WO2012160845A1 - Mems sensor - Google Patents

Abstract

[Problem] An objective of this invention is to provide a MEMS sensor that is compact and capable of achieving greater sensitivity than before. [Solution] A movable electrode has a plurality of movable supports (50) disposed at intervals in the X1-X2 direction, and a plurality of movable electrode members (60) that extend out from the side of each movable support (50) and are disposed at intervals in the Y1-Y2 direction on each movable support (50). A fixed electrode has a plurality of movable supports (50) disposed at intervals in the X1-X2 direction, and a plurality of fixed electrode members (62) that extend out from the side of each fixed support (51) and are disposed at intervals in the Y1-Y2 direction on each fixed support (51). The movable supports and fixed supports are alternately arranged in the X1-X2 direction, neighboring movable supports and fixed supports are made into groups (66), and the movable electrode members (60) and fixed electrode members (62) are alternately arranged between the movable support and fixed support of each group.

Description

MEMS sensor

The present invention relates to a capacitive MEMS sensor formed by processing a silicon (Silicon) layer or the like, and more particularly to an electrode structure.

The capacitive MEMS sensor is configured to have a weight portion, a movable electrode portion, and a fixed electrode portion. For example, when acceleration acts on the MEMS sensor, the weight portion and the movable electrode portion move, and a capacitance change occurs between the movable electrode portion and the fixed electrode portion. It is possible to detect acceleration based on the change in capacitance.

FIG. 17 is an explanatory view (plan view) schematically showing a movable electrode portion and a fixed electrode portion of a conventional MEMS sensor. The MEMS sensor detects an acceleration in the in-plane direction, and can detect an acceleration acting in, for example, the X1-X2 direction.

FIG. 17 (a) shows the stationary state of the MEMS sensor. As shown in FIG. 17A, the MEMS sensor includes a first detection unit 1 and a second detection unit 2, and the first detection unit 1 and the second detection unit 2 each have a plurality of comb teeth. The fixed electrodes 1a and 2a and the plurality of comb-teeth-shaped movable electrodes 1b and 2b are alternately arranged at intervals in the X1-X2 direction.

As shown in FIG. 17A, in the first detection unit 1, a first gap a having a predetermined distance between the movable electrode 1b and the fixed electrode 1a positioned on the X1 side with respect to the movable electrode 1b. ₀ is provided. Also the second detector 2, the second gap b ₀ of a predetermined distance between the fixed electrode 2a positioned on the X2 side and the movable electrode 2b with respect to the movable electrode 2b is provided.

As shown in FIG. 17B, when the movable electrode 1b in the first detection unit 1 and the movable electrode 2b in the second detection unit 2 respectively move in the X1 direction by the action of acceleration, FIG. first gap a ₁ in is smaller than the gap a ₀ in the stationary state shown in FIG. 17 (a), while the second gap b ₁ than the gap b ₀ in the stationary state shown in FIG. 17 (a) Will also grow.

Further, as shown in FIG. 17C, when the movable electrode 1b in the first detection unit 1 and the movable electrode 2b in the second detection unit 2 respectively move in the X2 direction due to the action of acceleration, FIG. ) the first gap a ₂ in is larger than the gap a ₀ in the stationary state shown in FIG. 17 (a), whereas, the gap b ₀ of the second gap b ₂ is at rest shown in FIG. 17 (a) It becomes smaller than.

As shown in FIGS. 17B and 17C, the accelerations acting in the X1-X2 direction change the gaps a and b between the movable electrodes 1b and 2b and the fixed electrodes 1a and 2a. This changes the capacitance. At this time, the change in electrostatic capacitance in the first detection unit 1 and the change in electrostatic capacitance in the second detection unit 2 are reversed.

Patent Document 1 describes an electrode structure that causes a capacitance change by a change in the gap between the movable electrode and the fixed electrode, as in FIG. 17 described above. In addition, Patent Document 1 also describes an electrode structure capable of detecting a capacitance change due to a change in the facing area between a movable electrode and a fixed electrode. The electrode structure which produces an electrostatic capacitance change by the fluctuation | variation of an opposing area is also described in patent document 2, 3. FIG.

JP 2007-139505 A Japanese Patent Application Laid-Open No. 2002-22446 JP 10-313123 A

However, in the conventional electrode structure, it has been difficult to sufficiently improve the sensitivity as well as to miniaturize the MEMS sensor.

Therefore, the present invention is intended to solve the above-mentioned conventional problems, and it is an object of the present invention to provide a MEMS sensor which is smaller and can obtain high sensitivity as compared with the prior art.

The present invention relates to a MEMS sensor having a movable electrode portion and a fixed electrode portion,
When two directions orthogonal to each other in a horizontal plane are a first direction and a second direction, the first direction is a moving direction of the movable electrode portion,
The movable electrode portions are arranged at intervals in the first direction, and extend in the second direction, and a plurality of movable support portions are formed, and each movable support portion in the first direction A plurality of movable electrode elements extending from the side portion of the second support and spaced apart in the second direction at each movable support portion,
The fixed electrode portion is arranged at intervals in the first direction, and a plurality of fixed support portions whose extension direction from the proximal end side to the distal end side is opposite to the movable support portion, and each fixed A plurality of fixed electrodes which extend from the side of the support in a direction opposite to the extending direction of the movable electrode and are spaced apart from each other in the second direction by each fixed support; Have
A plurality of the movable support portions and a plurality of the fixed support portions are alternately arranged at intervals in the first direction, and the adjacent movable support portions and the fixed support portions are combined. The plurality of movable electrode elements and the plurality of fixed electrode elements are alternately arranged at intervals in the second direction between the movable support portion and the fixed support portion of each set. Yes,
The movement of the movable electrode portion in the first direction detects a change in electrostatic capacitance based on a change in the facing area between each movable electrode and each fixed electrode.

In the present invention, in the same detection unit, a plurality of movable support portions constituting the movable electrode portion and a plurality of fixed support portions constituting the fixed electrode portion are alternately arranged in the first direction. Then, the movable support portions and the fixed support portions adjacent to each other are made in the same set, and a plurality of movable electrode elements and the fixed electrode elements are arranged in the second direction between the movable support portion and the fixed support portion in each set. Arranged alternately. As a result, a large number of movable electrode elements and fixed electrode elements can be efficiently disposed in the detection unit, and a smaller size and higher sensitivity can be obtained as compared with the conventional electrode structure. In Patent Documents 1 to 3, the plurality of movable support portions and the plurality of fixed support portions are not alternately arranged at intervals in the first direction. Then, as in the present invention, the movable support portion and the fixed support portion are divided into a plurality of sets, and in each set, the movable electrode element and the fixed electrode element are alternately arranged at an interval in the second direction. The electrode structure is not disclosed.

According to the electrode structure of the present invention, compared to the electrode structure disclosed in the patent document, it is possible to efficiently increase the variation area of the facing area between the movable electrode and the fixed electrode in the same detection unit. Can be raised enough.

Further, in the electrode structure in which the capacitance (the distance) between the movable electrode and the fixed electrode is changed to cause the capacitance change as shown in FIG. 17, the capacitance is in inverse proportion to the gap (the distance) As shown as an example, when the sensitivity is increased, the change in capacitance becomes abrupt with respect to the change in distance, and the effective detection range (dynamic range) of the physical quantity by the MEMS sensor becomes narrow. Furthermore, there is also a problem that the linearity of sensitivity within the effective detection range is deteriorated.

On the other hand, in the electrode structure in which the capacitance is changed by changing the facing area between the movable electrode and the fixed electrode as in the present invention, the capacitance is proportional to the facing area, and the electrode described above The effective detection range (dynamic range) of the physical quantity can be broadened and the linearity of the sensitivity within the effective detection range can be effectively improved, as compared with the method of changing the capacitance by the fluctuation of the distance between Become.

The present invention includes a first detection unit and a second detection unit, and each of the detection units includes the movable electrode unit and the fixed electrode unit.
The extending directions of the movable electrode element and the fixed electrode element in the first direction are reversed between the first detection unit and the second detection unit, and are obtained by the first detection unit. Preferably, a differential output can be obtained by the change in capacitance and the change in capacitance obtained by the second detection unit.

In the above configuration, each of the first detection unit and the second detection unit is divided into a plurality of detection areas, and each of the detection areas is provided with the movable electrode section and the fixed electrode section. Is preferred. As a result, the movable electrode portion and the fixed electrode portion can be efficiently arranged while maintaining the strength of each electrode portion, and the miniaturization of the MEMS sensor can be realized, and the sensitivity can be more effectively enhanced.

In the present invention, in the stationary state, the distance from the side portion of the movable support to the tip of the fixed electrode in the first direction is L1, and the second of the movable electrode and the fixed electrode is (L1-L2) ² / T1 is 2 (μm), where T1 is the width dimension in the direction of L and L2 is the maximum movable distance when the movable electrode moves in the direction toward the fixed support portion. Or more) is preferable. Thereby, the linearity of the sensitivity can be effectively improved.

Further, in the present invention, in the stationary state, the distance in the first direction between the movable support portion of the adjacent set and the fixed support portion is L3, and the movable electrode element and the fixed electrode element Assuming that the width dimension in the second direction is T1, and the maximum movable distance when the movable electrode element moves in the direction approaching the fixed support portion of the adjacent set is L4, (L3-L4) It is preferable that ² × T 1 be 4 (μm ³ ) or more. This can effectively improve the linearity of sensitivity.

According to the MEMS sensor of the present invention, it is possible to obtain a small size and high sensitivity as compared with the conventional electrode structure.

FIG. 1 is a plan view showing a functional layer of a MEMS sensor according to an embodiment of the present invention. Fig.2 (a) is a partial enlarged plan view of a stationary state which shows a part of a movable electrode part shown in FIG. 1 and a fixed electrode part, FIG.2 (b) receives acceleration from the stationary state of Fig.2 (a). It is a partial enlarged plan view which shows the state which the movable electrode part moved to X2 direction. 3 (a) is a partially enlarged plan view of a stationary state showing a part of the movable electrode portion and the fixed electrode portion shown in FIG. 1, and FIG. 3 (b) is a direction of the movable electrode portion X1 from the stationary state shown in FIG. 3 (c) is a partially enlarged plan view showing a state in which the movable electrode portion has moved in the X2 direction from the stationary state shown in FIG. FIG. 4 is a partial longitudinal cross-sectional view of the MEMS sensor shown in FIG. 1 taken along the line AA and viewed in the direction of the arrow. FIG. 5 (a) is a simulation result showing the relationship between the acceleration and the capacitance in the comparative example, and FIG. 5 (b) is a graph showing the relationship between FIG. 5 (a) without changing the size of the detection unit of the MEMS sensor. Is also a simulation result showing the relationship between the acceleration and the capacitance when the sensitivity is increased. FIG. 6 shows differential output curves of the capacitance change in the graph of (1) in FIG. 5A and the capacitance change in the graph of (2). FIG. 7 is a simulation result showing the relationship between acceleration and sensitivity. FIG. 8 is a simulation result showing the relationship between the acceleration and the capacitance in the example. FIG. 9 shows a differential output curve of the capacitance change shown in the graph (3) in FIG. 8 and the capacitance change shown in the graph (4). FIG. 10 is a simulation result showing the relationship between acceleration and sensitivity in the example. It is a simulation result which shows the relationship between the acceleration and the sensitivity in the Example which shows the relationship between the magnitude | size of L1, and the largest fluctuation range of a sensitivity. It is a simulation result which shows the relationship between L1-L2 (2 μm) and the maximum swing width of sensitivity. It is a simulation result which shows the relationship between (L1-L2) ² / T1 and the maximum swing width of sensitivity. It is a simulation result which shows the relationship between the acceleration and the sensitivity in the Example which shows the relationship between the magnitude | size of L3, and the largest fluctuation range of a sensitivity. It is a simulation result which shows the relationship between L3-L4 (2 μm) and the maximum swing width of sensitivity. It is a simulation result which shows the relationship between (L3-L4) ² × T 1 and the maximum swing of the sensitivity. FIG. 14 is an explanatory view (plan view) for schematically showing a conventional electrode structure and for explaining a change in electrostatic capacity due to the movement of the movable electrode in the X1-X2 direction.

FIG. 1 is a plan view showing a functional layer of a MEMS sensor according to an embodiment of the present invention, and FIG. 2 (a) is a partially enlarged plan view of a stationary state showing a part of a movable electrode portion and a fixed electrode portion shown in FIG. 2 (b) is a partially enlarged plan view showing the movable electrode portion moved in the X2 direction under acceleration from the stationary state of FIG. 2 (a), and FIG. 3 (a) is the movable electrode shown in FIG. 3 (b) is a partially enlarged plan view showing the movable electrode portion moved in the X2 direction from the stationary state shown in FIG. 1, FIG. (C) is a partial enlarged plan view showing a state in which the movable electrode part has moved in the X1 direction from the stationary state shown in FIG. 1, and FIG. 4 is a partial longitudinal sectional view of the MEMS sensor in the present embodiment.

As shown in FIG. 1, the MEMS sensor S has, for example, a rectangular shape having a long side in the X1-X2 direction (first direction) and a short side in the Y1-Y2 direction (second direction). The MEMS sensor S shown in FIG. 1 constitutes a single-axis detection acceleration sensor for detecting an acceleration acting in the X1-X2 direction.

As shown in FIG. 4, in the MEMS sensor S, the SOI substrate 13 in which the support substrate 10 and the functional layer 11 are stacked via the insulating layer 12, and the SOI substrate 13 facing in the height direction via the metal connection portion 14. And the wiring substrate 15 joined together. Here, in FIG. 1, only the functional layer 11 of the MEMS sensor S is taken up, and further, the weight 22 and the electrode portion positioned inside the frame 16 (see FIG. 4) of the functional layer 11 are illustrated.

For example, the support substrate 10 and the functional layer 11 are made of silicon, and the insulating layer 12 is made of SiO ₂ .

As shown in FIGS. 1 and 4, in the functional layer 11, the fixed electrode portions 20a to 20d, the movable electrode portions 21a to 21d, the weight portion 22 and the frame 16 are separated from the silicon substrate.

As shown in FIG. 1, the planar shape of the functional layer 11 is rotationally symmetrical 180 degrees with respect to the center (center of gravity) O in the X1-X2 direction and the Y1-Y2 direction, and passes through the center O in the X direction It is symmetrical in the vertical direction (Y1-Y2 direction) with respect to the extending line.

As shown in FIG. 1, the first detection unit 23 is provided on the X1 side with respect to the center O, and the second detection unit 24 is provided on the X2 side. Furthermore, the first detection unit 23 is divided into a first detection area 23a on the Y1 side and a first detection area 23b on the Y2 side. The second detection unit 24 is divided into a second detection area 24a on the Y1 side and a second detection area 24b on the Y2 side.

As shown in FIG. 1, the first detection area 23a on the Y1 side is composed of the fixed electrode portion 20a and the movable electrode portion 21a. The first detection area 23b on the Y2 side is composed of the fixed electrode portion 20b and the movable electrode portion 21b. Further, the second detection region 24a on the Y1 side is configured by the fixed electrode portion 20c and the movable electrode portion 21c. The second detection area 24b on the Y2 side is composed of the fixed electrode portion 20d and the movable electrode portion 21d. The insulating layer 12 is not formed between the movable electrode portions 21a to 21d and the support substrate 10 (see FIG. 4). On the other hand, the fixed electrode portions 20a to 20d are fixed to the support substrate 10 via the insulating layer 12.

The portion excluding the first detection unit 23 and the second detection unit 24 in the movable region is the weight 22. In FIG. 1, the weight 22 is located around the first detection unit 23 and the second detection unit 24.

As shown in FIG. 1, the weight portion 22 is configured to have an X1 side region 22a, a Y1 side region 22b, an X2 side region 22c, and a Y2 side region 22d.

As shown in FIG. 1, a first anchor portion 26 formed separately from the weight portion 22 is provided closer to the Y1 side region 22 b of the weight portion 22 than the Y1 side region 22 b. The first anchor portion 26 is formed to be elongated in the X1-X2 direction. The first anchor portion 26 is fixed via the support substrate 10 and the insulating layer 12 shown in FIG.

Further, as shown in FIG. 1, a second anchor portion 27 formed separately from the weight portion 22 is provided on the Y2 side of the Y2 side region 22 d of the weight portion 22. The second anchor portion 27 is formed to be elongated in the X1-X2 direction. The second anchor portion 27 is fixed via the support substrate 10 and the insulating layer 12 shown in FIG.

As shown in FIG. 1, the X1 side region 22 a of the weight portion 22 extends further to the X1 side than the first anchor portion 26 and the second anchor portion 27. A gap (interval) 28 having a predetermined width is formed between the Y1 side end 22a1 of the X1 side area 22a and the first anchor portion 26. In addition, a gap 29 having a predetermined width is formed between the Y2 side end 22a2 of the X1 side region 22a and the second anchor portion 27. The width dimensions of the gaps 28 and 29 in the X1-X2 direction are the same, and the gaps 28 and 29 restrict the dimension in which the weight 22 can move in the X1 direction from the resting state of FIG.

Further, as shown in FIG. 1, the X2 side region 22c of the weight portion 22 extends further to the X2 side than the first anchor portion 26 and the second anchor portion 27. A gap 30 having a predetermined width is formed between the Y1 side end 22c1 of the X2 side region 22c and the first anchor portion 26. Further, a gap 31 having a predetermined width is formed between the Y2 side end 22c2 of the X2 side region 22c and the second anchor portion 27. The width dimensions of the gaps 30 and 31 in the X1-X2 direction are the same, and the gaps 30 and 31 regulate the dimension in which the weight 22 can move in the X2 direction from the stationary state of FIG.

Further, as shown in FIG. 1, in the X1 side region 22 a of the weight portion 22, a space 35 which extends from the respective gaps 28 and 29 to the inside in the Y1-Y2 direction and has a width slightly larger than the respective gaps 28 and 29. , 36 are formed. Further, in the X2-side region 22c of the weight portion 22, space portions 37, 38 which extend from the respective gaps 30, 31 to the inside in the Y1-Y2 direction and whose width dimension is slightly wider than the respective gaps 30, 31 are formed There is.

In each of the space portions 35 to 38, spring portions 40 to 43 connecting the anchor portions 26 and 27 and the weight portion 22 are formed. The respective spring portions 40 to 43 are portions where the silicon substrate is cut out integrally with the respective anchor portions 26 and 27 and the weight portion 22 to have elasticity in the X1-X2 direction. The insulating layer 12 is not formed between the spring portions 40 to 43 and the weight portion 22 and the support substrate 10 (see FIG. 4). Therefore, when acceleration is received, the weight portion 22 can be moved in the X1-X2 direction by elastic deformation of the spring portions 40-43.

As shown in FIG. 1, the respective spring portions 40 to 43 are formed long in the Y1-Y2 direction, and are formed so as to be folded back between the respective anchor portions 26 and 27 and the weight portion 22. As a result, each of the spring portions 40 to 43 has rigidity in the Y1-Y2 direction, and suppresses the vibration of the weight portion 22 in the Y1-Y2 direction.

As shown in FIG. 1, the movable electrode portions 21a to 21d are formed integrally with the weight portion 22. Each of the movable electrode portions 21a to 21d is provided with a plurality of movable support portions 50 extending in the Y1-Y2 direction at intervals in the X1-X2 direction. Each movable support portion 50 extends inward from the Y1 side region 22b and the Y2 side region 22d of the weight portion 22. In FIG. 1, only one movable support portion 50 is denoted by a reference numeral for each of the movable electrode portions 21a to 21d. In addition, as shown in FIG. 1, the fixed electrode portions 20a to 20d are spaced apart from the fixed base 52 in the X1-X2 direction, and extend from the fixed base 52 in the Y1-Y2 direction. A plurality of fixed support portions 51 are provided. Note that, in FIG. 1, only one fixed support portion 51 is given a code for each of the fixed electrode portions 20a to 20d. In each detection area 23a, 23b, 24a, 24b, the extending direction of the movable support 50 and the fixed support 51 is reverse. In each of the detection areas 23a, 23b, 24a, 24b, a plurality of movable support portions 50 and a plurality of fixed support portions 51 are alternately arranged at intervals in the X1-X2 direction.

As shown in FIG. 4, each fixed base 52 is fixed via the support substrate 10 and the insulating layer 12. In addition, although the insulating layer 12 may be interposed between each fixed support 51 and the support substrate 10, since the fixed support 51 is thin, the insulating layer 12 between the fixed support 51 and the support substrate 10 is removed by etching. As shown in FIG. 4, the fixed support portion 51 floats from the support substrate 10 in the same manner as the movable support portion 50. However, since each fixed support portion 51 is connected to the fixed base 52, it does not move in the X1-X2 direction even if it receives acceleration.

As shown in FIG. 1, the comb-like movable members are spaced apart in the Y1-Y2 direction from the side in the X1-X2 direction of each movable support 50 and the side in the X1-X2 direction from each fixed support 51. An electrode and a fixed electrode are formed. The movable electrode element and the fixed electrode element will be described with reference to FIGS. 2 and 3.

FIG. 2 (a) shows a first detection area 23a and a second detection area 24a around the circle II shown in FIG. As shown in FIG. 2A, in the first detection area 23a, a movable support 50 elongated in the Y2 direction from the inner portion 22b1 of the Y1 side area 22b of the weight 22 is formed in a straight line. In the first detection area 23a, a plurality of movable support portions 50 are formed at intervals in the X1-X2 direction. Similarly, in the second detection area 24a, a movable support 50 elongated in the Y2 direction from the inner portion 22b1 of the Y1 side area 22b of the weight 22 is formed in a straight line. In the second detection area 24a, a plurality of movable support portions 50 are formed at intervals in the X1-X2 direction.

As shown in FIG. 2A, movable electrode elements 60 extending in the X2 direction from the X2 side end 50a of the movable support portion 50 provided in the first detection area 23a are spaced in the Y1-Y2 direction. Multiple bottles are formed. In FIG. 2A, only one movable electrode element 60 is given a code with respect to the movable support portion 50.

Further, as shown in FIG. 2A, movable electrode elements 61 extending in the X1 direction from the X1 side end 50b of the movable support portion 50 provided in the second detection area 24a are spaced in the Y1-Y2 direction. A plurality of bottles are formed. In FIG. 2A, only one movable electrode element 61 is attached to the movable support portion 50, and the reference numeral is attached. As shown in FIG. 2A, the length dimension of the movable electrode element 60, 61 in the X1-X2 direction is sufficiently shorter than the length dimension of the movable support 50 in the Y1-Y2 direction. There is.

Further, as shown in FIG. 2A, in each of the detection areas 23a and 24a, a fixed support portion 51 elongated from the fixed base 52 in the Y1 direction is formed in a linear shape. As shown in FIGS. 1 and 3, the fixed support portions 51 are formed at intervals in the X1-X2 direction in a plurality of detection regions 23 a and 24 a, and each fixed support portion 51 is a movable support portion 50. And are arranged alternately.

As shown in FIG. 2A, fixed electrode elements 62 extending in the X1 direction from the X1 side end 51b of the fixed support portion 51 provided in the first detection area 23a are spaced in the Y1-Y2 direction. Multiple bottles are formed. As shown in FIG. 2A, these fixed electrode elements 62 are alternately arranged in the Y1-Y2 direction at intervals from the movable electrode element 60. In FIG. 2A, only one fixed electrode element 62 is attached to the fixed support portion 51 with a reference numeral.

Further, as shown in FIG. 2A, fixed electrode elements 63 extending in the X2 direction from the X2 side end 51a of the fixed support portion 51 provided in the second detection area 24a are spaced in the Y1-Y2 direction. A plurality of bottles are formed. As shown in FIG. 2A, these fixed electrodes 63 are alternately arranged in the Y1-Y2 direction at intervals from the movable electrode 61. In FIG. 2A, only one fixed electrode 63 is attached to the fixed support portion 51, and the reference numeral is attached. As shown in FIG. 2A, the length dimension of the fixed electrode elements 62 and 63 in the X1-X2 direction is sufficiently shorter than the length dimension of the fixed support portion 51 in the Y1-Y2 direction. There is.

In FIG. 2A, the electrode structure of the first detection area 23a on the Y1 side and the second detection area 24a on the Y1 side shown in FIG. 1 has been described, but the first detection area 23b on the Y2 side and the second on the Y2 side Each electrode structure in the detection region 24b is in a line symmetrical relationship with the electrode structure of FIG. 2A with respect to a line extending in the X1-X2 direction through the center O.

FIG. 3 (a) illustrates the electrode structure around circle III shown in FIG.
As shown in FIG. 3A, in the same detection area 23a, the movable support portions 50 and the fixed support portions 51 alternately arranged in the X1-X2 direction are respectively combined into one set 66. A plurality of movable electrode elements 60 and a plurality of fixed electrode elements 62 are alternately arranged at intervals in the Y1-Y2 direction between the movable support portion 50 and the fixed support portion 51 of each set 66. There is.

In the stationary state (state in which no physical quantity is applied) shown in FIG. 3A, the distance from the X2-side end 50a of the movable support 50 to the tip 62a of the fixed electrode 62 in the X1-X2 direction is L1. is there. The width dimension of the movable electrode 60 and the fixed electrode 62 in the Y1-Y2 direction is T1. In FIG. 3A, the width dimension of the movable electrode 60 is represented by T1.

Further, in the stationary state shown in FIG. 3A, an interval in the X1-X2 direction between the movable support portion 50 of the adjacent pair 66 and the fixed support portion 51 is indicated by L3. Further, in the stationary state shown in FIG. 3A, the overlapping length of the movable electrode element 60 and the fixed electrode element 62 is L5.

Each movable electrode element 60 is located substantially at the center between the fixed electrode elements 62 located on both sides in the Y1-Y2 direction.

As shown in FIG. 3B, when the MEMS sensor S receives acceleration and the weight moves in the X2 direction, each movable support 50 also moves in the X2 direction, and each movable electrode 60 in each group 66 The facing area (the area facing in the Y1-Y2 direction) between each fixed electrode element 62 is larger than that in the stationary state of FIG. 3A. At this time, assuming that the maximum movable distance when the movable support portion 50 moves in the X2 direction is L2, and the movable support portion 50 moves L2 in FIG. 3B, the stationary state shown in FIG. The interval L1 in the state is L1-L2. The interval L3 in the stationary state in FIG. 3A is L3 + L2.

Further, as shown in FIG. 3C, when the MEMS sensor S receives acceleration and the weight 22 moves in the X1 direction, each movable support 50 also moves in the X1 direction, and each movable electrode in each group 66 The facing area between the element 60 and each fixed electrode element 62 is smaller than that in the stationary state of FIG. 3 (a). At this time, assuming that the maximum movable distance when the movable support portion 50 moves in the X1 direction is L4, and the movable support portion 50 moves L4 in FIG. 3B, the stationary state shown in FIG. The interval L3 in the state is L3-L4. The interval L1 in the stationary state in FIG. 3A is L1 + L4.

The variation relationships of the distances shown in FIGS. 3A, 3B, and 3C are the same in the first detection area 23b on the Y2 side shown in FIG.

On the other hand, as shown in FIG. 3 (b), when the MEMS sensor S receives acceleration and the weight moves in the X2 direction, the movable electrodes in the first detection areas 23a and 23b are as described in FIG. 3 (b). Although the facing area between the child 60 and the fixed electrode 62 increases, the facing area between the movable electrode 61 and the fixed electrode 63 decreases in the second detection regions 24a and 24b. As shown in FIGS. 1 and 2, in the first detection areas 23a and 23b and the second detection areas 24a and 24b, the X1-X2 directions of the movable electrode elements 60 and 61 and the fixed electrode elements 62 and 63. This is because the extending direction is reversed.

As a result, when the opposing area between the movable electrode 60 and the fixed electrode 62 increases in the first detection regions 23a and 23b and the capacitance increases, the movable electrode 61 and the second detection regions 24a and 24b increase. The opposing area between the fixed electrode pieces 63 is reduced to reduce the capacitance. On the other hand, when the opposing area between the movable electrode element 60 and the fixed electrode element 62 decreases in the first detection areas 23a and 23b and the capacitance decreases, the second detection areas 24a and 24b are fixed to the movable electrode element 61. The opposing area between the electrode elements 63 is increased to increase the capacitance.

The maximum movable distances L2 and L4 of the weight portion 22 and the movable electrode portions 21a to 21d described above are regulated by the sizes of the gaps 28 to 31 shown in FIG. 1 in the X1-X2 direction.

The frame 16 not shown in FIG. 1 is separated from the weight 22 shown in FIG. 1 and surrounds the periphery of the weight 22. As shown in FIG. It is fixed through twelve.

As shown in FIG. 4, the frame 16 and the fixed bases 52 constituting the functional layer 11 and the wiring board 15 are connected by the metal connection portion 14. In FIG. 4, the wiring substrate 15 is illustrated as a single layer structure, but in practice, an insulating layer is formed on the surface of the silicon substrate (the surface facing the functional layer 11), and the wiring layer 70 is formed inside the insulating layer. It is a formed structure. The wiring layer 70 is electrically connected to the fixed base 52 via the metal connection portion 14, and the wiring layer 70 is connected to the pad portion 71 outside the frame 16.
Further, although not shown in FIG. 4, a ground pad or the like is also formed on the outside of the frame 16.

In the present embodiment, it is possible to obtain a differential output from the capacitance change obtained from the first detection unit 23 and the capacitance change obtained from the second detection unit 24. The action direction of the acceleration can be known from the magnitude of the acceleration and the sign (plus value or minus value) of the differential output based on the differential output.

(Experiment 1; Relationship between Acceleration and Capacitance and Relationship between Acceleration and Sensitivity in Comparative Example)
The movable electrode elements 60 and 61 and the fixed electrode elements 62 and 63 shown in FIGS. 1 to 3 are not formed, and a plurality of movable support portions 50 and a plurality of fixed support portions 51 are comb-shaped electrodes. An experiment was conducted using the electrode structure as a comparative example. In the comparative example, when the weight 22 moves in the X1-X2 direction by receiving an acceleration, it is possible to obtain a capacitance change by changing the gap (distance) between the comb-like electrodes (see FIG. 17).

In addition, also in the comparative example shown by the following experiment, structures other than an electrode structure are the same as an Example. Also in the embodiment and the comparative example, the detection portions shown in FIG. 1 have the same size, but in the comparative example, the movable electrode elements 60 and 61 and the fixed electrode elements 62 and 63 are omitted as in the embodiment. The space between the movable electrode (portion corresponding to the movable support portion 50 of the embodiment) and the fixed electrode (portion corresponding to the fixed support portion 51 of the embodiment) is reduced to increase the number of electrodes. The principle of the capacitance change in the comparative example is as described in FIG.

FIG. 5A is a simulation result showing the relationship between the acceleration and the capacitance in the comparative example. In the experiment of FIG. 5A, the size of the gaps a and b shown in FIG. 17 is set to 1.7 μm. Here, in the graph (1) shown in FIG. 5A, when a positive acceleration is applied, the gap between the movable electrode and the fixed electrode is increased, the capacitance is decreased, and a negative acceleration is applied. The change in the electrostatic capacitance in the detection part which the gap between a movable electrode and a fixed electrode becomes small, and an electrostatic capacitance increases is shown. On the other hand, in the graph (2) shown in FIG. 5A, when a negative acceleration is applied, the gap between the movable electrode and the fixed electrode is increased, the capacitance is decreased, and a positive acceleration is applied. The change in the electrostatic capacitance in the detection part which the gap between a movable electrode and a fixed electrode becomes small, and an electrostatic capacitance increases is shown. Here, the “plus value” and the “minus value” indicate, for example, a relationship in which the minus value is the reverse X2 direction, assuming that the acceleration of the plus value is the X1 direction.

FIG. 5 (b) shows the acceleration and the electrostatics when the spring constant of the spring parts 40 to 43 is made smaller than that of FIG. 5 (a) to increase the sensitivity without changing the size of the detection part of the MEMS sensor. It is a simulation result which shows a relation with capacity. In the experiment of FIG. 5B, the size of the gaps a and b shown in FIG. 17 was set to 1.7 μm. As shown in FIG. 5 (b), the change in capacitance becomes sharper than in FIG. 5 (a), and the effective detection range (dynamic range) r2 of acceleration in FIG. 5 (b) is shown in FIG. 5 (a). It has been found that the dynamic range r1 is narrower than the dynamic range r1.

FIG. 6 shows a differential output curve based on the capacitance change in the graph of (1) in FIG. 5A and the capacitance change in the graph of (2). As shown in FIG. 6, it was found that as the acceleration (absolute value) increases, the change in capacitance (differential output) increases.

FIG. 7 is a simulation result showing the relationship between acceleration and sensitivity. The sensitivity is indicated by the slope of the differential output curve shown in FIG. As shown in FIG. 7, it was found that the sensitivity curve did not become flat and linear with respect to the acceleration (absolute value), and the sensitivity curve changed more greatly as the acceleration (absolute value) became larger.

(Experiment 2; Relationship between Acceleration and Capacitance and Relationship between Acceleration and Sensitivity in Example)
FIG. 8 is a simulation result showing the relationship between the acceleration and the capacitance in the example. In the experiment of FIG. 8, L1 and L3 shown in FIG. 3A were set in the range of 4 to 6 μm, and the width dimension T1 of the electrode was set to 1.2 μm. Here, in the graph of (3) shown in FIG. 8, when an acceleration with a positive value acts, the opposing area between the movable electrode and the fixed electrode decreases and the capacitance decreases (the state of FIG. 3 (c)) When a negative acceleration is applied, the opposing area between the movable electrode and the fixed electrode increases and the capacitance increases (state in FIG. 3B). ing. On the other hand, in the graph of (4) shown in FIG. 8, when an acceleration with a negative value acts, the opposing area between the movable electrode and the fixed electrode decreases, the capacitance decreases, and an acceleration with a positive value acts. The electrostatic capacitance change in the detection part which the opposing area between a movable electrode element and a fixed electrode element becomes large, and an electrostatic capacitance increases is shown. Here, the “plus value” and the “minus value” indicate, for example, a relationship in which the minus value is the reverse X2 direction, assuming that the acceleration of the plus value is the X1 direction.

FIG. 9 shows a differential output curve based on the capacitance change shown in the graph (3) in FIG. 8 and the capacitance change shown in the graph (4). Moreover, FIG. 10 is a simulation result which shows the relationship between the acceleration and the sensitivity in an Example. The sensitivity is indicated by the slope of the differential output curve shown in FIG.

In the embodiment, as shown in FIG. 9, the differential output curve is linearly inclined with respect to the acceleration (absolute value) (linear curve), and as shown in FIG. 10, the sensitivity is substantially equal to the acceleration (absolute value). It turned out to be flat.

Comparing the sensitivity in the comparative example of FIG. 7 with the sensitivity in the example of FIG. 10, it was found that the sensitivity of FIG. 10 is larger than the sensitivity at the bottom of the sensitivity curve shown in FIG.

Therefore, in the comparative example, if it is intended to obtain the same sensitivity as that of the example in the area with a small acceleration, for example, the number of comb-teeth electrodes must be increased to increase the opposing area of the electrodes. It can be seen that the size will increase. In the embodiment, while maintaining high sensitivity of the MEMS sensor as compared with the comparative example, it is possible to widen the effective detection range (dynamic range) of acceleration and to improve the linearity of the sensitivity within the effective detection range. I knew I could.

(Experiment 3; about experiment of L1 shown in FIG. 3 (a))
Next, the width dimension T1 of the electrode shown in FIG. 3A was set to 1.2 μm, 0.8 μm or 1.6 μm, and L3 in FIG. 3A was fixed at 5 μm.

Further, as shown in FIG. 3B, the maximum movable distance L2 of the movable support portion 50 when the movable electrode elements 60 approach the fixed support portion 51 which is a set is 2 μm. 2 μm corresponds to the case where an acceleration (absolute value) of 100 G acts.

As shown in FIG. 11, L1 is about 3 μm or more, the sensitivity (at rest) in the stationary state in FIG. 3A is measured, and the movable support 50 is 2 μm in the direction of the fixed support 51. The sensitivity when moving (100 G (absolute value)) was measured. Then, [Sensitivity (100 G (absolute value)) / Sensitivity (at rest)] × 100 (%) was taken as the maximum swing width of the vertical axis in FIG.

As shown in FIG. 11, it was found that the maximum fluctuation range of the sensitivity increases as L1 decreases. The smaller the maximum swing of the sensitivity, the better. For practical use, it is preferable to set the maximum swing (absolute value) to 10% or less. It was found that it is preferable to set L1 to about 3.6 μm or more in order to set the maximum fluctuation range of the sensitivity to 10% or less. As described above, the fact that the maximum swing width of sensitivity is increased due to the decrease in L1 is not only the change in the facing area between the movable electrode and the fixed electrode, but also the change in portions other than the facing area. This is because the capacitance is easily changed.

FIG. 12 shows the relationship between L1-L2 (L2 is 2 μm) shown in FIG. 3B and the maximum swing of the sensitivity. As shown in FIG. 12, it was found that the maximum fluctuation width (absolute value) of the sensitivity can be suppressed to 10% or less by setting L1-L2 to approximately 1.6 μm or more.

Subsequently, (L 1 −L ² ) ² / T 1 is calculated, and FIG. 13 shows the relationship between (L 1 −L ² ) ² / T 1 and the maximum fluctuation range of the sensitivity.

As shown in FIG. 13, it was found that (L 1 −L ² ) ² / T 1 has substantially the same curve regardless of the width dimension T 1 of the electrode element (normalization). Then, as shown in FIG. 13, it was found that the maximum swing width (absolute value) of the sensitivity can be suppressed to 10% or less by setting (L1−L2) ² / T1 to 2 (μm) or more.

(Experiment 4; about the experiment of optimization of L3 shown in FIG. 3 (a))
Next, the width dimension T1 of the electrode shown in FIG. 3A was 1.2 μm, and L1 in FIG. 3A (at rest) was fixed at 5 μm. Then, as shown in FIG. 3C, the maximum movable distance L4 of the movable support portion 50 when each movable electrode element 60 approaches the fixed support portion 51 of the adjacent set is 2 μm. 2 μm corresponds to an acceleration of 100 G (absolute value). As shown in FIG. 14, L3 is about 3 μm or more, the sensitivity (at rest) in the stationary state in FIG. 3 (a) is measured, and as described above, the movable support 50 is 2 μm, and the adjacent set is The sensitivity (100 G) when moving in the direction of the fixed support 51 of the above was measured. Then, [Sensitivity (100 G (absolute value)) / Sensitivity (at rest)] × 100 (%) was taken as the maximum swing width of the vertical axis in FIG. The experimental result is a graph of (5) shown in FIG.

Furthermore, an experiment was also conducted in which the width dimension T1 of the electrode shown in FIG. 3A was 1.2 μm, and L1 in FIG. 3A (at rest) was interlocked with L3. That is, when L3 is 4 μm, L1 is also set to 4 μm. Then, as in the experiment of the graph of (5) above, the maximum movable distance L4 of the movable support 50 when the movable electrode element 60 approaches the fixed support 51 of the next set is 2 μm (100 G ( [Sensitivity (100 G (absolute value)) / Sensitivity (at rest)] × 100 (%) was measured as the acceleration action (absolute value). The experimental result is a graph of (6) shown in FIG.

As shown in FIG. 14, in order to set the maximum amplitude (absolute value) of the sensitivity to 10% or less, it was found that it is preferable to set L3 to about 3.8 μm or more.

FIG. 15 shows the relationship between L3-L4 (L4 is 2 μm) shown in FIG. 3C and the maximum swing of the sensitivity. The graph of (5) shown in FIG. 15 is based on the graph of (5) of FIG. 14, and the graph of (6) shown in FIG. 15 is based on the graph of (6) of FIG. . In FIG. 15, L1 and L3 are interlocked with each other, the experiment (graph (7)) in which the width dimension T1 of the electrode is 0.8 μm, and L1 and L3 are interlocked with each other, and the width of the electrode is The experiment (the graph of (8)) which set dimension T1 to 1.6 micrometers was also conducted.

As shown in FIG. 15, it was found that the maximum swing width (absolute value) of the sensitivity can be suppressed to 10% or less by setting L3-L4 (L4 = 2 μm) to approximately 1.8 μm or more.

Subsequently, (L1−L2) ² × T1 is calculated, and FIG. 16 shows the relationship between (L3−L4) ² × T1 and the maximum amplitude of the sensitivity. Three curves shown in FIG. 16 are based on the graphs of (6), (7) and (8) shown in FIG.

As shown in FIG. 16, it was found that (L3−L4) ² × T1 has substantially the same curve regardless of the size of the width dimension T1 of the electrode element (normalization). Then, as shown in FIG. 16, it was found that by setting (L3−L4) ² × T1 to 4 (μm ³ ) or more, the maximum amplitude (absolute value) of the sensitivity can be suppressed to 10% or less.

When L1 and L3 are not interlocked with each other, it is preferable to set L3> L1 in the stationary state of FIG. 3 (a). In the experiment shown in FIG. 11, L1 is about 3.6 μm when the maximum fluctuation range of the sensitivity is 10 (%). At this time, L3 is 5 μm. On the other hand, in the experiment of FIG. 14, as shown in the graph of (5), L3 when the maximum swing of the sensitivity is 10 (%) is about 4.4 μm. At this time, L1 is 5 μm. As seen from the dimensional relationship between L1 and L3 at rest, the smaller dimension (L1) can be set smaller in the experiment of FIG. 11 where L3> L1. Therefore, miniaturization of the MEMS sensor can be promoted while maintaining high sensitivity and good linearity.

In FIG. 3, L5 is greater than or equal to L2 and L4. As a result, even if the movable electrode moves as much as possible in the X1-X2 direction as shown in FIGS. 3 (b) and 3 (c), the movable electrode does not come out of the fixed electrode, and the sensitivity linearity decreases. It can be suppressed.

The MEMS sensor S in the present embodiment includes a plurality of movable support portions 50 constituting the movable electrode portions 21a to 21d and a plurality of fixed support portions 51 constituting the fixed electrode portions 20a to 20d in the same detection portion. They are alternately arranged in the X1-X2 direction (first direction). Then, the movable support 50 and the fixed support 51 adjacent to each other are formed in the same set 66, and fixed between the movable support 60 and the plurality of movable electrodes 60 and 61 between the movable support 50 and the fixed support 51 in each set 66. Electrode elements 62 and 63 were alternately arranged in the Y1-Y2 direction (second direction). As a result, a large number of movable electrode elements 60, 61 and fixed electrode elements 62, 63 can be efficiently disposed in the detection section, and a smaller size and higher sensitivity can be obtained as compared with the conventional electrode structure. The electrode structure shown in each patent document obtains the capacitance change based on the change in the facing area between the movable electrode and the fixed electrode, but only one set of movable electrode and fixed electrode is provided in the same detection unit. . That is, in the electrode structure described in the patent document, a plurality of movable support portions 50 and a plurality of fixed support portions 51 are alternately arranged at intervals in the X1-X2 direction as in the present embodiment. Not Then, as in the present embodiment, the movable support 50 and the fixed support 51 are divided into a plurality of sets, and in each set, the movable electrode elements 60 and 61 and the fixed electrode elements 62 and 63 have an interval in the Y1-Y2 direction. There is no disclosure of open and alternately arranged electrode structures.

By using the electrode structure of this embodiment, compared with the electrode structure disclosed in the patent document, in the detection area of the same size, the opposing area between the movable electrode element 60, 61 and the fixed electrode element 62, 63 The fluctuation range can be effectively increased, and the sensitivity can be enhanced.

Further, in the method of changing the gap (distance) between the movable electrode and the fixed electrode to generate the capacitance change, the capacitance is inversely proportional to the gap (distance), as shown in FIG. 5 to FIG. When the sensitivity is increased, the electrostatic capacitance changes rapidly with respect to the distance fluctuation (see FIG. 5B), and the effective detection range (dynamic range) of the physical quantity by the MEMS sensor becomes narrow. Furthermore, there also arises a problem that the linearity of sensitivity within the effective detection range can not be improved (see FIG. 7).

On the other hand, in the method of changing the electrostatic capacitance by changing the facing area between the movable electrode 60, 61 and the fixed electrode 62, 63 as in this embodiment, the capacitance is made proportional to the facing area As compared with the method of the comparative example in which the capacitance is changed by the variation of the distance described above, the effective detection range (dynamic range) of the physical quantity can be broadened and the linearity of sensitivity within the effective detection range is improved. Becomes possible.

In the present embodiment, as described in the above experiment, (L1-L2) ² / T1 is set to 2 (μm) or more, and (L3-L4) ² × T1 is set to 4 (μm ³ ) or more. Thus, it is possible to effectively improve the linearity of sensitivity.

As shown in FIG. 1, the first detection unit 23 is divided into a plurality of detection areas 23a and 23b, the second detection unit 24 is divided into a plurality of detection areas 24a and 24b, and each detection area 23a, 23b, 24a and 24b is divided. By providing the movable electrode portions 21a to 21d and the fixed electrode portions 20a to 20d, respectively, it is not necessary to form the movable support portion 50 and the fixed support portion 51 of this embodiment extremely long, and the strength of each electrode portion And the sensitivity can be improved.

FIG. 1 shows a MEMS sensor for detecting an acceleration acting in the X1-X2 direction, but if rotated 90 degrees from the state of FIG. 1, a MEMS sensor for detecting an acceleration acting in the Y1-Y2 direction it can. In addition, a MEMS sensor for detecting acceleration in the X-axis direction shown in FIG. 1 and a MEMS sensor for detecting acceleration in the Y-axis direction obtained by rotating the MEMS sensor of FIG. It is also possible.

The present embodiment is applicable not only to acceleration sensors but also to physical quantity sensors in general, such as angular velocity sensors and impact sensors.

S MEMS sensor 10 support substrate 11 functional layer 12 insulating layer 13 SOI substrate 14 metal connection portion 15 wiring substrate 16 frame 20a to 20d fixed electrode portion 21a to 21d movable electrode portion 22 weight portion 23 first detection portion 23a, 23b first Detection area 24 Second detection section 24a, 24b Second detection area 26, 27 Anchor section 28 to 31 Gap 40 to 43 Spring section 50 Movable support section 51 Fixed support section 52 Fixed base 60, 61 Movable electrode element 62, 63 Fixed electrode Child 66 Pair 70 Wiring Layer

Claims (5)

In a MEMS sensor having a movable electrode portion and a fixed electrode portion,
When two directions orthogonal to each other in a horizontal plane are a first direction and a second direction, the first direction is a moving direction of the movable electrode portion,
The movable electrode portions are arranged at intervals in the first direction, and extend in the second direction, and a plurality of movable support portions are formed, and each movable support portion in the first direction A plurality of movable electrode elements extending from the side portion of the second support and spaced apart in the second direction at each movable support portion,
The fixed electrode portion is arranged at intervals in the first direction, and a plurality of fixed support portions whose extension direction from the proximal end side to the distal end side is opposite to the movable support portion, and each fixed A plurality of fixed electrodes which extend from the side of the support in a direction opposite to the extending direction of the movable electrode and are spaced apart from each other in the second direction by each fixed support; Have
A plurality of the movable support portions and a plurality of the fixed support portions are alternately arranged at intervals in the first direction, and the adjacent movable support portions and the fixed support portions are combined. The plurality of movable electrode elements and the plurality of fixed electrode elements are alternately arranged at intervals in the second direction between the movable support portion and the fixed support portion of each set. Yes,
A MEMS sensor characterized by detecting a change in electrostatic capacity based on a change in an opposing area between each movable electrode and each fixed electrode by moving the movable electrode portion in the first direction. A first detection unit and a second detection unit, wherein each of the detection units includes the movable electrode unit and the fixed electrode unit;
The extending directions of the movable electrode element and the fixed electrode element in the first direction are reversed between the first detection unit and the second detection unit, and are obtained by the first detection unit. The MEMS sensor according to claim 1, wherein a differential output can be obtained by the capacitance change and the capacitance change obtained by the second detection unit. The MEMS sensor according to claim 2, wherein each of the first detection unit and the second detection unit is divided into a plurality of detection regions, and the movable electrode unit and the fixed electrode unit are provided in each of the detection regions. . In the stationary state, the distance in the first direction from the side portion of the movable support to the tip of the fixed electrode is L1, and the width of the movable electrode and the fixed electrode in the second direction is L1. Assuming that the dimension is T1 and the maximum movable distance when the movable electrode moves toward the fixed support is L2, (L1-L2) ² / T1 is 2 (μm) or more. The MEMS sensor according to any one of Items 1 to 3. In the stationary state, the distance in the first direction between the movable support portion of the adjacent set and the fixed support portion is L3, and the second direction of the movable electrode element and the fixed electrode element is in the second direction. Assuming that the width dimension of the movable electrode element is T1 and the maximum movable distance when the movable electrode element moves in the direction approaching the fixed support portion of the adjacent group is L4, (L3−L4) ² × T1 is 4 The MEMS sensor according to any one of claims 1 to 4, which is (μm ³ ) or more.

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