JP3156453B2 - Semiconductor capacitive acceleration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-small semiconductor capacitive acceleration sensor which detects, for example, an acceleration state and a shaking state of an automobile, processes the detection signals, and is used for various controls.

[0002]

2. Description of the Related Art On a surface of a silicon substrate, a silicon layer made of, for example, polysilicon and a PSG (Phosp) are formed.
ho Silicate Glass, Phosphosilicate glass)
A technique for forming an ultra-compact multilayer structure by forming a sacrificial layer composed of a plurality of layers and removing the sacrificial layer after processing by micromachine technology using hydrofluoric acid or the like (hereinafter, referred to as a multilayer micromachine technique) has been developed. Ultra-compact semiconductor capacitive acceleration sensors have been developed using such techniques.

FIG. 5 is a perspective view showing an example of a conventional semiconductor capacitive acceleration sensor made by a multi-layer micromachine technology. The semiconductor substrate 1 is made of polysilicon, and the upper surface of the semiconductor substrate 1 is made of silicon oxide or the like. A support 21 provided via an insulating layer 1A made of a material, beams 22A and 22B having the same length in the horizontal direction, one end of which is connected to the support 21 at a right angle and arranged in parallel, and the beams 22A and 22B A movable electrode 23 connected to the other end of the movable electrode 23, a fixed electrode 31 provided on the upper surface of the silicon substrate 1 via a dielectric layer 1A with a predetermined gap on the lower surface of the movable electrode 23, 1. Supports 42A and 42B provided on the upper surface of 1 via an insulating layer 1A;
A fixed electrode 41 is provided around the supports 42A and 42B, the periphery of which is fixed to the upper surface of the movable electrode 23 with a predetermined gap.
The terminal M is connected to the fixed electrode 31
From the terminal S ₁ is, the terminal S ₂ is drawn from each of the fixed electrode 41 via the support member 42B.

Here, the polysilicon is doped with impurities, and the specific resistance is reduced to, for example, about 1 ohm-cm, and the polysilicon is conductive. Of course, it is possible to use single-crystal silicon which is made conductive by doping impurities instead of polysilicon, but polysilicon is lower in cost than single-crystal silicon (the same applies to the following).

The operation of this semiconductor capacitive acceleration sensor is as follows. When a vertical acceleration is applied to the movable electrode 23, the movable electrode 23 receives a vertical force, and the beam 22A,
Reference numeral 22B flexes with one end coupled to the support 21 as a fulcrum, and rotates the movable electrode 23 in the direction of the arrow P. The rotation of the movable electrode 23 causes the movable electrode 23 and the fixed electrode 31 to rotate.
Between, for example, close, the capacitance between them increases,
The distance between the movable electrode 23 and the fixed electrode 41 is reversed, and the capacitance therebetween decreases. These capacitance values are taken out between the terminals M and S _{1 and} between the terminals M and S ₂ and subjected to signal processing by a differential amplifier or the like to detect the applied acceleration.

FIG. 6 is a perspective view showing a different example of a conventional semiconductor capacitive acceleration sensor similarly made by a multi-layer micromachine technology. The semiconductor substrate 1 is made of polysilicon, and the semiconductor substrate 1 is made of polysilicon. Insulation layer 1
A, a support 21 provided via A, a horizontal beam 24A having one end connected to the support 21, and one end connected to the support 21 and having the same length as the beam 24A in the opposite direction. And a beam 24B provided on the other side of the rectangular window provided at a position shifted in the horizontal direction, for example, rightward from the center of gravity, and other beams 24A and 24B. The movable electrode 23 in the horizontal direction, the ends of which are respectively connected, and the insulating layer 1A on the upper surface of the silicon substrate 1 with a predetermined gap provided on one side of the beams 24A and 24B of the movable electrode 23, that is, on the lower surface on the left side in FIG. And a fixed electrode 41 provided on the upper surface of the silicon substrate 1 via the insulating layer 1A on the opposite side, that is, on the lower surface of the right side with a predetermined gap therebetween, and a movable electrode 23
The terminal M, the terminal S ₁ from the fixed electrode 31, and the terminal S ₂ from the fixed electrode 41 are pulled out through the beam 24 A (24 B) and the support 21.

The operation of this semiconductor capacitive acceleration sensor is as follows. When a vertical acceleration is applied to the movable electrode 23, the right and left portions of the movable electrode 23 receive vertical forces, respectively. However, since the left side is heavier than the right side, the beams 24A and 24B are supported by the support 21. The torsion movable electrode 23 is rotated in the direction of the arrow Q with one end coupled to the torsion as a fulcrum. Due to the rotation of the movable electrode 23, the capacitance between the movable electrode 23 and the fixed electrode 31 increases, for example, and the capacitance between the movable electrode 23 and the fixed electrode 31 increases.
And the capacitance decreases during this period. These capacitance values are taken out between the terminals M and S _{1 and} between the terminals M and S ₂ and subjected to signal processing by a differential amplifier or the like to detect the applied acceleration.

FIG. 7 is a perspective view showing still another example of a conventional semiconductor capacitive acceleration sensor similarly manufactured by a multi-layer micromachine technology. The semiconductor substrate 1 is made of polysilicon, and the upper surface of the semiconductor substrate 1 is made of polysilicon. 21A and 21B provided on the substrate via an insulating layer 1A
A pair of horizontal beams 24A and 24B, one end of which is connected to supports 21A and 21B, respectively, a horizontal movable electrode 23 connected between the other ends of the beams 24A and 24B, 7, a fixed electrode 31 provided on the upper surface of the silicon substrate 1 via the insulating layer 1A with a predetermined gap therebetween on the lower surface on the back side in FIG. A fixed electrode 41 is provided on the upper surface of the silicon substrate 1 via the insulating layer 1A with a predetermined gap on the lower surface on the side, and the terminal M is fixed from the movable electrode 23 via the beam 24A and the support 21A. A terminal S ₁ is drawn from the electrode 31 and a terminal S ₂ is drawn from the fixed electrode 41. Note that 25
Is a weight coupled to the back side of the movable electrode 23.

The operation of this semiconductor capacitive acceleration sensor is as follows. When a vertical acceleration is applied to the movable electrode 23, a vertical force is applied to the rear and front portions of the movable electrode 23, respectively. However, since the rear side is heavier than the front side, the beams 24A and 24B Are the supports 21A, 21
The torsion movable electrode 23 is rotated in the direction of the arrow R with the one end connected to B as a fulcrum. By the rotation of the movable electrode 23,
The distance between the movable electrode 23 and the fixed electrode 31 is, for example, short, and the capacitance therebetween is increased, and the distance between the movable electrode 23 and the fixed electrode 41 is reversed, and the capacitance therebetween is reduced. . These capacitance values are taken out between the terminals M and S _{1 and} between the terminals M and S ₂ and subjected to signal processing by a differential amplifier or the like to detect the applied acceleration.

FIGS. 8A and 8B show still another example of a conventional semiconductor capacitive acceleration sensor similarly manufactured by the multi-layer micromachine technology, wherein FIG. 8A is a perspective view and FIG. 8B is a perspective view.
FIG. 3 is a cross-sectional view taken along line CC of FIG. 1, showing a semiconductor substrate 1 and polysilicon, and an insulating layer 1
Supports 21A, 21 provided at each corner of the square via A
1B, 21C and 21D, one end of which is connected to the supports 21A, 21B, 21C and 21D respectively.
This diagonal beam 2 of this quadrangle that meets with a rotation of 2 °
4A, 24B, 24C and 24D and these beams 24
A, 24B, 24C, and 24D, a movable electrode 23 coupled to the other end, and a fixed electrode 31 provided on the lower surface of the movable electrode 23 on the upper surface of the silicon substrate 1 at a predetermined interval via an insulating layer 1A. And an insulating layer 1A on the upper surface of the silicon substrate 1.
And the periphery thereof is coupled to the supports 42A and 42B, and is provided with a predetermined gap on one side of the movable electrode 23, that is, on the upper surface on the left side in FIG. The movable electrode 23 includes a fixed electrode 41 and a terminal M via a beam 24B and a support 21B.
However, the terminal S ₁ is drawn out from the fixed electrode 31 and the terminal S ₂ is drawn out from the fixed electrode 41 via the support 42A.

The operation of the semiconductor capacitive acceleration sensor is as follows. When a vertical acceleration is applied to the movable electrode 23, the movable electrode 23 receives a vertical force and moves in the vertical direction. The distance between the movable electrode 23 and the fixed electrode 41 increases.
And the capacitance decreases during this period. These capacitance values are taken out between the terminals M and S _{1 and} between the terminals M and S ₂ and subjected to signal processing by a differential amplifier or the like to detect the applied acceleration.

[0012]

In the semiconductor capacitive acceleration sensors shown in FIGS. 5 to 7, when an acceleration is applied, the movable electrode rotates with respect to the fixed electrode, and is generated by the rotation of the movable electrode. The change in the electrode interval is detected as a change in the capacitance. However, since the amount of rotation of the movable electrode is not proportional to the amount of change in the electrode interval, there is a problem that the detection output has a non-linear characteristic. On the other hand, in the semiconductor capacitive acceleration sensor shown in FIG. 8, when acceleration is applied, the movable electrode moves perpendicularly to the fixed electrode, and the change in the electrode interval caused by the vertical movement of the movable electrode is regarded as the change in capacitance. The detection output has a linear characteristic because the amount of vertical movement of the movable electrode and the amount of change in the electrode interval are proportional. However, since the movable electrode is supported by four short beams, the vertical movement of the movable electrode is There is a problem that the amount is small and the detection sensitivity is low (for this reason, if the length of the beam is directly increased, the apparatus becomes large). Further, in the acceleration sensor shown in FIG. 8, since the area of one fixed electrode (indicated by 31 in FIG. 8) that generates the capacitance that changes reciprocally is different from the area of the other fixed electrode (indicated by 41 in FIG. 8), The values (absolute values) of these capacitances are different, and signal processing is performed. For example, the circuit of a differential amplifier becomes complicated and causes an increase in cost.

An object of the present invention is to provide a semiconductor capacitive acceleration sensor which is small, has high detection sensitivity, and has a linear detection output. Further, in the case where the capacitances for detecting the acceleration are oppositely changed, the areas of the one and the other fixed electrodes which generate the oppositely changed capacitances are configured to be substantially equal.

[0014]

According to the present invention, in order to achieve the above object, a semiconductor substrate and a regular polygon are formed on the upper surface of the semiconductor substrate via an insulating layer. A plurality of supports provided at each corner, one end of each of the supports is connected to each of the supports, and the beams in the side direction of the regular polygon which are respectively matched by rotational movement are provided at predetermined intervals to these beams. A movable electrode having a regular polygonal shape, a connecting body that couples the movable electrode and the other end of each of the beams, and an insulating layer formed on an upper surface of the semiconductor substrate at a predetermined interval on a lower surface of the movable electrode. A semiconductor capacitive acceleration sensor comprising a fixed electrode provided through a support,
It is assumed that the beam, the movable electrode, the connecting body, and the fixed electrode are each formed of polysilicon by a multi-layer micromachining technique. Alternatively, a semiconductor substrate, a plurality of supports each made of a conductive semiconductor and provided at each corner of a regular polygon on the upper surface of the semiconductor substrate via an insulating layer, and one end of each of the supports is coupled to each of the supports. Each of the beams in the direction of the sides of the regular polygon, which are matched by rotational movement, a movable electrode of a regular polygon provided at predetermined intervals to these beams, and the movable electrode and the other end of each beam. A first connecting member which is provided on the upper surface of the semiconductor substrate via an insulating layer at a predetermined interval on the lower surface of the movable electrode;
A fixed electrode, a plurality of supports provided on the upper surface of the semiconductor substrate with an insulating layer interposed therebetween, and a plurality of support members whose periphery is coupled to the support members and provided on the upper surface of the movable electrode at predetermined intervals. A semiconductor capacitive acceleration sensor comprising two fixed electrodes, a support, a beam, a movable electrode, a connecting body,
It is assumed that the first fixed electrode and the second fixed electrode are each formed of polysilicon by a multi-layer micromachining technique. In any of the semiconductor capacitive acceleration sensors, it is more preferable to attach a metal film to the movable electrode.

[0015]

In the semiconductor capacitive acceleration sensor of the present invention, the movable electrode is formed of a regular polygon, and the movable electrode is formed by a plurality of beams arranged in parallel on each side of the regular polygon with a predetermined gap therebetween. The movable electrode moves vertically with respect to the fixed electrode when acceleration is applied vertically. Then, the other end of each of the beams is connected to the end of the regular polygon of the movable electrode farther from the support to which one end of each of the beams is connected via a connector, so that the length of the beam is adjusted to the regular polygon. Can be lengthened according to the length of the side of. Therefore, the semiconductor capacitive acceleration sensor is small, has high detection sensitivity, and has a linear detection output.

In the case where the capacitance for detecting acceleration changes contradictingly, a predetermined electrode is provided on the lower surface of the movable electrode with a predetermined gap therebetween, and similarly, a predetermined electrode is provided on the entire upper surface of the movable electrode. Since the other fixed electrode is provided with the gap therebetween, the areas of the one and the other fixed electrodes are substantially equal. In addition, since a weight is provided to the movable electrode in these semiconductor capacitive acceleration sensors, the amount of movement of the movable electrode with respect to acceleration is increased, and the detection sensitivity is further improved.

[0017]

1A and 1B show an example of a semiconductor capacitive acceleration sensor according to the present invention, wherein FIG. 1A is a plan view, and FIG.
FIG. 3C is a cross-sectional view taken along line BB of FIG. 3A, which is made of polysilicon, and is provided at each corner of a square on the upper surface of the semiconductor substrate 1 via an insulating layer 1 </ b> A. Supports 21A, 21B, 21C and 21D,
One end of each of the supports 21A, 21B, 21C, and 21D is connected to the rectangular side beams 26A, 26B, 26C, and 26D, which meet at a rotation of 90 °, and the beams 26A, 26B, 26C, and 26D. 2
Movable electrode 23 provided at a predetermined gap e from 6D
And connecting members 27A, 27B, 2 connecting the movable electrode 23 and the other ends of the beams 26A, 26B, 26C, and 26D.
7C and 27D and a fixed electrode 31 provided on the upper surface of the silicon substrate 1 with a predetermined gap therebetween on the lower surface of the movable electrode 23 via an insulating layer 1A. The terminal M is pulled out from the fixed electrode 31 via the support 21A, and the terminal S ₁ is drawn out from the fixed electrode 31.

The operation of this semiconductor capacitive acceleration sensor is as follows. When a vertical acceleration is applied to the movable electrode 23, the movable electrode 23 receives a vertical force and moves in the vertical direction. Between the movable electrode 23 by a vertical movement of the movable electrode 23, for example close to this period the capacitance increases, retrieves the value of the capacitance terminal M, from between S _1, signal processing such as by an amplifier To detect the applied acceleration.

In this semiconductor capacitive acceleration sensor, the movable electrode 23 is formed in a rectangular shape, and beams 26A, 26B, 26 are arranged in parallel on each side of the rectangular shape with a predetermined gap e.
The movable electrode 23 is evenly supported from the periphery by C and 26D. When the acceleration is applied vertically, the movable electrode 23 moves vertically with respect to the fixed electrode 31. By connecting the other ends of these beams to the regular polygonal ends of the movable electrode 23 farther from the support to which the one ends of the beams are connected (a state shown in FIG. 1), The length of the beam can be increased according to the length of the side of the regular polygon. Therefore, the semiconductor capacitive acceleration sensor is small, has high detection sensitivity, and has a linear detection output.

FIGS. 2A and 2B show different examples of the semiconductor capacitive acceleration sensor according to the present invention. FIG. 2A is a plan view, FIG. 2B is a sectional view taken along line AA of FIG. It is -B sectional drawing.
FIG. 2 shows support members 42A, 42B, and 4 provided on the upper surface of the silicon substrate 1 via an insulating layer 1A in FIG.
2C and 42D and these supports 42A, 42B, 4
2C and 42D, the periphery of which is coupled to the movable electrode 23
Upper surface provided with a fixed electrode 41 which is provided at a predetermined gap, in which pulled out terminal S ₂ via the support member 42C from the fixed electrode 41.

The operation of this semiconductor capacitive acceleration sensor is as follows. When acceleration in the vertical direction is applied to the movable electrode 23, the capacitance between the movable electrode 23 and the fixed electrode 31 increases, for example, and the capacitance between the movable electrode 23 and the fixed electrode 31 increases.
3 and the fixed electrode 41 are separated in the opposite direction, and the capacitance between them decreases. These capacitance values are taken out between the terminals M and S _{1 and} between the terminals M and S ₂ and subjected to signal processing by a differential amplifier or the like to detect the applied acceleration.

In this semiconductor capacitance type acceleration sensor, the detection sensitivity is improved because the capacitances which change between the movable electrode 23 and the fixed electrode 31 and between the movable electrode 23 and the fixed electrode 41 are oppositely changed. I do. Further, since the fixed electrode 41 is provided on the entire upper surface of the movable electrode, the areas of the fixed electrodes 31 and 41 can be made substantially equal, and each capacitance between the fixed electrodes 31 and 41 and the movable electrode 23 can be obtained. (Absolute value) are substantially equal, and the signal processing, for example, the circuit of the differential amplifier is simplified and the cost is reduced.

3 and 4 show further different embodiments of the present invention. FIG. 3 (a) is a plan view, FIG. 3 (b) is an AA sectional view of FIG. 3 (a), and FIG. FIG. In these embodiments, the metal film 29 is formed on the movable electrode 23 in FIG. 1 or FIG.
Is attached. Since the weight of the movable electrode 23 is increased by the metal film 29, the acceleration detection sensitivity is further improved. Since the metal has a large specific gravity, the movable electrode portion is hardly enlarged by the metal film 29, but, of course, the distance between the movable electrode 23 and the fixed electrode 41 is increased by the thickness of the metal film 29. Correct the gap.

[0024]

According to the present invention, a semiconductor capacitive acceleration sensor is provided.
Since it is small in size, has high detection sensitivity, and has a linear detection output, it is suitable for various uses including automobiles. Further, in the case where the capacitances for detecting acceleration change oppositely, the values (absolute values) of the oppositely changing capacitances are equal, so that the signal processing, for example, the circuit of the differential amplifier is simplified. Cost is reduced.

[0025]

[Brief description of the drawings]

[0026]

1A and 1B show an embodiment of a semiconductor capacitive acceleration sensor according to the present invention, wherein FIG. 1A is a plan view, FIG. 1B is a cross-sectional view taken along the line AA of FIG. B sectional view

[0027]

2A and 2B show different embodiments of the semiconductor capacitive acceleration sensor according to the present invention, wherein FIG. 2A is a plan view and FIG. 2B is AA of FIG.
Sectional view, (c) is a BB section view of (a).

[0028]

3A and 3B show still another embodiment of the semiconductor capacitive acceleration sensor according to the present invention, wherein FIG. 3A is a plan view, and FIG.
-A sectional view, (c) is a BB sectional view of (a).

[0029]

FIGS. 4A and 4B show still another embodiment of the semiconductor capacitive acceleration sensor of the present invention, wherein FIG. 4A is a plan view and FIG.
-A sectional view, (c) is a BB sectional view of (a).

[0030]

FIG. 5 is a perspective view showing an example of a conventional semiconductor capacitive acceleration sensor.

[0031]

FIG. 6 is a perspective view showing a different example of a conventional semiconductor capacitive acceleration sensor.

[0032]

FIG. 7 is a perspective view showing still another example of the conventional semiconductor capacitive acceleration sensor.

[0033]

8A and 8B show still another example of a conventional semiconductor capacitive acceleration sensor, in which FIG. 8A is a perspective view and FIG. 8B is a cross-sectional view taken along line CC of FIG.

[0034]

[Explanation of symbols]

 Reference Signs List 1 semiconductor substrate 1A insulating layer 21A support 21B support 21C support 21D support 23 movable electrode 26A beam 26B beam 26C beam 26D beam 27A connector 27B connector 27C connector 27D connector 29 metal film 31 fixed electrode 41 42A support 42B support 42C support 42D support

Continuation of the front page (56) References JP-A-3-94168 (JP, A) JP-A-5-119060 (JP, A) JP-A-58-129318 (JP, A) JP-A-5-10968 (JP) JP-A-4-299267 (JP, A) JP-A-4-116772 (JP, A) JP-A-4-244968 (JP, A) JP-A-4-240569 (JP, A) 4-225166 (JP, A) JP-A-4-269659 (JP, A) JP-A-5-50364 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 15/125 H01L 29/84

Claims (3)

(57) [Claims] 1. A semiconductor substrate, a plurality of supports each made of a conductive semiconductor and provided at each corner of a regular polygon on an upper surface of the semiconductor substrate via an insulating layer; One end of the regular polygonal side beams that are coupled to each other and that are rotated and moved, a regular polygonal movable electrode provided at predetermined intervals to these beams, A semiconductor capacitive acceleration sensor comprising: a coupling body that couples the ends of the movable electrode; and a fixed electrode provided on an upper surface of the semiconductor substrate at a predetermined interval on the lower surface of the movable electrode via an insulating layer. A semiconductor capacitive acceleration sensor, wherein a support, a beam, a movable electrode, a connector, and a fixed electrode are each formed of polysilicon by a multi-layer micromachining technique. 2. A semiconductor substrate, a plurality of supports each made of a conductive semiconductor and provided at each corner of a regular polygon on an upper surface of the semiconductor substrate with an insulating layer interposed therebetween; One end of the regular polygonal side beams that are coupled to each other and that are rotated and moved, a regular polygonal movable electrode provided at predetermined intervals to these beams, A first fixed electrode provided on the upper surface of the semiconductor substrate via an insulating layer at a predetermined interval on the lower surface of the movable electrode; and an insulating layer on the upper surface of the semiconductor substrate. Semiconductor acceleration sensor comprising: a plurality of supports provided through a support; and a second fixed electrode provided at a predetermined interval on an upper surface of the movable electrode, the periphery of which is coupled to the supports. A support, a beam, and a movable electrode A connecting member, and the first fixed electrode,
A semiconductor capacitance type acceleration sensor, wherein each of the second fixed electrode and the second fixed electrode is formed of polysilicon by a multi-layer micromachining technique. 3. The semiconductor capacitive acceleration sensor according to claim 1, wherein a metal film is attached to the movable electrode.