JP5775281B2 - MEMS sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a MEMS sensor and a manufacturing method thereof.

In recent years, attention has been focused on MEMS (Micro Electro Mechanical Systems) sensors. As typical MEMS sensors, for example, an acceleration sensor, a pressure sensor, a gyro sensor, and the like are known.
For example, Patent Document 1 proposes an acceleration sensor including a cover glass, a silicon layer and a piezoresistive element formed on one surface of the cover glass, and an electrode pad formed on the other surface of the cover glass. Yes.

  The silicon layer includes a weight portion provided at the center of the cover glass, support portions at both ends of the cover glass, a flexible portion provided between the weight portion and the support portion, and formed with a piezoresistive element. And have a structure in which these are integrally formed. Then, the acceleration sensor is supported by the silicon substrate by bonding the support portion to the silicon substrate using an adhesive (adhesive layer). In the supported state, an airtight space surrounded by the support portion, the flexible portion, the adhesive layer, and the silicon substrate is formed in the center portion of the silicon layer.

JP 2007-17199 A

The acceleration sensor of Patent Document 1 detects acceleration by detecting a change in resistance value of the piezoresistive element due to deformation of the flexible portion due to external force applied to the acceleration sensor and deformation of the flexible portion.
However, the support portion of the silicon layer is completely adhered to the silicon substrate by the adhesive, and the gap immediately below the weight portion and the flexible portion is sealed. Therefore, even if the gap is compressed when the weight part and the flexible part are shaken, there is no escape space in the air in the gap, and the weight part and the flexible part are easily affected by the air damping effect. As a result, even if an external force is applied to the acceleration sensor, the weight and the movable part do not change in an amount corresponding to the external force, and the sensitivity of the sensor may be reduced.

  On the other hand, if the height of the support part is increased while the height of the weight part is maintained, and the distance between the weight part and the flexible part and the silicon substrate is increased, the flexible part and the weight part are shaken. Since the compressibility of the air gap is reduced, thereby reducing the pressure that the flexible part and the weight receive from the air gap, the influence of the air damping effect may be reduced. However, in order to increase the height of the support portion, it is necessary to deeply etch the silicon substrate. For this reason, it takes extra etching time, and the resist used as an etching mask needs to be thickened.

  The objective of this invention is providing the MEMS sensor which can reduce the influence of an air damping effect, and can manufacture it still more efficiently, and its manufacturing method.

  In order to achieve the above object, a MEMS sensor of the present invention has a front surface and a back surface, supports the vibration film formed on the front surface side, and the vibration film, and the surface side is directly below the vibration film. A semiconductor substrate having a frame portion that defines a space that is sealed by a vibration film and that opens the back surface side, and the frame portion forms a bottom surface of the semiconductor substrate and is joined to a support substrate; An inner surface facing the space and an outer surface facing the space are formed, and a groove extending from the inner surface to the outer surface of the frame portion is formed on the bottom wall of the frame portion. ing.

  According to this configuration, the groove is formed in the bottom wall of the frame portion. For this reason, when the MEMS sensor is mounted on the support substrate by bonding the bottom surface of the frame portion to the support substrate, the space between the space immediately below the diaphragm and the space outside the frame portion is partitioned by the groove and the support substrate. It is possible to communicate with the passage. As a result, when the vibrating membrane vibrates and the MEMS sensor operates, the air in the space can escape to the outside of the sensor, and the pressure that the vibrating membrane receives from the space can be reduced. As a result, the influence of the air damping effect on the diaphragm can be suppressed. Therefore, it is possible to suppress a decrease in sensitivity of the sensor.

If the groove is formed in the frame part, such an operational effect can be sufficiently exerted even under conditions where the volume of the space is small and the compression rate of the space when the vibrating membrane vibrates easily increases. Therefore, when manufacturing the MEMS sensor, it is not necessary to etch the semiconductor substrate deeply, so that a reduction in manufacturing efficiency can be suppressed.
The “space compression ratio” means (volume V1 of the space when compressed by vibration of the vibrating membrane) / (volume V2 of the space before the vibrating membrane vibrates) × 100 (%). .

  The MEMS sensor of the present invention may further include a weight that is held by the vibrating membrane in the space and has a bottom surface that faces an open surface of the space. In that case, when the bottom wall of the frame is joined to the support substrate between the bottom surface of the frame portion and the bottom surface of the weight, the weight is floated with respect to the support substrate. A step is provided, and the step may be equal to the depth of the groove.

In order to make the step between the bottom surface of the frame portion and the bottom surface of the weight equal to the depth of the groove in the frame portion, for example, a MEMS sensor may be manufactured by the manufacturing method of the present invention.
That is, the MEMS sensor manufacturing method of the present invention forms a space in which the front side is sealed and the back side is opened by selectively etching a semiconductor substrate having a front side and a back side from the back side. A weight having a bottom wall that forms the back surface inside the space, and a bottom wall that forms the back surface outside the space and a frame portion having an inner surface facing the space. Forming a groove extending outwardly from the inner surface to the bottom wall of the frame part by selectively etching the bottom wall of the frame part and the bottom wall of the weight, Forming a step equal to the depth of the groove between the bottom surface of the weight and the bottom surface of the frame portion.

According to this manufacturing method, since the step between the bottom surface of the frame portion and the bottom surface of the weight and the groove of the frame portion are formed simultaneously in the same process, the number of processes can be reduced and the manufacturing efficiency can be improved. .
In the MEMS sensor of the present invention, it is preferable that the plurality of grooves having the same shape are formed at equal intervals along the circumferential direction surrounding the space.

  In this configuration, in a state where the frame portion is bonded to the support substrate, when the vibration film vibrates in a direction approaching the support substrate and compresses the space, the air in the space is formed at a plurality of intervals. The same amount can be escaped through the groove. Thereby, since the bias of the pressure applied with respect to a diaphragm can be reduced, more precise detection can be performed.

1 is a schematic plan view of an acceleration sensor according to an embodiment of the present invention. It is a typical bottom view of the acceleration sensor shown in FIG. It is typical sectional drawing of the acceleration sensor shown in FIG. 1, Comprising: The cross section in cut surface AA is shown. It is a figure which shows a part of manufacturing process of the acceleration sensor shown in FIG. It is a figure which shows the next process of FIG. 4A. It is a figure which shows the next process of FIG. 4B. It is a figure which shows the next process of FIG. 4C. It is a figure which shows the 1st modification of the groove | channel shown in FIG. It is a figure which shows the 2nd modification of the groove | channel shown in FIG. It is a figure which shows the 3rd modification of the groove | channel shown in FIG. It is a figure which shows the 4th modification of the groove | channel shown in FIG. It is typical sectional drawing of the acceleration sensor which concerns on other embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic plan view of an acceleration sensor according to an embodiment of the present invention. FIG. 2 is a schematic bottom view of the acceleration sensor shown in FIG. FIG. 3 is a schematic cross-sectional view of the acceleration sensor shown in FIG. 1, and shows a cross section taken along the section AA.
The acceleration sensor 1 is a sensor that detects acceleration acting on, for example, three axes (X axis, Y axis, and Z axis) orthogonal to each other in a three-dimensional space, and is a plane as a semiconductor substrate having a front surface 21 and a back surface 22. An SOI (Silicon On Insulator) substrate having a rectangular shape is provided. The surface 21 of the SOI substrate 2 is, for example, an element forming surface on which detection elements, detection circuits, and the like are formed, and the back surface 22 is bonded to, for example, a support substrate 25 (for example, a sealing substrate such as a glass substrate). It is a mounting surface.

  In the following, for convenience, the direction parallel to one pair of opposing sides of the SOI substrate 2 is defined as the X-axis direction, and the direction parallel to the other pair of opposing sides of the SOI substrate 2 is defined as the Y-axis direction. This embodiment will be described with the direction parallel to the vertical direction as the Z-axis direction. Further, the Z-axis direction may be referred to as the vertical direction with reference to the basic posture of the acceleration sensor 1 in which the back surface 22 of the SOI substrate 2 is disposed on the lower side.

  The SOI substrate 2 has a structure in which a silicon substrate 3, an insulating layer 4 made of silicon oxide, and an active layer 5 made of silicon are stacked in order from the back surface 22 side to the front surface 21 side. The total thickness of the SOI substrate 2 is, for example, about 557.5 μm, and the thickness of each layer is, for example, the silicon substrate 3 is about 550 μm, the insulating layer 4 is about 1.5 μm, and the active layer 5 is about 6 μm. .

In the SOI substrate 2, the silicon substrate 3 and the insulating layer 4 are selectively removed along the Z-axis direction from the back surface 22 to the active layer 5, thereby forming an annular space 6 in a bottom view. ing. In this space 6, the surface 21 side of the SOI substrate 2 is sealed by the active layer 5, and the back surface 22 side of the SOI substrate 2 is open.
In the active layer 5, a circular portion facing the space 6 is formed as the vibration film 7. The entire periphery of the vibrating membrane 7 is integrally supported by the active layer 5 of the outer frame (frame portion 8) of the SOI substrate 2 having a laminated structure of the silicon substrate 3, the insulating layer 4, and the active layer 5. . In addition, a cylindrical portion having a laminated structure of the silicon substrate 3 and the insulating layer 4 disposed in the space 6 is held in the active layer 5 as a weight 9 hanging from the vibration film 7.

  The frame portion 8 has an outer surface 81 that forms the side surface of the SOI substrate 2, an inner surface 82 that defines the space 6 from the outside, and a bottom surface 83 (bottom wall) that forms the back surface 22 of the SOI substrate 2. A groove 10 is formed in the bottom wall of the frame portion 8 from the inner side 82 to the outer side 81. A plurality (four in this embodiment) of grooves 10 are provided along the outer circumferential direction of the space 6 with an equal interval (for example, every 1/4 L interval (L: outer circumferential length of the space 6)). More specifically, the four grooves 10 are one by one from the center position of each of the four outer surfaces 81 of the frame portion 8 toward the center O of the annular space 6 in the bottom view (in the X-axis direction or Y-direction). The direction along the axial direction) is provided in a cross shape in a bottom view. Moreover, the some groove | channel 10 has the mutually same depth D, The depth D is 20 micrometers-100 micrometers, for example. In this embodiment, the plurality of grooves 10 are formed with the same length and width.

  The weight 9 has a desired bottom surface 91 on the open surface 61 of the space 6, and a step S is provided between the bottom surface 91 and the bottom surface 83 of the frame portion 8. The step S secures a gap for allowing the weight 9 to vibrate between the support substrate 25 and the weight 9 when the acceleration sensor 1 is mounted on the support board 25 (described later). Further, in this embodiment, the step S is equal to the depth D of the groove 10 of the frame portion 8 (for example, 20 μm to 100 μm). Further, the radius r of the bottom surface 91 of the weight 9 is, for example, about 40 to 60% with respect to the radius R of the space 6 in the bottom view.

Further, the inner side surface 82 of the frame portion 8 extends from the reference surface 821 facing the side surface (circumferential surface) of the weight 9 to the position of the depth D of the groove 10 from the bottom surface 83, and outside the reference surface 821. The step surface has an offset surface 822 that is offset. That is, the groove 10 of the frame portion 8 is formed so as to extend from the offset surface 822 to the outer surface 81.
An NSG (Nondoped Silicate Glass) film 11 (thickness of about 2500 mm) is formed on the surface 21 (element formation surface) of the SOI substrate 2.

On this NSG film 11, a piezoelectric body 13 (for example, PZT (lead zirconate titanate)) is formed by a pair of upper electrode 14 (for example, Pt / Ti) and lower electrode 15 (for example, Ir / IrO ₂ ). A plurality of sandwiched piezoelectric elements 12 are provided.
The plurality of piezoelectric elements 12 include a Z-axis detecting element 12Z provided at intervals along the periphery of the weight 9, and an X-axis detecting element 12X and a Y-axis detecting element 12Y surrounding the Z-axis detecting element 12Z. Yes. One X-axis detection element 12X is provided on each of the one side and the other side across the weight 9 in the X-axis direction. One Y-axis detection element 12Y is provided on each of one side and the other side of the weight 9 in the Y-axis direction.

On the piezoelectric element 12, an interlayer insulating film 16 (about 5000 mm thick) made of SiO ₂ is laminated. A plurality of wirings 17 (for example, AL wirings) that are electrically connected to the piezoelectric elements 12 are formed on the interlayer insulating film 16. The wiring 17 is electrically connected to the upper electrode 14 or the lower electrode 15 of the piezoelectric element 12 through a contact hole 18 formed in the interlayer insulating film 16. Further, the wiring 17 is routed on the interlayer insulating film 16 to the periphery of the X-axis detection element 12X and the Y-axis detection element 12Y. In FIG. 1, for convenience, a part of the connection form of the plurality of wirings 17 is omitted, and the connection form of the wirings 17 can be appropriately designed in accordance with the usage state of the acceleration sensor 1. Further, the wiring 17 may be composed only of metal wiring, may be composed only of piezo wiring manufactured by injecting impurities into the active layer 5, or may be a combination of metal wiring and piezo wiring. It may be configured.

On the interlayer insulating film 16, a PSG (Phosphorus Silicate Glass) film 19 (thickness of about 750 mm) and a SiN film 20 (thickness of about 7000 mm) are sequentially laminated. The PSG film 19 and the SiN film 20 are formed with a pad opening 24 that exposes a part of the wiring 17 routed around the piezoelectric element 12 as a pad 23.
In the acceleration sensor 1, for example, a support substrate 25 (a ceramic substrate, a silicon substrate 3, a glass substrate, or the like is bonded to the bottom surface 83 of the frame portion 8 to seal the space 6 (see FIG. 3).

  When acceleration acts on the acceleration sensor 11 and the weight 9 swings, distortion (twisting and / or bending) occurs in the vibration film 7. Due to the distortion of the vibration film 7, the piezoelectric body 13 on the vibration film 7 expands and contracts, and the resistance value of the piezoelectric body 13 changes. By taking out the change in the resistance value as a signal through the pad 23 (wiring 17), the direction (three-axis direction) and the magnitude of the acceleration acting on the weight 9 (acceleration sensor 1) are determined based on this signal. Can be detected. At this time, since the groove 10 is formed in the frame portion 8, a space defined by the groove 10 and the support substrate 25 is provided between the space 6 immediately below the diaphragm 7 and the space 6 outside the frame portion 8. Can communicate. Thereby, the air in the space 6 can be released outside the sensor when the weight 9 vibrates, and the pressure that the weight 9 and the vibration film 7 receive from the space 6 can be reduced. As a result, the influence of the air damping effect on the weight 9 and the diaphragm 7 can be suppressed. Therefore, it is possible to suppress a decrease in sensitivity of the sensor.

Further, since the groove 10 is provided in a cross shape when viewed from the bottom, when the weight 9 vibrates in a direction approaching the support substrate 25 and compresses the space 6, the air in the space 6 is formed in a cross shape. The same amount can be escaped through the plurality of grooves 10. Thereby, since the bias of the pressure applied to the weight 9 and the diaphragm 7 can be reduced, more precise detection can be performed.
4A to 4D are diagrams showing the manufacturing process of the acceleration sensor shown in FIG. 1 in the order of steps.

In order to manufacture the acceleration sensor 1, first, as shown in FIG. 4A, an NSG is formed on the surface 21 of the SOI substrate 2 including the silicon substrate 3, the insulating layer 4, and the active layer 5 by, for example, the CVD (Chemical Vapor Deposition) method. A film 11 is formed. Next, a lower electrode 15 made of Ir / IrO ₂ , a piezoelectric body 13 made of PZT, and an upper electrode 14 made of Pt / Ti are formed on the NSG film 11 by a known sputtering technique and a known patterning technique. Thereby, the piezoelectric element 12 for detecting each axis (X axis, Y axis, and Z axis) is formed. Next, an interlayer insulating film 16 is laminated on the NSG film 11 so as to cover the piezoelectric element 12. Next, the interlayer insulating film 16 is selectively etched to form a contact hole 18 for making contact with the upper electrode 14 and the lower electrode 15 of the piezoelectric element 12. Next, a metal for the wiring 17 is sputtered, and this metal is patterned to form the wiring 17. Subsequently, the PSG film 19 and the SiN film 20 are sequentially stacked on the interlayer insulating film 16. Then, a pad opening 24 is formed so as to penetrate the PSG film 19 and the SiN film 20 by a known etching technique.

  Next, as shown in FIG. 4B, an NSG film 26 (about 750 mm thick) is formed on the SiN film 20 by, eg, CVD. The NSG film 26 is for protecting the element formation surface when the back surface 22 side of the SOI substrate 2 is processed in a later step. Subsequently, the back surface 22 is ground until the silicon substrate 3 has a thickness of about 550 μm. That is, the silicon substrate 3 having a thickness of about 725 μm is ground by about 175 μm. After grinding, a first mask 27 (about 5000 mm thick) made of NSG is formed on the back surface 22 of the SOI substrate 2 by, for example, a CVD method. Next, a portion of the first mask 27 covering the region where the groove 10, the weight 9 and the space 6 are to be formed is removed by a known patterning technique.

Next, as shown in FIG. 4C, on the first mask 27, on the region other than the region where the space 6 is to be formed (that is, the region where the weight 9 and the frame portion 8 are to be formed) Two masks 28 (thickness of about 100,000 mm) are formed. The second mask 28 is formed so as to cover (overlapping) the inner peripheral side end of the first mask 27. Subsequently, the SOI substrate 2 is dry-etched through the second mask 28 from the back surface 22 side to the middle of the silicon substrate 3 (about 500 μm). For dry etching, for example, SF ₆ gas is used. As a result, the shapes of the weight 9 and the frame portion 8 are formed, and at the same time, an annular groove 29 having a reference surface 821 is formed so as to separate the weight 9 and the frame portion 8. Next, the first mask 27 is exposed by removing the second mask 28 by, for example, an ashing process.

  Next, as shown in FIG. 4D, the entire bottom surface 91 of the weight 9 is dry-etched through the exposed first mask 27, and the frame portion 8 is selectively dry-etched. This dry etching is continued until, for example, the silicon substrate 3 is removed by about 50 μm. Thereby, the groove 10 is formed in the bottom wall of the frame portion 8, and at the same time, a step S between the bottom surface 91 of the weight 9 and the bottom surface 83 of the frame portion 8 is formed. Further, the etching gas is also supplied to the silicon substrate 3 remaining above the groove 29, whereby the silicon substrate 3 above the groove 29 is completely removed and the space 6 is formed.

Thereafter, the etching solution is supplied into the space 6, whereby the insulating layer 4 in the space 6 is removed by wet etching, and at the same time, the vibration film 7 made of the active layer 5 is formed. Next, the NSG film 26 on the SiN film 20 is removed. Through the above steps, the acceleration sensor 1 shown in FIGS. 1 to 3 is obtained.
According to the above manufacturing method, the step S between the bottom surface 83 of the frame portion 8 and the bottom surface 91 of the weight 9 and the groove 10 of the frame portion 8 are simultaneously formed in the same step (step in FIG. 4D). The number of steps can be reduced as compared with the case of forming in separate steps. As a result, the acceleration sensor 1 can be manufactured efficiently.

  Moreover, if the groove | channel 10 is formed in the flame | frame part 8, the above-mentioned air dumping suppression effect is that the silicon substrate 3 is thin and the volume of the space 6 is small, and the compressibility of the space 6 when the weight 9 vibrates is large. Even under easy-to-be-prone conditions, it can be fully demonstrated. Therefore, it is not necessary to increase the volume of the space 6 by increasing the depth of the space 6. That is, when manufacturing the acceleration sensor 1, the silicon substrate 3 does not have to be etched deeply. Therefore, it is only necessary to grind the silicon substrate 3 from the back surface 22 to a certain thickness regardless of the thickness of the silicon substrate 3 (step of FIG. 4B), and then etch the necessary amount. As a result, the etching time can be shortened, so that a reduction in manufacturing efficiency can be suppressed.

The “compression ratio of the space 6” is (volume V1 of the space 6 when compressed by the vibration of the weight 9) / (volume V2 of the space 6 before the weight 9 vibrates) × 100 (%). That means.
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.
For example, as shown in FIG. 5, the groove 10 of the frame portion 8 may be formed in a cross shape along the diagonal line of the SOI substrate 2 in a bottom view. Moreover, as shown in FIG. 6, you may form in the linear form along the radial direction of the weight 9 (it follows an X-axis direction in FIG. 6). Moreover, as shown in FIG. 7, only one may be formed along the radial direction of the weight 9 (in FIG. 7, along the Y-axis direction). Further, the widths of the plurality of grooves 10 do not have to be all the same. For example, as shown in FIG. 8, a straight portion along one direction of the cross-shaped groove 10 (in FIG. 8, in the Y-axis direction). The width of the groove 10 </ b> Y) may be wider than the width of the straight portion along the other direction (the groove 10 </ b> X along the X-axis direction in FIG. 8).

Moreover, the shape of the weight 9 does not have to be a columnar shape, and may be, for example, a polygonal column shape (for example, a rectangular parallelepiped shape).
Moreover, the acceleration sensor does not need to have the weight 9 for generating distortion in the vibration film 7 like the acceleration sensor 31 of FIG.
In the above-described embodiment, the acceleration sensor is taken as an example of the MEMS sensor. However, the present invention is not limited to the acceleration sensor, and is applied to various devices manufactured by the MEMS technology such as a pressure sensor and a gyro sensor. Can do.

  In addition, various design changes can be made within the scope of matters described in the claims.

DESCRIPTION OF SYMBOLS 1 Acceleration sensor 2 SOI substrate 6 Space 7 Vibration film 8 Frame part 9 Weight 10 Groove 21 Surface (of SOI substrate) 22 Back surface (of SOI substrate) 61 (Space) Open surface 81 (Outside surface) 81 (Frame portion) Inside surface 83 bottom surface (frame portion) 91 bottom surface (weight) S step

Claims (9)

A semiconductor substrate having a front surface and a back surface, a vibration film formed on the front surface side, and a frame portion that supports the vibration film and defines a space in which the back surface side is opened immediately below the vibration film ; ,
A weight held by the vibrating membrane in the space and having a bottom surface facing an open surface of the space ;
The frame portion has a bottom wall that forms the back surface of the semiconductor substrate and is joined to a support substrate, an inner surface that faces the space, and an outer surface that faces the space,
In the bottom wall of the frame part, a groove is formed from the inner side surface of the frame part to the outer side surface,
The groove extends from the outer surface toward the center of the space ,
The inner surface of the frame portion includes a reference surface that surrounds the side surface of the weight, and an offset that surrounds the side surface of the weight that is offset from the bottom surface of the frame portion to the depth position of the groove and offset outward from the reference surface. A MEMS sensor having a stepped surface including a surface . Depth position of the groove, than the junction position of the weight relative to the vibrating membrane is disposed on the rear surface side of the semiconductor substrate, MEMS sensor according to claim 1. A step between the bottom surface of the frame portion and the bottom surface of the weight to make the weight float with respect to the support substrate when the bottom wall of the frame is joined to the support substrate. It is provided, MEMS sensor according to claim 1 or 2. The MEMS sensor according to claim 3 , wherein the step is equal to the depth of the groove. The MEMS sensor as described in any one of Claims 1-4 with which the center part of the said space corresponds with the gravity center of the said weight. The semiconductor substrate is an SOI substrate having a structure in which a silicon substrate, an insulating layer, and an active layer are stacked;
The vibration membrane is composed of the active layer, the weight is a laminated structure of the silicon substrate and the insulating layer, MEMS sensor according to any one of claims 1 to 5. Said groove, said formed with a plurality at an equal interval along a circumferential direction surrounding the space, MEMS sensor according to any one of claims 1-6. The MEMS sensor according to claim 7 , wherein the plurality of grooves are formed in a cross shape in a bottom view when the semiconductor substrate is viewed from the bottom surface side of the frame portion. Forming a first mask on the back surface so as to surround a part of the etching region of the back surface of the semiconductor substrate having the front surface and the back surface ;
Forming a second mask so as to surround the etching region and to cover an inner peripheral side end of the first mask;
By selectively etching the semiconductor substrate through the second mask from the back surface side, a space where the back surface side is opened is formed, and at the same time, the bottom surface forming the back surface inside the space. Forming a weight having a wall, a bottom wall forming the back surface outside the space, and a frame portion having an inner surface facing the space; and after removing the second mask, The frame portion extends from the outer surface of the frame portion toward the center of the space by selectively etching the bottom wall of the frame portion and the bottom wall of the weight through one mask. said bottom to form a groove between the inner side surface of the wall and the outer side, at the same time, the depth and equal level difference of the groove between the bottom surface of the bottom and the frame portion of the weight, of the frame portion of the A stepped surface including a reference surface that surrounds the side surface of the weight, and an offset surface that surrounds the side surface of the weight that is offset from the bottom surface of the frame part to the depth position of the groove and offset outward from the reference surface. And a method of manufacturing the MEMS sensor.

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