be heated.

[0088] A window 95 is provided on one surface of the chamber 89. The window 95 is made of sapphire glass. The surface of the sapphire glass is coated with an AR (anti-reflective) coating. A laser light source 15 is provided on the outside of the chamber 89, and the laser light source 15 irradiates the workpiece 92 with a focused laser beam 14. Note that a material that is transparent to the laser light source 15 is suitable for the window 95, so sapphire glass is selected.

[0089] In Figure 26, a bonded substrate 98 is placed in a chamber 89, a vacuum is drawn, and the bonded substrate 98 is heated to a predetermined temperature T1 by a sheath heater 94. After the degree of vacuum reaches 100 Pa or less and the process waits for 10 minutes or more until the temperature of the substrate 83m reaches T1, a laser beam 14 is irradiated onto the first through-hole 83a and the third recess 83g on the angular velocity sensor 3 side, causing them to melt. Because heat is difficult to transfer in a vacuum, a relatively high temperature T1 of 300°C to 400°C is preferable. The first through-hole 83a and the third recess 83g become the first molten zone 83c.

[0090] 27, next, with the bonded substrate 98 still in the chamber 89, an inert gas such as nitrogen gas is introduced into the chamber 89, and the temperature of the bonded substrate 98 is controlled to T2. Since the thermal conductivity of nitrogen gas is good when the pressure inside the chamber 89 is 100 Pa or higher, the heating temperature may be 300°C or lower.

[0091] The second through hole 83b and the fourth recess 83h on the acceleration detecting element 22 side are irradiated with laser light 14 and melted. The irradiation energy can be lower than when the first through hole 83a on the angular velocity detecting element 3 side is used. Therefore, dross, debris, cracks, etc. are less likely to occur. The second through hole 83b and the fourth recess 83h become the second melted portion 83d.

[0092] After all the second through-holes 83b on the wafer have been melted, the temperature inside the chamber 89 is returned to room temperature. The bonded substrate 98 is then removed from the chamber 89.

[0093] FIG. 28 shows the trajectory of the laser beam 14. The first through holes 83a and the third recesses 83g are arranged in multiple parallel lines on the substrate 83m. The first trajectory 96 follows the multiple arrays of the first through holes 83a and the third recesses 83g. In the step of forming the first fusion zone 83c shown in FIG. 26, the temperature of the joined substrate 98 is maintained at T1, and the laser beam 14 moves along the first trajectory 96. The laser beam 14 may be irradiated continuously along the first trajectory 96, or may be irradiated only when passing through the areas of the first through holes 83a and the third recesses 83g. In other words, the laser beam 14 may be irradiated discontinuously in pulses along the first trajectory 96.

[0094] Similarly, second through holes 83b and fourth recesses 83h are arranged in multiple parallel lines on the substrate 83m. A second locus 97 follows the multiple arrays of the second through holes 83b and fourth recesses 83h. In the process of forming the second fusion zones 83d shown in FIG. 27, the temperature of the joined substrate 98 is maintained at T2, and the laser beam 14 moves along the second locus 97. The laser beam 14 may be irradiated continuously along the second locus 97, or may be irradiated only when passing through the areas of the second through holes 83b and the fourth recesses 83h. In other words, the laser beam 14 may be irradiated discontinuously in pulses along the second locus 97.

[0095] In both the step of forming the first fusion zone 83c and the step of forming the second fusion zone 83d, the base 82 is placed in the same chamber 89. The air pressure, temperature, and type of gas are changed. It takes time to change the inside of the chamber 89 from atmospheric pressure, room temperature, and air to the predetermined air pressure, temperature, and type of gas. Therefore, the first fusion zone 83c and the second fusion zone 83d can be formed with better productivity than in a method in which, after the first fusion zone 83c is formed, the bonded substrate 98 is removed from the chamber 89 and placed in another chamber 89 to form the second fusion zone 83d.

[0096] 29, the bonded substrate 98 is removed from the chamber 89, and at least one side of the bonded substrate 98 is cut out by half-dicing using a dicing blade 18. This exposes the electrode pads 19, allowing for wire bonding. Thereafter, the four sides of the bonded substrate 98 are cut, completing the inertial sensor 81 incorporating the angular velocity detecting element 3 and the acceleration detecting element 22. The depths of the first molten zone 83c and the second molten zone 83d are different because the laser irradiation energies are different.

[0097] Fourth embodiment In this embodiment, an example of an inertial measurement unit 2000 equipped with the angular velocity sensor 1, the acceleration sensor 21, or the inertial sensor 81 will be described.

[0098] 30 is a device that detects inertial momentum such as the posture and behavior of a moving body such as an automobile or a robot. The inertial measurement unit 2000 is also called an IMU (Inertial Measurement Unit). The inertial measurement unit 2000 functions as a so-called six-axis motion sensor that includes an acceleration sensor 21 that detects accelerations Ax, Ay, and Az in directions along three axes, and an angular velocity sensor 1 that detects angular velocities ωx, ωy, and ωz about the three axes.

[0099] The inertial measurement unit 2000 is a rectangular parallelepiped with a substantially square planar shape. Screw holes 2110 are formed near two vertices located diagonally across the square. Two screws can be inserted into these two screw holes 2110 to fix the inertial measurement unit 2000 to the mounting surface of a mounting body such as an automobile. By selecting parts and modifying the design, it is possible to miniaturize the unit to a size that can be mounted in a smartphone or digital camera, for example.

[0100] Inertial measurement unit 2000 has an outer case 2100, a joining member 2200, and a sensor module 2300, and is configured such that sensor module 2300 is inserted inside outer case 2100 with joining member 2200 interposed therebetween. Sensor module 2300 also has an inner case 2310 and a substrate 2320.

[0101] The external shape of outer case 2100 is a rectangular parallelepiped with a substantially square planar shape, similar to the overall shape of inertial measurement unit 2000, and screw holes 2110 are formed near each of two vertices located diagonally across the square. Outer case 2100 is also box-shaped, and houses sensor module 2300 inside.

[0102] Inner case 2310 is a member that supports substrate 2320, and is shaped to fit inside outer case 2100. Inner case 2310 is formed with recess 2311 for preventing contact with substrate 2320 and opening 2312 for exposing connector 2330. Inner case 2310 is joined to outer case 2100 via joining member 2200. In addition, substrate 2320 is joined to the bottom surface of inner case 2310 via adhesive.

[0103] 31, a connector 2330, an angular velocity sensor 2340z that detects angular velocity around the Z axis, and an acceleration sensor unit 2350 that detects acceleration in the directions of the X, Y, and Z axes are mounted on the top surface of the substrate 2320. In addition, an angular velocity sensor 2340x that detects angular velocity around the X axis and an angular velocity sensor 2340y that detects angular velocity around the Y axis are mounted on the side surface of the substrate 2320.

[0104] The acceleration sensor unit 2350 can detect acceleration in one axis direction, or in two or three axes directions, as required.

[0105] In addition, a control IC 2360 is mounted on the underside of substrate 2320. Control IC 2360, which performs control based on detection signals output from each sensor, is an MCU (Micro Controller Unit) that incorporates a storage unit including nonvolatile memory, an A / D converter, etc., and controls each part of inertial measurement unit 2000. The storage unit stores programs that define the order and content for detecting acceleration and angular velocity, a program that digitizes the detection data and incorporates it into packet data, accompanying data, etc. Note that multiple other electronic components are mounted on substrate 2320.

[0106] The angular velocity sensor 2340z, the angular velocity sensor 2340x, and the angular velocity sensor 2340y use the angular velocity sensor 1 or the inertial sensor 81. The acceleration sensor unit 2350 uses the acceleration sensor 21 or the inertial sensor 81.

[0107] Therefore, inertial measurement unit 2000 includes the above-described angular velocity sensor 1, acceleration sensor 21, or inertial sensor 81. According to this configuration, inertial measurement unit 2000 includes the above-described angular velocity sensor 1, acceleration sensor 21, or inertial sensor 81. The above-described angular velocity sensor 1, acceleration sensor 21, or inertial sensor 81 has a structure that makes it difficult for cracks to occur in lid body 4, lid body 23, or lid body 83. Therefore, inertial measurement unit 2000 can be an inertial measurement unit 2000 that includes a physical quantity sensor that makes it difficult for cracks to occur in lid body 4, lid body 23, or lid body 83.

[0108] Fifth embodiment In the first embodiment, the second recess 4g is formed by the first groove 9 and the second groove 10 which are concentric with the through hole 4b in a plan view seen from the Z direction.

[0109] As shown in FIG. 32, the through hole 200 corresponding to the through hole 4b in a plan view from the Z direction may be rectangular. The recess 201 corresponding to the second recess 4g in a plan view from the Z direction may also be rectangular. The recess 201 is arranged around the through hole 200. In this case, too, a portion of the laser light 14 is diffracted in the recess 201, so the laser light 14 advances in multiple directions around the through hole 200. Therefore, the change in residual stress in the molten portion 4c is gradual, so the occurrence of cracks can be suppressed. Additionally, the shapes of the through hole 200 and the recess 201 in a plan view from the Z direction may be a diamond, a triangle, or a checkerboard pattern.

[0110] As shown in FIG. 33, in a plan view seen from the Z direction, the through hole 210 corresponding to the through hole 4b is circular. In a plan view seen from the Z direction, the recess 211 corresponding to the second recess 4g may be a radial rectangle extending from the through hole 210. The recess 211 is arranged around the through hole 210. In this case, too, a portion of the laser light 14 is diffracted in the recess 211, so the laser light 14 advances in multiple directions around the through hole 210. Therefore, since the change in residual stress in the molten portion 4c is gradual, the occurrence of cracks can be suppressed. Alternatively, the recess corresponding to the second recess 4g in a plan view seen from the Z direction may be spiral-shaped. [Explanation of symbols]

[0111] 1...angular velocity sensor as physical quantity sensor, 2...base, 3...angular velocity detection element as movable body, 4...lid body, 4b, 23b, 200, 210...through hole, 4c, 23c...molten portion, 4g...second recess as recess, 6...space, 14...laser light, 21...acceleration sensor as physical quantity sensor, 22...acceleration detection element as movable body, 81...inertial sensor as physical quantity sensor, 83a...first through hole as through hole, 83b...second through hole as through hole, 83c...first molten portion as molten portion, 83d...second molten portion as molten portion, 84...first space as space, 85...second space as space, 2000...inertial measurement unit.

Claims

1. forming a first recess in a substrate; bonding a silicon substrate to the base body so as to face the first recess; The silicon substrate is processed using photolithography and etching techniques. A functional element is formed by The first side, which is the front and back of the first side, is created using photolithography and etching techniques. and forming a second recess by processing the first surface of the lid body including the second surface; The second surface of the lid is processed using a photolithography technique and an etching technique. This forms a through hole and a third recess, The second recess of the lid and the first recess of the base are opposed to each other. By joining the lid and the base, the functional element is accommodated in the space between the lid and the base. Payment, the lid and the base are heated to make the space hydrophobic; irradiating the through hole and the third recess with laser light; A molten portion is formed by melting a peripheral area of the through hole and the third recess of the lid body. death, The through hole is closed by the fused portion, thereby sealing the space; The moisture content of the space is 100 ppm or less due to the hydrophobic treatment. A method for manufacturing a physical quantity sensor.

2. In claim 1, The laser light is Irradiation is performed in a chamber under reduced pressure. The lid is heated through the base in the chamber. A method for manufacturing a physical quantity sensor.

3. In claim 1 or 2, The third recess includes a first groove and a second groove that are concentric with the through hole in a plan view. A method for manufacturing a physical quantity sensor.

4. In claim 3, The groove width of the first groove and the second groove is 10 μm or more and 20 μm or less. A method for manufacturing a physical quantity sensor.

5. In claim 3 or 4, The groove depth of the first groove and the second groove is 20 μm or more and 40 μm or less. A method for manufacturing a physical quantity sensor.

6. In any one of claims 1 to 5, The physical quantity sensor is characterized in that the fused portion includes a continuous curved surface including concaves and convexes. Manufacturing method.

7. In claim 6, The method for manufacturing a physical quantity sensor, wherein the center of the curved surface is concave in cross section. 。

8. In any one of claims 1 to 7, The method for manufacturing a physical quantity sensor, wherein the molten portion has a substantially circular shape in a plan view.

9. In any one of claims 1 to 8, The lid is a single crystal, The method for manufacturing a physical quantity sensor, wherein the molten portion is polycrystalline.

10. In any one of claims 1 to 9, The method for manufacturing a physical quantity sensor, wherein the material of the lid is silicon.

11. In any one of claims 1 to 10, The length from the second surface to the end of the fusion zone on the first surface side is D, When the diameter of the fusion portion on the second surface side in a plan view is L, 0.50≦D / L≦3.00 A method for manufacturing a physical quantity sensor, characterized in that

12. In any one of claims 1 to 10, The length from the second surface to the end of the fusion zone on the first surface side is D, When the diameter of the fusion portion on the second surface side in a plan view is L, 0.01≦D / L≦0.50 A method for manufacturing a physical quantity sensor, characterized in that

13. In any one of claims 1 to 12, The joining of the lid body and the base body is performed by Frit bonding using glass frit, anodic bonding, direct bonding, metal eutectic bonding, and plasma A method for manufacturing a physical quantity sensor, characterized in that the physical quantity sensor is either a polymer activated junction or a polymer activated junction.

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