JP2019124616A - Physical quantity sensor - Google Patents

Abstract

To provide a physical quantity sensor with which it is possible to suppress a beam that supports a movable unit from being fastened.SOLUTION: The physical quantity sensor comprises: a mass body provided in a gap part formed in plane of a semiconductor substrate and displaceable in a direction parallel to the plane of the semiconductor substrate in accordance with an inputted physical quantity; an elastic support part connected at one end to the mass body and fixed at other end to the semiconductor substrate, extending in a direction parallel to the plane of the semiconductor substrate in the gap part, and elastically deformed in accordance with the displacement of the mass body; and a fixed electrode provided on the semiconductor substrate, for detecting capacitance generated between the mass body and itself in accordance with the displacement of the mass body. The elastic support part includes a beam formed by being folded back in multiplicity at a plurality of fold-back positions from one end to the other end. The beam includes a plurality of beam elements extending between each of the plurality of fold-back positions. The cross sectional shape of one beam element among the plurality of beam elements includes a slope in a counterface surface facing an other beam element adjacent to the one beam element.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a physical quantity sensor, and more particularly to a physical quantity sensor using MEMS (Micro Electro Mechanical System) technology.

  As a capacitance-type physical quantity sensor using MEMS technology, an acceleration sensor, an angular velocity sensor, and the like are known. For example, the acceleration sensor has a movable part that displaces with respect to the input of the physical quantity and a fixed part that does not displace, and the movable part is supported by the beam. Patent Document 1 discloses an acceleration sensor as a semiconductor device. The acceleration sensor includes a movable detection mass as a movable portion and a fixed electrode as a fixed portion, and supports the beam as a beam for supporting the movable detection mass. It further has a spring. The capacitance-type physical quantity sensor detects a change in capacitance depending on the distance between the movable part and the fixed part and the area where the movable part and the fixed part face each other, and converts it into the input physical quantity .

JP, 2009-16717, A

  In order for the acceleration sensor to detect acceleration with high sensitivity, it is required that the beam supporting the movable part be easily displaced. In addition, since it is also necessary to increase the capacitance, it is preferable that the fixed portion and the movable portion be provided in close proximity to each other as narrow as possible. However, when components such as the movable part and the beam that constitute the acceleration sensor are formed in a range close to each other, the beam that supports the movable part contacts other beams due to the vibrations generated during processing and transportation. There is something to do. The physical quantity sensor to which the beam is fixed can not exhibit desired characteristics or can not detect the physical quantity, because the movable part does not displace normally with respect to the input physical quantity.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a physical quantity sensor capable of suppressing the fixation of a beam supporting a movable part.

  A physical quantity sensor according to the present invention is provided in an air gap formed in a plane of a semiconductor substrate, and a mass body displaceable in a direction parallel to the plane of the semiconductor substrate according to an input physical quantity, An elastic support portion which is connected to the mass body, the other end is fixed to the semiconductor substrate, extends in a direction parallel to the surface of the semiconductor substrate in the air gap, and elastically deforms according to the displacement of the mass body; And a fixed electrode provided on the substrate and detecting a capacitance generated between the mass body in response to the displacement of the mass body. The elastic support includes a beam which is folded back in a plurality of folding positions from one end to the other end. The beam includes a plurality of beam elements extending between each of the plurality of folding positions. The cross-sectional shape of one beam element of the plurality of beam elements includes an inclined surface in an opposing surface that is a surface facing another beam element adjacent to the one beam element.

  According to the present invention, it is possible to provide a physical quantity sensor that suppresses sticking of a beam that supports a movable part.

  The objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description and the accompanying drawings.

It is a top view which shows typically the structure of the physical quantity sensor in embodiment. It is sectional drawing which shows the structure of the beam element in embodiment. It is sectional drawing which shows the structure of the 1st comb tooth of the mass in embodiment, and the 2nd comb tooth of fixed electrode. It is a top view which shows the structure of the elastic support part in embodiment. It is a top view which shows the state which two beam elements which adjoin each other in the base technology adhered. It is sectional drawing which shows the state which two beam elements which adjoin each other in the base technology adhered. It is a sectional view showing a state where two beam elements which adjoin each other in an embodiment contact. It is sectional drawing which shows the structure of the beam element in the modification 1 of embodiment. It is sectional drawing which shows the structure of the beam element in the modification 2 of embodiment.

(Configuration of physical quantity sensor)
The physical quantity sensor is, for example, a capacitive physical quantity sensor. In the present embodiment, the physical quantity sensor will be described by taking an acceleration sensor as an example of a capacitive physical quantity sensor. FIG. 1 is a plan view schematically showing the configuration of the physical quantity sensor in the present embodiment.

  The physical quantity sensor is composed of a mass body 1, an elastic support 2 and a fixed electrode 3, which are provided in an air gap 4 formed in the plane of the semiconductor substrate. Moreover, although illustration is abbreviate | omitted, the surface side of the mass body 1, the elastic support part 2, and the fixed electrode 3 is covered by the protection member. In FIG. 1, the surface side is the + z direction. A gap is provided between the mass body 1 and the elastic support 2 and the protection member. The protective member is, for example, a glass substrate or a silicon substrate. In addition, a semiconductor substrate is provided on the back surface side of the mass body 1 and the elastic support portion 2 via the air gap 4, and the fixing portion such as the fixed electrode 3 is fixed to the semiconductor substrate. In FIG. 1, the back side is the −z direction. In addition, the physical quantity sensor is provided with a junction with the protective member and an electrode unit that transmits and receives an electrical signal with the outside.

  The mass body 1 is provided in the space 4 formed in the plane of the semiconductor substrate. The mass body 1 has a first comb tooth 11 facing the fixed electrode 3 described later. The mass body 1 is displaceable in a direction parallel to the plane of the semiconductor substrate according to the physical quantity input to the physical quantity sensor. The direction parallel to the plane of the semiconductor substrate is the direction parallel to the xy plane in FIG. Moreover, a physical quantity is acceleration here.

  The elastic support portion 2 has one end 2 a connected to the mass body 1 and the other end 2 b fixed to the semiconductor substrate to support the mass body 1. In the present embodiment, the other end 2 b is held by the anchor 5 provided in the plane of the semiconductor substrate, and is fixed to the semiconductor substrate on the back side via the anchor 5. The elastic support portion 2 extends in a direction parallel to the surface of the semiconductor substrate in the air gap portion 4. The elastic support portion 2 elastically deforms according to the displacement of the mass body 1.

  The elastic support portion 2 includes a beam which is folded in multiples at a plurality of folding positions 21 from the one end 2a to the other end 2b. The beam includes a plurality of beam elements 22 extending between each of a plurality of fold points 21. That is, the elastic support portion 2 includes a plurality of beam elements 22 arranged in multiple from the one end 2a to the other end 2b. FIG. 2 is a cross-sectional view showing the configuration of the beam element 22, and shows a cross-section at A-A 'shown in FIG. The cross-sectional shape of one beam element 22a of the plurality of beam elements 22 includes an inclined surface in the opposing surface 23, which is a surface facing the other beam element 22b adjacent to one beam element 22a. In the present embodiment, the cross-sectional shape of the beam element 22 has a trapezoidal shape including an inclined surface on the facing surface 23.

  The fixed electrode 3 is provided and fixed to the semiconductor substrate. That is, the fixed electrode 3 is not displaced by the physical quantity. The fixed electrode 3 has a second comb tooth 31 facing the first comb tooth 11 of the mass 1. FIG. 3 is a cross-sectional view showing the configuration of the first comb teeth 11 of the mass body 1 and the second comb teeth 31 of the fixed electrode 3, and shows a cross section along B-B 'shown in FIG. The first comb teeth 11 and the second comb teeth 31 are disposed at opposing positions with a predetermined distance therebetween, and a capacitance is formed between the two. In the physical quantity sensor, the mass body 1 is displaced according to the input acceleration, and the distance between the first comb tooth 11 and the second comb tooth 31 changes. Then, the capacitance generated between the first comb tooth 11 and the second comb tooth 31 changes, and the fixed electrode 3 detects the change in the capacitance. The change in capacitance detected is used to calculate the acceleration. The capacitance is determined by the distance and the facing area between the first and second comb teeth 11 and 31. It is preferable that the distance between the first comb teeth 11 and the second comb teeth 31 be short, and the opposing areas thereof be large, in order to relatively reduce the influence of foreign matter. Therefore, in the physical quantity sensor in the present embodiment, each of the side surface of the first comb tooth 11 and the side surface of the second comb tooth 31 is processed vertically.

  As mentioned above, the physical quantity sensor in this embodiment is a sensor which detects acceleration from displacement of mass body 1 which is a movable part.

(Operation of physical quantity sensor)
The rigidity of the elastic support portion 2 of the physical quantity sensor is determined according to the acceleration of the detection target. The rigidity of the elastic support portion 2 is adjusted by the length and width of the beam. For example, when the acceleration sensor detects low acceleration or detects acceleration with high sensitivity, the mass body 1 is required to be easily displaced with respect to the input acceleration. Therefore, the elastic support portion 2 having a long length and a narrow width is used. FIG. 4 is a plan view showing the configuration of the elastic support portion 2 in the present embodiment. The elastic support portion 2 in the present embodiment includes a beam which is folded in multiple turns at a plurality of folding positions 21 from one end 2 a to the other end 2 b, and the beams extend between each of the plurality of folding positions 21. It has a plurality of beam elements 22. The elastic support portion 2 of the physical quantity sensor in the present embodiment is longer than the elastic support portion connecting the mass 1 and the anchor 5 without the beam being folded back. Since the mass body 1 is easy to move, the acceleration is detected with high sensitivity. On the other hand, when the elastic support portion 2 is long, the elastic support portion 2 is displaced by various forces generated during processing or conveyance of the physical quantity sensor, for example, impact force or electrostatic force, and the two beam elements 22 adjacent to each other Contact may occur near the folding point 21.

  FIG. 5 is a plan view showing a state in which two beam elements 22 adjacent to each other are in contact with each other. Hereinafter, a point at which two beam elements 22 adjacent to each other are in contact with each other is referred to as a contact portion 24. FIG. 6 is a cross-sectional view showing a state in which two beam elements 22 adjacent to each other are fixed when the cross-sectional shape of beam element 22 is rectangular, and shows a cross-section at C-C 'shown in FIG. If the cross-sectional shape of the beam element 22 is rectangular, the facing surface 23 has a vertical surface and does not include a slope. The facing surface 23 of one beam element 22a of the plurality of beam elements 22 is the entire surface of one beam element 22a that is a rectangle. The entire surface is fixed to the other beam element 22b adjacent to one beam element 22a at the contact portion 24, and the state is maintained.

  FIG. 7 is a cross-sectional view showing a state in which two beam elements 22 adjacent to each other in the present embodiment are in contact with each other, and shows a cross-section at C-C 'shown in FIG. When the cross-sectional shape of the beam element 22 is trapezoidal, one beam element 22 a contacts another beam element 22 b adjacent to one beam element 22 a at a part of the facing surface 23. The contact area of the contact part 24 is smaller than the area of the contact part 24 in the beam element 22 whose cross-sectional shape is rectangular. As a result, fixation of the beam element 22 is less likely to occur.

(Manufacturing method of physical quantity sensor)
The semiconductor substrate on which the mass body 1, the elastic support portion 2, the fixed electrode 3 and the like are formed is, for example, a silicon substrate. The structures constituting the physical quantity sensor such as the mass body 1, the elastic support 2 and the fixed electrode 3 are formed by the MEMS technology, that is, by the semiconductor process such as etching. In the beam element 22 having a trapezoidal cross-sectional shape, the first comb teeth 11 and the second comb teeth 31 having a rectangular cross-sectional shape are formed in separate steps. As a result, it is possible to manufacture a physical quantity sensor that has the beam element 22 that is less likely to cause sticking and that has the first comb teeth 11 and the second comb teeth 31 that enhance the detection sensitivity of acceleration.

(effect)
Summarizing the above, the physical quantity sensor according to the embodiment is provided in the air gap 4 formed in the plane of the semiconductor substrate, and can be displaced in the direction parallel to the plane of the semiconductor substrate according to the input physical quantity. The mass 1 and the one end 2 a are connected to the mass 1, the other end 2 b is fixed to the semiconductor substrate, extends in a direction parallel to the surface of the semiconductor substrate in the gap 4, and the displacement of the mass 1 An elastic support portion 2 elastically deformed in accordance with the fixed electrode 3 and a fixed electrode 3 provided in the plane of the semiconductor substrate to detect an electrostatic capacitance generated between the mass 1 and the mass 1 according to the displacement of the mass 1 Equipped with The elastic support portion 2 includes a beam which is folded in multiples at a plurality of folding positions 21 from the one end 2a to the other end 2b. The beam includes a plurality of beam elements 22 extending between each of a plurality of fold points 21. The cross-sectional shape of one beam element 22a of the plurality of beam elements 22 includes an inclined surface in the opposing surface 23, which is a surface facing the other beam element 22b adjacent to one beam element 22a.

  With the above configuration, it is possible to provide a physical quantity sensor that suppresses the fixation of the beam supporting the mass body 1 that is the movable portion, that is, the fixation of the beam element 22. A physical sensor is obtained which has an elastic supporting portion 2 which is difficult to be fixed but which is difficult to be fixed. For example, even when a physical quantity such as an excessive impact force or electrostatic force is input from the outside, adhesion between one beam element 22a and the beam element 22b adjacent thereto is suppressed. Therefore, the yield in the manufacturing process of the physical quantity sensor is improved, and the reliability of the physical quantity sensor is improved. The physical quantity sensor in the present embodiment is provided with a first comb tooth 11 and a second comb tooth 31 having side surfaces perpendicular to each other in proximity to each other, and has an elastic supporting portion 2 which is hard to be fixed and easily displaced. Therefore, the physical quantity sensor can detect acceleration with high sensitivity and high accuracy.

  In the physical quantity sensor according to the embodiment, the cross-sectional shape of one beam element 22 a has a trapezoidal shape including an inclined surface in the facing surface 23.

  According to the above configuration, since one beam element 22a and the beam element 22b adjacent thereto have inclined surfaces which are not parallel to each other on their respective side surfaces, their contact is more effectively suppressed.

(Modification 1 of Embodiment)
FIG. 8 is a cross-sectional view showing the configuration of the beam element 22 in the first modification of the embodiment. The cross-sectional shape of the beam element 22 is an inverted trapezoid having a long upper side and a short lower side unlike the trapezoidal shape shown in FIG. Even if one beam element 22a comes in contact with another beam element 22b adjacent thereto, since the contact area is small, the fixation of the beam element 22 is suppressed.

(Modification 2 of the embodiment)
FIG. 9 is a cross-sectional view showing the configuration of the beam element 22 in the second modification of the embodiment. The cross-sectional shape of one beam element 22 a includes an apex 25 having a convex shape on the facing surface 23. That is, in the cross section of one beam element 22a, a portion where the distance to the other beam element 22b adjacent to one beam element 22a is provided is provided halfway in the depth direction. Even if one beam element 22a comes in contact with another beam element 22b adjacent thereto, since the contact area is small, the fixation of the beam element 22 is suppressed. Further, in the second modification, since the apex 25 of the convex shape has an obtuse angle, breakage of the beam element 22 due to contact can be suppressed. Thus, the reliability of the physical quantity sensor is improved.

  Although an acceleration sensor is shown as an example of a physical quantity sensor in the embodiment and each modification, similar effects can be obtained as long as the physical quantity sensor is a physical quantity sensor such as an angular velocity sensor or a vibration sensor having a beam element 22.

  In the present invention, within the scope of the invention, the embodiment can be appropriately modified or omitted.

  Although the present invention has been described in detail, the above description is an exemplification in all aspects, and the present invention is not limited thereto. It is understood that countless variations not illustrated are conceivable without departing from the scope of the present invention.

  1 mass body, 2 elastic support portion, 2a one end, 2b other end, 21 return position, 22 beam element, 23 facing surface, 25 apex, 3 fixed electrode, 4 gap portion.

Claims (3)

A mass body provided in an air gap formed in a plane of the semiconductor substrate and displaceable in a direction parallel to the plane of the semiconductor substrate according to an input physical quantity;
One end is connected to the mass body, the other end is fixed to the semiconductor substrate, extends in a direction parallel to the surface of the semiconductor substrate in the void portion, and is elastically deformed according to the displacement of the mass body And a fixed electrode provided on the semiconductor substrate and detecting an electrostatic capacitance generated between the mass body and the mass body according to the displacement of the mass body,
The elastic support portion includes a beam which is multiply folded at a plurality of folding positions from the one end to the other end,
The beam includes a plurality of beam elements extending between each of the plurality of folding positions;
The physical quantity sensor, wherein a cross-sectional shape of one beam element among the plurality of beam elements includes an inclined surface on an opposite surface that is a surface facing another beam element adjacent to the one beam element.   The physical quantity sensor according to claim 1, wherein the cross-sectional shape of the one beam element has a trapezoidal shape including the inclined surface on the facing surface.   The physical quantity sensor according to claim 1, wherein the cross-sectional shape of the one beam element includes a vertex having a convex shape on the facing surface.

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