Inertial Sensors and Inertial Measurement Units

Abstract

To provide an inertial sensor and an inertial measurement unit that can release stiction of a movable body.SOLUTION: An inertial sensor 1 comprises: a first stationary electrode 31 and a second stationary electrode 32; a first movable body 51 that has a first movable electrode 52 arranged opposite to the first stationary electrode 31 and the second stationary electrode 32 and is movable with a first spring 54 as the center of rotation; a second movable body 61 that is arranged to be contactable with the first movable body 51, has a second movable electrode 62, and is movable with a second spring 64 as the center of rotation; and a third stationary electrode 33 that is arranged opposite to the second movable electrode 62.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an inertial sensor and an inertial measurement unit. [Background technology]

[0002] In recent years, physical quantity sensors manufactured using MEMS (Micro Electro Mechanical Systems) technology have been developed. Patent Document 1, for example, describes an example of such a physical quantity sensor, which detects acceleration and includes a support substrate, a movable body including first and second mass portions, first and second fixed electrodes provided on the support substrate and facing the first and second mass portions, and a protrusion disposed in the region where the first and second fixed electrodes are provided and protruding from the support substrate toward the first and second mass portions. By providing the protrusion, when excessive acceleration is applied, the movable body, which is displaced, comes into contact with the protrusion, thereby limiting further displacement of the movable body and preventing damage to the movable body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-45172 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the physical quantity sensor described in Patent Document 1, when the movable body collides with the protrusion and the movable body acts as a rigid body and repeatedly collides with a certain amount of energy, a sticking phenomenon called stiction occurs between the movable body and the protrusion, and there is a risk that the sensor will not be able to detect acceleration thereafter. [Means for solving the problem]

[0005] The inertial sensor includes a first movable body having a first fixed electrode and a second fixed electrode, a first movable electrode arranged opposite the first fixed electrode and the second fixed electrode, and movable around a first spring as a center of rotation, a second movable body arranged to be in contact with the first movable body, having a second movable electrode, and movable around a second spring as a center of rotation, and a third fixed electrode arranged opposite the second movable electrode.

[0006] The inertial measurement device includes the inertial sensor described above and a control unit that performs control based on a detection signal output from the inertial sensor. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a perspective view showing a schematic structure of an inertial sensor according to a first embodiment. [Figure 2] Cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 2 is a plan view showing a schematic structure of a sensor unit. [Figure 4] FIG. 4 is a cross-sectional view taken along line BB in FIG. 3 . [Figure 5] FIG. 4 is a cross-sectional view taken along line CC in FIG. 3 . [Figure 6] 10 is a cross-sectional view illustrating a method for releasing stiction. FIG. [Figure 7] 10 is a cross-sectional view illustrating a method for releasing stiction. FIG. [Figure 8] 10 is a cross-sectional view illustrating a method for releasing stiction. FIG. [Figure 9] FIG. 4 is a flowchart showing a method for manufacturing a sensor unit. [Figure 10] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 11] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 12] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 13] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 14] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 15]5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 16] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 17] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 18] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 19] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 20] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 21] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 22] 5A to 5C are cross-sectional views showing a manufacturing method of the sensor portion. [Figure 23] FIG. 10 is a plan view showing a schematic structure of an inertial sensor according to a second embodiment. [Figure 24] 24 is a cross-sectional view taken along line EE in FIG. 23. [Figure 25] FIG. 10 is an exploded perspective view showing a schematic configuration of an inertial measurement unit including an inertial sensor according to a third embodiment. [Figure 26] FIG. 26 is a perspective view of the substrate of FIG. 25. DETAILED DESCRIPTION OF THE INVENTION

[0008] 1. First embodiment 1.1.Inertial Sensor First, the inertial sensor 1 according to the first embodiment will be described with reference to FIGS. 1 and 2, taking an acceleration sensor that detects acceleration in the vertical direction as an example.

[0009] For ease of explanation, the following perspective views, cross-sectional views, and plan views illustrate three mutually orthogonal axes: the X-axis, the Y-axis, and the Z-axis. The direction along the X-axis is referred to as the "X-direction," the direction along the Y-axis as the "Y-direction," and the direction along the Z-axis as the "Z-direction." The tip of the arrow in each axial direction is referred to as the "plus side," the base end as the "minus side," the plus side of the Z direction as the "upper," and the minus side of the Z direction as the "lower." The Z direction is vertical, and the XY plane is horizontal. In this specification, the plus Z direction and the minus Z direction are collectively referred to as the Z direction.

[0010] The inertial sensor 1 according to this embodiment can be used as an acceleration sensor that can detect acceleration in the Z direction. 1 and 2, the inertial sensor 1 has a package 7, and a sensor unit 20 and an IC 40 housed in a housing space SS1 of the package 7. The sensor unit 20 has a lower surface 20r attached to an upper surface 11h, which is the inner bottom surface of the package 7, via a resin adhesive 18. The IC 40 is attached to the sensor unit 20, in other words, to the surface of the sensor unit 20 opposite the lower surface 20r, via an adhesive 41. Electrode pads 44 and 45 provided on the IC 40 are electrically connected to internal terminals 19 provided in the package 7 and connection terminals 29 provided on the sensor unit 20 by bonding wires 42 and 43.

[0011] 1 and 2, the package 7 is a container that houses the sensor unit 20 and the IC 40. The package 7 has a rectangular outer edge when viewed from above in the Z direction, and includes a base unit 10 that is made up of a first substrate 11, a second substrate 12, a third substrate 13, and a sealing member 14, and a conductive lid 15 that is joined to the third substrate 13 via the sealing member 14. The first substrate 11, the second substrate 12, the third substrate 13, and the sealing member 14 are layered in this order to form the base unit 10.

[0012] The first substrate 11 is flat, the second substrate 12 and the third substrate 13 are each annular substrate with the center portion removed, and a sealing member 14 such as a seal ring or conductive low-melting-point glass is formed around the periphery of the upper surface of the third substrate 13. The first substrate 11, the second substrate 12, and the third substrate 13 form a storage space SS1 in which the sensor unit 20 and the IC 40 are stored, and the storage space SS1 of the package 7 is hermetically sealed in a reduced pressure atmosphere lower than atmospheric pressure or in an inert gas atmosphere such as nitrogen, argon, or helium.

[0013] A plurality of internal terminals 19 are arranged on the upper surface of the second substrate 12, and a plurality of external terminals 16 are arranged on the lower surface 11r of the first substrate 11, which is the lower surface of the package 7. Each internal terminal 19 is electrically connected to a corresponding external terminal 16 via internal wiring (not shown) formed in the base portion 10 and via through-wires (not shown) that penetrate the first substrate 11 and the second substrate 12. The lid 15 is electrically connected to the external terminal 16, which serves as a ground electrode, via through-wires (not shown) that penetrate the first substrate 11, the second substrate 12, and the third substrate 13.

[0014] Ceramics and the like are preferably used as the constituent material of the first base material 11, the second base material 12, and the third base material 13. Note that the constituent material of the first base material 11, the second base material 12, and the third base material 13 may be glass, resin, metal, or the like, other than ceramic. The constituent material of the lid body 15 may be any material as long as it is conductive, and for example, metal materials such as Kovar, glass materials, silicon materials, ceramic materials, and the like metallized with metal can be used.

[0015] The external terminals 16 and the internal terminals 19 can be formed by a method such as screen-printing metal wiring material such as tungsten (W) or molybdenum (Mo) at predetermined locations, firing it, and then plating it with nickel (Ni), gold (Au), or the like.

[0016] Next, the sensor unit 20 housed in the package 7 will be described with reference to FIGS. For ease of explanation, the cover 22 is not shown in Fig. 3. Furthermore, in Figs. 3, 4, and 5, the wiring that electrically connects the connection terminal 29 to the movable bodies 51, 61, and 71 and the fixed electrodes 31, 32, 33, and 34 is not shown.

[0017] The sensor unit 20 has a substrate 21, a first movable body 51, a second movable body 61, and a third movable body 71 arranged on the substrate 21, and a cover body 22 that covers the first movable body 51, the second movable body 61, and the third movable body 71.

[0018] As shown in Fig. 3, the substrate 21 extends in the X and Y directions and has a thickness in the Z direction. As shown in Figs. 4 and 5, the substrate 21 has a first fixed electrode 31, a second fixed electrode 32, a third fixed electrode 33, a fourth fixed electrode 34, and a connection terminal 29 formed on an upper surface 21h of the substrate 21 with an insulating layer 21g interposed therebetween. The first fixed electrode 31, the second fixed electrode 32, the third fixed electrode 33, and the fourth fixed electrode 34 have rectangular planar shapes and are formed in an area covered by the lid 22. The first fixed electrode 31, the second fixed electrode 32, the third fixed electrode 33, and the fourth fixed electrode 34 are each electrically connected to the connection terminal 29 via wiring (not shown), and are arranged in this order from the connection terminal 29 side.

[0019] The first fixed electrode 31 and the second fixed electrode 32 have approximately the same area. The first fixed electrode 31 and the second fixed electrode 32 are each connected to a QV amplifier (not shown) of an external device, and the capacitance difference between them is detected as an electrical signal by a differential detection method. Therefore, it is desirable that the first fixed electrode 31 and the second fixed electrode 32 have the same area.

[0020] A silicon substrate can be used as the constituent material of the substrate 21. However, the substrate 21 is not particularly limited, and for example, a glass substrate or a quartz substrate can also be used.

[0021] Furthermore, the fixed electrodes 31, 32, 33, and 34 and the connection terminals 29 may be made of polysilicon, and the insulating layer 21g may be made of silicon oxide (SiO2).

[0022] As shown in FIG. 3 , the first movable body 51 has a rectangular shape with its longer sides in the X direction and its thickness in the Z direction. The first movable body 51 has a first movable electrode 52, a support portion 53, a first spring 54, and a connecting portion 55. The support portion 53 is disposed in an opening 56 in the center of the first movable body 51, and the first spring 54 is connected to it. The first spring 54 extends from the support portion 53 to the positive side and the negative side in the Y direction. The first movable electrode 52 is disposed on the negative side and the positive side in the X direction of the first spring 54. The first movable electrode 52 on the negative side in the X direction of the support portion 53 and the first movable electrode 52 on the positive side in the X direction of the support portion 53 are connected by connecting portions 55 at both ends in the Y direction of the first movable electrode 52 on the first spring 54 side. Furthermore, the connecting portion 55 is connected to a first spring 54 that extends from the support portion 53 at approximately the center in the X direction to the positive side and the negative side in the Y direction. The first spring 54 extends from the support portion 53 at approximately the center in the X direction to the positive side and the negative side in the Y direction.

[0023] 4, the support portion 53 is disposed in the center of the first movable body 51, and is thicker than the first movable electrode 52, etc. By joining the support portion 53 to the upper surface 21h of the substrate 21 via the insulating layer 21g, the first movable body 51 can arrange the first movable electrode 52 facing the first fixed electrode 31 and the second fixed electrode 32 provided on the substrate 21, with a desired distance between them.

[0024] By fixing the support part 53 to the substrate 21, the first movable body 51 becomes movable around the first spring 54 as the center of rotation. Therefore, when acceleration is applied along the Z direction, the first movable body 51 swings around the swing axis P1, with the first spring 54 as the swing axis P1, causing torsional deformation of the first spring 54. In other words, the first movable body 51 is configured to be able to swing in a seesaw manner relative to the support part 53, with the swing axis P1 as the central axis.

[0025] The first movable electrode 52 located on the negative side of the X direction with respect to the oscillation axis P1 has a recess 57 formed at approximately the center of the first movable electrode 52, recessed toward the substrate 21. Therefore, the first movable electrode 52 located on the negative side of the X direction with respect to the oscillation axis P1 has a smaller mass than the first movable electrode 52 located on the positive side of the X direction with respect to the oscillation axis P1, and therefore has a smaller rotational moment when acceleration is applied than the first movable electrode 52 located on the positive side of the X direction. Due to this difference in rotational moment, when acceleration in the Z direction is applied, the first movable electrode 52 undergoes a seesaw oscillation around the oscillation axis P1. Note that the seesaw oscillation means that when the first movable electrode 52 on the positive side of the X direction is displaced in the positive Z direction, the first movable electrode 52 on the negative side of the X direction is displaced in the negative Z direction. Conversely, when the first movable electrode 52 on the positive side of the X direction is displaced in the negative Z direction, the first movable electrode 52 on the negative side of the X direction is displaced in the positive Z direction.

[0026] When the sensor unit 20 is driven, a drive signal is applied to the first movable electrode 52, and thus a capacitance C1 is formed between the first movable electrode 52 on the negative side in the X direction and the first fixed electrode 31. Similarly, a capacitance C2 is formed between the first movable electrode 52 on the positive side in the X direction and the second fixed electrode 32. In a natural state where no acceleration is applied, the capacitances C1 and C2 are approximately equal to each other.

[0027] When acceleration in the Z direction is applied to the sensor unit 20, the first movable body 51 undergoes a seesaw oscillation around the oscillation axis P1. This seesaw oscillation of the first movable body 51 causes the distance between the first movable electrode 52 on the negative side in the X direction and the first fixed electrode 31 and the distance between the first movable electrode 52 on the positive side in the X direction and the second fixed electrode 32 to change in opposite phases, and accordingly, the capacitances C1 and C2 change in opposite phases to each other. Therefore, the sensor unit 20 can detect acceleration in the Z direction based on the difference between the capacitance values of the capacitances C1 and C2.

[0028] As shown in FIG. 3, the second movable body 61 is disposed on the negative side in the X direction of the first movable body 51. The second movable body 61 has a second movable electrode 62, a support portion 63, a second spring 64, and an extending portion 66. The support portion 63 is disposed within an opening 65 located approximately in the center of the second movable body 61, and the second spring 64 is connected to it. The second spring 64 extends from the support portion 63 to the positive side in the Y direction and the negative side in the Y direction. The second movable electrode 62 is disposed on the negative side in the X direction of the support portion 63, and is connected to the second spring 64 together with the second movable body 61 on the positive side in the X direction of the support portion 63.

[0029] 4, the support portion 63 is disposed approximately in the center of the second movable body 61, and is thicker than the second movable electrode 62 and the like. By joining the support portion 63 to the upper surface 21h of the substrate 21 via an insulating layer 21g, the second movable body 61 can arrange the second movable electrode 62 at a desired distance opposite the third fixed electrode 33 provided on the substrate 21. Note that the second movable electrode 62 is arranged at a position overlapping the third fixed electrode 33 in a plan view from the Z direction. In other words, the third fixed electrode 33 is arranged opposite the second movable electrode 62.

[0030] By fixing the support portion 63 to the substrate 21, the second movable body 61 becomes movable around the second spring 64 as the center of rotation. Therefore, the second movable body 61 swings around the swing axis P2 while torsionally deforming the second spring 64, with the second spring 64 as the swing axis P2.

[0031] The second movable body 61 on the positive side in the X direction of the second spring 64 is provided with an extension 66 that extends toward the first spring 54 of the first movable body 51 and is arranged so as to be able to come into contact with the first movable body 51. In other words, in a plan view from the Z direction, a part of the extension 66 of the second movable body 61 is arranged in a position where it overlaps with the first movable body 51. Therefore, when excessive acceleration is applied in the positive Z direction, the first movable body 51 that has oscillated in a seesaw motion comes into contact with the extension 66 of the second movable body 61, thereby restricting further displacement of the first movable body 51.

[0032] Furthermore, the width W2, which is the length in the X direction of the second spring 64 of the second movable body 61, is narrower than the width W1 of the first spring 54 of the first movable body 51. In other words, the torsional rigidity of the second spring 64 is smaller than the torsional rigidity of the first spring 54. Therefore, the second movable body 61 is more movable than the first movable body 51, and it is possible to mitigate the impact when the first movable body 51 and the extension portion 66 of the second movable body 61 come into contact with each other.

[0033] As shown in FIG. 3 , the third movable body 71 is disposed on the positive side in the X direction of the first movable body 51. Therefore, the second movable body 61 and the third movable body 71 are disposed on either side of the first spring 54, sandwiching the first spring 54 therebetween. The third movable body 71 has a third movable electrode 72, a support portion 73, a third spring 74, and an extending portion 76. The support portion 73 is disposed within an opening 75 located approximately in the center of the third movable body 71, and is connected to the third spring 74, which extends from the support portion 73 to the positive side and the negative side in the Y direction. The third movable electrode 72 is disposed on the positive side in the X direction of the support portion 73, and is connected to the third spring 74 together with the third movable body 71 on the negative side in the X direction of the support portion 73.

[0034] 4, the support portion 73 is disposed approximately in the center of the third movable body 71 and is thicker than the third movable electrode 72 and the like. By joining the support portion 73 to the upper surface 21h of the substrate 21 via an insulating layer 21g, the third movable body 71 makes it possible to arrange the third movable electrode 72 opposite the fourth fixed electrode 34 provided on the substrate 21 at a desired distance. Note that the third movable electrode 72 is arranged at a position overlapping the fourth fixed electrode 34 in a plan view from the Z direction. In other words, the fourth fixed electrode 34 is arranged opposite the third movable electrode 72.

[0035] By fixing the support portion 73 to the substrate 21, the third movable body 71 becomes movable around the third spring 74 as the center of rotation. Therefore, the third movable body 71 swings around the swing axis P3 while torsionally deforming the third spring 74, with the third spring 74 as the swing axis P3.

[0036] The third movable body 71 on the negative side in the X direction of the third spring 74 is provided with an extension 76 that extends toward the first spring 54 of the first movable body 51 and is arranged so as to be able to come into contact with the first movable body 51. In other words, in a plan view from the Z direction, a portion of the extension 76 of the third movable body 71 is arranged in a position where it overlaps with the first movable body 51. Therefore, when excessive acceleration is applied in the negative Z direction, the first movable body 51, which is oscillating in a seesaw motion, comes into contact with the extension 76 of the third movable body 71, thereby restricting further displacement of the first movable body 51.

[0037] Furthermore, the width W3 of the third spring 74 of the third movable body 71 is narrower than the width W1 of the first spring 54 of the first movable body 51, that is, the torsional rigidity of the third spring 74 is smaller than the torsional rigidity of the first spring 54. Therefore, the third movable body 71 is more movable than the first movable body 51, and it is possible to mitigate the impact when the first movable body 51 and the extension portion 76 of the third movable body 71 come into contact with each other.

[0038] The extension portion 66 of the second movable body 61 and the extension portion 76 of the third movable body 71 function as stoppers that restrict excessive displacement of the first movable body 51, but when the first movable body 51 and the extension portions 66, 76 collide and the first movable body 51 repeatedly collides with a certain amount of energy as a single rigid body, a sticking phenomenon called stiction occurs between the first movable body 51 and the extension portions 66, 76. However, the sensor unit 20 of this embodiment is capable of releasing the stiction that occurs between the first movable body 51 and the extension portions 66, 76.

[0039] Next, a method for releasing stiction when it occurs will be described with reference to FIGS. 6, 7, and 8. FIG. As shown in FIG. 6, when stiction occurs between the first movable body 51 and the extension 66 as indicated by arrow D due to repeated collisions between the first movable body 51 and the extension 66, a voltage is applied to the second movable electrode 62 and the third fixed electrode 33. By applying a voltage, the second movable body 61 can be moved counterclockwise about the oscillation axis P2 as shown in FIG. 7, thereby releasing the stiction. Thereafter, by stopping the application of the voltage, the first movable body 51 and the second movable body 61 become parallel to the substrate 21 as shown in FIG. 8, and acceleration can be detected. In this embodiment, the second movable body 61 and the third movable body 71 are arranged on both sides of the first movable body 51, but this is not limited to this and it is also possible to arrange only one of them, and there may be three or more movable bodies with stoppers.

[0040] A plurality of through holes 58 penetrating the upper and lower planes are provided in the movable bodies 51, 61, 71. By providing the through holes 58, it is possible to reduce air resistance that occurs when the movable bodies 51, 61, 71 are displaced in the Z direction.

[0041] The movable bodies 51, 61, and 71 are formed by etching stacked polysilicon, particularly by vertical processing using the Bosch process, which is a deep etching technique.

[0042] 4 and 5, the lid body 22 has a recess 23 formed therein that is recessed upward from the surface of the lid body 22 facing the substrate 21. The lid body 22 accommodates the movable bodies 51, 61, 71 and the fixed electrodes 31, 32, 33, 34 in the recess 23, and is joined to the upper surface 21h of the substrate 21 via a joining member 27 such as glass frit. The lid body 22 and the substrate 21 form an accommodation space SS2 therein that accommodates the movable bodies 51, 61, 71 and the fixed electrodes 31, 32, 33, 34.

[0043] The lid 22 has a through hole 24 that communicates in the thickness direction between the top surface 22h and the inner bottom surface 22r of the recess 23. A metal layer 25 is provided on the side surface of the through hole 24, and the through hole 24 is closed and sealed by a sealing member 26 that contacts the metal layer 25. The metal layer 25 is provided to improve adhesion between the through hole 24 and the sealing member 26.

[0044] The storage space SS2, in which the through-hole 24 is closed by the sealing member 26, is an airtight space, and is preferably filled with an inert gas such as nitrogen, helium, or argon, and is maintained at a temperature of about -40°C to 125°C and at approximately atmospheric pressure. However, the atmosphere in the storage space SS2 is not particularly limited, and may be, for example, in a reduced pressure state or a pressurized state.

[0045] A silicon substrate can be used as the constituent material of the lid 22. However, this is not particularly limited, and for example, a glass substrate or a quartz substrate may also be used. Furthermore, the method of bonding the substrate 21 and the lid 22 is not limited to a bonding method using a bonding member 27 such as glass frit, and may be appropriately selected depending on the materials of the substrate 21 and the lid 22. For example, anodic bonding, activation bonding in which bonding surfaces activated by plasma irradiation are bonded together, or metal eutectic bonding in which metal films formed on the upper surface 21h of the substrate 21 and the lower surface of the lid 22 are bonded together can be used.

[0046] 2, the IC 40 is attached to the upper surface of the sensor unit 20 via an adhesive 41. The adhesive 41 is not particularly limited as long as it can fix the IC 40 on the sensor unit 20, and examples thereof include solder, silver paste, and resin-based adhesives.

[0047] The IC 40 includes a drive circuit that drives the sensor unit 20, a detection circuit that detects acceleration in the Z direction based on a signal from the sensor unit 20, and an output circuit that converts the signal from the detection circuit into a predetermined signal and outputs it. The IC 40 also has multiple electrode pads 44, 45 arranged on its top surface, with the electrode pad 44 electrically connected to the internal terminal 19 in the package 7 via a bonding wire 42 and the electrode pad 45 electrically connected to the connection terminal 29 of the sensor unit 20 via a bonding wire 43. This allows the acceleration signal detected by the sensor unit 20 to be output to the outside and the sensor unit 20 to be controlled.

[0048] In the inertial sensor 1 of this embodiment, the third fixed electrode 33 is disposed opposite the second movable electrode 62, so that if the first movable body 51 and the second movable body 61 experience stiction, the stiction can be released by applying a voltage between the second movable electrode 62 and the third fixed electrode 33, and acceleration can continue to be detected thereafter. Furthermore, the fourth fixed electrode 34 is disposed opposite the third movable electrode 72, so that if the first movable body 51 and the third movable body 71 experience stiction, the stiction can be released by applying a voltage between the third movable electrode 72 and the fourth fixed electrode 34, and acceleration can continue to be detected thereafter.

[0049] 1.2.Method of manufacturing the sensor part Next, a method for manufacturing the sensor unit 20 included in the inertial sensor 1 according to this embodiment will be described with reference to FIGS. As shown in FIG. 9, the manufacturing method of the sensor unit 20 of this embodiment includes a substrate preparation process, a fixed electrode formation process, a first sacrificial layer formation process, a support portion formation process, an extension portion formation process, a second sacrificial layer formation process, a movable body formation process, a sacrificial layer removal process, a lid body bonding process, a sealing process, and a singulation process.

[0050] 1.2.1.Substrate preparation process First, in step S1, a large, flat substrate 100 is prepared as shown in Fig. 10 in order to simultaneously manufacture a plurality of sensor units 20. The large substrate 100 is a silicon substrate, and is finally divided into individual substrates 21.

[0051] 1.2.2. Fixed electrode formation process In step S2, as shown in Fig. 11, a silicon oxide film (SiO2) that will become the insulating layer 21g is formed on the large substrate 100. The silicon oxide film may be formed by sputtering or the like, or by thermally oxidizing the large substrate 100. Thereafter, a first polysilicon layer 101 is formed on the insulating layer 21g by sputtering or the like, and fixed electrodes 31, 32, 33, and 34 are formed by photolithography and etching as shown in Fig. 12.

[0052] 1.2.3. First Sacrificial Layer Formation Process In step S3, as shown in FIG. 13, a first sacrificial layer 102 made of silicon oxide film (SiO2) is formed on the fixed electrodes 31, 32, 33, and 34 formed on the large substrate 100 by sputtering or the like.

[0053] 1.2.4. Support part forming process In step S4, as shown in Fig. 14, recesses 102a are formed in the first sacrificial layer 102 by photolithography and etching to form support portions 53, 63, and 73. Thereafter, a second polysilicon layer 103 is formed in the recesses 102a and on the first sacrificial layer 102 by sputtering or the like, and movable bodies 51, 61, and 71 and support portions 53, 63, and 73 are formed by photolithography and etching as shown in Fig. 15. The cross sections of Figs. 14 and 15 correspond to the cross section positions of Fig. 4.

[0054] 1.2.5. Extending part forming process 16, in step S5, the second polysilicon layer 103 formed on the first sacrificial layer 102 in step S4 is subjected to photolithography and etching to form movable bodies 51, 61, 71, springs 54, 64, 74, extensions 66, 76, etc. The cross section in FIG. 16 corresponds to the cross section position in FIG. 5, and all cross sections from FIG. 17 onwards also correspond to the cross section position in FIG. 5. The extensions 66, 76 are formed simultaneously with the support portions 53, 63, 73 formed on the second polysilicon layer 103 in step S4 by photolithography and etching.

[0055] 1.2.6. Second Sacrificial Layer Formation Process In step S6, as shown in FIG. 17, a second sacrificial layer 104 of silicon oxide (SiO2) is formed by sputtering or the like on the movable bodies 51, 61, 71, supporting portions 53, 63, 73, and extending portions 66, 76 formed in steps S4 and S5.

[0056] 1.2.7.Movable body formation process In step S7, a third polysilicon layer 105 is formed on the second sacrificial layer 104 by sputtering or the like, and movable bodies 51, 61, and 71 are formed by photolithography and etching, as shown in FIG. 18. Thereafter, as shown in FIG. 19, the second sacrificial layer 104 is removed by etching using the third polysilicon layer 105 as a mask. Next, as shown in FIG. 20, a fourth polysilicon layer 106 is formed to a desired thickness on the second polysilicon layer 103 and the third polysilicon layer 105 by sputtering or the like. Thereafter, an outer pattern mask for the movable bodies 51, 61, and 71 is formed on the fourth polysilicon layer 106 by photolithography and etching, and vertical processing is performed by the Bosch process, a deep etching technique, to form the movable bodies 51, 61, and 71, as shown in FIG.

[0057] 1.2.8. Sacrificial layer removal process In step S8, the first sacrificial layer 102 and the second sacrificial layer 104 are removed by etching, as shown in Fig. 22. As a result, the movable bodies 51, 61, and 71 are formed facing the fixed electrodes 31, 32, 33, and 34 at a desired interval.

[0058] 1.2.9. Lid joining process In step S9, a lid body 22 is prepared having a recess 23 capable of accommodating the movable bodies 51, 61, 71 and the fixed electrodes 31, 32, 33, 34, and the movable bodies 51, 61, 71 and the fixed electrodes 31, 32, 33, 34 are accommodated in the recess 23 of the lid body 22, and the lid body 22 is joined to the upper surface 21h of the substrate 21 via a joining member 27 such as glass frit.

[0059] 1.2.10. Sealing process In step S10, the sealing member 26 is placed in the through-hole 24, and then the sealing member 26 is irradiated with laser light L to melt the sealing member 26, thereby closing and sealing the through-hole 24.

[0060] 1.2.11.Singulation process In step S11, the large substrate 100 that has been processed up to step S10 is cut into individual pieces using a dicing saw or the like. Through the above steps, the sensor unit 20 shown in FIGS. 3, 4, and 5 is completed. Furthermore, it is preferable to form the second movable body 61 and the third movable body 71 simultaneously with forming the first movable body 51. In particular, it is preferable to form the extension portion 66 of the second movable body 61 and the extension portion 76 of the third movable body 71 simultaneously with forming the structure of the first movable body 51. That is, in this embodiment, the extension portion 66 of the second movable body 61 and the extension portion 76 of the third movable body 71 are formed simultaneously with forming the recess 57 of the first movable body 51, but they may be formed by different processes. Furthermore, although the first movable body 51 has the recess 57 in this embodiment, the first movable body 51 does not necessarily have to have the recess 57. Furthermore, it is preferable to form the third fixed electrode 33 and the fourth fixed electrode 34 on the upper surface 21h of the substrate 21 simultaneously with forming the first fixed electrode 31 and the second fixed electrode 32.

[0061] 2. Second embodiment Next, an inertial sensor 1a according to a second embodiment will be described with reference to Fig. 23 and Fig. 24. For ease of description, Fig. 23 does not show the cover 22. Figs. 23 and 24 also do not show the wiring that electrically connects the connection terminals 29 to the movable bodies 51a, 61a, 71a and the fixed electrodes 31a, 32a, 33a, 34a.

[0062] The inertial sensor 1a of this embodiment is similar to the inertial sensor 1 of the first embodiment except that the shapes of the movable bodies 51a, 61a, 71a and the fixed electrodes 31a, 32a, 33a, 34a in the accommodation space SS3 of the sensor unit 20a are different from those of the inertial sensor 1 of the first embodiment. Note that the following description will focus on the differences from the first embodiment described above, and a description of similar points will be omitted.

[0063] As shown in FIG. 23, in the inertial sensor 1a, the second movable body 61a and the third movable body 71a of the sensor unit 20a are disposed inside the first movable body 51a in plan view from the Z direction. The first movable body 51a has a rectangular shape with its longer sides in the X direction and includes a first movable electrode 52a, a support portion 53, a first spring 54, and a connecting portion 55. The support portion 53 is disposed within an opening 56 in the center of the first movable body 51a, and is connected to a first spring 54 extending from the support portion 53 to the positive side and the negative side in the Y direction. The first movable electrode 52a is disposed on the negative side and the positive side in the X direction of the first spring 54, and the first movable electrode 52a on the negative side in the X direction of the first spring 54 and the first movable electrode 52a on the positive side in the X direction of the first spring 54 are connected by connecting portions 55 at both ends in the Y direction of the first movable electrode 52a on the first spring 54 side. The connecting portion 55 is connected to the first spring 54 extending from the support portion 53 to the positive side in the Y direction and the negative side in the Y direction at approximately the center in the X direction.

[0064] Openings 59, 60 are provided at approximately the center of the first movable electrode 52a on the negative side in the X direction of the first spring 54 and the first movable electrode 52a on the positive side in the X direction of the first spring 54. A second movable body 61a is disposed in the opening 59 of the first movable electrode 52a on the negative side in the X direction of the first spring 54, and a third movable body 71a is disposed in the opening 60 of the first movable electrode 52a on the positive side in the X direction of the first spring 54.

[0065] The first movable electrode 52a located on the negative side in the X direction with respect to the oscillation axis P1 has a recess 57 formed on the negative side in the X direction of the opening 59, recessed toward the substrate 21. Therefore, the first movable electrode 52a located on the negative side in the X direction with respect to the oscillation axis P1 has a smaller mass than the first movable electrode 52a located on the positive side in the X direction with respect to the oscillation axis P1, and therefore the rotation moment when acceleration is applied is smaller than that of the first movable electrode 52a located on the positive side in the X direction.

[0066] 23, the second movable body 61a is disposed within the opening 59 of the first movable body 51a. The second movable body 61a has a second movable electrode 62a, a support portion 63, a second spring 64, and an extending portion 66. The support portion 63 is disposed within an opening 65 located approximately in the center of the second movable body 61a, and is connected to a second spring 64 extending from the support portion 63 to the positive side and the negative side in the Y direction. The second movable electrode 62a is disposed on the positive side of the second spring 64 in the X direction, and is connected to the second spring 64 together with the second movable body 61a on the negative side of the second spring 64 in the X direction.

[0067] The second movable body 61a on the negative side in the X direction of the second spring 64 is provided with an extension 66 that extends toward the opposite side of the first movable body 51a from the first spring 54, and is positioned so as to be able to come into contact with the first movable body 51a. In other words, in a plan view from the Z direction, a portion of the extension 66 of the second movable body 61a is positioned so as to overlap with the first movable body 51a. Therefore, when excessive acceleration is applied in the positive Z direction, the first movable body 51a, which is oscillating in a seesaw motion, comes into contact with the extension 66 of the second movable body 61a, thereby restricting further displacement of the first movable body 51a.

[0068] As shown in Fig. 23, the third movable body 71a is disposed within the opening 60 of the first movable body 51a. The third movable body 71a has a third movable electrode 72a, a support portion 73, a third spring 74, and an extending portion 76. The support portion 73 is disposed within an opening 75 located approximately in the center of the third movable body 71a, and is connected to a third spring 74 extending from the support portion 73 to the positive side and the negative side in the Y direction. The third movable electrode 72a is disposed on the negative side in the X direction of the third spring 74, and is connected to the third spring 74 together with the third movable body 71a on the positive side in the X direction of the third spring 74.

[0069] The third movable body 71a on the positive side in the X direction of the third spring 74 is provided with an extension 76 that extends toward the opposite side of the first movable body 51a from the first spring 54, and is positioned so as to be able to come into contact with the first movable body 51a. In other words, in a plan view from the Z direction, a portion of the extension 76 of the third movable body 71a is positioned so as to overlap with the first movable body 51a. Therefore, when excessive acceleration is applied in the negative Z direction, the first movable body 51a, which is swinging in a seesaw motion, comes into contact with the extension 76 of the third movable body 71a, thereby restricting further displacement of the first movable body 51a.

[0070] As shown in Figures 23 and 24, the substrate 21 has a first fixed electrode 31a, a second fixed electrode 32a, a third fixed electrode 33a, a fourth fixed electrode 34a, and a connection terminal 29 formed on the upper surface 21h of the substrate 21 via an insulating layer 21g.

[0071] There are two first fixed electrodes 31a, one of which is positioned so as to overlap with the first movable electrode 52a sandwiched between openings 56 and 59 when viewed in a plane from the Z direction, and the other first fixed electrode 31a is positioned so as to overlap with the first movable electrode 52a located on the negative X-direction side of opening 59 when viewed in a plane from the Z direction.

[0072] There are two second fixed electrodes 32a, one of which is positioned so as to overlap the first movable electrode 52a sandwiched between the openings 56 and 60 when viewed in a plane from the Z direction, and the other second fixed electrode 32a is positioned so as to overlap the first movable electrode 52a located on the positive side of the opening 60 in the X direction when viewed in a plane from the Z direction.

[0073] The third fixed electrode 33a is positioned so as to overlap the second movable electrode 62a when viewed in a plane from the Z direction, and the fourth fixed electrode 34a is positioned so as to overlap the third movable electrode 72a when viewed in a plane from the Z direction. Although a description of the manufacturing method of the second embodiment will be omitted, the sensor portion 20a can be manufactured using the same manufacturing method as in the first embodiment.

[0074] With this configuration, it is possible to obtain the same effects as the inertial sensor 1 of the first embodiment. Furthermore, since the second movable body 61a and the third movable body 71a are positioned inside the first movable body 51a when viewed in a plane from the Z direction, the length from the first spring 54 to the end of the first movable electrode 52a can be increased, and the area of the first movable electrode 52a can be increased, thereby improving the detection sensitivity of the inertial sensor 1a.

[0075] 3. Third embodiment Next, an inertial measurement device 2000 including the inertial sensors 1, 1a according to the third embodiment will be described with reference to Fig. 25 and Fig. 26. In the following description, a configuration to which the inertial sensor 1 is applied will be exemplified.

[0076] 25 is a device that detects inertial momentum such as the attitude and behavior of a moving body such as an automobile or a robot. The inertial measurement unit 2000 functions as a so-called six-axis motion sensor that includes acceleration sensors that detect accelerations Ax, Ay, and Az in directions along three axes, and angular velocity sensors that detect angular velocities ωx, ωy, and ωz around the three axes.

[0077] The inertial measurement unit 2000 has a rectangular parallelepiped shape with a substantially square planar shape. Screw holes 2110 are formed as fixing portions near two diagonal vertices of the square. Two screws can be inserted into these two screw holes 2110 to fix the inertial measurement unit 2000 to the mounting surface of a mounting body such as an automobile. By selecting parts and modifying the design, it is possible to reduce the size of the inertial measurement unit 2000 to a size that can be mounted in a smartphone or digital camera, for example.

[0078] Inertial measurement unit 2000 has outer case 2100, joining member 2200, and sensor module 2300, and is configured such that sensor module 2300 is inserted inside outer case 2100 with joining member 2200 interposed therebetween. Sensor module 2300 also has inner case 2310 and substrate 2320.

[0079] The external shape of outer case 2100 is a rectangular parallelepiped with a substantially square planar shape, similar to the overall shape of inertial measurement unit 2000, and screw holes 2110 are formed near each of two vertices located diagonally across the square. Outer case 2100 is also box-shaped, and houses sensor module 2300 inside.

[0080] Inner case 2310 is a member that supports substrate 2320, and is shaped to fit inside outer case 2100. Inner case 2310 is formed with recess 2311 for preventing contact with substrate 2320 and opening 2312 for exposing connector 2330, which will be described later. Inner case 2310 as described above is joined to outer case 2100 via joining member 2200. In addition, substrate 2320 is joined to the bottom surface of inner case 2310 via an adhesive.

[0081] 26, a connector 2330, an angular velocity sensor 2340z that detects angular velocity around the Z axis, and an acceleration sensor unit 2350 that detects acceleration in the directions of the X, Y, and Z axes are mounted on a substrate 2320. In addition, an angular velocity sensor 2340x that detects angular velocity around the X axis and an angular velocity sensor 2340y that detects angular velocity around the Y axis are mounted on a side surface of the substrate 2320.

[0082] The acceleration sensor unit 2350 includes at least the inertial sensor 1 for measuring acceleration in the Z direction, and can detect acceleration in one axis direction, or in two or three axes directions as needed. Note that the angular velocity sensors 2340x, 2340y, and 2340z are not particularly limited, and for example, vibration gyro sensors that utilize the Coriolis force can be used.

[0083] In addition, a control IC 2360 is mounted on the underside of substrate 2320. Control IC 2360, which serves as a control unit that performs control based on the detection signal output from inertial sensor 1, is an MCU (Micro Controller Unit) that incorporates a storage unit including nonvolatile memory, an A / D converter, and the like, and controls each unit of inertial measurement unit 2000. The storage unit stores programs that define the order and content for detecting acceleration and angular velocity, a program that digitizes the detection data and incorporates it into packet data, and associated data. Note that multiple other electronic components are also mounted on substrate 2320.

[0084] Such an inertial measurement unit 2000 uses an acceleration sensor unit 2350 including an inertial sensor 1, and therefore an inertial measurement unit 2000 with excellent shock resistance and high reliability can be obtained. [Explanation of symbols]

[0085] 1,1a...inertial sensor, 7...package, 10...base portion, 11...first substrate, 11h...upper surface, 11r...lower surface, 12...second substrate, 13...third substrate, 14...sealing member, 15...lid body, 16...external terminal, 18...resin adhesive, 19...internal terminal, 20...sensor portion, 20r...lower surface, 21...substrate, 21h...upper surface, 21g...insulating layer, 22...lid body, 22h...upper surface, 22r...inner bottom surface, 23...recess, 24...through hole, 25...metal layer, 26...sealing member, 29...connection terminal, 31...first fixed electrode, 32...second fixed electrode, 33...third fixed electrode, 34...fourth fixed electrode, 40...IC, 41...adhesive, 4 2,43...bonding wire, 44,45...electrode pad, 51...first movable body, 52...first movable electrode, 53...support portion, 54...first spring, 55...connecting portion, 56...opening, 57...recess, 58...through hole, 61...second movable body, 62...second movable electrode, 63...support portion, 64...second spring, 65...opening, 66...extension portion, 71...third movable body, 72...third movable electrode, 73...support portion, 74...third spring, 75...opening, 76...extension portion, 2000...inertial measurement unit, C1,C2...capacitance, D...arrow, P1,P2,P3...oscillation axis, SS1,SS2,SS3...accommodation space, W1,W2,W3...width.

Claims

1. When the three mutually orthogonal axes are the X-axis, Y-axis, and Z-axis, a first spring disposed along the Y-axis direction; a first movable body that can swing around the first spring as a swing axis; a first movable body facing the first movable body in the Z-axis direction along the Z-axis, and a capacitance between the first movable body and the first movable body; a first fixed electrode forming a volume; a first movable body facing the first movable body in the Z-axis direction and forming a capacitance between the first movable body and the first movable body; A second fixed electrode; a second spring disposed along the Y-axis direction; a second movable body that can swing around the second spring as a swing axis; a third fixed electrode facing the second movable body in the Z-axis direction; a third spring disposed along the Y-axis direction; a third movable body that is arranged so as to be in contact with the first movable body and that is swingable around the third spring as a swing axis; With moving objects, a fourth fixed electrode facing the third movable body in the Z-axis direction; Including, In a plan view from the Z-axis direction, the first spring is placed between the second movable body includes a first extension portion extending toward the first spring, the third movable body includes a second extension portion extending toward the first spring, the first extending portion overlaps with the first movable body in the plan view, The inertial sensor, wherein the second extension portion overlaps with the first movable body in the planar view.

2. When the three mutually orthogonal axes are the X-axis, Y-axis, and Z-axis, a first spring disposed along the Y-axis direction; a first movable body that can swing around the first spring as a swing axis; a first movable body facing the first movable body in the Z-axis direction along the Z-axis, and a capacitance between the first movable body and the first movable body; a first fixed electrode forming a volume; a first movable body facing the first movable body in the Z-axis direction and forming a capacitance between the first movable body and the first movable body; A second fixed electrode; a second spring disposed along the Y-axis direction; a second movable body that can swing around the second spring as a swing axis; a third fixed electrode facing the second movable body in the Z-axis direction; a third spring disposed along the Y-axis direction; a third movable body that is arranged so as to be in contact with the first movable body and that is swingable around the third spring as a swing axis; With moving objects, a fourth fixed electrode facing the third movable body in the Z-axis direction; Including, In a plan view from the Z-axis direction, the first spring is placed between The second movable body and the third movable body are disposed inside the first movable body in the plan view. R, the second movable body includes a third extension portion extending to a side opposite to the first spring, the third movable body includes a fourth extension portion extending to a side opposite to the first spring, the third extension portion overlaps with the first movable body in the plan view, The inertial sensor, wherein the fourth extension portion overlaps with the first movable body in the planar view.

3. In claim 1 or 2, a substrate facing the first movable body in the Z-axis direction, The first fixed electrode, the second fixed electrode, and the third fixed electrode are disposed on the substrate. Inertial sensors.

4. In claim 3, The fourth fixed electrode is disposed on the substrate, forming an inertial sensor.

5. In any one of claims 1 to 4, The torsional stiffness of the second spring is less than the torsional stiffness of the first spring.

6. In any one of claims 1 to 5, The torsional stiffness of the third spring is less than the torsional stiffness of the first spring.

7. An inertial sensor according to any one of claims 1 to 6; a control unit that performs control based on a detection signal output from the inertial sensor; an inertial measurement unit,

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