Inertial force sensor and manufacturing method of inertial force sensor

Abstract

To provide an inertial force sensor with a sensor part hermetically sealed in a highly vacuumed package.SOLUTION: An inertial force sensor includes a package having a rectangular opening frame. The inertial force sensor includes a sensor part disposed inside the package. The inertial force sensor includes a lid part covering an entire opening frame. The inertial force sensor includes a first joining ring and a second joining ring disposed along the opening frame, having a closed ring shape, and joining the opening frame and the lid part. The first joining ring is disposed to surround an outer periphery of the second joining ring. A closed space surrounded by the first joining ring, the second joining ring, the opening frame, and the lid portion is formed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present specification relates to an inertial force sensor and a method for manufacturing an inertial force sensor. [Background technology]

[0002] Patent Document 1 discloses an electronic component that includes a first package that airtightly encloses an inertial force sensor, and a second package that airtightly encloses the first package. The double package structure improves the hermetic sealing performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-257803 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology of Patent Document 1 has a double package structure, which may increase the overall size of the electronic component. [Means for solving the problem]

[0005] The inertial force sensor disclosed in this specification includes a package with a rectangular opening frame. The inertial force sensor includes a sensor unit disposed inside the package. The inertial force sensor includes a lid that covers the entire opening frame. The inertial force sensor is disposed along the opening frame, has a closed ring shape, and includes a first joining ring and a second joining ring that join the opening frame and the lid. The first joining ring is disposed surrounding the outer periphery of the second joining ring. A closed space is formed surrounded by the first joining ring, the second joining ring, the opening frame, and the lid.

[0006] According to the above structure, the opening frame and lid of the package are doubly closed by the outer first bonding ring and the inner second bonding ring. A closed space is formed between the first bonding ring and the second bonding ring. Even when gas enters through the inside of the first bonding ring or through the bonding interface between the lid or the frame of the package and the first bonding ring, the closed space prevents the gas from entering the internal space of the package. Because the closed space can temporarily prevent gas from entering the package, it is possible to maintain high airtightness inside the package for a long period of time. Furthermore, a double bonding frame structure is provided in which both the first and second bonding rings are used to maintain airtightness for one package. Compared to a double package structure using two packages, this structure reduces the increase in size, allowing for the inertial force sensor to be miniaturized. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a top view of the gyro sensor 1. [Figure 2] FIG. 2 is a cross-sectional view of the gyro sensor 1. [Figure 3] FIG. 2 is an enlarged cross-sectional view of a region in the vicinity of the bonded interface. [Figure 4] FIG. 2 is an enlarged cross-sectional view of a region in the vicinity of the bonded interface. [Figure 5] FIG. 10 is an enlarged cross-sectional view of the vicinity of a groove 103t. [Figure 6] FIG. 1 is a perspective view showing a state before bonding of the Si wafers. [Figure 7] 2 is a diagram showing a cross-sectional structure of a sensor element 240. FIG. [Figure 8] 8 is a bottom view of the lid portion 230 taken along the line VIII-VIII in FIG. 7. FIG. [Figure 9] 1 is a flowchart showing the manufacturing process of the WLP structure 201. [Figure 10] 1A to 1C are cross-sectional views showing the manufacturing process of the WLP structure 201. [Figure 11] 1A to 1C are cross-sectional views showing the manufacturing process of the WLP structure 201. [Figure 12]1A to 1C are cross-sectional views showing the manufacturing process of the WLP structure 201. [Figure 13] 2 is a diagram showing a cross-sectional structure of a sensor element 240. FIG. [Figure 14] 10A to 10C are cross-sectional views showing the manufacturing process of the lid portion 430. [Figure 15] 10A to 10C are cross-sectional views showing the manufacturing process of the lid portion 430. [Figure 16] 10A to 10C are cross-sectional views showing the manufacturing process of the lid portion 430. DETAILED DESCRIPTION OF THE INVENTION [Example]

[0008] FIG. 1 shows a top view of a gyro sensor 1 according to this embodiment. For clarity, FIG. 1 shows a state in which the lid 130 has been removed. FIG. 2 shows a cross-sectional view taken along line II-II in FIG. 1. FIG. 2 is a cross-sectional view passing through the central axis CA. FIG. 3 shows an enlarged view of the bonding region JR in FIG. 2. The gyro sensor 1 mainly comprises a sensor element 10, a package 100, and a lid 130. The sensor element 10 is vacuum-tightly sealed in the package 100.

[0009] (Configuration of sensor element 10) The sensor element 10 mainly comprises a base electrode 20, a glass oscillator 30, and paste 40. The base electrode 20 has a structure in which a silicon substrate 22 is laminated on a glass substrate 21.

[0010] The glass substrate 21 is made of a glass material that can be anodically bonded to the silicon substrate 22. An annular ring groove 21r is formed on the surface 21f of the glass substrate 21. A rim portion 30r of the glass vibrator 30 is inserted into the ring groove 21r.

[0011] The silicon substrate 22 includes a ring electrode 22c, multiple segmented electrodes 22d, and an outer peripheral electrode 22o. The ring electrode 22c is disposed on the surface 21f of the glass substrate 21. The ring electrode 22c has a cylindrical shape about a central axis CA and includes a through-hole 22h. The central axis CA passes through the center of the glass substrate 21 and is perpendicular to the surface 21f. The multiple segmented electrodes 22d are disposed rotationally symmetrically on a circle centered on the central axis CA. The multiple segmented electrodes 22d surround the ring electrode 22c. An electrode pad 23 is formed on each of the multiple segmented electrodes 22d. An annular ring-shaped through-hole 22r is formed between the outer periphery of the ring electrode 22c and the inner periphery of the multiple segmented electrodes 22d. A rim portion 30r of the glass vibrator 30 is inserted into the ring-shaped through-hole 22r. The outer peripheral electrode 22o surrounds the periphery of the segmented electrode 22d. The peripheral electrode 22o is connected to the annular electrode 22c by four wires 25. In this embodiment, the wires 25 are made of an Al film. BR pads 24 are disposed at the four corners of the peripheral electrode 22o.

[0012] The glass vibrator 30 includes a pillar portion 30p and a peripheral portion 30c. The pillar portion 30p is a tubular portion having a central axis CA. The peripheral portion 30c is a hollow, approximately hemispherical portion centered on the central axis CA. The cross-sectional shape of the glass vibrator 30 in a plane passing through the central axis CA is approximately M-shaped. The material of the glass vibrator 30 is fused silica (quartz).

[0013] A conductive film (not shown) is formed on the surface of the glass vibrator 30. Various materials can be used for the conductive film. In this example, the conductive film was a TiN film.

[0014] The glass vibrator 30 is fixed to the annular electrode 22c so that the central axis CA of the column portion 30p coincides with the central axis CA of the annular electrode 22c. Specifically, the bottom of the column portion 30p is adhered to the annular electrode 22c by paste 40. The paste 40 is a so-called conductive paste. The material form of the paste 40 is the same as that of the die bond material 50 described below. The paste 40 electrically connects the conductive film on the surface of the glass vibrator 30 to the annular electrode 22c. The annular electrode 22c is connected to the BR pad 24 via the wiring 25 and the peripheral electrode 22o. Therefore, the conductive film on the surface of the glass vibrator 30 and the BR pad 24 are electrically connected.

[0015] A die bond material 50 is disposed between the rear surface 21b of the glass substrate 21 and the mounting surface 101 of the package 100. The die bond material 50 is a conductive material used to bond and fix the glass substrate 21 to the mounting surface 101. Various materials can be used for the die bond material 50. For example, it may be a paste material (Ag paste) in which Ag particles are mixed into an organic binder material.

[0016] (Configuration of package 100 and lid 130) The configuration of the package 100 will be described with reference to Figures 1 and 2. A metal mounting surface 101 is disposed on the bottom surface inside the package 100. The multiple electrodes 102 are arranged to surround the mounting surface 101. The multiple electrode pads 23 of the sensor element 10 are connected to the corresponding electrodes 102 by wires 110. In this embodiment, the wires 110 are Au wires. As shown in FIG. 2, multiple pads 102p are arranged outside the package 100. The multiple pads 102p correspond to the multiple electrodes 102 and are connected to the multiple electrodes 102, respectively. The gyro sensor 1 can be connected to an external control circuit (not shown) via the multiple pads 102p.

[0017] A rectangular frame 103 is disposed around the outer periphery of the multiple electrodes 102. The frame 103 may be made of any insulating material (e.g., ceramic). An opening frame 103a is formed on the upper surface of the frame 103. As shown in FIG. 1, the opening frame 103a has a rectangular shape surrounded by a frame of a certain width. The opening frame 103a also has four corners 103c.

[0018] As shown in Fig. 2, the lid 130 has a flat plate shape. The lid 130 covers the entire opening frame 103a. A gas adsorption portion 60 is disposed on the entire lower surface 130u of the lid 130. The gas adsorption portion 60 is a getter film. The gas adsorption portion 60 can be formed by sputtering.

[0019] The lid 130 may be made of various materials. For example, a material called borosilicate glass may be used. Alternatively, a metal material based on nickel or Kovar may be used. The thickness of the lid 130 may be adjusted as needed.

[0020] A first lower frame 121L and a second lower frame 122L are disposed around the entire periphery of the opening frame 103a. Similarly, a first upper frame 121U and a second upper frame 122U are disposed on the surface of the gas adsorption unit 60 on the lower surface 130u of the lid 130. A first joining ring 121 is disposed between the first lower frame 121L and the first upper frame 121U. A second joining ring 122 is disposed between the second lower frame 122L and the second upper frame 122U. The first lower frame 121L, the first joining ring 121, and the first upper frame 121U all have a closed ring shape and are all the same shape. Similarly, the second lower frame 122L, the second joining ring 122, and the second upper frame 122U all have a closed ring shape and are all the same shape. That is, when viewed from a direction perpendicular to the lid 130 (z direction), the first lower frame 121L, the first joining ring 121, and the first upper frame 121U overlap one another. Also, the second lower frame 122L, the second joining ring 122, and the second upper frame 122U overlap one another.

[0021] The first lower frame 121L, the first joining ring 121, and the first upper frame 121U are arranged to surround the outer peripheries of the second lower frame 122L, the second joining ring 122, and the second upper frame 122U. This forms a double seal between the first joining ring 121 and the second joining ring 122. A closed space SS is formed between the first joining ring 121, the second joining ring 122, the opening frame 103a, and the lid 130. The closed space SS is a space formed between the first joining ring 121 and the second joining ring 122, and is a closed ring-shaped space arranged along the opening frame 103a. In other words, the closed space SS is a space located between the double seals. An internal space IS is also formed between the interior of the package 100, the lid 130, and the second joining ring 122. The sensor element 10 is housed in the internal space IS.

[0022] Before the package 100 is hermetically vacuum sealed, the first lower frame 121L and the second lower frame 122L are formed on the opening frame 103a, and the first upper frame 121U and the second upper frame 122U are formed on the lower surface 130u of the lid 130. On the other hand, the first bonding ring 121 and the second bonding ring 122 are separate, independent components.

[0023] The first bonding ring 121 and the second bonding ring 122 may be made of various materials, such as AuSn. The thickness of the first bonding ring 121 and the second bonding ring 122 can be adjusted as needed. In this example, the thickness was set to approximately 100 μm. The first lower frame 121L, the second lower frame 122L, the first upper frame 121U, and the second upper frame 122U may be made of various materials and have various configurations, as long as an Au film is positioned on the outermost surface. In this example, an Au / Ti laminate film was used.

[0024] The vacuum airtight sealing process will be described below: The first and second joining rings 121 and 122 are placed on the first and second lower frames 121L and 122L, respectively. The lid 130 is positioned so that the first bonding ring 121 and the first upper frame 121U are aligned, and the second bonding ring 122 and the second upper frame 122U are aligned. While the entire assembly is heated in a vacuum atmosphere, a jig (not shown) presses the bonding portions together. This results in AuSn eutectic bonding. Thus, the first bonding ring 121 is bonded to the first lower frame 121L and the first upper frame 121U. The second bonding ring 122 is bonded to the second lower frame 122L and the second upper frame 122U. That is, the opening frame 103a and the lid 130 are bonded via the first bonding ring 121 and the second bonding ring 122. This allows the interior of the package 100 to be vacuum-tightly sealed. Finally, a heat treatment is performed after sealing. This activates the getter film of the gas adsorption unit 60, allowing it to adsorb gas remaining in the internal space IS and the closed space SS. As a result, it becomes possible to create a high vacuum state inside the internal space IS.

[0025] (Configuration of gas adsorption section 60) The gas adsorption unit 60 is exposed on the upper wall surface (the lower surface 130u of the lid 130) that closes the closed space SS and the internal space IS. That is, the gas adsorption unit 60 is disposed in the closed space SS and the internal space IS.

[0026] 3, the gas adsorption units 60 are arranged in the vicinity of the bonding interfaces between the first and second bonding rings 121 and 122 and the lid 130 (see region R1). That is, the gas adsorption units 60 arranged in the closed space SS and the gas adsorption units 60 arranged in the internal space IS are a continuous, integrated film. This allows the gas adsorption units 60 to be formed on the lower surface 130u by full-surface sputtering, simplifying the film formation process.

[0027] The metal used to bond the first bonding ring 121 and the second bonding ring 122 to the lid 130 diffuses and penetrates into the gas adsorption portion 60 (see region R1) located near the bonding interface. That is, a portion of the Au contained in the first upper frame 121U and the second upper frame 122U penetrates into the gas adsorption portion 60 at the bonding interface. The effect will be explained below. In the vacuum airtight sealing process, the metal melted by heating is diffused and penetrated into the gas adsorption portion 60 near the bonding interface. This makes it possible to improve the sealing performance with the penetrated metal.

[0028] (Gyro sensor 1 operation) A capacitor is formed between each of the multiple split electrodes 22d and the glass vibrator 30. An electrical signal is applied to the multiple split electrodes 22d from an external control circuit (not shown) via the multiple pads 102p. By generating an electrostatic attraction between the glass vibrator 30 and the multiple split electrodes 22d, the glass vibrator 30 is excited in wine-glass mode at the resonant frequency. When an angular velocity ωz is applied around the z-axis in this state, a Coriolis force is generated. An amplitude corresponding to the generated Coriolis force is then generated in the detection direction. The generated amplitude can be detected by a change in capacitance of a capacitor formed between the split electrode 22d and the glass vibrator 30. As described above, gyro sensor 1, which is an inertial force sensor, functions.

[0029] (effect) The problem is explained below. A double package structure is known in which a first package is airtightly enclosed by a second package to improve airtightness. However, a double package structure can increase the overall size. Therefore, the technology described herein provides a double bonded frame structure in which a single package maintains airtightness using two components, a first bonding ring 121 and a second bonding ring 122. A closed space SS is provided between the first bonding ring 121 and the second bonding ring 122. Even when gas infiltrates through the interior of the first bonding ring 121 or through the bonding interface between the lid 130 or the opening frame 103a of the package 100 and the first bonding ring 121, the closed space SS can prevent the gas from infiltrating into the internal space IS. Because the closed space SS can temporarily prevent gas from infiltrating into the package 100, it is possible to maintain high airtightness within the package 100 for a long period of time. Furthermore, since the increase in size can be suppressed compared to a double package structure, the gyro sensor 1 can be made smaller.

[0030] In the technology of this specification, a gas adsorption unit 60 is disposed in the closed space SS. This allows the gas adsorption unit 60 to adsorb gas that initially remains in the closed space SS and gas that has infiltrated into the closed space SS from the outside. This makes it possible to maintain the closed space SS in a high vacuum state. This makes it possible to maintain a small pressure difference between the closed space SS and the internal space IS. This makes it possible to suppress gas intrusion into the internal space IS.

[0031] In the technology of this specification, a gas adsorption unit 60 is disposed in the internal space IS. This allows the gas adsorption unit 60 to adsorb gas that initially remains in the internal space IS and gas that has entered the internal space IS from the closed space SS. This makes it possible to maintain the internal space IS in a high vacuum state for a long period of time.

[0032] (First Modification of the First Embodiment) The gas adsorption unit 60 may be arranged in various ways. For example, the gas adsorption unit 60 may be arranged only in the closed space SS. In this case, the gas adsorption unit 60 may be selectively arranged in the region between the first upper frame 121U and the second upper frame 122U on the lower surface 130u of the lid 130. Alternatively, for example, the gas adsorption unit 60 may be arranged only in the internal space IS. In this case, the gas adsorption unit 60 may be arranged in at least a part of the region surrounded by the second upper frame 122U on the lower surface 130u of the lid 130. Alternatively, for example, the gas adsorption unit 60 may not be arranged. In this case, the step of sputtering the gas adsorption unit 60 on the lower surface 130u can be omitted.

[0033] (Second Modification of the First Embodiment) The gas adsorption unit 60 may be arranged in various ways. For example, as shown in Fig. 4, the gas adsorption unit 60 may be selectively arranged in the closed space region SR and the internal space region IR on the underside 130u of the lid 130. The closed space region SR is the region where the closed space SS is formed, and the internal space region IR is the region where the internal space IS is formed.

[0034] In this arrangement, the gas adsorbing section 60 is not disposed in the first region A1 including the bonding interface between the first bonding ring 121 and the lid 130, and in the second region A2 including the bonding interface between the second bonding ring 122 and the lid 130. In other words, the first bonding ring 121 and the second bonding ring 122 are directly bonded to the lid 130. As a result, the gas adsorbing portion 60 does not exist at the bonding interfaces between the first bonding ring 121 and the second bonding ring 122 and the lid 130, and therefore the first bonding ring 121 and the second bonding ring 122 ensure sealing properties.

[0035] The structure shown in FIG. 4 can be realized by selectively forming the gas adsorption portion 60 in the closed space region SR and the internal space region IR using a stencil mask.

[0036] (Third Modification of the First Embodiment) The widths of the first bonding ring 121 and the second bonding ring 122 can be set in various ways. For example, the width of the first bonding ring 121 located on the outside may be wider than the width of the second bonding ring 122 located on the inside. The effect will be explained below. The pressure difference between the outside and the closed space SS is greater than the pressure difference between the closed space SS and the internal space IS. Therefore, the first bonding ring 121 is subjected to a larger pressure difference than the second bonding ring 122. Therefore, by increasing the width of the first bonding ring 121, it is possible to appropriately improve the sealing performance of the first bonding ring 121. [Example]

[0037] In Example 2, an embodiment in which a groove 103t is formed in an aperture frame 103a will be described. Portions common to Examples 1 and 2 are designated by the same reference numerals, and descriptions thereof will be omitted. FIG. 5 shows an enlarged cross-sectional view of the vicinity of the groove 103t. FIG. 5 is a cross-sectional view of the same portion as FIG. 3 of Example 1. The groove 103t is formed in the aperture frame 103a. When viewed from above (+z direction), the groove 103t is formed around the entire periphery of the aperture frame 103a. That is, when viewed from above (+z direction), the aperture frame 103a and the groove 103t have a rectangular shape with a frame of a constant width. The groove 103t is included within the frame of the aperture frame 103a.

[0038] As shown in FIG. 5, the cross section of the groove 103t is rectangular. Here, in the cross-sectional structure of FIG. 5, a closed space region SR is defined. The closed space region SR is a region in which the closed space SS is formed. In other words, the closed space region SR is a region between the first bonding ring 121 and the second bonding ring 122. The groove 103t is formed in at least a part of the closed space region SR. In the example of FIG. 5, the groove 103t is formed throughout the entire closed space region SR. As a result, the groove 103t is in communication with the closed space SS.

[0039] The grooves 103t may be formed in various ways. For example, the package 100 may be formed from a low-temperature co-fired ceramic laminate substrate known as an LTCC (Low Temperature Co-fired Ceramics) substrate. In this case, the package 100 can be formed by laminating a plurality of ceramic layers known as green sheets and then firing the laminate. By forming slits corresponding to the grooves 103t in the green sheets before firing, the package 100 having the grooves 103t can be formed.

[0040] (effect) The groove 103t can expand the volume of the closed space SS. This makes it possible to suppress pressure fluctuations in the closed space SS even when a relatively large amount of gas has entered from outside the package. As a result, it is possible to suppress the amount of gas that enters the internal space IS through the second bonding ring 122.

[0041] (Modification of Example 2) The grooves 103t may have various shapes. For example, the grooves 103t may be formed in a part of the closed space region SR. The cross-sectional shape of the grooves 103t may be tapered or curved. [Example]

[0042] In the third embodiment, a WLP (Wafer Level Packaging) structure using a Si wafer bonding technique will be described. The state before the Si wafer bonding is shown in FIG. 6. The WLP structure 201 includes a package base 210 and a lid 230.

[0043] The package base 210 includes a Si substrate 211, an oxide film layer 212, and a Si element substrate 213. The Si element substrate 213 and the Si substrate 211 are bonded via the oxide film layer 212. In other words, the package base 210 is an SOI (Silicon On Insulator) wafer. A plurality of sensor elements 240 are formed on the Si element substrate 213. The structure of the sensor elements 240 will be described later.

[0044] 7 shows the cross-sectional structure of a typical sensor element 240. The sensor element 240 mainly comprises an oscillator 241 and an electrode portion 242. The oscillator 241 and the electrode portion 242 are formed on the Si element substrate 213 by deep etching of Si. The oscillator 241 and the electrode portion 242 have a structure that is generally used in MEMS (Micro Electro Mechanical Systems) sensors. Therefore, a detailed description thereof will be omitted. The sensor element 240 can detect the angular velocity by reading the change in capacitance that occurs between the vibrator 241 and the electrode portion 242 having a comb-tooth structure.

[0045] FIG. 8 shows a bottom view of the lid 230 taken along line VIII-VIII in FIG. 7. The lid 230 is made of a single single-crystal Si substrate. A groove 230t and a recess 230d are formed on the bottom surface 230u of the lid 230 by deep etching of Si. This forms a first bonding ring 230r1 and a second bonding ring 230r2 in the lid 230. The first bonding ring 230r1 and the second bonding ring 230r2 are integral parts of the lid 230 and are made of Si. As shown in FIG. 8, the first bonding ring 230r1 and the second bonding ring 230r2 have a closed ring shape when viewed from the bottom. The first bonding ring 230r1 is disposed so as to surround the outer periphery of the second bonding ring 230r2. This forms a double seal ring structure. The groove 230t disposed between the two rings defines the upper part of the closed space SS. A bonding layer 220 made of a silicon oxide film is disposed on the surfaces of the first bonding ring 230r1 and the second bonding ring 230r2.

[0046] As shown in FIG. 7 , a groove 213t is formed in the Si element substrate 213 by deep etching of Si. Like the groove 230t, the groove 213t has a closed ring shape. The groove 213t forms a first bonding ring 213r1 and a second bonding ring 213r2 in the Si element substrate 213. The first bonding ring 213r1 and the second bonding ring 213r2 are integral parts of the package base 210 and are made of Si. The first bonding ring 213r1 and the second bonding ring 213r2 of the Si element substrate 213 have the same shapes as the first bonding ring 230r1 and the second bonding ring 230r2 of the lid portion 230. This forms a double seal ring structure. The groove 213t located between the two rings forms the lower part of the closed space SS. The depths of the groove 230t and the groove 213t may be the same or different.

[0047] A gas adsorption section 260 is exposed on the upper wall surface (the lower surface of the lid section 230) that closes the closed space SS and the internal space IS. The gas adsorption section 260 is a getter film similar to the gas adsorption section 60 described in the first embodiment. This allows the gas adsorption section 260 to adsorb the gas in the closed space SS and the gas in the internal space IS. This makes it possible to maintain the internal space IS in a high vacuum state for a long period of time.

[0048] (Method of manufacturing the sensor element 240) FIG. 9 shows a flowchart illustrating the manufacturing process of a WLP structure 201 including multiple sensor elements 240. In step S1, a resonator 241 and an electrode portion 242 are formed on an SOI substrate constituting the package base 210. Specifically, a resist mask 270 corresponding to the shapes of the resonator 241, the electrode portion 242, and the groove 213t is formed using a well-known photolithography technique. Deep reactive ion etching (DRIE) of Si is performed through the resist mask 270, using the oxide film layer 212 as a stopper. This completes the structure shown in FIG. 10. Next, the oxide film layer 212 below the resonator 241 is removed by isotropic etching (see region R2). The resonator 241 has multiple etching holes (not shown), through which the oxide film layer 212 below the resonator 241 is selectively etched away. This completes the structure of the package base 210 shown in the lower half of FIG. 7.

[0049] In step S2, the lid portion 230 is formed. This will be explained in detail. A Si substrate having a bonding layer 220 formed on its surface is prepared. Resist is applied to the surface of the bonding layer 220. A resist mask 271 corresponding to the shapes of the recesses 230d and the grooves 230t is formed using well-known photolithography techniques. Deep etching of Si is performed through the resist mask 271. This completes the first bonding ring 230r1 and the second bonding ring 230r2 (see FIG. 11).

[0050] In step S3, the gas adsorption portions 260 are formed. Specifically, a stencil mask 272 having openings corresponding to the recesses 230d and grooves 230t is positioned and placed. Next, a getter film is formed by sputtering. As a result, the gas adsorption portions 260 are selectively formed on the bottom surfaces of the recesses 230d and grooves 230t (see FIG. 12).

[0051] In step S4, the package base 210 and the lid 230 are bonded together in a vacuum via the bonding layer 220 (see arrow Y1 in FIG. 6). The bonding is performed by surface activated bonding. The groove 230t and the groove 213t are joined together to form a closed space SS. Furthermore, the space in which the vibrator 241 and the electrode portion 242 are formed is joined together with the recess 230d to form an internal space IS. The internal space IS and the closed space SS are then hermetically sealed in a vacuum.

[0052] In step S5, the sealed state is subjected to a heat treatment. This activates the getter film of the gas adsorption unit 260, allowing it to adsorb gas remaining in the internal space IS and the closed space SS. As a result, the vibrator 241 and the electrode unit 242 are hermetically sealed in the internal space IS at a higher degree of vacuum.

[0053] In step S6, TSVs (Through Silicon Vias) (not shown) are formed to fabricate a structure for drawing out wiring, thereby completing a plurality of sensor elements 240.

[0054] (effect) The sensor of Example 3 can be fabricated using MEMS technology, and therefore can be made smaller in size than the sensors of Examples 1 and 2, which do not use MEMS technology. Furthermore, in the sensor of Example 3, the grooves 230t and 213t can be formed using deep etching of silicon. Deep etching can form deep grooves with a high aspect ratio, ensuring a sufficient volume of the closed space SS relative to the sensor's size. Therefore, even when a relatively large amount of gas has infiltrated from outside the package, pressure fluctuations in the closed space SS can be suppressed. As a result, the amount of gas infiltrating into the internal space IS through the second bonding rings 230r2 and 213r2 can be suppressed.

[0055] (First Modification of the Third Embodiment) The grooves may be arranged in various ways. For example, the grooves 230t may be formed in the lid portion 230, but the grooves 213t may not be formed in the Si element substrate 213. Alternatively, the grooves 213t may be formed in the Si element substrate 213, but the grooves 230t may not be formed in the lid portion 230. This arrangement also makes it possible to configure a double seal ring structure.

[0056] (Second Modification of the Third Embodiment) The gas adsorption section 260 may be arranged in various ways. For example, the gas adsorption section 260 may be arranged only in the closed space SS, or only in the internal space IS. Furthermore, when the grooves 213t are formed in the Si element substrate 213, the gas adsorption section 260 may be arranged inside the grooves 213t. Furthermore, for example, the gas adsorption section 260 does not need to be arranged. In this case, the step of forming the gas adsorption section 260 by sputtering can be omitted.

[0057] (Third Modification of the Third Embodiment) In step S2, the recesses 230d and the grooves 230t may be formed by isotropic etching. This allows the cross sections of the recesses 230d and the grooves 230t to have curved shapes. An oxide film layer may be disposed on the inner walls and bottom surfaces of the recesses 230d and the grooves 230t. In this case, the gas adsorption section 260 may be disposed on the surface of the oxide film layer.

[0058] (Fourth Modification of the Third Embodiment) The depths of the recesses 230d and the grooves 230t can be set as appropriate in the lid 230. For example, the depth of the recesses 230d and the depth of the grooves 230t may be different. That is, the gas adsorbing section 260 arranged in the recesses 230d and the gas adsorbing section 260 arranged in the grooves 230t do not have to be located on the same plane. [Example]

[0059] In Example 4, an embodiment will be described in which the cross-sectional shape of the groove formed in the lid portion is different from that of Example 3. Components common to Examples 3 and 4 are given the same reference numerals and descriptions thereof will be omitted. Components unique to Example 4 are distinguished by being given reference numerals in the 400s.

[0060] Fig. 13 shows the cross-sectional structure of a representative sensor element 240. Fig. 13 is a cross-sectional view similar to Fig. 7 of Example 3. A first bonding ring 430r1 and a second bonding ring 430r2 are bonded to the lid portion 430. This forms a groove 430t and a recess 430d. The lid portion 430, the first bonding ring 430r1, and the second bonding ring 430r2 are formed from a Si single crystal substrate with a (100) surface orientation.

[0061] Consider the bonded interface BI between the first and second bonding rings 430r1 and 430r2 and the first and second bonding rings 213r1 and 213r2. In a plan view passing through the bonded interface BI, an opening OP is formed between the first and second bonding rings 430r1 and 430r2. Also consider the interface IF between the first and second bonding rings 430r1 and 430r2 and the lid 430. In a plan view passing through the interface IF, a bottom surface 430tb of the groove 430t is formed between the first and second bonding rings 430r1 and 430r2. The opening OP and the bottom surface 430tb face each other in the vertical direction (z direction). The opening OP has a width W1. The bottom surface 430tb has a width W2. The width W1 is smaller than the width W2.

[0062] The recess 430d and the groove 430t are formed by anisotropic wet etching of Si, as described below. Therefore, the taper angle TA of the opening OP can be set to 54.7° in the crystal axis direction. Here, if the thickness of the first bonding ring 430r1 and the second bonding ring 430r2 is t, the following formula (1) is established: tan54.7°=t / ((W2-W1) / 2)...Equation (1) From equation (1), the correlation between width W1 and width W2 can be expressed by the following equation (2). W2=1.416t+W1...Equation (2)

[0063] (Manufacturing method) A method for manufacturing the lid 430 including the first bonding ring 430r1 and the second bonding ring 430r2 will be described. First, as shown in FIG. 14, a Si substrate 480 is prepared, with a bonding layer 220 made of a silicon oxide film disposed on the back surface. The Si substrate 480 is a single-crystal Si substrate with a (100) surface orientation. A hard mask 481 made of an SiO2 film is formed on the surface of the Si substrate 480 by well-known CVD, photolithography, and dry etching techniques.

[0064] 15, anisotropic wet etching of Si is performed. The etching is performed until it reaches the bonding layer 220 on the rear surface. As a result, a recess 430d and a groove 430t are formed. The taper angle TA is 54.7°.

[0065] Next, as shown in FIG. 16, the Si substrate 480 is turned upside down. Furthermore, the bonding layer 220 located on the bottom surfaces of the recess 430d and the groove 430t is removed. This completes the first bonding ring 430r1 and the second bonding ring 430r2. The first bonding ring 430r1 and the second bonding ring 430r2 are then bonded to the lid portion 430 by Si direct bonding (see arrow Y2). This completes the lid portion 430 including the first bonding ring 430r1 and the second bonding ring 430r2.

[0066] (effect) The groove 430t has an inverted tapered shape, with its width increasing from the opening OP to the bottom surface 430tb. This allows for both a reduction in the width W1 of the opening OP and an increase in the volume of the closed space SS. By reducing the width W1, the width of the bonding interface between the first bonding ring 430r1 and 213r1 can be increased, and the width of the bonding interface between the second bonding ring 430r2 and 213r2 can be increased, thereby improving sealing performance. Furthermore, by increasing the closed space SS, pressure fluctuations in the closed space SS can be suppressed.

[0067] (Modification of Example 4) The groove having a reverse tapered shape is not limited to the groove 430t. The groove 213t of the package base 210 may also have a reverse tapered shape. In this case, both the groove 213t and the groove 430t may have a reverse tapered shape.

[0068] Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives itself has technical utility.

[0069] (Variation) A triple or more seal ring structure is also possible. For example, to achieve a triple seal ring structure, a third joining ring is placed between the first joining ring and the second joining ring. This further improves airtightness.

[0070] Aspects of the present technology are listed below. [Aspect 1] a package having a rectangular opening frame; a sensor unit disposed inside the package; a lid portion covering the entire opening frame; a first joining ring and a second joining ring disposed along the opening frame, each having a closed ring shape, and joining the opening frame and the lid portion; An inertial force sensor comprising: the first joining ring is disposed so as to surround the outer periphery of the second joining ring, a closed space is formed surrounded by the first joining ring, the second joining ring, the opening frame, and the lid portion; Inertial force sensor. [Aspect 2] the inertial force sensor has an internal space surrounded by an interior of the package, the lid, and the second bonding ring, 2. The inertial force sensor according to aspect 1, further comprising a gas adsorption unit disposed in at least one of the internal space and the closed space. [Aspect 3] the first and second joining rings are separate components from the lid portion and joined to the lid portion; the gas adsorption unit is disposed in a region of the lid between the first and second joining rings and in a region inside the second joining ring; 3. The inertial force sensor according to aspect 2, wherein the first and second joining rings are directly joined to the lid. [Aspect 4] the first and second joining rings are separate components from the lid portion and joined to the lid portion; the first and second joining rings are made of metal; the gas adsorption unit is disposed in the lid at a bonding interface between the lid and the first bonding ring and between the lid and the second bonding ring; 3. The inertial force sensor according to aspect 2, wherein a metal used to join the first and second bonding rings to the lid portion diffuses and penetrates into the gas adsorbing portion. [Aspect 5] a groove is formed along the opening frame, Aspect 5. The inertial force sensor according to any one of Aspects 1 to 4, wherein the groove communicates with the closed space. [Aspect 6] an opening is formed between the first joining ring and the second joining ring in a plan view passing through a joining interface between the first joining ring and the opening frame, and between the second joining ring and the opening frame; a bottom surface is formed between the first joining ring and the second joining ring in a plan view passing through interfaces between the first joining ring and the lid and between the second joining ring and the lid; the opening and the bottom surface face each other, Aspects 6. The inertial force sensor according to any one of Aspects 1 to 5, wherein the width of the opening is smaller than the width of the bottom surface. [Aspect 7] The inertial force sensor according to any one of aspects 1 to 6, wherein the width of the first bonding ring is greater than the width of the second bonding ring. [Aspect 8] the first and second joining rings are made of metal, The lid is made of glass or metal, The inertial force sensor according to any one of aspects 1 to 7, wherein the first and second joining rings are separate components from the lid portion and joined to the lid portion. [Aspect 9] the first bonding ring, the second bonding ring, and the lid are made of silicon; the first and second joining rings are integral parts with the lid; The inertial force sensor according to any one of aspects 1 to 7. [Aspect 10] a package having a rectangular opening frame; a sensor unit disposed inside the package; a lid portion covering the entire opening frame; a first joining ring and a second joining ring disposed along the opening frame, each having a closed ring shape, and joining the opening frame and the lid portion; A method for manufacturing an inertial force sensor comprising: the first joining ring is disposed so as to surround the outer periphery of the second joining ring, a closed space is formed surrounded by the first joining ring, the second joining ring, the opening frame, and the lid portion, an internal space is formed surrounded by the interior of the package, the second bonding ring, and the lid portion; fixing the sensor unit inside the package; disposing a gas adsorption unit in at least one of the internal space and the closed space; a step of joining the opening frame and the lid portion in a vacuum atmosphere via the first joining ring and the second joining ring; performing a heat treatment; A method for manufacturing an inertial force sensor, comprising: [Explanation of symbols]

[0071] 1: Gyro sensor 10: Sensor element 60: Gas adsorption portion 100: Package 103a: Opening frame 121: First joining ring 122: Second joining ring 130: Lid SS: Closed space IS: Internal space

Claims

1. a package having a rectangular opening frame; a sensor unit disposed inside the package; a lid portion covering the entire opening frame; a first joining ring and a second joining ring disposed along the opening frame, each having a closed ring shape, and joining the opening frame and the lid portion; An inertial force sensor comprising: the first joining ring is disposed so as to surround the outer periphery of the second joining ring, a closed space is formed surrounded by the first joining ring, the second joining ring, the opening frame, and the lid portion; Inertial force sensor.

2. the inertial force sensor has an internal space surrounded by an interior of the package, the lid, and the second bonding ring, The inertial force sensor according to claim 1 , further comprising a gas adsorption unit disposed in at least one of the internal space and the closed space.

3. the first and second joining rings are separate components from the lid portion and joined to the lid portion; the gas adsorption unit is disposed in a region of the lid between the first and second joining rings and in a region inside the second joining ring; The inertial force sensor according to claim 2 , wherein the first and second joining rings are directly joined to the lid portion.

4. the first and second joining rings are separate components from the lid portion and joined to the lid portion; the first and second joining rings are made of metal, the gas adsorption unit is disposed in the lid at a bonding interface between the lid and the first bonding ring and between the lid and the second bonding ring; 3. The inertial force sensor according to claim 2, wherein a metal used to join the first and second joining rings to the lid portion diffuses and penetrates into the gas adsorption portion.

5. a groove is formed along the opening frame, The inertial force sensor according to claim 1 , wherein the groove communicates with the closed space.

6. an opening is formed between the first joining ring and the second joining ring in a plan view passing through a joining interface between the first joining ring and the opening frame, and between the second joining ring and the opening frame; a bottom surface is formed between the first joining ring and the second joining ring in a plan view passing through interfaces between the first joining ring and the lid and between the second joining ring and the lid; the opening and the bottom surface face each other, The inertial force sensor according to claim 1 , wherein a width of the opening is smaller than a width of the bottom surface.

7. The inertial force sensor according to claim 1 , wherein the width of the first joining ring is greater than the width of the second joining ring.

8. the first joining ring and the second joining ring are made of metal, The lid is made of glass or metal, The inertial force sensor according to claim 1 , wherein the first and second joining rings are separate components from the lid portion and are joined to the lid portion.

9. the first bonding ring, the second bonding ring, and the lid are made of silicon; the first and second joining rings are integral parts of the lid; The inertial force sensor according to claim 1 .

10. a package having a rectangular opening frame; a sensor unit disposed inside the package; a lid portion covering the entire opening frame; a first joining ring and a second joining ring disposed along the opening frame, each having a closed ring shape, and joining the opening frame and the lid portion; A method for manufacturing an inertial force sensor comprising: the first joining ring is disposed so as to surround the outer periphery of the second joining ring, a closed space is formed surrounded by the first joining ring, the second joining ring, the opening frame, and the lid portion, an internal space is formed surrounded by the interior of the package, the second bonding ring, and the lid portion; fixing the sensor unit inside the package; disposing a gas adsorption unit in at least one of the internal space and the closed space; a step of joining the opening frame and the lid portion in a vacuum atmosphere via the first joining ring and the second joining ring; performing a heat treatment; A method for manufacturing an inertial force sensor, comprising:

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