JP6921010B2 - Physical quantity sensor - Google Patents

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.

Accelerometers, angular velocity sensors, and the like are known as capacitance type physical quantity sensors using MEMS technology. For example, an accelerometer has a movable portion that is displaced with respect to an input of a physical quantity and a fixed portion that is not displaced, and the movable portion is supported by a beam. Patent Document 1 discloses an acceleration sensor as a semiconductor device, and the acceleration sensor has a movable detection mass body as a movable portion and a fixed electrode as a fixed portion, and is supported as a beam that supports the movable detection mass body. It also has a spring. The capacitance type physical quantity sensor detects the 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. ..

Japanese Unexamined Patent Publication No. 2009-16717

In order for the acceleration sensor to detect acceleration with high sensitivity, it is required that the beam supporting the movable part is easily displaced. Further, since it is necessary to increase the capacitance, it is preferable that the fixed portion and the movable portion are provided as close to each other as possible. However, when components such as movable parts and beams that make up the acceleration sensor are formed in a range close to each other, the beams that support the movable parts come into contact with other beams and stick to each other due to vibrations that occur during machining or transportation. I have something to do. Since the moving portion of the physical quantity sensor to which the beam is fixed does not normally displace with respect to the input physical quantity, the desired characteristic cannot be exhibited or the physical quantity cannot be detected.

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

The physical quantity sensor according to the present invention has a first side surface, is provided in a gap formed in the surface of the semiconductor substrate, and is displaced in a direction parallel to the surface of the semiconductor substrate according to the input physical quantity. A possible mass body, 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 gap, and elastically deforms according to the displacement of the mass body. It has an elastic support portion and a second side surface facing the first side surface of the mass body, is provided on a semiconductor substrate, and is generated between the second side surface and the first side surface of the mass body according to the displacement of the mass body. It is provided with a fixed electrode for detecting the electrostatic capacity to be generated. The elastic support includes a beam that is multiplely folded back at a plurality of folded positions from one end to the other end. Beam includes a plurality of beam elements which extend respectively between the plurality of folded position. The cross-sectional shape of one beam element among the plurality of beam elements includes a slope in the facing surface which is a surface facing the other beam element adjacent to the one beam element. The vertical inclination of the facing surfaces of the beam elements is greater than the vertical inclination of the first side surface of the mass body and the vertical inclination of the second side surface of the fixed electrode.

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

Objectives, features, aspects, and advantages of the present invention will become more apparent with the following detailed description and 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 body and the 2nd comb tooth of a fixed electrode in an embodiment. 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 adjacent to each other are fixed in the prerequisite technique. It is sectional drawing which shows the state which two beam elements adjacent to each other are fixed in the prerequisite technique. It is sectional drawing which shows the state which two beam elements adjacent to each other are in contact with each other in embodiment. 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.

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

The physical quantity sensor is composed of a mass body 1, an elastic support portion 2, and a fixed electrode 3, and these are provided in a gap portion 4 formed in the plane of the semiconductor substrate. Although not shown, the surface side of the mass body 1, the elastic support portion 2, and the fixed electrode 3 is covered with a protective member. In FIG. 1, the surface side is the + z direction. A gap is provided between the mass body 1 and the elastic support portion 2 and the protective member. The protective member is, for example, a glass substrate or a silicon substrate. Further, a semiconductor substrate is provided on the back surface side of the mass body 1 and the elastic support portion 2 via the gap portion 4, and the fixed portion such as the fixed electrode 3 is fixed to the semiconductor substrate. In FIG. 1, the back surface side is the −z direction. Further, the physical quantity sensor is provided with a joint portion with the protective member and an electrode portion for transmitting and receiving an electric signal to and from the outside.

The mass body 1 is provided in the gap portion 4 formed in the plane of the semiconductor substrate. The mass body 1 has a first comb tooth 11 facing a fixed electrode 3 described later. The mass body 1 can be displaced in a direction parallel to the surface of the semiconductor substrate according to the physical quantity input to the physical quantity sensor. The direction parallel to the surface of the semiconductor substrate is the direction parallel to the xy plane in FIG. Further, the physical quantity is an acceleration here.

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

The elastic support portion 2 includes a beam that is multiplely folded back at a plurality of folded-back positions 21 from one end 2a to the other end 2b. The beam includes a plurality of beam elements 22 extending between each of the plurality of folding positions 21. That is, the elastic support portion 2 includes a plurality of beam elements 22 that are multiplely arranged from 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 in AA'shown in FIG. The cross-sectional shape of one beam element 22a among the plurality of beam elements 22 includes a slope on the facing surface 23 which is a surface facing the other beam element 22b adjacent to the one beam element 22a. In the present embodiment, the cross-sectional shape of the beam element 22 has a trapezoidal shape including a slope on the facing surface 23.

The fixed electrode 3 is provided on the semiconductor substrate and fixed. 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 body 1. FIG. 3 is a cross-sectional view showing the configuration of the first comb tooth 11 of the mass body 1 and the second comb tooth 31 of the fixed electrode 3, and shows the cross section in BB'shown in FIG. The first comb tooth 11 and the second comb tooth 31 are arranged at opposite positions with a predetermined distance from each other, and a capacitance is formed between the first comb tooth 11 and the second comb tooth 31. 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 detected change in capacitance is used to calculate the acceleration. The capacitance is determined by the distance between the first comb tooth 11 and the second comb tooth 31 and the facing area. In order to relatively reduce the influence of the outpatient, it is preferable that the distance between the first comb tooth 11 and the second comb tooth 31 is short and the areas facing each other are large. Therefore, in the physical quantity sensor of 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 described above, the physical quantity sensor in the present embodiment is a sensor that detects acceleration from the displacement of the 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 high sensitivity, it is required that the mass body 1 is 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 that is multiplely folded back at a plurality of folded-back positions 21 from one end 2a to the other end 2b, and the beam extends between each of the plurality of folded-back 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 that connects the mass body 1 and the anchor 5 without the beam being folded back. Since the mass body 1 is easy to move, 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 transportation of the physical quantity sensor, for example, an impact force or an electrostatic force, and the two beam elements 22 adjacent to each other are displaced. Contact may occur near the folding position 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, the portion where the two beam elements 22 adjacent to each other come into 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 to each other when the cross-sectional shape of the beam element 22 is rectangular, and shows a cross section in CC'shown in FIG. When 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 of the plurality of beam elements 22 is the entire surface of one of the beam elements 22a forming a rectangle. The entire surface thereof is fixed to another 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 contact with each other in the present embodiment, and shows a cross section in CC'shown in FIG. When the cross-sectional shape of the beam element 22 is trapezoidal, one beam element 22a comes into contact with another beam element 22b adjacent to the one beam element 22a at a part of the facing surface 23. The contact area of the contact portion 24 is smaller than the area of the contact portion 24 in the beam element 22 having a rectangular cross-sectional shape. As a result, the beam element 22 is less likely to be stuck.

(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 portion 2, and the fixed electrode 3 are formed by MEMS technology, that is, by a semiconductor process such as etching. The beam element 22 having a trapezoidal cross section is formed by a separate process from the first comb tooth 11 and the second comb tooth 31 having a rectangular cross section. As a result, it is possible to manufacture a physical quantity sensor having a beam element 22 in which sticking is unlikely to occur and having a first comb tooth 11 and a second comb tooth 31 that enhance the detection sensitivity of acceleration.

(effect)
Summarizing the above, the physical quantity sensor according to the embodiment is provided in the gap 4 formed in the surface of the semiconductor substrate, and can be displaced in a direction parallel to the surface of the semiconductor substrate according to the input physical quantity. The mass body 1 and one end 2a are connected to the mass body 1, the other end 2b is fixed to the semiconductor substrate, and the gap portion 4 extends in a direction parallel to the surface of the semiconductor substrate, and the displacement of the mass body 1 An elastic support portion 2 that elastically deforms in response to the above, a fixed electrode 3 that is provided in the plane of the semiconductor substrate and detects a capacitance generated between the mass body 1 and the mass body 1 according to the displacement of the mass body 1. To be equipped. The elastic support portion 2 includes a beam that is multiplely folded back at a plurality of folded-back positions 21 from one end 2a to the other end 2b. The beam includes a plurality of beam elements 22 extending between each of the plurality of folding positions 21. The cross-sectional shape of one beam element 22a among the plurality of beam elements 22 includes a slope on the facing surface 23 which is a surface facing the other beam element 22b adjacent to the one beam element 22a.

With the above configuration, it is possible to provide a physical quantity sensor that suppresses the sticking of the beam supporting the mass body 1 which is the movable portion, that is, the sticking of the beam element 22. A physical quantity sensor having an elastic support portion 2 that is easily displaced but not easily fixed can be obtained. For example, even when a physical quantity such as an excessive impact force or an electrostatic force is input from the outside, the sticking of one beam element 22a and the adjacent beam element 22b 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 according to the present embodiment has an elastic support portion 2 in which the first comb teeth 11 and the second comb teeth 31 having side surfaces perpendicular to each other are provided in close proximity to each other, and the first comb teeth 11 and the second comb teeth 31 are not easily fixed and easily displaced. Therefore, the physical quantity sensor can detect the acceleration with high sensitivity and high accuracy.

Further, in the physical quantity sensor of the embodiment, the cross-sectional shape of one beam element 22a has a trapezoidal shape including a slope on the facing surface 23.

With the above configuration, one beam element 22a and the beam element 22b adjacent thereto have slopes that are not parallel to each other on their side surfaces, so that their contact is more effectively suppressed.

(Modification 1 of the embodiment)
FIG. 8 is a cross-sectional view showing the configuration of the beam element 22 in the modified example 1 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 trapezoid shown in FIG. Even if one beam element 22a and another beam element 22b adjacent thereto come into contact with each other, the contact area is small, so that the beam element 22 is suppressed from being fixed.

(Modification 2 of the embodiment)
FIG. 9 is a cross-sectional view showing the configuration of the beam element 22 in the modified example 2 of the embodiment. The cross-sectional shape of one beam element 22a includes vertices 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 from the other beam element 22b adjacent to the one beam element 22a is minimized is provided in the middle in the depth direction. Even if one beam element 22a and another beam element 22b adjacent thereto come into contact with each other, the contact area is small, so that the beam element 22 is suppressed from being fixed. Further, in the present modification 2, since the apex 25 of the convex shape has an obtuse angle, damage to the beam element 22 due to contact can be suppressed. Therefore, the reliability of the physical quantity sensor is improved.

Further, in the embodiment and each modification, the acceleration sensor is shown as an example of the physical quantity sensor, but if the physical quantity sensor is a physical quantity sensor having a beam element 22 such as an angular velocity sensor or a vibration sensor, the same effect can be obtained.

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

Although the present invention has been described in detail, the above description is exemplary in all embodiments and the present invention is not limited thereto. It is understood that innumerable variations not illustrated can be assumed without departing from the scope of the present invention.

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

Claims (3)

A mass body having a first side surface, provided in a gap formed in the surface of the semiconductor substrate, and displaceable in a direction parallel to the surface 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 gap portion, and elastically deforms according to the displacement of the mass body. With elastic support
It has a second side surface facing the first side surface of the mass body, is provided on the semiconductor substrate, and is between the second side surface and the first side surface of the mass body according to the displacement of the mass body. With a fixed electrode to detect the capacitance generated in,
The elastic support includes a beam that is multiplely folded back at a plurality of folded positions from one end to the other end.
The beam includes a plurality of beam elements which extend respectively between the plurality of folded position location,
The cross-sectional shape of one beam element of the plurality of beam elements are seen including a slope on the opposite surface said which is a surface facing the other beam element adjacent to one of the beam element,
A physical quantity sensor in which the inclination of the beam element with respect to the vertical direction of the facing surface is larger than the inclination of the first side surface of the mass body with respect to the vertical direction and the inclination of the fixed electrode with respect to the vertical direction of the second side surface. The physical quantity sensor according to claim 1, wherein the cross-sectional shape of the one beam element has a trapezoidal shape including the slope on the facing surface. The cross-sectional shape of the one beam element, viewed contains a vertex in the shape of a convex to the facing surface,
The physical quantity sensor according to claim 1, wherein the apex is located closer to the lower surface than the upper surface of the beam element.

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