Physical quantity sensor and inertial measurement unit

Abstract

To provide a physical quantity sensor that can prevent the occurrence of stiction.SOLUTION: A physical quantity sensor 100 comprises a support substrate 10, and a movable body 20 that is movably provided on the support substrate 10. The movable body 20 has, on a lower surface 20f facing the support substrate 10, a holed area D1 having through holes 26, a blank area D2 not having the through holes 26, and a conductive film 27 provided in the blank area D2. The support substrate 10 has projections 15 overlapping the conductive film 27 in plan view.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a physical quantity sensor and an inertial measurement unit including the physical quantity sensor. [Background technology]

[0002] In recent years, physical quantity sensors using MEMS (Micro Electro Mechanical System) technology have been developed. As one such physical quantity sensor, Patent Document 1 describes a physical quantity sensor that detects acceleration in the Z-axis direction. The physical quantity sensor described in Patent Document 1 includes a substrate and a movable body that is arranged to be able to swing relative to the substrate, and the substrate has a protrusion that comes into contact with the movable body when the movable body swings excessively, thereby suppressing further swinging. The protrusions are not provided in the area that comes into contact with the openings that penetrate the movable body so as not to damage the movable body. The openings are provided to reduce the drag caused by the air that occurs between the movable body and the substrate, in other words, damping caused by the viscosity of the gas. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-45167 Summary of the Invention [Problem to be solved by the invention]

[0004] In such a conventional physical quantity sensor, when a movable body comes into contact with a protrusion, occurrence of sticking, in which the movable body sticks to the protrusion, is suppressed. [Means for solving the problem]

[0005] A physical quantity sensor according to one aspect of the present application comprises a substrate and a movable body movably arranged relative to the substrate, the movable body having, on a first surface facing the substrate, a first region having a through hole, a second region not having the through hole, and a first conductive film arranged in the second region, and the substrate has a protrusion that overlaps the first conductive film in a planar view.

[0006] An inertial measurement unit according to one aspect of the present application includes the above-described physical quantity sensor. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view of a physical quantity sensor according to a first embodiment. [Figure 2A] Cross-sectional view of the physical quantity sensor along line AA in Figure 1. [Figure 2B] Cross-sectional view of the physical quantity sensor along line BB in Figure 1. [Figure 3A] An enlarged cross-sectional view of area III in FIG. 2A. [Figure 3B] 3B is an enlarged cross-sectional view of a region III in FIG. 2A according to a modified example of FIG. 3A. [Figure 4] 1. FIG. 4 is an enlarged plan view of the area IV in FIG. 1 as viewed from the bottom of the movable body. [Figure 5] 1 is a flowchart illustrating a manufacturing process of a physical quantity sensor. [Figure 6] 6 is a flowchart showing details of a silicon substrate preparation step S2 in FIG. 5. [Figure 7] 6 is a flowchart showing details of a movable body forming step S5 in FIG. 5. [Figure 8A] FIG. [Figure 8B] FIG. 8B is a plan view showing an embodiment in a manufacturing process according to the modified example of FIG. 8A. [Figure 9] 1A to 1C are cross-sectional views showing one embodiment of a manufacturing process. [Figure 10] 1A to 1C are cross-sectional views showing one embodiment of a manufacturing process. [Figure 11] 1A to 1C are cross-sectional views showing one embodiment of a manufacturing process. [Figure 12]1A to 1C are cross-sectional views showing one embodiment of a manufacturing process. [Figure 13] 1A to 1C are cross-sectional views showing one embodiment of a manufacturing process. [Figure 14] 1A to 1C are cross-sectional views showing one embodiment of a manufacturing process. [Figure 15] FIG. 10 is an exploded perspective view showing a schematic configuration of an inertial measurement unit according to a second embodiment. [Figure 16] FIG. 1 is a perspective view of a substrate on which a physical quantity sensor is mounted. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the embodiments of the present invention, components shown in the drawings may be shown with different scales for clarity. Drawings may show three mutually perpendicular axes: the X-axis, the Y-axis, and the Z-axis. In the following explanation, the tip of the arrows on the three axes may be referred to as the "plus side," and the base of the arrows may be referred to as the "minus side." The direction parallel to the X-axis may be referred to as the "X-axis direction," the direction parallel to the Y-axis may be referred to as the "Y-axis direction," and the direction parallel to the Z-axis may be referred to as the "Z-axis direction." Viewing in the Z-axis direction may be referred to as "planar view."

[0009] In the following description, for example, the expression "on the substrate" in relation to a substrate means that the substrate is placed in contact with the substrate, that the substrate is placed via another structure, or that a portion of the substrate is placed in contact with the substrate and a portion of the substrate is placed via another structure. The term "top surface" of a certain structure refers to the surface on the positive side of the Z axis direction of the structure, for example, "top surface of a movable body" refers to the surface on the positive side of the Z axis direction of the movable body. The term "bottom surface" of a certain component refers to the surface on the negative side of the Z axis direction of the component, for example, "the bottom surface of the movable body" refers to the surface on the negative side of the Z axis direction of the movable body. The term "surface" as used herein refers to the surface of a structure that is visible on the outside.

[0010] 1. Embodiment 1 1, 2A, and 2B show a schematic configuration of a physical quantity sensor 100 according to this embodiment. Fig. 1 is a plan view schematically showing a physical quantity sensor 100 according to embodiment 1, and for the sake of convenience, the lid 30 is omitted from the illustration. Fig. 2A is a cross-sectional view taken along line AA in Fig. 1. Fig. 2B is a cross-sectional view taken along line BB in Fig. 1.

[0011] The physical quantity sensor 100 of this 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 physical quantity based on the displacement of the movable body 20. The physical quantity is, for example, acceleration. In this embodiment, the physical quantity sensor 100 is an acceleration sensor element that detects acceleration in the Z-axis direction, and specifically, is a capacitance-type Z-axis acceleration sensor element that uses MEMS technology.

[0012] The physical quantity sensor 100 has a flat plate-shaped movable body 20, a support substrate 10 that supports the movable body 20, and a lid body 30 that is joined to the support substrate 10. In this embodiment, the support substrate 10 is an example of a substrate.

[0013] 1.1. Support substrate configuration As shown in FIGS. 2A and 2B, the support substrate 10 has a recessed cavity 16 . The support substrate 10 is a glass substrate made of borosilicate glass, which is an insulating material, but may also be a silicon substrate or a ceramic substrate. The support substrate 10 has a first fixed electrode 11, a second fixed electrode 12, a dummy electrode 13, pillars 14, and protrusions 15 on an upper surface 10f within the cavity 16. The pillars 14 and protrusions 15 are formed integrally with the support substrate 10.

[0014] The first fixed electrode 11 is provided on the negative side of the support column 14 in the X-axis direction, and overlaps with the first mass region 21 of the movable body 20 in plan view. The second fixed electrode 12 is provided on the positive side of the support column 14 in the X-axis direction, and overlaps with the second mass region 22 of the movable body 20 in plan view. First fixed electrode 11 and second fixed electrode 12 are detection electrodes that detect a change in capacitance occurring between themselves and movable body 20.

[0015] Dummy electrode 13 is provided on the negative side of first fixed electrode 11 in the X-axis direction, on the positive side of second fixed electrode 12 in the X-axis direction, and between support pillars 14. On the negative side of the support 14 in the X-axis direction, the dummy electrode 13 overlaps with the third mass region 23 and the first mass region 21 of the movable body 20 in a plan view, and the portion of the dummy electrode 13 that overlaps with the first mass region 21 covers the protrusion 15. On the positive side of the support 14 in the X-axis direction, the dummy electrode 13 overlaps with the second mass region 22 of the movable body 20 in a plan view, and the portion of the dummy electrode 13 that overlaps with the second mass region 22 covers the protrusion 15. In this embodiment, the dummy electrode 13 covering the protrusion 15 is an example of a second conductive film. Note that, as will be described later, the conductive film covering the protrusion 15 may be the first fixed electrode 11 or the second fixed electrode 12.

[0016] The dummy electrode 13 is insulated from the first fixed electrode 11 and the second fixed electrode 12 . The dummy electrode 13 is electrically connected to the movable body 20. Therefore, the dummy electrode 13 has the same potential as the movable body 20, and substantially no electrostatic attraction occurs between them. Therefore, the physical quantity sensor 100 of this embodiment can effectively prevent malfunction of the movable body 20 and sticking, in which the movable body 20 sticks to the protrusion 15.

[0017] The portion of the dummy electrode 13 that overlaps with the third mass region 23 of the movable body 20 is provided in a recess 10fc on the top surface 10f. The recess 10fc is a recessed portion on the top surface 10f, and is provided as a relief to prevent the end of the movable body 20 from colliding with it.

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

[0019] The protrusion 15 is a stopper that restricts the movable body 20 from swinging with an excessive swing amplitude, and prevents the end of the movable body 20 from colliding with the upper surface 10f of the support substrate 10. The protrusion 15 protrudes from the upper surface 10f of the support substrate 10 toward the positive side in the Z axis direction, and is provided so as to face the first mass region 21 and the second mass region 22 of the movable body 20.

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

[0021] Two protrusions 15 are provided along the extension direction of beam portion 25 of movable body 20. Beam portion 25 functions as a rotation axis or oscillation axis of movable body 20, and center line CL2 overlaps with the rotation axis or oscillation axis of movable body 20. In this way, by providing multiple protrusions 15 along the extension direction of the beam portion 25 of the movable body 20, the physical quantity sensor 100 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 at a distance R2 that are line-symmetrical with respect to the center line CL1 that divides the movable body 20 into two equal parts in the Y-axis direction. In this way, by arranging the multiple protrusions 15 symmetrically with respect to the center line CL1, the physical quantity sensor 100 can prevent 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 provided at positions symmetrical with respect to the center line CL2 at a distance R1. In this way, by arranging the multiple protrusions 15 line-symmetrically with respect to the center line CL2, the physical quantity sensor 100 can make the maximum swing angle of the first mass region 21 of the movable body 20 the same as the maximum swing angle of the second mass region 22 of the movable body 20. This can improve the accuracy of the physical quantity sensor 100. The swing angle can be rephrased as a rotation angle.

[0024] The protrusion 15 is provided at a position that does not overlap, in plan view, with the perforated region D1 in which the through-hole 26 of the movable body 20 is provided. In other words, the protrusion 15 is provided at a position that overlaps, in plan view, with the blank region D2 in which the through-hole 26 of the movable body 20 is not provided. Therefore, the movable body 20 comes into contact with the protrusion 15 in the blank area D2. Therefore, the contact of the movable body 20 with the protrusion 15 can prevent defects such as cracks, fissures, and chips from occurring in the movable body 20 starting from the edge of the through-hole 26.

[0025] 1.2. Lid structure The lid body 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 as a recess on the underside. The lid body 30 is bonded to the periphery of the support substrate 10 using a bonding material (not shown). The cavity 31 of the lid body 30 and the cavity 16 of the support substrate 10 form a storage space S. The storage space S stores the movable body 20.

[0026] The cover 30 has a communication hole (not shown). After the desired atmosphere is created in the storage space S using the communication hole, the movable body 20 is sealed in the storage space S by closing the communication hole. The storage space S is preferably filled with an inert gas such as nitrogen, helium, or argon, and is at approximately atmospheric pressure at the operating temperature (approximately -40°C to 80°C). By keeping the storage space S at atmospheric pressure, viscous resistance increases, a damping effect is exhibited, and vibration of the movable body 20 can be quickly converged or stopped.

[0027] In this embodiment, the lid 30 is made of a silicon substrate. The lid 30 is not limited to a silicon substrate. The lid 30 may be made of, for example, a glass substrate or a ceramic substrate.

[0028] The lid 30 is preferably connected to ground, which makes it possible to keep the potential of the lid 30 constant and, for example, to reduce fluctuations in the capacitance between the lid 30 and the movable body 20.

[0029] The distance between the lower surface of the lid 30 and the upper surface 20g of the movable body 20 is, for example, preferably 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 lid 30 and the movable body 20, which is effective in improving the accuracy of acceleration detection.

[0030] 1.3.Configuration of the moving body The movable body 20 is provided so as to be movable relative to the support substrate 10. Specifically, the movable body 20 is provided so as to be swingable relative to the support substrate 10 like a seesaw. The movable body 20 is made of a conductive silicon substrate. By using a conductive silicon substrate for the movable body 20, it is possible to give the movable body 20 the function of an electrode. Note that a non-conductive substrate may be used for the movable body 20, and a conductive electrode layer may be formed on the lower surface 20f of the movable body 20.

[0031] The movable body 20 has a support portion 24 , a beam portion 25 as a rotation axis, a through hole 26 , and a conductive film 27 . The support portion 24 is connected to the support posts 14 of the support substrate 10 . Beam portion 25 is a rotation axis or oscillation axis of movable body 20. Beam portion 25 is supported by support portion 24, has a portion extending in the Y-axis direction from support portion 24, and functions as a torsion spring. The movable body 20 is supported on the support substrate 10 so as to be able to swing in a seesaw manner with the beam portion 25 as a fulcrum.

[0032] The movable body 20 has a first movable part 20a and a second movable part 20b. The first movable portion 20a is the portion on the negative side of the center line CL2 in the X-axis direction, and the second movable portion 20b is the portion on the positive side of the center line CL2 in the X-axis direction. The first movable portion 20a has a first mass region 21, a third mass region 23, and a connecting region . The second movable portion 20b has a second mass region 22 and a connecting region .

[0033] The distance Ra from the center line CL2 to the end of the first movable part 20a is different from the distance Rb from the center line CL2 to the end of the second movable part 20b because the first movable part 20a has the third mass region 23. Therefore, the first movable part 20a and the second movable part 20b have different masses.

[0034] Because the mass of the first movable part 20a and the mass of the second movable part 20b are different, the rotational force of the first movable part 20a and the rotational force of the second movable part 20b that are generated when acceleration in the Z-axis direction is applied to the movable body 20 are unbalanced. Therefore, when acceleration in the Z-axis direction is applied to the physical quantity sensor 100, the movable body 20 tilts. The physical quantity sensor 100 outputs the tilt of the movable body 20 as changes in the capacitances C1 and C2 via the first fixed electrode 11 and the second fixed electrode 12.

[0035] The changes in the capacitances C1 and C2 are monitored by a circuit element 200 of the physical quantity sensor device 1, which will be described later, and the physical quantity sensor device 1 outputs a detection signal of acceleration in the Z-axis direction based on the changes in the capacitances C1 and C2.

[0036] The through-hole 26 is a through-hole that penetrates in the Z-axis direction between the upper surface 20g and the lower surface 20f of the movable body 20. In this embodiment, the lower surface 20f is an example of a first surface, and the upper surface 20g is an example of a second surface.

[0037] The through holes 26 are provided to reduce damping caused by the viscosity of gas when the movable body 20 oscillates. Damping is a function that tries to stop the movement of the movable body 20, and can be rephrased as flow resistance. In this way, by providing the through-hole 26 in the movable body 20, the physical quantity sensor 100 of this embodiment can improve the detection sensitivity of acceleration. In this embodiment, the through-hole 26 is a rectangular hole having a square planar shape. The length w1 of one side of the opening of the through-hole 26 is preferably 5 μm to 20 μm, and in this embodiment, it is approximately 10 μm. The length w1 corresponds to the inner diameter of the through-hole 26.

[0038] 4 is an enlarged plan view of the lower surface 20f of the movable body 20, as viewed from the lower surface 20f side of the movable body 20 in range IV in FIG. 1. As shown in FIG. 4, the movable body 20 has a perforated region D1 in which a plurality of through-holes 26 are provided, and a blank region D2 in which no through-holes 26 are provided. In FIG. 4, a two-dot chain line indicates the boundary between the blank region D2 and the perforated region D1, with the inside of the region surrounded by the two-dot chain line being the blank region D2 and the outside of the region surrounded by the two-dot chain line being the perforated region D1. In this embodiment, the perforated region D1 is an example of a first region, and the blank region D2 is an example of a second region.

[0039] The size of the blank area D2 is, for example, a size equivalent to an area in the perforated area D1 where 2×2 through holes 26 are provided. The size of the perforated area D1 may be larger or smaller. The size of the perforated area D1 may be, for example, a size equivalent to an area in the perforated area D1 where 5×5 through holes 26 are provided.

[0040] The blank region D2 is surrounded by the perforated region D1. In other words, the blank region D2 is a region in the perforated region D1 where no through holes 26 are provided. Therefore, among the through holes 26 in the perforated region D1 facing the blank region D2, the spacing between adjacent through holes 26 is different on the blank region D2 side and the side opposite the blank region D2. In this embodiment, the multiple through holes 26 are arranged at equal intervals in the perforated region D1. That is, the arrangement of the multiple through holes 26 at the boundary between the blank region D2 and the perforated region D1 is different from that in the perforated region D1. Note that the arrangement of at least some of the multiple through holes 26 may be different in the perforated region D1. Furthermore, in this embodiment, the blank region D2 is surrounded on all four sides by the perforated region D1. However, in this embodiment, the blank region D2 may be configured to be surrounded on at least three sides by the perforated region D1.

[0041] The blank area D2 is provided in an area corresponding to the protrusion 15 of the support substrate 10. In this way, by making the area of ​​the movable body 20 corresponding to the protrusion 15 the blank area D2, even if the movable body 20 comes into contact with the protrusion 15, the movable body 20 comes into contact with the protrusion 15 in the blank area D2, and therefore, the occurrence of defects such as cracks in the movable body 20 can be suppressed. In this embodiment, the blank areas D2 are provided at positions that are line-symmetrical with respect to the center line CL1, and at positions that are line-symmetrical with respect to the center line CL2.

[0042] The conductive film 27 is provided in a blank area D2 on the lower surface 20f of the movable body 20 at a position that overlaps with the protrusion 15 of the support substrate 10 in a plan view. In this manner, in this embodiment, the conductive film 27 and the protrusion 15 are provided so as to overlap with each other, thereby preventing the occurrence of sticking, in which the movable body 20 adheres to the protrusion 15.

[0043] 1.4.Configuration to prevent sticking 3A, 3B, and 4 are explanatory diagrams showing a configuration for suppressing the occurrence of sticking. Fig. 3A is an enlarged cross-sectional view of a region III in Fig. 2A, and Fig. 3B is an enlarged cross-sectional view of a region III in Fig. 2A according to a modification of Fig. 3A.

[0044] 3A and 4, the shape of the protrusion 15 is preferably a cylinder with a circular top 15p. The shape of the protrusion 15 is not limited to a cylinder. For example, as shown in FIG. 3B, the shape of the protrusion 15 may be a truncated cone with a circular top 15p.

[0045] The conductive film 27 is provided opposite the protrusion 15 . In this embodiment, the planar shape of the conductive film 27 is a rounded rectangle with rounded corners, but the planar shape of the conductive film 27 is not limited to a rounded rectangle.

[0046] The planar shape of the conductive film 27 is larger than the top 15p of the protrusion 15 in plan view. In this way, by making the planar shape of the conductive film 27 larger than the protrusion 15, the conductive film 27 can be brought into contact with the protrusion 15 whenever the movable body 20 comes into contact with the protrusion 15. Therefore, the physical quantity sensor 100 of this embodiment can reliably prevent the occurrence of sticking, in which the movable body 20 sticks to the protrusion 15.

[0047] Furthermore, it is preferable that the planar shape of the conductive film 27 is as small as possible. For example, it is sufficient that the conductive film 27 is provided only in an area on the lower surface 20f of the movable body 20 where contact with the protrusion 15 is expected. This is because a smaller planar shape of the conductive film 27 can suppress an increase in the weight of the movable body 20, thereby suppressing a decrease in the sensitivity of the physical quantity sensor 100.

[0048] A dummy electrode 13 is provided on the protrusion 15 . The dummy electrode 13 is a laminated film formed by stacking multiple conductive films. In this embodiment, the dummy electrode 13 is a two-layer laminated film made of a conductive film made of titanium (Ti) and a conductive film made of platinum (Pt). The first layer 13a is made of titanium, and the second layer 13b is made of platinum. The thickness n21 of the first layer 13a is approximately 130 nm, and the thickness n22 of the second layer 13b is approximately 65 nm. Therefore, the thickness n2 of the dummy electrode 13 is approximately 195 nm.

[0049] As will be described later, first fixed electrode 11 and second fixed electrode 12 are formed in the same process as dummy electrode 13. Therefore, first fixed electrode 11 and second fixed electrode 12 have the same layer structure as dummy electrode 13. First layer 11a of first fixed electrode 11 is a conductive film made of titanium, similar to first layer 13a of dummy electrode 13, and second layer 11b of first fixed electrode 11 is a conductive film made of platinum, similar to second layer 13b of dummy electrode 13.

[0050] The conductive film 27 is made of platinum. In other words, the conductive film 27 is made of the same material as the second layer 13b of the dummy electrode 13. In this way, by forming the conductive film 27 from the same material as the second layer 13b of the dummy electrode 13, the difference in work function between the conductive film 27 and the second layer 13b of the dummy electrode 13 can be made zero. Therefore, even if the conductive film 27 comes into contact with the dummy electrode 13, it is possible to prevent contact electrification from occurring. Therefore, even if the movable body 20 comes into contact with the protrusion 15, it is possible to prevent sticking, in which the movable body 20 sticks to the protrusion 15.

[0051] The thickness n1 of the conductive film 27 is 10 nm. In other words, the thickness n1 of the conductive film 27 is thinner than the thickness n2 of the dummy electrode 13. In this way, by forming the conductive film 27 thinner than the dummy electrode 13, it is possible to prevent an increase in the weight of the movable body 20. Therefore, it is possible to prevent a decrease in the sensitivity of the physical quantity sensor 100.

[0052] Etching damage 20r is formed on the lower surface 20f of the movable body 20. The etching damage 20r is a portion of the surface that has been roughened by etching when forming the through-hole 26. The region where the etching damage 20r is formed is a damage region D3. In this embodiment, the damage region D3 is an example of a third region.

[0053] Etching damage 20r is not formed in the region of lower surface 20f of movable body 20 where conductive film 27 is formed. In other words, damaged region D3 and conductive film 27 do not overlap in plan view. This is because conductive film 27 is formed before through-hole 26 is formed, but has resistance to the etching that forms through-hole 26, and therefore functions as a protective film that protects lower surface 20f of movable body 20 from etching. Therefore, the surface of the conductive film 27 is smoother than the surface of the damaged region D3. In other words, the surface roughness of the damaged region D3 is greater than the surface roughness of the conductive film 27.

[0054] The surface roughness of the conductive film 27 can be quantified by Sku, which is also called kurtosis (pointedness), and the larger the Sku value, the more sharp the peaks and valleys there are on the surface, and the smaller the Sku value, the smoother and flatter the surface.

[0055] The Sku of the surface of the conductive film 27 was 4 to 6. On the other hand, when etching was performed to form the through-hole 26 without forming the conductive film 27 in the region facing the protrusion 15 on the lower surface 20f of the movable body 20, the Sku of that region was 12 to 21. In this embodiment, by providing the conductive film 27, the incidence of sticking, in which the movable body 20 sticks to the protrusion 15, was significantly improved from a rating of △ when the conductive film 27 was not provided to a rating of ◎, in which the incidence was zero.

[0056] 1.5.Method of manufacturing physical quantity sensors 5 to 14 are explanatory views showing a method for manufacturing the physical quantity sensor 100. Fig. 5 is a flowchart illustrating the manufacturing process of the physical quantity sensor 100. Fig. 6 is a flowchart showing details of the silicon substrate preparation step S2 in Fig. 5. Fig. 7 is a flowchart showing details of the movable body formation step S5 in Fig. 5. Figs. 8A to 14 are cross-sectional views or plan views in each manufacturing process of the physical quantity sensor 100. The position of the cross section shown in each cross-sectional view is the position of line CC in Fig. 1.

[0057] As shown in FIG. 5, the manufacturing method of the physical quantity sensor 100 includes a support substrate preparation step S1, a silicon substrate preparation step S2, a cap substrate preparation step S3, a substrate bonding step S4, a movable body formation step S5, and a sealing step S6.

[0058] In the support substrate preparation step S1, a support substrate 10 is formed from a glass substrate (not shown). In this step S1, first, an etching mask is formed on the glass substrate, and then the glass substrate is wet-etched to form a cavity 16, support posts 14, and protrusions 15. Thereafter, a first fixed electrode 11, a second fixed electrode 12, and a dummy electrode 13 made of a laminated film of titanium and platinum are formed on the upper surface 10f of the cavity 16 using a wrist-off method.

[0059] As shown in Fig. 8A, in this embodiment, the electrode covering the protrusion 15 is a dummy electrode 13. However, the electrode covering the protrusion 15 may be a first fixed electrode 11 or a second fixed electrode 12, as shown in Fig. 8B.

[0060] When the shape of the protrusions 15 is to be a truncated cone as shown in Fig. 3B, in the support substrate preparation step S1, cylindrical protrusions 15 are formed by etching using an etching mask, and then wet etching is performed without using an etching mask, thereby making the shape of the protrusions 15 a truncated cone. The protrusions 15 according to the modified example shown in Fig. 3B have inclined surfaces 15t of the protrusions 15 and base portions 15c with a concave curved surface.

[0061] In the silicon substrate preparation step S2, a conductive film 27 is formed on the silicon substrate 20s by using a lift-off method. As shown in Fig. 6, the silicon substrate preparation step S2 includes a resist mask formation step S21, a conductive film formation step S22, and a resist mask removal step S23.

[0062] In the resist mask forming step S21, as shown in FIG. 9, a resist is applied to the lower surface 20f of the silicon substrate 20s, and then patterned to form a resist mask 4. In the conductive film forming step S22, a sputtered film 27s made of platinum is formed by sputtering on the resist mask 4 and the lower surface 20f of the silicon substrate 20s, as shown in FIG. In the resist mask removal step S23, as shown in FIG. 11, the resist mask 4 is removed, and a patterned conductive film 27 is formed on the lower surface 20f of the silicon substrate 20s.

[0063] 12, the support substrate 10 formed in the support substrate preparation step S1 is bonded to the silicon substrate 20s formed in the silicon substrate preparation step S2. The support substrate 10 and the silicon substrate 20s can be bonded to each other by, for example, anodic bonding.

[0064] In the movable body forming step S5, the movable body 20 is formed from a silicon substrate 20s. As shown in Fig. 7, the movable body forming step S5 includes a hard mask forming step S51, an etching step S52, and a hard mask removing step S53.

[0065] In the hard mask formation step S51, the silicon substrate 20s is thinned, and then a hard mask 5 is formed. In this step S51, first, the silicon substrate 20s is thinned using a grinder and a polisher, as shown in Fig. 13, and then a silicon oxide (SiO2) film is formed on the upper surface 20g of the thinned silicon substrate 20s, and then patterned to form the hard mask 5.

[0066] In the etching step S52, the silicon substrate 20s is dry-etched using a hard mask 5 to form the movable body 20 having the support portions 24, the beam portions 25, and the through-holes 26, as shown in Fig. 14. By the dry etching in this step S52, etching damage 20r is formed on the lower surface 20f of the movable body 20, as shown in Fig. 4.

[0067] In this way, in the etching step 52, the upper surface 20g of the movable body 20 is protected by the hard mask 5. Therefore, etching damage 20r due to dry etching is not formed on the upper surface 20g of the movable body 20. Therefore, the surface roughness of the lower surface 20f of the movable body 20, on which the etching damage 20r is formed, is greater than the surface roughness of the upper surface 20g of the movable body 20, on which the etching damage 20r is not formed.

[0068] In the hard mask removal step S53, the hard mask 5 on the upper surface 20g of the movable body 20 is removed. In the cap substrate preparation step S3, a lid 30 having a cavity 31 is formed from a silicon substrate (not shown). In the sealing step S6, the lid body 30 formed in the cap substrate preparation step S3 is bonded to the support substrate 10, and the movable body 20 is sealed in the storage space S between the lid body 30 and the support substrate 10. For example, glass frit bonding can be used to bond the lid body 30 and the support substrate 10. In this way, the physical quantity sensor 100 is obtained.

[0069] As described above, the physical quantity sensor 100 of this embodiment includes a support substrate 10 as a substrate, and a movable body 20 movably arranged relative to the support substrate 10, and the movable body 20 has, on its underside 20f as a first surface facing the support substrate 10, a perforated region D1 as a first region having a through-hole 26, a blank region D2 as a second region not having the through-hole 26, and a conductive film 27 as a first conductive film arranged in the blank region D2, and the support substrate 10 has a protrusion 15 that overlaps with the conductive film 27 in a planar view.

[0070] As described above, the movable body 20 has the conductive film 27 in the blank area D2, and the support substrate 10 has the protrusion 15 that overlaps the conductive film 27 in a plan view. Therefore, even if the movable body 20 comes into contact with the protrusion 15 due to excessive swinging, it is possible to prevent sticking, in which the movable body 20 sticks to the protrusion 15.

[0071] In the physical quantity sensor 100 of this embodiment, the conductive film 27 serving as the first conductive film is made of a noble metal. In this way, because conductive film 27 is made of a precious metal, conductive film 27 is prevented from being damaged by etching to form through-holes 26 in movable body 20, and the surface of conductive film 27 is maintained in a smooth state. Therefore, even if movable body 20 comes into contact with protrusion 15 due to excessive swinging, sticking, in which movable body 20 sticks to protrusion 15, can be prevented.

[0072] In the physical quantity sensor 100 of this embodiment, the support substrate 10 has a dummy electrode 13 as a second conductive film that covers the protrusion 15, and the material of the conductive film 27 as the first conductive film and the material of the dummy electrode 13 are the same. Therefore, the work function difference between the conductive film 27, the movable body 20, and the dummy electrode 13 can be set to zero, thereby suppressing the occurrence of contact electrification even when the conductive film 27 comes into contact with the dummy electrode 13. Therefore, even if the movable body 20 swings excessively and comes into contact with the protrusion 15, the occurrence of sticking, in which the movable body 20 sticks to the protrusion 15, can be suppressed.

[0073] In the physical quantity sensor 100 of this embodiment, the film thickness of the conductive film 27 serving as the first conductive film is thinner than the film thickness of the dummy electrode 13 serving as the second conductive film. In this way, since the film thickness of the conductive film 27 is thinner than the film thickness of the dummy electrode 13, it is possible to minimize an increase in the weight of the movable body 20 due to the conductive film 27. Therefore, the physical quantity sensor 100 of this embodiment can suppress the occurrence of sticking, in which the movable body 20 sticks to the protrusion 15, while also suppressing a decrease in the sensitivity of the physical quantity sensor 100.

[0074] In the physical quantity sensor 100 of this embodiment, the conductive film 27 serving as the first conductive film is larger than the protrusion 15 in plan view. Therefore, even if the movable body 20 swings excessively, the movable body 20 comes into contact with the protrusion 15 via the conductive film 27. This makes it possible to prevent the movable body 20 from sticking to the protrusion 15.

[0075] In the physical quantity sensor 100 of this embodiment, the surface roughness of the damaged region D3 as the third region where the conductive film 27 as the first conductive film on the lower surface 20f of the movable body 20 as the first surface is not provided is greater than the surface roughness of the conductive film 27. Thus, the surface roughness of the damaged region D3 is greater than the surface roughness of the conductive film 27. Therefore, even if the movable body 20 swings excessively and comes into contact with the protrusion 15, the occurrence of sticking, in which the movable body 20 sticks to the protrusion 15, can be suppressed.

[0076] In the physical quantity sensor 100 of this embodiment, the surface roughness of the lower surface 20f of the movable body 20 as the first surface is greater than the surface roughness of the upper surface 20g of the movable body 20 as the second surface opposite the lower surface 20f of the movable body 20. Thus, the surface roughness of the lower surface 20f of the movable body 20 is large. Therefore, by providing the conductive film 27 on the lower surface 20f of the movable body 20 and configuring the movable body 20 to come into contact with the protrusion 15 via the conductive film 27, it is possible to prevent sticking, in which the movable body 20 adheres to the protrusion 15.

[0077] 2. Embodiment 2 2.1.Inertial Measurement Unit Overview FIG. 15 is an explanatory diagram of a sensor module 300 as an inertial measurement unit (IMU) equipped with a physical quantity sensor 100. FIG. 15 is an exploded perspective view showing a schematic configuration of the sensor module 300. As shown in FIG.

[0078] The sensor module 300 is mounted on a wearable device such as an automobile, a robot, a smartphone, or a portable activity monitor, and is used as a device for detecting the posture, behavior, etc. of the wearable device.

[0079] As shown in FIG. 15, the sensor module 300 includes an outer case 301, a joining member 310, and a sensor unit 325, and is configured such that the sensor unit 325 is fitted or inserted into the interior 303 of the outer case 301 with the joining member 310 interposed therebetween.

[0080] Outer case 301 is a box-like container with a rectangular parallelepiped exterior and no lid, and its interior 303 is an internal space surrounded by wall surface 304, bottom surface 305, and joint surface 306. Outer case 301 is made of aluminum, for example. The material of outer case 301 may also be other metals such as zinc or stainless steel, resin, or a composite material of metal and resin.

[0081] The outer shape of the outer case 301 is a rectangular parallelepiped with a substantially square planar shape, and through-holes 302 are formed near each of two vertices located diagonally across the square. The sensor module 300 is attached to the device to be mounted using the through-holes 302 by screwing or the like.

[0082] The sensor unit 325 includes an inner case 320 and a substrate 315 . The substrate 315 mounts the physical quantity sensor device 1 incorporating the physical quantity sensor 100, a connector 316 for external connection, and the like.

[0083] Inner case 320 supports substrate 315 and is housed inside 303 of outer case 301. The thickness of inner case 320, in other words, the height in the Z-axis direction, is equal to or smaller than the height from top surface 307 of outer case 301 to joint surface 306. The same material as that of outer case 301 can be used for inner case 320. The bottom surface of the inner case 320 is formed with a recess 331 for preventing contact with the physical quantity sensor device 1 and an opening 321 for exposing the connector 316 .

[0084] 2.2.Outline of the board FIG. 16 is a perspective view of a substrate 315 on which the physical quantity sensor 100 is mounted. 16, the physical quantity sensor device 1, a connector 316, and angular velocity sensors 317x, 317y, and 317z are mounted on the top and side surfaces of the substrate 315. A control IC 319 is mounted on the bottom surface of the substrate 315.

[0085] The substrate 315 is a multi-layer substrate with a plurality of through holes formed therein. The substrate 315 is a glass epoxy substrate. The substrate 315 may also be a rigid substrate such as a composite substrate or a ceramic substrate.

[0086] The physical quantity sensor device 1 includes a physical quantity sensor 100, a circuit element 200, and a package in which the physical quantity sensor 100 and the circuit element 200 are mounted. The circuit element 200 includes a detection circuit that detects acceleration in the Z-axis direction based on a signal from the physical quantity sensor 100, an output circuit that converts the signal from the detection circuit into a predetermined detection signal and outputs it, and the like.

[0087] The connector 316 is a plug-type connector and has two rows of connection terminals arranged at equal pitches in the X-axis direction. In this embodiment, the connector has two rows of connection terminals with 10 pins per row, for a total of 20 pins, but the number of connection terminals may be changed as appropriate depending on the design specifications.

[0088] The angular velocity sensor 317z is a gyro sensor that detects a uniaxial angular velocity in the Z-axis direction. The angular velocity sensor 317z is preferably a vibration gyro sensor that uses a quartz crystal as an oscillator and detects the angular velocity from the Coriolis force acting on a vibrating object. The oscillator is not limited to a quartz crystal, and may be one that uses ceramic or silicon.

[0089] Angular velocity sensor 317x that detects angular velocity along one axis in the X-axis direction is mounted on a side surface of substrate 315 in the X-axis direction, with the mounting surface perpendicular to the X-axis. Similarly, angular velocity sensor 317y that detects angular velocity along one axis in the Y-axis direction is mounted on a side surface of substrate 315 in the Y-axis direction, with the mounting surface perpendicular to the Y-axis.

[0090] The angular velocity sensors 317x, 317y, and 317z are not limited to a configuration using one angular velocity sensor for each axis, for a total of three, but any sensor capable of detecting angular velocity on three axes may be used. For example, a sensor device capable of detecting angular velocity on three axes in one device or package may be used.

[0091] The physical quantity sensor device 1 is an acceleration sensor for measuring acceleration in the Z-axis direction, but may also measure acceleration in the X-axis direction or the Y-axis direction. The physical quantity sensor device 1 may be equipped with a physical quantity sensor 100 that measures acceleration in the X-axis and / or Y-axis directions, and may detect acceleration in the Z-axis and Y-axis directions, the Z-axis and X-axis directions, or in the three XYZ-axis directions.

[0092] The control IC 319 is an MCU (Micro Controller Unit) that includes a storage unit including a nonvolatile memory and an arithmetic circuit that performs temperature correction processing and the like, and is a control unit that controls each part of the sensor module 300.

[0093] 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, etc. The board 315 also has multiple electronic components mounted thereon, such as a temperature sensor.

[0094] According to such a sensor module 300, since the physical quantity sensor device 1 equipped with the physical quantity sensor 100 is used, it is possible to provide a sensor module 300 that is excellent in impact resistance and has improved reliability.

[0095] As described above, according to the sensor module 300 as an inertial measurement unit including the physical quantity sensor 100 of this embodiment, in addition to the effects of the first embodiment, it is possible to provide a highly reliable inertial measurement unit.

[0096] Although the preferred embodiment has been described above, the present invention is not limited to the above embodiment. The configuration of each part of the present invention can be replaced with any configuration that exhibits the same function as the above embodiment. [Explanation of symbols]

[0097] 1...physical quantity sensor device, 4...resist mask, 5...hard mask, 10...support substrate, 10f...upper surface, 10fc...recess, 11...first fixed electrode, 11a...first layer, 11b...second layer, 12...second fixed electrode, 13...dummy electrode, 13a...first layer, 13b...second layer, 14...post, 15...protrusion, 15p...top, 16...cavity, 20...movable body, 20a...first movable part, 20b...second movable part, 20f...lower surface, 20g...upper surface, 20r...etching damage, 20s...silicon substrate, 21...first mass region, 22...second mass region, 23...third mass region, 24...support part, 25...beam part, 26...through hole, 27...conductive film, 27s...sputtered film, 28...connecting region, 30...lid Body, 31...cavity, 100...physical quantity sensor, 200...circuit element, 300...sensor module, 301...outer case, 302...through hole, 303...inside, 304...wall surface, 305...bottom surface, 306...bonding surface, 307...top surface, 310...bonding member, 315...substrate, 316...connector, 317x, 317y, 317z...angular velocity sensor, 319...control IC, 320...inner case, 321...opening, 325...sensor unit, 331...recess, C1, C2...capacitance, CL1, CL2...center line, D1...perforated area, D2...blank area, D3...damaged area, R1, R2...distance, Ra, Rb...distance, S...storage space, n1, n2, n21, n22...thickness.

Claims

1. A substrate; a movable body provided so as to be movable relative to the substrate, the movable body has, on a first surface facing the substrate, a first region having a through hole, a second region not having the through hole, and a first conductive film provided in the second region; the substrate has a protrusion that overlaps the first conductive film in a plan view; Physical quantity sensor.

2. the first conductive film is made of a noble metal; The physical quantity sensor according to claim 1 .

3. the substrate has a second conductive film covering the protrusion; The material of the first conductive film and the material of the second conductive film are the same. The physical quantity sensor according to claim 1 .

4. The thickness of the first conductive film is thinner than the thickness of the second conductive film. The physical quantity sensor according to claim 3 .

5. the first conductive film is larger than the protrusion in a plan view; The physical quantity sensor according to claim 1 .

6. a third region of the first surface where the first conductive film is not provided has a surface roughness greater than a surface roughness of the first conductive film; The physical quantity sensor according to claim 1 .

7. The surface roughness of the first surface is greater than the surface roughness of a second surface opposite to the first surface. The physical quantity sensor according to claim 1 .

8. An inertial measurement unit comprising the physical quantity sensor according to any one of claims 1 to 7.

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