Inertial sensor and inertial measurement unit

Abstract

To provide an inertial sensor that can prevent sticking due to the loss of a projection.SOLUTION: An inertial sensor 100 comprises: a support substrate 10; a first stationary electrode 11 and a second stationary electrode 12 that are provided on a principal surface 17 of the support substrate 10; a movable body 20 that is provided swingably relative to the first stationary electrode 11 and the second stationary electrode 12; and projections 15 that are provided on the principal surface 17. The projection 15 has a flat surface f1 at a top 15p, and has a concave curved surface c1 continuing to the principal surface 17 at a root part 15r.SELECTED DRAWING: Figure 3A

Description

Technical Field

[0001] The present invention relates to an inertial sensor and an inertial measurement device including the inertial sensor.

Background Art

[0002] In recent years, inertial sensors using MEMS (Micro Electro Mechanical System) technology have been developed. As such an inertial sensor, Patent Document 1 describes an inertial sensor that detects acceleration in the Z-axis direction. The inertial sensor described in Patent Document 1 includes a movable body that is swingably provided with respect to a substrate, a protrusion that protrudes from the substrate toward the movable body side, and a coating electrode that is provided on the protrusion and has the same potential as the movable body. The protrusion is a stopper that restricts excessive swinging of the movable body. When the movable body swings excessively, the protrusion restricts further displacement of the movable body by contacting the movable body. The coating electrode suppresses the occurrence of a phenomenon in which the movable body adheres to the protrusion when the movable body contacts the protrusion, that is, so-called sticking.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even with the inertial sensor of Patent Document 1, it is difficult to completely suppress the occurrence of sticking, and further improvement is desired for sticking suppression.

Means for Solving the Problems

[0005] An inertial sensor according to one aspect of the present application includes a substrate, a fixed electrode provided on a first surface of the substrate, a movable body provided so as to be swingable with respect to the fixed electrode, and a protrusion provided on the first surface. The protrusion has a flat surface at the top and a concave curved surface continuous with the first surface at the base.

[0006] An inertial measurement device according to one aspect of the present application includes the inertial sensor described above.

Brief Description of Drawings

[0007]

Figure 1

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8A

Figure 8B

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Best Mode for Carrying Out the Invention

[0008] In the embodiments of the present invention, the components shown in each drawing may be shown with different dimensional scales for ease of viewing. In the drawings, three axes of an X-axis, a Y-axis, and a Z-axis orthogonal to each other may be shown. In the following description, the tip side of the arrow of the three axes may be described as the "plus side" and the base end side of the arrow may be described as the "minus side". A direction parallel to the X-axis may be described as the "X-axis direction", a direction parallel to the Y-axis may be described as the "Y-axis direction", and a direction parallel to the Z-axis may be described as the "Z-axis direction". Looking in the Z-axis direction may be described as "plan view", and looking from the Y-axis direction with respect to a cross section including the Z-axis may be described as "cross-sectional view".

[0009] In the following description, for example, with respect to a substrate, the description "on the substrate" represents any of the cases where it is disposed in contact with the upper surface of the substrate, where it is disposed via another structure on the substrate, or where a part thereof is disposed in contact with the upper surface of the substrate and a part thereof is disposed via another structure. The description of the upper surface of a certain structure indicates the surface on the plus side in the Z-axis direction of the said structure. For example, the "upper surface of the protrusion" indicates the surface on the plus side in the Z-axis direction of the protrusion. The description of the lower surface of a certain structure indicates the surface on the minus side in the Z-axis direction of the said structure. For example, the "lower surface of the movable body" indicates the surface on the minus side in the Z-axis direction of the movable body.

[0010] 1. Embodiment 1 FIG. 1, FIG. 2A, and FIG. 2B show a schematic configuration of an inertial sensor 100 according to the present embodiment. FIG. 1 is a plan view schematically showing the inertial sensor 100 according to Embodiment 1. For convenience of explanation, the illustration of the lid body 30 is omitted. FIG. 2A is a cross-sectional view taken along line A-A in FIG. 1. FIG. 2B is a cross-sectional view taken along line B-B in FIG. 1.

[0011] The inertial sensor 100 of the present embodiment is a physical quantity sensor that detects a change in capacitance based on the displacement of the movable body 20, in other words, a change in a physical quantity based on the displacement of the movable body 20. The physical quantity is, for example, acceleration. In this embodiment, the inertial sensor 100 is an acceleration sensor element that detects acceleration in the Z-axis direction. Specifically, it is a capacitive Z-axis acceleration sensor element using MEMS technology.

[0012] As shown in FIGS. 1, 2A, and 2B, the inertial sensor 100 includes a flat plate-shaped movable body 20, a support substrate 10 that supports the movable body 20, and a lid body 30 joined to the support substrate 10. In this embodiment, the support substrate 10 is an example of a substrate.

[0013] 1.1. Configuration of the support substrate As shown in FIGS. 2A and 2B, the support substrate 10 has a concave cavity 16. On the main surface 17 inside the cavity 16, a first fixed electrode 11, a second fixed electrode 12, a dummy electrode 13, a support column 14, and a protrusion 15 are provided. In this embodiment, the main surface 17 is an example of a first surface, and the first fixed electrode 11 or the second fixed electrode 12 is an example of a fixed electrode.

[0014] The support substrate 10 is a glass substrate made of borosilicate glass, which is an insulating material. The support substrate 10 may be a silicon substrate or a ceramic substrate. The first fixed electrode 11, the second fixed electrode 12, and the dummy electrode 13 are formed on the main surface 17 of the support substrate 10. The support column 14 and the protrusion 15 are formed integrally with the support substrate 10.

[0015] The first fixed electrode 11 is located on the minus side in the X-axis direction of the support column 14 in a cross-sectional view, and is provided in a region that overlaps with the first mass portion 21 of the movable body 20 and does not overlap with the protrusion 15 in a plan view. The second fixed electrode 12 is located on the plus side in the X-axis direction of the support column 14 in a cross-sectional view, and is provided in a region that overlaps with the second mass portion 22 of the movable body 20 and does not overlap with the protrusion 15 in a plan view.

[0016] The dummy electrode 13 is provided to cover the surface of the protrusion 15. The dummy electrode 13 is insulated from the first fixed electrode 11 and the second fixed electrode 12. Of the dummy electrodes 13, the portion facing the third mass portion 23 of the movable body 20 is provided in the concave portion 17c of the main surface 17. The concave portion 17c is a portion that is recessed in one step on the main surface 17 and is provided as a relief so that the third mass portion 23 of the movable body 20 does not collide.

[0017] As materials for the first fixed electrode 11, the second fixed electrode 12, and the dummy electrode 13, for example, conductive films such as Pt (platinum), Al (aluminum), Mo (molybdenum), Cr (chromium), Ti (titanium), Ni (nickel), Cu (copper), Ag (silver), Au (gold), or ITO (Indium Tin Oxide) can be adopted.

[0018] The support column 14 supports the movable body 20 with a predetermined gap on the first fixed electrode 11 and the second fixed electrode 12.

[0019] The protrusion 15 is a stopper that restricts the movable body 20 from swinging with an excessive swing width and prevents the movable body 20 from colliding with the main surface 17 of the support substrate 10. The protrusion 15 protrudes from the main surface 17 of the support substrate 10 in the positive Z-axis direction, and the top portion 15p of the protrusion 15 is provided so as to face the first mass portion 21 or the second mass portion 22.

[0020] As shown in FIG. 1, a total of four protrusions 15 are provided, one each at a total of four locations, two locations overlapping the first mass portion 21 of the movable body 20 and two locations overlapping the second mass portion 22 of the movable body 20. The locations where the protrusions 15 are provided are not limited to four. The protrusions 15 may be provided at two locations, six locations, or eight or more locations.

[0021] The protrusions 15 are provided along the extending direction of the beam portion 25 of the movable body 20. In other words, two protrusions 15 are provided on a straight line parallel to the center line CL2 that overlaps the rotation axis or the swing axis of the movable body 20. Such an arrangement of the protrusions 15 can disperse the impact when the movable body 20 and the protrusions 15 come into contact.

[0022] The centers of the two protrusions 15 provided on a straight line parallel to the center line CL2 are provided at positions with a line-symmetric distance R2 with respect to the center line CL1 that bisects the movable body 20 in the Y-axis direction. Such an arrangement of the protrusions 15 can suppress the posture of the movable body 20 from becoming unstable when the movable body 20 comes into contact with the protrusions 15.

[0023] The plurality of protrusions 15 are each provided at a position with a line-symmetric distance R1 with respect to the center line CL2. The plurality of protrusions 15 provided symmetrically can make the maximum swing angle of the first mass portion 21 that swings about the beam portion 25 as a rotation axis or a swing axis the same as the maximum swing angle of the second mass portion 22, and can improve the accuracy of detecting the physical quantity of the inertial sensor 100. The swing angle can be rephrased as a rotation angle.

[0024] The protrusions 15 are provided at positions that do not overlap with the opening 26 of the movable body 20 in a plan view. More specifically, the protrusions 15 are provided at positions that overlap with the blank region k1 of the movable body 20 in a plan view. The blank region k1 is a region in the movable body 20 where two by two openings 26 are not provided. The size of the blank region k1 may be larger than the size of two by two of the openings 26. Such an arrangement of the protrusions 15 can avoid collisions between the peripheral portion of the opening 26 and the protrusions 15 and suppress the occurrence of defects such as cracks starting from the peripheral portion of the opening 26.

[0025] 1.2. Configuration of the movable body The movable body 20 has a first movable body 20a and a second movable body 20b. The first movable body 20a is a portion on the minus side in the X-axis direction from the center line CL2, and the second movable body 20b is a portion on the plus side in the X-axis direction from the center line CL2. The first movable body 20a has a first mass portion 21, a third mass portion 23, and a connecting portion 28. The second movable body 20b has a second mass portion 22 and a connecting portion 28.

[0026] Since the first movable body 20a has the third mass portion 23, the distance Ra from the center line CL2 to the end face of the first movable body 20a and the distance Rb from the center line CL2 to the end face of the second movable body 20b are different. Therefore, the first movable body 20a and the second movable body 20b have different masses from each other.

[0027] Since the masses of the first movable body 20a and the second movable body 20b are different, the rotational forces of the first movable body 20a and the second movable body 20b that occur when an acceleration in the Z-axis direction is applied to the movable body 20 are unbalanced. Therefore, when an acceleration in the Z-axis direction is applied to the inertial sensor 100, the movable body 20 tilts. The inertial sensor 100 converts the tilt of the movable body 20 into changes in the capacitances C1 and C2 and outputs them.

[0028] The first mass portion 21, the second mass portion 22, and the third mass portion 23 have a plurality of openings 26. The opening 26 is a through-hole that penetrates the movable body 20 in the Z-axis direction. The opening 26 is provided to reduce the damping caused by the viscosity of the gas when the movable body 20 swings. Damping is a function that tries to stop the movement of the movable body 20. Damping can be rephrased as fluid resistance. The opening 26 can reduce the damping of the movable body 20, thereby improving the detection sensitivity of the acceleration of the inertial sensor 100.

[0029] In the present embodiment, the opening 26 is a square corner hole in planar shape. The length w1 of one side of the opening 26 is preferably 5 μm to 20 μm, and in this embodiment, it is about 10 μm. The length w1 corresponds to the inner diameter of the opening 26. The planar shape of the opening 26 is not limited to a square. The planar shape of the opening 26 may be, for example, circular. The planar shapes and inner diameters of the plurality of openings 26 do not all have to be the same.

[0030] In the first mass portion 21 and the second mass portion 22, a blank region k1 is provided at a position overlapping the protrusion 15 in plan view.

[0031] The support part 24 is provided in an H shape in plan view, and has two rectangular parts extending in the Y-axis direction and a part extending in the X-axis direction between the two rectangles. The two rectangular parts of the support part 24 are arranged along the beam part 25, and the part extending in the X-axis direction intersects the beam part 25 and is connected to the beam part 25 at the intersection point.

[0032] The beam part 25 is a rod-shaped member extending in the Y-axis direction. The central part is connected to the support part 24, and both end parts are respectively connected to the connecting parts 28. The connecting part 28 is a part that connects the first mass part 21, the second mass part 22, and the beam part 25. The beam part 25 is the rotation axis or swing axis of the movable body 20. The beam part 25 has a function as a torsion spring and supports the movable body 20 so as to be swingable around the axis of the beam part 25.

[0033] The beam part 25 is arranged at a position deviated from the center of gravity of the movable body 20 in the X-axis direction so that the movable body 20 tilts when an acceleration in the Z-axis direction is applied to the inertial sensor 100. When an acceleration in the Z-axis direction is applied to the inertial sensor 100, the movable body 20 swings around the axis of the beam part 25. Specifically, the movable body 20 alternately tilts like a seesaw with the beam part 25 as a fulcrum. Such a swing of the movable body 20 can be rephrased as a seesaw swing.

[0034] Due to the seesaw swing of the movable body 20, the gaps between the first mass part 21 and the first fixed electrode 11 and between the second mass part 22 and the second fixed electrode 12 change, and accordingly, the capacitances C1 and C2 change.

[0035] When the gap between the first mass part 21 and the first fixed electrode 11 increases, the capacitance C1 decreases, and when the gap between the second mass part 22 and the second fixed electrode 12 decreases, the capacitance C2 increases. When the gap between the first mass part 21 and the first fixed electrode 11 decreases, the capacitance C1 increases, and when the gap between the second mass part 22 and the second fixed electrode 12 increases, the capacitance C2 decreases.

[0036] Changes in the capacitances C1 and C2 are monitored by the circuit element 200 of the inertial sensor device 1 described later, and the inertial sensor device 1 outputs a detection signal of the acceleration in the Z-axis direction based on the changes in the capacitances C1 and C2.

[0037] The gap between the first mass portion 21 and the first fixed electrode 11 and the gap between the second mass portion 22 and the second fixed electrode 12 are preferably, for example, not less than h1 (height of the protrusion 15 described later) plus α μm and not more than 3.5 μm when the movable body 20 is at rest. Thereby, while sufficiently securing the movable range of the movable body 20, the capacitances C1 and C2 can be made sufficiently large.

[0038] 1.3. Structure of the protrusion FIGS. 3A and 3B show the specific structure of the protrusion 15. FIG. 3A is an enlarged cross-sectional view of the protrusion 15 in the range III surrounded by a broken line in FIG. 2A. FIG. 3B is an enlarged plan view of the protrusion 15 corresponding to FIG. 3A, and is a plan view of the protrusion 15 viewed from the +Z-axis direction side to the -Z-axis direction side.

[0039] As shown in FIG. 3A, the protrusion 15 is formed to protrude from the main surface 17 toward the +Z-axis direction side, and has a top portion 15p, a tapered portion 15t, and a corner portion 15e between the top portion 15p and the tapered portion 15t. The three-dimensional shape of the protrusion 15 is a frustum of a cone.

[0040] The top portion 15p has a flat surface f1. The shape of the flat surface f1 is a circle in plan view. The flat surface f1 of the top portion 15p of the protrusion 15 contributes to keeping the height h1 of the protrusion 15 low, and thus realizes thinning of the inertial sensor 100.

[0041] The height h1 from the main surface 17 to the flat surface f1 of the top portion 15p is about 1.5 μm. The diameter d1 of the flat surface f1 is smaller than the length w1 of the opening 26, and is preferably from 3 μm to 15 μm. In this embodiment, it is about 7.5 μm or 9 μm.

[0042] The diameter d1 becomes smaller according to the diameter of the temporary projection 15a in the forming process of the projection 15 described later and the maskless etching amount of the temporary support substrate 10a. The taper angle or the chamfer angle of the tapered portion 15t becomes larger according to the maskless etching amount of the temporary support substrate 10a.

[0043] The tapered portion 15t includes a root portion 15r continuous with the main surface 17, and the root portion 15r has a concave curved surface c1. In the present embodiment, the diameter d2 of the root portion 15r is about 11 μm. The diameter d1 of the flat surface f1 becomes a value about 1 to 4 μm smaller than the diameter d2 of the root portion 15r according to the etching amount of the temporary projection 15a described later.

[0044] Since the projection 15 has the concave curved surface c1 in the root portion 15r, the projection 15 has a larger area than the flat surface f1. Therefore, when the movable body 20 collides with the projection 15, the impact force can be widely dispersed to the support substrate 10.

[0045] Since the projection 15 has the concave curved surface c1 continuous with the main surface 17 in the root portion 15r, there is no clear boundary between the projection 15 and the main surface 17. Such a configuration in which the root portion 15r has the concave curved surface c1 continuous with the main surface 17 can suppress problems such as the projection 15 peeling off from the main surface 17. This is because the boundary between the projection 15 and the main surface 17 is, for example, a step or a groove, and the impact force when the movable body 20 collides with the projection 15 tends to concentrate and become a starting point for problems such as the projection 15 peeling off.

[0046] As described above, since the projection 15 of the present embodiment can widely disperse the impact force when the movable body 20 collides with the projection 15, it is possible to avoid or suppress the projection 15 from peeling off, cracking, or being damaged.

[0047] When the projection 15 is damaged, the movable body 20 may come into contact with the first fixed electrode 11 or the second fixed electrode 12. Contact between the movable body 20 and the first fixed electrode 11 or the second fixed electrode 12 easily causes sticking. However, since the occurrence of defects is avoided or suppressed in the protrusion 15 of the present embodiment, the occurrence of sticking caused by the defect of the protrusion 15 can be suppressed.

[0048] The corner portion 15e is a corner portion between the top portion 15p and the tapered portion 15t. The angle a1 formed by the top portion 15p and the tapered portion 15t is larger than 90°. The angle of the angle a1 increases according to the etching amount in the forming process of the protrusion 15 described later, and the inclination of the tapered portion 15t becomes gentle.

[0049] When the movable body 20 is largely tilted, the movable body 20 collides with the corner portion 15e of the protrusion 15. Since the corner portion 15e is a sharp corner, the contact area between the movable body 20 and the protrusion 15 is small. Therefore, the corner portion 15e of the protrusion 15 has a high effect in suppressing sticking. The corner portion 15e may have a roundness with a radius on the sub-micron order, for example.

[0050] The protrusion 15 is covered by the dummy electrode 13. Since the dummy electrode 13 is a thin film, the upper surface of the dummy electrode 13 faithfully transfers the shape of the protrusion 15. Therefore, even if the protrusion 15 is covered with the dummy electrode 13, the operation and effect of the protrusion 15 are not impaired.

[0051] In FIGS. 3A and 3B, the lead lines indicating the top portion 15p, the flat surface f1, the tapered portion 15t, the corner portion 15e, the root portion 15r, the concave curved surface c1, the diameter d1, and the height h1 indicate the surface of the protrusion 15, but may also indicate the surface of the dummy electrode 13. In this case, the film thickness of the dummy electrode 13 is added to the values of the diameter d1 and the height h1.

[0052] The dummy electrode 13 is electrically connected to the movable body 20 via a connection wiring (not shown), and the dummy electrode 13 has the same potential as the movable body 20. Therefore, an electrostatic attraction does not substantially occur between the protrusion 15 covered with the dummy electrode 13 and the movable body 20. Thus, the dummy electrode 13 covering the protrusion 15 can suppress the occurrence of sticking.

[0053] 1.4. Structure of the cover The cover 30 has a rectangular shape in plan view, similar to the support substrate 10. As shown in FIGS. 2A and 2B, the cover 30 has a cavity 31 formed by a recess on the lower surface side. The cover 30 is joined to the periphery of the support substrate 10 using a joining material (not shown). The cavity 31 of the cover 30 and the cavity 16 of the support substrate 10 form a storage space S. The movable body 20 is stored in the storage space S.

[0054] The cover 30 has a communication hole (not shown). After setting the storage space S to a desired atmosphere using the communication hole, the communication hole is blocked, and the movable body 20 is sealed in the storage space S. It is preferable that the storage space S is filled with an inert gas such as nitrogen, helium, or argon and has a pressure approximately equal to atmospheric pressure at the operating temperature (about -40°C to 80°C). By setting the pressure in the storage space S to atmospheric pressure, the viscous resistance increases and the damping effect is exerted, enabling the vibration of the movable body 20 to converge or stop quickly.

[0055] In this embodiment, the cover 30 is made of a silicon substrate. Note that the cover 30 is not limited to a silicon substrate. For example, a glass substrate or a ceramic substrate may be used for the cover 30.

[0056] The cover 30 is preferably connected to the ground. This can keep the potential of the cover 30 constant and, for example, reduce fluctuations in the capacitance between the cover 30 and the movable body 20.

[0057] The separation distance between the lower surface of the cavity 31 and the upper surface of the movable body 20 is preferably, for example, 15 μm or more, more preferably 20 μm or more, and even more preferably 25 μm or more. This configuration can sufficiently reduce the capacitance between the cover 30 and the movable body 20 and is effective for improving the detection accuracy of acceleration.

[0058] 1.5. Manufacturing method of the inertial sensor and the protrusion Figures 4 to 10 are explanatory diagrams showing a method for manufacturing the inertial sensor 100 and the protrusion 15. Figure 4 is a flowchart for explaining the manufacturing process of the inertial sensor 100. Figure 5 is a flowchart showing the detailed process of the support substrate forming step which is step S1 in Figure 4, and particularly, it is a flowchart for explaining the manufacturing method of the protrusion 15. Figures 6 to 10 are cross-sectional views or plan views in each manufacturing process of the inertial sensor 100, and the cross-sectional position of the cross-sectional view is the same as that in Figure 2A.

[0059] In step S1, the support substrate 10 is formed. The details of step S1 will be described with reference to the flowchart in Figure 5. Step S11 includes a step of forming an etching mask on the glass substrate and a step of wet-etching the glass substrate using the etching mask to form the intermediate support substrate 10a shown in Figure 6. Buffered hydrofluoric acid can be used as the etching solution.

[0060] The intermediate support substrate 10a includes a concave cavity 16 having a main surface 17 including a recess 17c, and support columns 14 and intermediate protrusions 15a provided on the main surface 17. The cross-sectional shape of the intermediate protrusion 15a is rectangular. Although not shown, the planar shape of the intermediate protrusion 15a is circular and the three-dimensional shape is a cylinder.

[0061] In step S12, the intermediate support substrate 10a is wet-etched without using an etching mask to remove the intermediate support substrate 10a by about several μm. The etching amount of the intermediate support substrate 10a is preferably from 1 μm to 3 μm. Buffered hydrofluoric acid is used as the etching solution.

[0062] As described above, according to the etching amount of the intermediate support substrate 10a, the diameter d1 of the top 15p of the protrusion 15 becomes smaller. When the diameter of the intermediate protrusion 15a is about 11 μm, when the intermediate support substrate 10a is etched by 1 μm, the diameter d1 of the top 15p of the protrusion 15 becomes about 9 μm, and a tapered portion 15t is formed.

[0063] When the diameter of the workpiece protrusion 15a is about 11 μm, if the workpiece support substrate 10a is etched by 3 μm, the diameter d1 of the top 15p of the protrusion 15 becomes about 7.5 μm, and the tapered portion 15t is formed. When the workpiece support substrate 10a is etched by 3 μm, the taper angle or the chamfer angle of the tapered portion 15t formed is larger than that when the workpiece support substrate 10a is etched by 1 μm.

[0064] In step S12, as shown in FIG. 7, the support substrate 10 is formed from the workpiece support substrate 10a, and the protrusion 15 is formed from the workpiece protrusion 15a. In FIG. 7, only the side surface of the protrusion 15 appears to be etched and the other components do not appear to be etched, but this is due to the difference in scale. The protrusion 15 is described as being enlarged about 10 times with respect to the other components.

[0065] In step S2, the first fixed electrode 11, the second fixed electrode 12, and the dummy electrode 13 are formed. As shown in FIGS. 8A and 8B, after forming a conductive film on the main surface 17 of the support substrate 10 by a sputtering method or the like, the first fixed electrode 11, the second fixed electrode 12, and the dummy electrode 13 are formed by patterning the conductive film.

[0066] In step S3, as shown in FIG. 9, the support substrate 10 and the silicon substrate 20s are joined. For joining the support substrate 10 and the silicon substrate 20s, direct joining such as anodic bonding or indirect joining using an adhesive, metal, low melting point glass, or the like can be used.

[0067] In step S4, as shown in FIG. 10, the silicon substrate 20s is processed to form the movable body 20. The silicon substrate 20s is ground to be thinned to a predetermined thickness, and then the silicon substrate 20s is patterned to form the movable body 20. For the etching of the silicon substrate 20s, a Bosch process using a RIE (Reactive Ion Etching) apparatus can be employed. The movable body 20 is formed in a state of being fixed on the support column 14.

[0068] In step S5, the movable body 20 is sealed. By joining the lid body 30 to the support substrate 10, the movable body 20 is sealed in the storage space S. The support substrate 10 and the lid body 30 are joined using, for example, anodic bonding or an adhesive. Thus, the inertial sensor 100 is obtained.

[0069] 1.6. Modification Example The above-described embodiment of the protrusion 15 can be variously modified. FIG. 11 is an enlarged plan view of the protrusion 151 according to the modification example, and is a drawing corresponding to FIG. 3B.

[0070] The protrusion 151 is formed to protrude from the main surface 17 in the positive Z-axis direction, and has a top portion 151p, a tapered portion 151t, and a corner portion 151e between the top portion 151p and the tapered portion 151t. The three-dimensional shape of the protrusion 151 is a truncated elliptical cone.

[0071] The top portion 151p has a flat surface f1. The shape of the flat surface f1 is an ellipse in plan view. The longer diameter d1 of the flat surface f1 is smaller than the length w1 of the opening 26. The tapered portion 151t includes a root portion 151r continuous with the main surface 17, and the root portion 151r has a concave curved surface c1. The longer diameter d2 of the root portion 151r is equal to the length w1 of the opening 26.

[0072] At the corner portion 151e, the angle formed by the top portion 151p and the tapered portion 151t is larger than 90°, and the angle of the corner increases according to the etching amount in the formation process of the protrusion 15, and the inclination of the tapered portion 151t becomes gentle.

[0073] Although not shown, the planar shape of the flat surface f1 of the protrusion 15 may be a polygon such as a quadrilateral, and the three-dimensional shape of the protrusion 15 may be a truncated pyramid. By making the planar shape of the flat surface f1 a polygon, management within the production process becomes easier. This is because when measuring the height h1 of the protrusion 15 by the stylus method of two-dimensional measurement, even if the stylus position fluctuates in the X and Y directions, it is easy to accurately measure the height h1 of the protrusion 15.

[0074] As described above, the inertial sensor 100 of the present embodiment includes a support substrate 10 as a substrate, a first fixed electrode 11 and a second fixed electrode 12 as fixed electrodes provided on the main surface 17 as the first surface of the support substrate 10, a movable body 20 provided so as to be swingable with respect to the first fixed electrode 11 and the second fixed electrode 12, and a protrusion 15 provided on the main surface 17. The protrusion 15 has a flat surface f1 at the top portion 15p and a concave curved surface c1 continuous with the main surface 17 at the root portion 15r.

[0075] Thus, since the protrusion 15 has the concave curved surface c1 continuous with the main surface 17 at the root portion 15r, even if the movable body 20 comes into contact with the protrusion 15, it is possible to avoid or suppress the protrusion 15 from being peeled off from the main surface 17 and being damaged. Therefore, it is possible to avoid or suppress the risk of sticking from increasing due to the protrusion 15 being damaged. Furthermore, since the top portion 15p has the flat surface f1, by having the concave curved surface c1 at the root portion 15r, even if the skirt portion becomes wider, the height h1 of the protrusion 15 can be kept low. Therefore, the thickness of the inertial sensor 100 can be reduced.

[0076] In the inertial sensor 100 of the present embodiment, the planar shape of the flat surface f1 is circular or elliptical. In the inertial sensor 100 of the present embodiment, since the planar shape of the flat surface f1 of the protrusion 15 is circular or elliptical, the skirt area can be widened. Therefore, the inertial sensor 100 of the present embodiment can suppress the peeling of the protrusion 15.

[0077] The inertial sensor 100 of this embodiment is provided on the surface of the protrusion 15 and includes a dummy electrode 13 as a coating electrode having the same potential as the movable body 20. The protrusion 15 is covered with a dummy electrode 13 having the same potential as the movable body 20. Therefore, the movable body 20 and the protrusion 15 have the same potential, and substantially no electrostatic attraction is generated between the movable body 20 and the protrusion 15. Therefore, the inertial sensor 100 of this embodiment can suppress sticking of the movable body 20 to the protrusion 15.

[0078] In the inertial sensor 100 of this embodiment, the movable body 20 has an opening 26 as a through hole, and the diameter d1 of the flat surface f1 is smaller than the length w1 of one side as the inner diameter of the opening 26. In the inertial sensor 100 of this embodiment, it is preferable that the diameter d1 of the flat surface f1 is smaller than the length w1 of one side of the opening 26. With such a configuration, after forming the opening 26, the processing of the surface of the protrusion 15 becomes easy. This processing of the surface of the protrusion 15 includes removal of organic impurities by oxygen plasma. By removing impurities from the surface of the protrusion 15, charging of the surface of the protrusion 15 can be prevented, and an effect of suppressing sticking can be obtained.

[0079] In the inertial sensor 100 of this embodiment, the protrusion 15 has a tapered portion 15t including a concave curved surface c1, and a corner portion 15e between the top portion 15p and the tapered portion 15t. Since the protrusion 15 has the corner portion 15e, even if the movable body 20 collides with the first fixed electrode 11 or the second fixed electrode 12, the contact area between the movable body 20 and the first fixed electrode 11 or the second fixed electrode 12 can be reduced. Therefore, the inertial sensor 100 of this embodiment can suppress the occurrence of sticking.

[0080] 2. Embodiment 2 2.1. Outline of the inertial measurement device FIG. 12 is an explanatory diagram of a sensor module 300 as an inertial measurement device (IMU: Inertial Measurement Unit) including an inertial sensor 100. FIG. 12 is an exploded perspective view showing a schematic configuration of the sensor module 300.

[0081] The sensor module 300 is mounted on a wearable device such as an automobile, a robot, a smartphone, or a portable pedometer, and is used as a device for detecting the posture and behavior of the wearable device.

[0082] As shown in FIG. 12, the sensor module 300 includes an outer case 301, a joining member 310, and a sensor unit 325, and has a configuration in which the sensor unit 325 is fitted or inserted into the interior 303 of the outer case 301 with the joining member 310 interposed therebetween.

[0083] The outer case 301 is a box-shaped container having a rectangular parallelepiped outer shape without a lid, and its interior 303 is an internal space surrounded by a wall surface 304, a bottom surface 305, and a joining surface 306. The material of the outer case 301 is, for example, aluminum. The material of the outer case 301 may be other metals such as zinc or stainless steel, resin, or a composite material of metal and resin.

[0084] The outer shape of the outer case 301 is a rectangular parallelepiped having a substantially square planar shape, and through holes 302 are formed near two vertices located in the diagonal direction of the square. The sensor module 300 is attached to the wearable device by screwing or the like using the through holes 302.

[0085] The sensor unit 325 includes an inner case 320 and a substrate 315. The substrate 315 mounts an inertial sensor device 1 incorporating an inertial sensor 100, an external connection connector 316, and the like.

[0086] The inner case 320 supports the substrate 315 and is housed inside the outer case 301. The thickness of the inner case 320, that is to say, the height in the Z-axis direction, is equal to or lower than the height from the upper surface 307 of the outer case 301 to the joint surface 306. As the material of the inner case 320, the same material as that of the outer case 301 can be used. On the lower surface of the inner case 320, a recess 331 for preventing contact with the inertial sensor device 1 and an opening 321 for exposing the connector 316 are formed.

[0087] 2.2. Overview of the Substrate FIG. 13 is a perspective view of the substrate 315 on which the inertial sensor 100 is mounted. As shown in FIG. 13, on the upper surface and the side surface of the substrate 315, an inertial sensor device 1, a connector 316, and angular velocity sensors 317x, 317y, 317z, etc. are mounted. On the lower surface of the substrate 315, a control IC 319 is mounted.

[0088] The substrate 315 is a multilayer substrate in which a plurality of through-holes are formed. The substrate 315 is a glass epoxy substrate. As the substrate 315, a rigid substrate such as a composite substrate or a ceramic substrate may be used.

[0089] The inertial sensor device 1 includes an inertial sensor 100, a circuit element 200, and a package on which the inertial sensor 100 and the circuit element 200 are mounted. The circuit element 200 includes a detection circuit that detects the acceleration in the Z-axis direction based on the signal from the inertial sensor 100, an output circuit that converts the signal from the detection circuit into a predetermined detection signal and outputs it, and the like.

[0090] The connector 316 is a plug-type connector and includes two rows of connection terminals arranged at equal pitches in the X-axis direction. In this embodiment, it includes two rows of connection terminals with 10 pins in one row and a total of 20 pins, but the number of connection terminals may be appropriately changed according to the design specifications.

[0091] The angular velocity sensor 317z is a gyro sensor that detects the angular velocity of one axis in the Z-axis direction. The angular velocity sensor 317z is preferably a vibrating gyro sensor that uses a crystal as a vibrator and detects the angular velocity from the Coriolis force applied to the vibrating object. The vibrator is not limited to a crystal, and those using ceramics or silicon may also be used.

[0092] On the side surface of the substrate 315 in the X-axis direction, an angular velocity sensor 317x that detects the angular velocity of one axis in the X-axis direction is mounted so that the mounting surface is orthogonal to the X-axis. Similarly, on the side surface of the substrate 315 in the Y-axis direction, an angular velocity sensor 317y that detects the angular velocity of one axis in the Y-axis direction is mounted so that the mounting surface is orthogonal to the Y-axis.

[0093] The angular velocity sensors 317x, 317y, and 317z are not limited to a configuration using a total of three angular velocity sensors, one for each axis. Any sensor that can detect the angular velocity of three axes may be used. For example, a sensor device that can detect the angular velocity of three axes in one device or package may be used.

[0094] The inertial sensor device 1 is an acceleration sensor for measuring the acceleration in the Z-axis direction, but it may also measure the X-axis direction or the Y-axis direction. The inertial sensor device 1 may be equipped with an inertial sensor 100 that measures the acceleration in the X-axis direction and / or the Y-axis direction to detect the acceleration in the Z-axis direction and the Y-axis direction, the Z-axis direction and the X-axis direction, or the three axes of XYZ.

[0095] The control IC 319 is an MCU (Micro Controller Unit), which incorporates a storage unit including a non-volatile memory, an arithmetic circuit that performs temperature correction processing, etc., and is a control unit that controls each part of the sensor module 300.

[0096] The memory unit stores a program that defines the order and content for detecting acceleration and angular velocity, a program that digitizes the detection signals and incorporates them into packet data, and accompanying data. The substrate 315 has a plurality of electronic components such as temperature sensors mounted thereon.

[0097] According to such a sensor module 300, since the inertial sensor device 1 equipped with the inertial sensor 100 is used, it is possible to provide a sensor module 300 that is excellent in shock resistance and has improved reliability.

[0098] As described above, according to the sensor module 300 as the inertial measurement device equipped with the inertial sensor 100 of the present embodiment, in addition to the effects of the first embodiment, it is possible to provide a highly reliable inertial measurement device.

[0099] Although the preferred embodiments have been described above, the present invention is not limited to the above-described embodiments. The configuration of each part of the present invention can be replaced with any configuration that exhibits the same function as that of the above-described embodiments.

Explanation of Reference Numerals

[0100] 1... Inertial sensor device, 10... Support substrate, 10a... Work-in-progress support substrate, 11... First fixed electrode, 12... Second fixed electrode, 13...Dummy electrode, 14... Support pillar, 15... Protrusion, 15a... Work-in-progress protrusion, 15e... Corner, 15p... Top, 15r... Root, 15t... Tapered portion, 16... Cavity, 17... Main surface, 17c... Recess, 20... Movable body, 20a... First movable body, 20b... Second movable body, 20s... Silicon substrate, 21... First mass portion, 22... Second mass portion, 23... Third mass portion, 24... Support portion, 25... Beam portion, 26... Opening, 28... Connecting portion, 30... Cover, 31... Cavity, 100... Inertial sensor, 151... Protrusion, 151e... Corner, 151p... Top, 151r... Root, 151t... Tapered portion, 200... Circuit element, 300... Sensor module, 301... Outer case, 302... Through hole, 303... Inside, 304... Wall surface, 305... Bottom surface, 306... Joint surface, 307... Upper surface, 310... Joint member, 315... Substrate, 316... Connector, 317x, 317y, 317z... Angular velocity sensor, 319... Control IC, 320... Inner case, 321... Opening, 325... Sensor unit, 331... Recess, a1... Angle, d1, d2... Diameter, w1... Length, h1... Height, f1... Flat surface, c1... Concave curved surface, k1... Blank area, C1, C2... Capacitance, CL1, CL2... Center line, R1, R2, Ra, Rb... Distance, S... Storage space.

Claims

1. A substrate, a fixed electrode provided on a first surface of the substrate, a movable body provided so as to be swingable with respect to the fixed electrode, and a protrusion provided on the first surface, wherein the protrusion has a flat surface at the top and a concave curved surface continuous with the first surface at the base, an inertial sensor.

2. The planar shape of the flat surface is circular or elliptical, The inertial sensor according to claim 1.

3. and a coating electrode provided on the surface of the protrusion and having the same potential as the movable body, The inertial sensor according to claim 1.

4. The movable body has a through hole, and the diameter of the flat surface is smaller than the inner diameter of the through hole, The inertial sensor according to claim 1.

5. The protrusion has a tapered portion including the concave curved surface and a corner portion between the top and the tapered portion, The inertial sensor according to claim 1.

6. An inertial measurement device including the inertial sensor according to any one of claims 1 to 5.

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