JPH10206457A - Capacitive acceleration sensor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sensor structure having a relatively simple detection circuit of good detection accuracy without servo control performed. SOLUTION: The sensor has center beams 102a, 102b; 102c, 102d fixed to a surface of a substrate, a movable electrode 101 supported by the center beams via a space to the substrate and movable in a direction parallel to the substrate surface, fixed electrodes 104, 105 set at the substrate to confront the movable electrode, and side electrodes 106-111 located sideways of the movable electrode and projecting from the substrate surface. A change of a confronting area of the movable electrode and fixed electrode 104, 105 is detected as a change of a static capacity. In this case, a half length L2 of the center beam and a length L1 of the movable electrode at a part fixed to the center beam are set to hold a relationship L2/L1 of 0.8-2.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting acceleration, and more particularly to a capacitance type acceleration sensor suitable for use in a safety device for controlling an airbag or a seat belt of an automobile.

[0002]

2. Description of the Related Art An acceleration sensor for detecting a collision of an automobile is incorporated in a safety device such as an airbag system and a seat belt system of the automobile. This safety device is very dangerous if operated at times other than the collision of a motor vehicle, since the safety device deprives the driver of freedom. On the other hand, if it does not operate reliably in the event of a collision, the original purpose of the safety device, which protects the life of the driver and passengers, cannot be achieved. Therefore, extremely high reliability is required for an acceleration sensor that is incorporated in a vehicle safety device and detects a collision of a vehicle.

[0003] As the acceleration sensor, an acceleration detecting section comprising a movable mass supported by a beam and having a function of a movable electrode, and a fixed electrode disposed opposite to the movable mass,
"ELECTRONIC DESIGN", August 1991, pages 45 to 56, has a structure in which a signal processing circuit that converts the movement of a movable mass that changes in accordance with acceleration into an acceleration signal is integrated on a silicon substrate. Have been described.

[0004]

The conventional acceleration sensor described above is used to improve the accuracy of acceleration detection and to prevent the movable mass (movable electrode) from being displaced and the acceleration detecting portion of the sensor from being destroyed. Then, the acceleration detector is servo-controlled so that the movable mass has a predetermined positional relationship with respect to the fixed electrode, and an acceleration signal is obtained from the control output. For this reason, the signal processing circuit is complicated. Also,
The structure of the acceleration detection unit is easily affected by the manufacturing process such as the pattern accuracy of a mask used for processing, and has large variations in sensor characteristics.

Further, an acceleration sensor used in an airbag system of an automobile has a predetermined discrimination ratio (other-axis sensitivity) characteristic with respect to an acceleration component applied from a direction other than the detection direction.
It must have a predetermined frequency characteristic, a self-diagnosis function executed when an engine switch is turned on, and the like.

The present invention has been made in view of the current situation of such an acceleration sensor, and uses a relatively simple detection circuit and an acceleration capable of detecting an acceleration with high accuracy without performing servo control of an acceleration detection unit. It is intended to provide a sensor. Another object of the present invention is to provide an acceleration sensor that has less variation in characteristics between sensors, satisfies requirements for other axis sensitivity characteristics and a self-diagnosis function, and has the smallest structure and the highest detection accuracy. I do.

[0007]

According to the present invention, a fixed electrode provided on a substrate and a movable mass having an electrode function which is supported by a beam on the substrate and opposed to the fixed electrode are used. The object is achieved by adopting a sensor structure in which the facing area between the and the movable mass changes. When the facing area between the fixed electrode and the movable mass (movable electrode) changes, the capacitance between them changes, so that the acceleration can be detected by detecting the change in the capacitance.

FIG. 1 is a schematic diagram showing a basic configuration of an example of a capacitive acceleration sensor according to the present invention. FIG. 1A is a schematic plan view showing a positional relationship between a fixed electrode and a movable mass (movable electrode), and FIG. 1B is a cross-sectional view taken along line AA. The fixed electrode 14 is formed on a substrate 16 made of silicon or the like, and the movable mass (movable electrode) 11 having an electrode function is disposed above the fixed electrode 14 so as to partially overlap the fixed electrode 14. The movable mass 11 includes anchor portions 13a and 13b.
Are supported above the fixed electrode 14 with a predetermined gap by beams 12a and 12b fixed to the substrate 16.

When an acceleration is applied in the horizontal direction of FIG. 1 in parallel with the substrate 16, the movable electrode 11 is displaced relative to the fixed electrode 14 by an inertial force. Due to the relative displacement between the movable electrode 11 and the fixed electrode 14, the two electrodes 11, 1
The facing area of No. 4 changes. Therefore, the acceleration can be detected by grasping this as a change in the capacitance of the capacitor formed by the pair of electrodes 11 and 14.

FIG. 2 is a schematic diagram showing a basic configuration of another example of the capacitive acceleration sensor according to the present invention. FIG. 2 (a)
Is a schematic plan view showing the positional relationship between the fixed electrode and the movable mass, and FIG.
(B) is the AA sectional view. The example of FIG.
6, a fixed electrode 14 is provided in addition to the fixed electrode 14, and a movable mass (movable electrode) 11 is provided so as to partially overlap the two fixed electrodes 14, 15.
The movable mass 11 is fixed to the substrate 16 by the anchor portions 13a and 13b.
The electrodes 12a, 12b fixed to the
Is supported with a predetermined gap above.

When acceleration is applied from the left and right directions in FIG. 2 in parallel with the substrate 16, the movable electrode 11 is displaced relative to the fixed electrodes 14 and 15 by inertial force. This movable electrode 1
1 and the fixed electrode 14 cause the movable electrode 11 to move.
The facing area of the fixed electrode 14 and the facing area of the movable electrode 11 and the fixed electrode 15b change. Accordingly, the first electrode constituted by the movable electrode 11 and the fixed electrode 14
The acceleration can be detected by grasping the change in the capacitance of the capacitor and the change in the capacitance of the second capacitor formed by the movable electrode 11 and the fixed electrode 15. Specifically, the capacitance of the two capacitors changes in such a way that if one increases, the other decreases.
The acceleration can be detected from the change in the difference between the capacitances of the two capacitors. At this time, in an equilibrium state where the acceleration is zero, it is preferable that the electrode shapes are determined so that the capacitances of the two capacitors are equal.

[0012] The capacitive acceleration sensor according to the present invention comprises:
A doubly-supported beam fixed to the substrate surface, a movable electrode supported by the doubly-supported beam with an air gap and displaceable in a direction parallel to the substrate surface, and provided on the substrate in opposition to the movable electrode. A fixed electrode, and a side electrode provided on the side of the movable electrode and protruding from the substrate surface, and detecting a change in an opposing area between the movable electrode and the fixed electrode as a change in capacitance. I do.

A ratio L2 / L1 of a half length L2 of the doubly supported beam and a length L1 at which the movable electrode is fixed to the doubly supported beam is as follows.
It is preferably 0.8 to 2.2. Further, the ratio h / d of the thickness h of the movable electrode to the gap d is preferably 1.2 to 3.4.

The fixed electrode comprises a first electrode and a second electrode, and the area of the movable electrode facing the first electrode and the area of the movable electrode facing the second electrode are equal to the movable electrode. Detecting the difference between the capacitance between the movable electrode and the first electrode and the capacitance between the movable electrode and the second electrode, wherein the displacement is such that one increases and the other decreases by displacement. Can be used to perform acceleration detection.

The movable electrode can be composed of a plurality of electrodes extending in a direction substantially perpendicular to the displacement direction and connected to each other. The side electrode may be formed of the same material as the movable electrode. The fixed electrode can be an electrode formed by diffusing impurities on the surface of the single crystal silicon substrate. The fixed electrode can be formed of a polycrystalline silicon electrode that is stacked on the surface of the single crystal silicon substrate and contains impurities.

The capacitance type acceleration sensor according to the present invention can be provided with an adjusting mechanism for adjusting the facing area between the movable electrode and the fixed electrode. The adjustment mechanism can include an electrode pattern for adjusting the area provided on the substrate surface and switching means for selectively connecting the electrode pattern to the fixed electrode. The electrode pattern for area adjustment is always arranged at a position facing the movable electrode regardless of the displacement of the movable electrode.

Further, the adjusting mechanism includes voltage applying means for applying a predetermined voltage between the movable electrode and the side electrode,
The movable electrode can be forcibly displaced by applying a voltage to the side electrode. The adjusting mechanism further includes voltage applying means for applying a voltage between the movable electrode and the side electrode, and switching means for selectively connecting the side electrode to the voltage applying means. The movable electrode can be forcibly displaced by application.

The switching means included in the adjusting mechanism may be a zener zap trimming, a polycrystalline silicon fuse or a digital adjusting means composed of an EEPROM. Further, the capacitance type acceleration sensor according to the present invention,
A doubly supported beam fixed to the bottom of the recess formed by engraving the substrate surface, a movable electrode supported by the doubly beam with a gap with respect to the substrate and displaceable in a direction parallel to the substrate surface, A fixed electrode provided on the substrate with a gap on the side is provided, and a change in a gap distance between the movable electrode and the fixed electrode is detected as a change in capacitance.

The movable electrode is made of conductive polycrystalline silicon, the fixed electrode is made of conductive single crystal silicon,
It can be made of conductive polycrystalline silicon or metal. The ratio L2 / L1 of the half length L2 of the doubly supported beam and the length L1 at which the movable electrode is fixed to the doubly supported beam is 0.
It is preferably from 8 to 2.2.

Further, the capacitive acceleration sensor according to the present invention is a doubly supported beam fixed to the substrate surface, and is supported by the doubly supported beam with a gap with respect to the substrate and can be displaced in a direction parallel to the substrate surface. A movable electrode and a fixed electrode protruding from the substrate surface with a gap beside the movable electrode, and detecting a change in a gap distance between the movable electrode and the fixed electrode as a change in capacitance. I do.

The movable electrode can be made of conductive polysilicon, and the fixed electrode can be made of conductive polysilicon or metal. Alternatively, the movable electrode and the fixed electrode can be made of conductive single-crystal silicon. The movable electrode may be shaped to surround the fixed electrode. Alternatively, a frame surrounding the outer periphery of the movable electrode can be provided so as to protrude from the substrate.

Also in this sensor, a half length L2 of the double-supported beam and a length L1 at which the movable electrode is fixed to the double-supported beam are used.
Is preferably 0.8 to 2.2. The above-mentioned, a doubly-supported beam fixed to the substrate surface, a movable electrode that is supported with a gap with respect to the substrate by the doubly-supported beam and that can be displaced in a direction parallel to the substrate surface, A static electrode provided with a fixed electrode provided, and a side electrode positioned on a side of the movable electrode and protruding from the surface of the substrate, and detecting a change in an opposing area between the movable electrode and the fixed electrode as a change in capacitance. The capacitance type acceleration sensor includes: (a) forming a first film for a mask on a single crystal silicon substrate;
(B) forming a pattern on the first film, doping the substrate with impurities using the film on which the pattern is formed as a mask, and forming a fixed electrode on the substrate; and (c) removing the first film;
(D) forming a second film for a mask after that;
Forming, in the second film, a hole serving as an anchor portion of the doubly supported beam and a hole to which the side electrode is to be coupled; and (e) forming a polycrystalline silicon film thereon, and subjecting the polycrystalline silicon film to a conductive treatment. After that, a step of forming a third film for a mask thereon, (f) a step of forming a pattern for processing a polycrystalline silicon film on the third film, and (g) a pattern are formed. Forming a doubly supported beam, a movable electrode coupled to the doubly supported beam, and a side electrode using the etched film as a mask, and (h) a second step located below the polycrystalline silicon film. And a step of removing the film. As the film for the mask, an oxide film or a nitride film can be used.

Further, the capacitance type acceleration sensor is
(A) A polycrystalline silicon film is formed on a substrate, and after the polycrystalline silicon film is made conductive, a first masking mask is formed thereon.
(B) forming a pattern on the first film, etching the polycrystalline silicon film using the patterned film as a mask to form a fixed electrode, and (c) forming a fixed electrode. The first film is removed, and then the second film for the mask is removed.
(D) forming a hole serving as an anchor portion of a doubly supported beam and a hole to which a side electrode is coupled in the second film; and (e) forming a polycrystalline silicon film thereon. Forming and conducting a polycrystalline silicon film to make it conductive, and then forming a third film for a mask thereon, and (f) forming a pattern for processing the polycrystalline silicon film in the third film (H) etching the polycrystalline silicon film using the film on which the pattern is formed as a mask to form a doubly supported beam, a movable electrode and a side electrode coupled to the doubly supported beam, and (h) A second layer located below the polycrystalline silicon film;
And a step of removing the film.

The above-mentioned doubly supported beam fixed to the bottom of the recess formed by engraving the surface of the substrate, and supported by the doubly supported beam with a gap with respect to the substrate and displaceable in a direction parallel to the surface of the substrate. A movable electrode and a fixed electrode provided on the substrate with a gap beside the movable electrode, and a capacitance type acceleration sensor that detects a change in a gap distance between the movable electrode and the fixed electrode as a change in capacitance. (A) forming a first film for a mask on a single crystal silicon substrate;
(B) forming a pattern on the first film, doping the substrate with impurities using the film on which the pattern is formed as a mask, and forming a fixed electrode on the substrate; and (c) removing the first film;
(D) forming a second film for a mask after that;
Forming a pattern on the second film, etching the substrate and the fixed electrode using the pattern as a mask to expose the fixed electrode on the side surface of the groove formed in the substrate, and (e) forming an electric insulating film and Laminating a third film for a mask;
(F) a step of forming a hole serving as an anchor portion of the doubly supported beam in the third film; and (g) forming a polycrystalline silicon film thereon and subjecting the polycrystalline silicon film to a conductive treatment. Forming a fourth film for a mask, (h) forming a pattern for processing a polycrystalline silicon film on the fourth film, and (i) using the film on which the pattern is formed as a mask. Etching the polycrystalline silicon film;
(J) a step of removing a third film located between the polycrystalline silicon film and the electrical insulating film.

Also, the above-mentioned doubly supported beam fixed to the substrate surface, a movable electrode supported by the doubly beam with a gap to the substrate and displaceable in a direction parallel to the substrate surface, The capacitance-type acceleration sensor includes a fixed electrode protruding from the surface of the substrate with a gap on a side, and detects a change in a gap distance between the movable electrode and the fixed electrode as a change in capacitance. Forming a wiring for a fixed electrode, (b) depositing an oxide film on the substrate, and (c) etching the oxide film so that the vertical wall of the oxide film is positioned on the wiring. (D) forming a fixed electrode so as to be connected to a wiring on a vertical wall of the oxide film, and (e) laminating an electric insulating film and a first film for a mask on a substrate. (F) The first film on the electrical insulating film has a double-ended beam Forming a hole serving as the over section,
(G) A polycrystalline silicon film is formed thereon, and the polycrystalline silicon film is subjected to a conductive treatment.
(H) forming a pattern for processing a polycrystalline silicon film on the second film;
(I) a step of etching the polycrystalline silicon film using the film on which the pattern is formed as a mask, and (j) a step of removing the first film located between the polycrystalline silicon film and the electric / electrical insulating film. It can be manufactured by a manufacturing method including:

According to the present invention, it is possible to obtain a relatively high-accuracy acceleration sensor capable of satisfying desired frequency characteristics, self-diagnosis characteristics, and the like with a simple configuration without increasing the number of manufacturing processes.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a plan view showing an example of a capacitive acceleration sensor according to the present invention, and FIG. 4 is a sectional view thereof. 4A, 4B, and 4C are cross-sectional views taken along lines AA, BB, and CC indicated in FIG. 3, respectively.

This capacitance type acceleration sensor comprises a pair of fixed electrodes 10 provided on a single crystal silicon substrate 114.
4, 105, side electrodes 106, 107, 108, 109, 110, 11 provided to protrude from the substrate 114.
1. A movable mass (movable electrode) 101 provided on a substrate 114 via an area adjustment pattern 121a to 121c, a gap 120, and four beams 1 supporting the movable mass 101
02a to 102d and beams 102a to 102d
Are provided with anchor portions 103a to 103d. Beams 102a, 102b; 102c, 102d are 2 × L in length
The movable mass 101 is supported on both sides of the movable mass 101 over the length L1. The pair of fixed electrodes 104 and 105 are interdigitated comb-shaped electrodes.

In the illustrated example, the movable mass 101 has six elongated electrode portions separated by four slits, a window portion into which the side electrodes 108 and 109 and 110 and 111 enter,
It has through grooves 112 and 113 provided at the center, and functions as a movable electrode that can be displaced in parallel to the surface of the substrate 114 with the anchor portions 103a to 103d as fulcrums. The elongated electrode portion of the movable mass 101 divided by the slit overlaps with one or both of the fixed electrodes 104 and 105, respectively, and when the movable mass 101 is displaced in the left-right direction of FIG. 3, the overlap with the fixed electrodes 104 and 105 respectively. Changes.

Horizontal direction to the substrate surface (left-right direction in FIG. 3)
Is applied, the movable mass 101 is relatively displaced with respect to the fixed electrodes 104 and 105, and the movable mass 10
1 and the area of the counter electrode between the fixed electrodes 104 and 105 changes. Here, the movable mass (movable electrode) 101 and the fixed electrode 1
Consider the difference between the capacitance of the first capacitor constituted by the element 04 and the capacitance of the second capacitor constituted by the movable mass (movable electrode) 101 and the fixed electrode 105. The facing area between the movable mass 101 and the fixed electrode 104 is S
1. The facing area between the movable mass 101 and the fixed electrode 105 is S
2. Assuming that the distance of the gap 120 formed between the movable mass 101 and the fixed electrodes 104 and 105 is d and the dielectric constant is ε, the change ΔC in the difference between the capacitances of the two capacitors when acceleration is applied is It is expressed by the following [Equation 1].

[0031]

ΔC = ε (S1−S2) / d

Therefore, when acceleration is applied to the acceleration sensor, the capacitance of the first capacitor formed by the movable mass 101 and the fixed electrode 104 and the movable mass 10
The capacitance of the second capacitor constituted by 1 and the fixed electrode 105 changes, and the magnitude of the acceleration can be detected by detecting the difference. When acceleration is detected by this method, the movable mass 101 and the movable electrodes 104, 1
Since the gap 120 between the positions 05 does not change, the capacitance detection characteristic is substantially linear with respect to the input acceleration. Therefore, this acceleration sensor has better characteristics than a conventional type acceleration sensor that detects that the gap changes due to acceleration.

When an excessive acceleration is applied, the beam 1
02a to 102c prevent excessive stress from being applied to the side electrodes 106 to 1 functioning as stoppers.
11 are provided. The side electrodes 106 to 111
Narrows the gap between the movable mass 101 and the movable mass 101 (for example, 1 μm).
m) also has a function of suppressing resonance of the movable mass 101 by air damping by the squeeze film effect. Further, the movable mass 101 and the side electrodes 106 to
By applying a voltage between the two electrodes, an electrostatic force acts between the two electrodes, and the movable mass 101 can be forcibly displaced. This makes it possible to perform self-diagnosis of the detection unit.

The movable mass 101 is provided on the substrate 114.
Even when the movable electrodes 101 move, the electrodes 121 and 121 are arranged so as to be surely covered without protruding from the electrode pattern of the movable mass 101, so that the areas 121 a to 121 for adjusting the area of the fixed electrodes 104 and 105.
1c is provided. This area adjustment pattern 121
a to 121c are connected to the fixed electrode 104 or the fixed electrode 105, thereby switching the movable mass 1
2 caused by misalignment between the fixed electrodes 104 and 105 and the fixed electrodes 104 and 105
It is possible to compensate for the capacitance imbalance of the two capacitors. That is, this area adjustment pattern 1
The area of the fixed electrode 104 or 105 facing the movable mass 101 is effectively increased by electrically connecting one or more of the movable masses 101a to 121c to the fixed electrode 104 or 105. 104
And a second capacitor formed by the movable mass 101 and the fixed electrode 105.
Is made substantially equal to the capacitance of the capacitor.

With such a configuration, a detection output that changes substantially linearly with respect to the applied acceleration is obtained, so that a highly accurate acceleration sensor can be obtained. Beams 102 a are provided by side electrodes 106 to 111 provided on the side of the movable mass (movable electrode) 101 so as to protrude from the substrate 114.
It is possible to prevent an excessive stress from being applied to to -102d, and to simultaneously realize the resonance prevention and the self-diagnosis function. Further, the area adjustment pattern 12 is provided on the substrate 114.
By providing 1a to 121c, the variation in the capacitance of the two capacitors formed by the movable electrode 101 and the fixed electrodes 104 and 105 can be compensated inside the detection element, so that the configuration of the detection circuit connected to the subsequent stage is simplified. Can be

FIG. 5 is a plan view showing another example of the capacitive acceleration sensor according to the present invention, and FIG. 6 is a sectional view thereof. 6A, 6B, and 6C are cross-sectional views taken along lines AA, BB, and CC indicated in FIG. 5, respectively.

The capacitance type acceleration sensor of this example is composed of a pair of fixed electrodes 2 provided on a single crystal silicon substrate 214.
04, 205, and side electrodes 206, 207, 208, 209, 210, 21 provided to protrude from the substrate 214.
1. A movable mass (movable electrode) 201 provided on a substrate 214 via an area adjustment pattern 221a to 221c, a gap 220, and four beams 2 supporting the movable mass 201
02a to 202d and beams 202a to 202d
Is provided with anchor portions 203a to 203d. Beams 202a, 202b; 202c, 202d are 2 × L in length
The movable mass 201 is supported on both sides of the movable mass 201 over the length L1. The pair of fixed electrodes 204 and 205 are interdigitated comb-shaped electrodes.

The movable mass 201 of this example has six elongated electrode portions as in the previous example. However, fixing bracing beams 215 and 216 connecting the six elongated electrode portions are provided.
Unlike the case of FIG. 3 which is arranged at the end of the movable mass 201, it differs from the previous example in that it is arranged inside. Therefore, the side electrodes 208 to 211 are not completely surrounded by the movable mass 201. By adopting such a structure, the side electrodes 208, 20
Wirings 9, 210 and 211 can be easily taken out. Through holes 212 and 213 are provided in the center of the movable mass.

The movable mass 201 is mounted on the substrate 21 with the anchor portions 203a to 203d fixed to the substrate 214 as fulcrums.
4 functions as a movable electrode that can be displaced in parallel to the surface.
The elongated electrode portions of the movable mass 201 are fixed electrodes 204,
The movable mass 201 overlaps one or both of the
Are displaced in the left and right directions of the fixed electrodes 204,
The degree of overlap with 205 changes.

The principle of detecting the acceleration and the like are the same as those of the previous example described with reference to FIGS. By adopting the structure as shown in FIG. 5, the side electrodes 208, 209,
The wires 210 and 211 can be easily taken out.

FIG. 7 is a schematic diagram showing an example of the overall circuit configuration of the capacitive acceleration sensor according to the present invention. This circuit includes a signal application unit 231, an acceleration detection unit 232, a capacitance detection unit 233, and an output adjustment unit 234. The signal application unit 231 includes a power supply VDD, analog switches SW1, S
W2. The acceleration detection unit 232 has a capacitance CS
1 and CS2, and these variable capacitance capacitors are composed of a movable mass (movable electrode) 101; 201 and a set of fixed electrodes 104, 105; 204, described with reference to FIGS. 205. The capacitance detection unit 233 includes analog switches SW3 and S
W4, SW5, operational amplifier OP1, capacitors CT, C
F. The output adjustment unit 234 is connected to the power supply VD
D, operational amplifier OP2, resistors R4, R5, 6, R7, V
R, capacitor C4, and Zenerrom ZR.

The signal application section 231 and the acceleration detection section 232,
The capacitance detection unit 233 has a switched capacitor circuit configuration, and an output proportional to the capacitance value is obtained by ON / OFF operation of each switch. Assuming that the output voltage (output of OP1) of the capacitance detection unit 233 is Vo, the operation of this circuit is expressed by the following [Equation 2]. In [Equation 2], n represents a measurement timing in digital processing, and Vo (n−1)
Represents the output voltage one timing before the measurement timing n.

[0043]

## EQU2 ## CF.Vo (n) = CF.Vo (n-1) -CT.
Vo (n-1) -CS1.VDD + CS2.VDD

The above [Equation 2] finally becomes the following [Equation 3].
The relationship is represented by

[0045]

## EQU3 ## Vo = (CS2-CS1) .VDD / CT

Therefore, when acceleration is applied to the detecting element, the difference between the capacitances of two capacitors formed by the movable mass (movable electrode) and the two fixed electrodes (CS2-C
The value of S1) is converted to a voltage output Vo. The output voltage Vo is adjusted by the output adjustment circuit 234 to a predetermined offset voltage (usually 2.5 V when no acceleration is applied) and sensitivity [usually about 40 mV / G (1 G is 9.8 m / G).
s ² )]. With such a circuit configuration,
The acceleration signal can be relatively easily compared to the voltage signal.

FIG. 8 shows a characteristic example of the capacitance type acceleration sensor according to the present invention. As shown in FIGS. 3 and 5, the fixed length of the doubly supported beam and the movable mass is L1, the half length of the doubly supported beam is L2, and the ratio L2 / L1 is λ. Further, assuming that the value of the difference (CS2−CS1) between the capacitances of the two capacitors when acceleration is applied is ΔC, as shown in FIG. 8, the capacitance change ΔC at λ of 1.33 is obtained. Be the largest. The larger the capacitance change ΔC, the higher the acceleration detection resolution. Since the magnitude of the capacitance change ΔC affects the detection accuracy, it is sufficient if there is a sensitivity of 95% or more of the peak value in consideration of the detection accuracy. The ratio λ of the half length L2 of the doubly supported beam is 0.8 to 2.2. Therefore, if the size of the movable mass is determined in a range where λ (= L2 / L1) is in the range of 0.8 to 2.2, it is possible to obtain the largest sensitivity (ΔC) most efficiently with the smallest area.

FIG. 9 is a sectional view of a capacitance type acceleration sensor according to the present invention. FIG. 9 shows FIG. 4 (a) or FIG.
It is sectional drawing corresponding to (a). Movable mass (movable electrode)
101; 201 and side electrodes 106 to 109; 206 to
209 and the fixed electrodes 104, 105;
When the pattern 205 can be properly patterned without variation, as shown in FIG.
01; 201 and two fixed electrodes 104, 105;
The lengths W1 and W2 of the 4,205 facing portions are equal to each other. However, when the patterning of these electrodes is displaced, the lengths W1 and W2 of the opposing portions are not equal, as shown in FIG. 9B. For this reason, the substrate 11
4: acceleration is applied in the vertical direction to 124, and the movable mass 10
1, the displacement Δy in the vertical direction with respect to the substrate 114;
Occurs, the capacitance change represented by the following [Equation 4] occurs.

[0049]

## EQU4 ## ΔC _ax = ε (S2−S1) / (d + Δy) The ratio of ΔC _{ax to} capacitance change ΔC when acceleration is applied in the detection direction becomes the sensitivity of the other axis, which is a factor of the detection error.

The thickness of the movable masses 101 and 201 is h,
FIG. 10 shows the relationship between β and ΔC _ax / ΔC, where d is the gap between the substrates 114 and 214 and the movable masses 101 and 201, and β is the ratio h / d between h and d. As shown in FIG. 10, when β is 2, the other axis sensitivity (ΔC _ax / ΔC) is minimized, and the detection error is minimized. The other axis sensitivity characteristic required for the acceleration sensor is generally ± 4 to 5% or less. The other axis sensitivity of the capacitive acceleration sensor of the present invention is ±
The value of β that becomes 5% or less is 1.2 to 3.4 from FIG. 10, and it is understood that the value of β should be set within this range.

Next, a method of using the area adjusting pattern formed on the substrate will be described. In the plan views shown in FIGS. 3 and 5, an enlarged view of a portion where the area adjustment pattern is formed is shown in FIG. 11A, and schematic sectional views for explaining the adjustment method are shown in FIGS. 11B and 11C. Shown in Note that FIG.
(B) and (c) are BB sectional drawing and B'-B 'sectional drawing of FIG.11 (a), respectively.

Due to the manufacturing process, the movable mass 10
FIG. 11B illustrates a state in which the portion 201 is formed so as to be shifted to the right of the paper surface with respect to the substrate. In this case, the movable mass (movable electrode) 101; 201
The movable mass (movable electrode) 101; 201 and the fixed electrode 105;
The capacitance between 05 becomes large. To compensate for this,
By switching the switches SWa1, SWa2, SWa3,
The fixed electrode 104;
1: 221 is connected. This operation allows the fixed electrode 10
4: the area of 204 is effectively increased and the movable mass 10
1; 201 and the fixed electrode 104; 204, the capacitance between the movable mass 101; 201 and the fixed electrode 105;
And the capacitance between them.

Similarly, FIG. 11C shows a state where the movable masses 101 and 201 are displaced from the substrate to the left in the drawing. In this case, the capacitance between the movable mass (movable electrode) 101; 201 and the fixed electrode 105;
1 and the fixed electrodes 104 and 204 increase in capacitance. To compensate for this, switches SWb1 and SWb
2, SWb3 is switched, and the fixed electrode 105;
05 is connected to patterns 121 and 221 for area adjustment. By this operation, the area of the fixed electrodes 105; 205 is effectively increased, and the movable mass 101;
05; 205, the movable mass 101; 201
And the capacitance between the fixed electrodes 104 and 204 can be adjusted.

As described above, by providing on the substrate a pattern for adjusting the area which can be selectively connected to the fixed electrode by the switch, the static electricity generated between the two capacitors due to the pattern shift in the manufacturing process. The electric capacity imbalance can be easily compensated. Also, from the viewpoint of the circuit configuration of the entire acceleration sensor, the variation of the capacitance can be compensated in the preceding stage by using the area adjustment pattern, so that the configuration of the subsequent capacitance detecting circuit is simplified. Is done.

FIG. 12 shows an example of an adjustment circuit for switching a switch. This adjustment method uses zener zapping. This adjustment circuit has an input terminal IN,
Power supply Vcc, transistor MN1, zener diode ZR1, inverter INV, switch Swab (FIG. 11)
(Adjustment switch). Input terminal IN
When a predetermined voltage and current waveform are applied to the
R1 is short-circuited and destroyed, the anode and the cathode are short-circuited, and the input terminal IN is short-circuited to ground. As a result, the inverter INV is inverted, and ON / OFF of the switch SWab is controlled. By using such a switching method, it is possible to digitally and easily adjust the area of the facing electrode.

FIG. 13 is a diagram showing another example of the adjustment circuit. This adjustment circuit includes an input terminal IN, a power supply voltage Vcc, a transistor MN1, a resistor PR1, an inverter INV, and a switch Swab (the adjustment switch shown in FIG. 11). The resistor PR1 is made of polycrystalline silicon,
When a predetermined voltage and current waveform are applied to the input terminal IN, the resistor PR1 is short-circuited and broken, the anode-cathode is short-circuited, and the input terminal IN is short-circuited to ground. As a result, the inverter INV is inverted, and ON / OFF of the switch SWab is similarly controlled. By using this method, it is possible to digitally and easily adjust the area of the facing electrode.

In addition, a circuit such as an EEPROM can be used to form an electrode area adjusting circuit in the same manner. FIG.
FIG. 4 is an explanatory view showing another method for adjusting the capacitance of two capacitors constituted by a movable mass, a (movable electrode) and two fixed electrodes.

In the example shown in FIG. 14A, the adjusting voltage 241 is applied to the movable mass 101; 201 and the side electrode 106;
Apply between 206. This method uses a movable mass 101; 2.
01 and the side electrode 106; 206, the movable mass 101;
4, 105; Lengths W1, W facing portions facing 204, 205
This is a method of forcibly compensating for a pattern shift by displacing to a position where 2 is equal. The magnitude of the electrostatic force is adjusted by changing the voltage value of the adjustment voltage 241. According to this method, it is possible to adjust the capacitances of the two capacitors without adding a special pattern such as the above-described area adjustment pattern on the substrate.

FIG. 14 (b) shows that the movable mass 101; 201 is applied by applying an adjustment voltage 242 between the movable masses 101 and 01 and the side electrodes 106 and 206, similarly to the method of FIG. This is a method of forcibly compensating for a pattern shift by displacing to a position where W1 and W2 are equal. The adjustment of the electrostatic force is performed by changing the connection with a part of the side electrode (108; 208 in the illustrated example) connected to the adjustment voltage 242 via the switch 243 to change the area of the side electrode. That is, the electrostatic force between the movable mass 101; 201 and the side electrode is adjusted by controlling the area of the side electrode. With this method,
The capacitance of the two capacitors can be adjusted without adding a special pattern such as the area adjustment pattern described above.

Next, a method for manufacturing the capacitance type acceleration sensor according to the present invention will be described. Since the acceleration sensor described with reference to FIGS. 3 and 4 and the acceleration sensor described with reference to FIGS. 5 and 6 can be manufactured by the same manufacturing process, the acceleration sensor illustrated in FIGS. An example will be described.

FIGS. 15 and 16 are process diagrams illustrating an example of a method of manufacturing a capacitance type acceleration sensor according to the present invention. 15 and 16 are views corresponding to the AA cross section of FIG. First, a thermal oxide film (SiO ₂ film) 301 is deposited on a substrate 114 made of single crystal silicon, and a nitride film (Si ₃ N ₄ film) 302 is further deposited thereon (a).

Next, the Si ₃ N ₄ film 302 is formed through a pattern formed on the photoresist applied to the Si ₃ N ₄ film 302.
Is dry-etched to transfer a photoresist pattern to the Si ₃ N ₄ film 302. Subsequently, using the Si ₃ N ₄ film 302 as a mask, impurities such as boron and phosphorus are doped by ion implantation and thermally diffused to form the fixed electrodes 104 and 105 (b).

Thereafter, the SiO ₂ film 301 and the Si ₃ N ₄ film 3
02 by etching, and then an oxide film (SiO ₂ film)
303 is deposited by CVD (c). SiO
₂ Dry etching is performed on the film 303 by photoresist processing, and holes 3 serving as anchor portions of the beams and side electrodes are formed.
04 is formed (d).

A polycrystalline silicon film 305 is formed thereon by LPC.
After deposition by VD and conductivity treatment by phosphorus treatment, the SiO ₂ oxide film 306 is deposited by CVD (e). Subsequently, the SiO ₂ film 306 by the photoresist process, dry etching is carried out, SiO ₂
A pattern for processing the polycrystalline silicon film 305 is transferred to the film 306 (f).

Next, using the SiO ₂ film 306 as a mask,
The polycrystalline silicon film 305 is processed by dry etching (g). Finally, the S under the polycrystalline silicon film 305
The iO ₂ film 303 is removed by hydrofluoric acid treatment, and a void is formed between the substrate 114 and the movable mass except for the anchor portion, thereby completing the process. At this time, the through groove 112 shown in FIG.
Numeral 113 functions as a passage for efficiently guiding hydrofluoric acid to the SiO ₂ film 303 (h).

By adopting such a manufacturing process, the semiconductor device can be manufactured by using a general IC manufacturing process. Therefore, it is possible to integrate the circuit portion into one chip, and to reduce the size and the cost. In addition, since the movable mass 101 and the side electrodes 106 to 109 can be manufactured by the same member and the same process, a special process for forming the side electrodes is not required, and no cost increase factor occurs. Further, the thickness of the gap between the fixed electrode and the movable mass on the substrate can be controlled with a SiO ₂ film formed by CVD, and can be controlled with high precision. On the other hand, in the conventional example, since the gap between the movable mass and the fixed electrode depends on the accuracy of photolithography and dry etching, the gap is large.

FIGS. 17, 18 and 19 are process diagrams for explaining another example of the method of manufacturing the capacitive acceleration sensor according to the present invention. First, a substrate 11 made of single crystal silicon
In step 4, a thermal oxide film (SiO ₂ film) 311 is deposited.
Further, a nitride film (Si ₃ N ₄ film) 312 is deposited thereon (a).

Further, the polycrystalline silicon film 313, SiO ₂
The film 314 is deposited and made conductive by phosphorous treatment (b). The SiO ₂ film 314 is dry-etched through a pattern formed in the photoresist to form the SiO ₂ film 3.
The pattern of the photoresist is transferred to 14 (c).

Next, the polycrystalline silicon 313 is dry-etched using the SiO ₂ film 314 as a mask to form the fixed electrode 1.
04, 105 and wiring 315 for side electrodes are formed. After that, the SiO ₂ film 314 is removed (d). Next, Si
The O ₂ film 316 is deposited by CVD (e).

Next, the SiO ₂ film 316 is dry-etched by photoresist process, to form a hole 317 made in the anchor portion and the side electrode of the beam (f). A polycrystalline silicon film 318 is deposited thereon by LPCVD,
After the conductive treatment by the phosphorus treatment, the SiO ₂ film 319 is
Deposition by VD (g).

The SiO ₂ film 319 is dry-etched by photoresist processing, and a pattern for processing the polycrystalline silicon film 318 is transferred to the SiO ₂ film 319 (h). Next, after the polycrystalline silicon film 318 is processed by dry etching using the SiO ₂ film 319 as a mask, the SiO ₂ film 319 is removed (i).

Finally, the SiO ₂ film 316 below the polycrystalline silicon film 318 is removed by hydrofluoric acid treatment,
A gap is formed between the movable mass 14 and the movable mass to complete the process. At this time, the through grooves 112 and 113 shown in FIG. 3 function as passages for efficiently leading hydrofluoric acid to the SiO ₂ film 316 to be removed.

By employing such a manufacturing process, the semiconductor device can be manufactured by using a general IC manufacturing process. Therefore, it is possible to integrate the circuit portion into one chip, and to reduce the size and cost. In addition, since the movable mass and the side electrode can be manufactured by the same member and the same process, a special process for forming the side electrode is not required, and no cost increase factor occurs. Furthermore, the thickness of the gap between the fixed electrode and the movable mass on the substrate can be controlled with a CVD SiO ₂ film, and can be controlled with high precision. Furthermore, since the fixed electrode wiring is not formed by pn separation by impurities but is formed by using polycrystalline silicon completely separated by an oxide film, the floating capacitance is small and high-precision capacitance detection is performed. Can be. The fixed electrode may use metal.

FIG. 20 is a plan view of another example of the capacitive acceleration sensor according to the present invention. FIGS. 21A and 21B are cross-sectional views thereof, and FIGS. 21A and 21B are AA and AB indicated in FIG.
3 shows a cross-sectional shape taken along line BB.

The capacitance type acceleration sensor of this example has a pair of fixed electrodes 404 and 405 arranged opposite to a single crystal silicon substrate 407 and four beams fixed to the substrate 407 by anchor portions 403a to 403d. The movable mass 401 is supported on the substrate 407 by 402a to 402d. The beams 402a and 402b; 402c and 402d constitute a doubly supported beam having a length of 2 × L2, and the movable mass 401 has a length L
The two sides are supported by a doubly supported beam.
Si serving as a protective film is formed on the surface of the single crystal silicon substrate 407.
An O ₂ film 411 and a Si ₃ N ₄ film 412 are stacked. The movable mass 401 has three slits 40 in the example of this figure.
6 are provided and have an electrode function. As shown in FIG. 21A, the fixed electrodes 404 and 405 are
01 is located on the side of the movable mass (movable electrode) 401 by entering the slit 406 provided in the same.

When an acceleration is applied to the substrate surface in the horizontal direction (the horizontal direction in FIGS. 20 and 21), the movable mass 401 is displaced with respect to the fixed electrodes 404 and 405, and fixed to the end surface of the slit 406 of the movable mass 401. The gap between the electrodes 404 and 405 changes respectively.

The movable mass 401 and the fixed electrodes 404 and 405
If the gap between the movable mass 401 and the fixed electrodes 404 and 405 in an equilibrium state at zero acceleration is d, the dielectric constant is ε, and the amount of change in the gap when acceleration is applied is Δd, Mass 401 and fixed electrode 40
4, the capacitance of a first capacitor constituted by
The capacitance difference ΔC of the second capacitor formed by the movable mass 401 and the fixed electrode 405 is represented by the following [Equation 5]. In this manner, the difference between the capacitances of the two sets of capacitors formed in the acceleration sensor is changed by the action of the acceleration, and the acceleration can be detected by detecting the change.

[0078]

ΔC = 2ε · S · Δd / {d ² − (Δd) ² }

In the acceleration sensor of this example, the movable mass 40
1 has a structure that completely surrounds the fixed electrodes 404 and 405. By adopting such a structure, even if an excessive impact is applied to the acceleration sensor from any direction, the displacement of the movable mass 401 is limited and protected by the fixed electrodes 404 and 405 which also serve as a stopper. The detector is not destroyed.

FIG. 22 is a diagram showing characteristics of the acceleration sensor shown in FIGS. As shown in FIG. 20, the fixed length of the beams 402a to 402d and the movable mass 401 is L1, and the beams 402a and 402b;
The length of half of d is L2, and the ratio L2 / L1 is λ. When the horizontal axis is λ and the vertical axis is ΔC in the above equation (5), the relationship between λ and ΔC is obtained. As shown in FIG. 22, ΔC becomes the maximum when λ is 1.33. Capacity change Δ
The larger C is, the higher the acceleration detection resolution is. Since the magnitude of the capacitance change ΔC affects the detection accuracy, it is sufficient if there is a sensitivity of 95% or more of the peak value in consideration of the detection accuracy. The ratio λ of the half length L2 of the beam is 0.8
~ 2.2. Therefore, λ (= L2 / L1) is 0.8
When the size of the movable mass is determined in the range of 2.2 to 2.2, it is possible to obtain a large sensitivity (ΔC) most efficiently with a minimum area.

FIGS. 23 to 25 are process diagrams illustrating an example of a method of manufacturing the capacitance type acceleration sensor shown in FIGS. This process diagram is a diagram corresponding to a cross section along AA in FIG.

First, a substrate 407 made of single crystal silicon is used.
Next, a thermal oxide film (SiO ₂ film) 501 is deposited, and a nitride film (Si ₃ N ₄ film) 502 is further deposited thereon (FIG. 5A).

Next, the Si ₃ N ₄ film 502 is dry-etched through the pattern formed in the photoresist,
In ₃ N ₄ film 502 to transfer the pattern of the photoresist. Subsequently, using the Si ₃ N ₄ film 502 as a mask, impurities such as boron and phosphorus are doped by ion implantation and thermally diffused to form fixed electrodes 404 and 405 (b).

Thereafter, the SiO ₂ film 501 and the Si ₃ N ₄ film 5
02 is removed, and an oxide film (SiO ₂ film) 503 is deposited by CVD (c). The SiO ₂ film 503 is dry-etched by photoresist processing (d).

Using the SiO ₂ film 503 as a mask, the single crystal silicon substrate 407 is etched, and
_{2 The} film 503 is removed. By this step, the surface of the substrate 407 is carved to form a concave portion 504, and the fixed electrode 4
04, 405 appear as vertical walls of the recess 504 (e). Next, the SiO ₂ film 411 and the Si ₃ N ₄ film 412 are deposited thereon by CVD, and the SiO ₂ film 505 is further deposited by CVD (f).

The SiO ₂ film 505 is dry-etched by a photoresist process to process a portion 506 to be an anchor portion (g). After that, the polycrystalline silicon film 507 is
After deposition by PCVD and conductivity treatment by phosphorous treatment, the SiO ₂ film 508 is deposited by CVD (h).

Next, the SiO ₂ film 508 is dry-etched by photoresist processing to form a polycrystalline silicon film 507.
Is transferred (i). continue,
The polycrystalline silicon film 507 is processed by dry etching using the SiO ₂ film 508 to which the pattern has been transferred as a mask,
After the processing, the SiO ₂ film 508 is removed (j). Finally,
A part of the SiO ₂ film 505 existing between the polycrystalline silicon film 507 and the Si ₃ N ₄ film 412 is removed by hydrofluoric acid treatment to complete the sensor detection part (k).

By adopting such a manufacturing process, the detecting portion of the sensor can be manufactured by using a general IC manufacturing process, so that it can be integrated with the circuit portion on one chip, and the size and the size can be reduced. Pricing is possible. The gap between the fixed electrodes 404 and 405 on the substrate and the movable mass 401 can be controlled with high precision by controlling the CVD film thickness by the SiO ₂ film 505.

FIG. 26 is a plan view of another example of the capacitive acceleration sensor according to the present invention, and FIG. 27 is a sectional view thereof. FIGS. 27 (a) and 27 (b) respectively show A-
The cross-sectional shape along line A, BB is shown.

The acceleration sensor of this example has a pair of fixed electrodes 60 protruding from a single crystal silicon substrate 607.
9, 610, a movable mass (movable electrode) 601 and a frame 608 provided on the surface of the substrate 607 so as to surround the movable mass. The fixed electrodes 609 and 610 are connected by wirings 604 and 605. On the surface of the single crystal silicon substrate 607, a SiO ₂ film 61 serving as a protective film
1 and a Si ₃ N ₄ film 612 are stacked. The movable mass 611 having an electrode function is provided with a slit 606, and a pair of fixed electrodes 609 and 610 are arranged in the slit 606 so as to face the end surface of the slit 606. The movable mass 611 is supported on the substrate 607 via a gap 613 by four beams 602a to 602d fixed to the substrate 607 by anchor portions 603a to 603d. The beams 602a, 602b; 602c, 602d constitute a doubly supported beam having a length of 2 × L2, and the movable mass 601 is supported by the doubly supported beam on both sides over a length L1.

When an acceleration is applied to the substrate surface in the horizontal direction (the horizontal direction in FIG. 26), the movable mass 601
09, 610, and the gap between the movable mass 601 and the fixed electrodes 609, 610 changes respectively. Therefore, the capacitance of the first capacitor constituted by the movable mass 601 and the fixed electrode 609 and the movable mass 60
The difference between the capacitance of the first capacitor and the capacitance of the second capacitor formed by the fixed electrode 610 changes. By detecting the change, the acceleration can be detected.

By employing such a structure, the single crystal silicon substrate 607 is not carved, so that the wiring can be easily taken out. Also, a frame 6 is provided around the movable mass 601.
08, the movable mass 6 can be moved by the frame 608 even if an excessive impact is applied to the sensor detector from any direction.
Since the displacement of 01 is limited, the sensor does not break.

FIGS. 28 to 30 are process diagrams showing an example of a method of manufacturing the acceleration sensor shown in FIGS. 26 and 27. First, a thermal oxide film (SiO ₂ ) 701 is deposited on a substrate 607 made of single crystal silicon, and a nitride film (Si ₃ N ₄ film) 702 is further deposited thereon (a).

[0094] Then the Si ₃ N ₄ film 702 and dry etching through a pattern formed photoresist, Si ₃
A photoresist pattern is transferred to the N ₄ film 702. Subsequently, using the Si ₃ N ₄ film 702 as a mask, impurities such as boron and phosphorus are doped by ion implantation, and thermally diffused to form fixed electrode wirings 604 and 605 (b).

Thereafter, the SiO ₂ film 701 and the Si ₃ N ₄ film 7
02 is removed, and an oxide film (SiO ₂ film) 703 is deposited by CVD (c). The SiO ₂ film 703 is dry-etched by photoresist processing. By this processing, a wall part partially overlapping the wirings 604 and 605 is formed so as to protrude above the substrate (d).

A polycrystalline silicon film 704 is formed thereon by LPC.
Deposition is performed by VD, and phosphorus treatment for conductivity is performed (e). Next, the polycrystalline silicon film 704 is etched to form fixed electrodes 609 and 610 on the side of the wall.
To form The fixed electrodes 609 and 610 are connected to the wirings 604 and 6
05 (f).

Then, a SiO ₂ film 611, a Si ₃ N ₄ film 612 and a SiO ₂ film 705 are deposited by CVD (g). The SiO ₂ film 705 is dry-etched by a photoresist process, and a portion 706 serving as an anchor portion is processed (h).

Then, the polycrystalline silicon film 707 is
After deposition by VD and conductivity treatment by phosphorous treatment, the SiO ₂ film 708 is deposited by CVD (i). The SiO ₂ film 708 is dry-etched by photo-resist processing to obtain a polycrystalline silicon film 7.
07 is transferred (j).

The polycrystalline silicon film 707 is processed by dry etching, and the movable mass 701 and the beam and the beam anchor 6 are formed.
03 is formed, and then the SiO ₂ film 708 is removed (k).

Finally, the SiO ₂ film 705 partly located between the polycrystalline silicon film 707 and the Si ₃ N ₄ film 612 is removed by hydrofluoric acid treatment, and the portion between the fixed electrode 609.610 and the movable mass 601 is removed. The gap 606 is formed to complete the sensor detection section (l).

By adopting such a manufacturing process, the detecting portion of the sensor can be manufactured using a general IC manufacturing process, so that it can be integrated with the circuit portion on one chip, and the size and the cost can be reduced. It becomes possible. The gap between the fixed electrodes 609 and 610 on the substrate and the movable mass 601 is S
The thickness of the CVD film can be controlled by the iO ₂ film, and the control can be performed with high accuracy. Further, wiring can be easily performed since the wiring can be laminated on the substrate surface. Further, a metal may be used for the fixed electrode.

[0102]

According to the present invention, the output changes linearly with respect to the detected acceleration, and an extremely accurate acceleration sensor can be obtained. In addition, it is possible to simultaneously realize the resonance prevention and the self-diagnosis function by using the side electrode for preventing damage due to excessive stress. Further, by providing the area adjustment pattern, the variation in the capacitance can be compensated inside the detection element, so that the configuration of the detection circuit connected to the subsequent stage is simplified. Furthermore, the most efficient large sensitivity (Δ
C) can be obtained, and the detection error due to the sensitivity of the other axis can be minimized.

The acceleration sensor of the present invention can be manufactured by using a general IC manufacturing process, so that it can be integrated with the circuit section on one chip, and can be reduced in size and cost. Further, since the movable mass and the side electrode can be manufactured by the same member and the same process, there is no special factor for increasing the cost for forming the side electrode. Further, the gap between the fixed electrode and the movable mass on the substrate can be controlled with high precision by controlling the CVD film thickness by the SiO ₂ film.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of an example of a capacitive acceleration sensor according to the present invention.

FIG. 2 is a schematic diagram showing a basic configuration of another example of a capacitive acceleration sensor according to the present invention.

FIG. 3 is a plan view showing an example of a capacitive acceleration sensor according to the present invention.

FIG. 4 is a sectional view taken along lines AA, BB, and CC indicated in FIG. 3;

FIG. 5 is a plan view showing another example of the capacitive acceleration sensor according to the present invention.

FIG. 6 is a sectional view taken along lines AA, BB, and CC indicated in FIG. 5;

FIG. 7 is a schematic diagram showing an example of the overall circuit configuration of a capacitive acceleration sensor according to the present invention.

FIG. 8 is a diagram showing a characteristic example of the capacitance type acceleration sensor according to the present invention.

FIG. 9 is a sectional view of a capacitive acceleration sensor according to the present invention.

FIG. 10 is a diagram showing another axis sensitivity characteristic of the capacitance type acceleration sensor according to the present invention.

FIG. 11 is an enlarged view of a portion where an area adjustment pattern is formed, and a schematic cross-sectional view illustrating an adjustment method.

FIG. 12 illustrates an example of an adjustment circuit for switching a switch.

FIG. 13 is a diagram showing another example of the adjustment circuit.

FIG. 14 is an explanatory diagram showing another method for adjusting the capacitance of two capacitors constituted by a movable mass, a (movable electrode), and two fixed electrodes.

FIG. 15 is a process chart illustrating an example of a method for manufacturing a capacitance type acceleration sensor according to the present invention.

FIG. 16 is a process chart illustrating an example of a method for manufacturing a capacitance type acceleration sensor according to the present invention.

FIG. 17 is a process chart for explaining another example of the method of manufacturing the capacitive acceleration sensor according to the present invention.

FIG. 18 is a process chart for explaining another example of the method of manufacturing the capacitive acceleration sensor according to the present invention.

FIG. 19 is a process chart for explaining another example of the method of manufacturing the capacitive acceleration sensor according to the present invention.

FIG. 20 is a plan view of another example of the capacitive acceleration sensor according to the present invention.

FIG. 21 is a diagram showing a cross-sectional shape taken along line AA and BB indicated in FIG. 20;

FIG. 22 is a diagram showing characteristics of the acceleration sensor shown in FIGS. 20 and 21.

FIG. 23 is a process chart illustrating an example of a method of manufacturing the capacitance type acceleration sensor shown in FIGS. 20 and 21.

FIG. 24 is a process chart illustrating an example of a method of manufacturing the capacitance type acceleration sensor shown in FIGS. 20 and 21.

FIG. 25 is a process chart illustrating an example of a method of manufacturing the capacitance type acceleration sensor shown in FIGS. 20 and 21.

FIG. 26 is a plan view of another example of the capacitive acceleration sensor according to the present invention.

FIG. 27 is a view showing a cross-sectional shape taken along line AA and BB indicated in FIG. 26;

FIG. 28 is a process chart showing an example of a method for manufacturing the acceleration sensor shown in FIGS. 26 and 27.

FIG. 29 is a process chart showing an example of a method for manufacturing the acceleration sensor shown in FIGS. 26 and 27.

FIG. 30 is a process chart showing an example of a method for manufacturing the acceleration sensor shown in FIGS. 26 and 27.

[Explanation of symbols]

101: movable mass (movable electrode), 102a to 102d ...
Beams, 103a to 103d ... anchor parts, 104, 105
... fixed electrodes, 106 to 110 ... side electrodes, 112, 1
13 ... through-groove, 114 ... substrate, 120 ... gap, 12
1a to 121c: area adjustment pattern, 201: movable mass (movable electrode), 202a to 202d: beam, 203a to
203d: anchor part, 204, 205: fixed electrode, 2
06 to 211: side electrode, 212, 213: through groove,
214: substrate, 220: gap, 221a to 221c
... area adjustment pattern, 231 ... signal application section, 232 ...
Acceleration detector, 233 ... Capacitance detector, 234 ... Output adjuster, 241,242 adjusting voltage, 243 ... Switch, 3
01: SiO ₂ thermal oxide film, 302: Si ₃ N ₄ film, 303
... SiO ₂ film, 304, hole, 305, polycrystalline silicon film, 306, SiO ₂ film, 311, SiO ₂ thermal oxide film, 3
12 ... Si ₃ N ₄ film, 313 ... polycrystalline silicon film, 314
... SiO ₂ film, 315 ... side electrode wiring, 316 ... S
iO ₂ film, 317 ... holes, 318 ... polycrystalline silicon film, 3
19: SiO ₂ film, 401: movable mass (movable electrode), 4
02a to 402d: beam, 403a to 403d: anchor portion, 404, 405: fixed electrode, 406: through groove, 40
7: substrate, 411: SiO ₂ film, 412: Si ₃ N ₄ film,
501: SiO ₂ thermal oxide film, 502: Si ₃ N ₄ film, 50
Reference numeral 3 denotes an oxide film, 505 denotes a SiO ₂ film, 506 denotes a portion serving as an anchor portion, 507 denotes a polycrystalline silicon film, and 508 denotes Si.
O ₂ film, 601... Movable mass (movable electrode), 602 a to 6
02d: beam, 603a to 603d: anchor part, 60
4, 605, 609, 610: fixed electrode, 606: through groove, 607: substrate, 608: frame, 611: SiO ₂ film,
612: Si ₃ N ₄ film, 701: SiO ₂ thermal oxide film, 70
2. Si ₃ N ₄ film, 703 oxide film, 704 polycrystalline silicon film, 705 SiO ₂ film, 706 anchor part, 7
07: polycrystalline silicon film, 708: SiO ₂ film, SW1
To SW5: analog switch, CS1, CS2: capacitance, OP1, OP2: operational amplifier, CT, CF: capacitor, VDD: power supply, R4 to R7, VR: resistor, C4 ...
Capacitor, ZR: Zener rom, SWa1-Swa
3, SWb1 to SWb3 ... switch, IN ... input terminal,
Vcc: power supply, MN1: transistor, ZR1: zener diode, INV: inverter, PR1: polycrystalline silicon resistor

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kiyomitsu Suzuki 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside the Hitachi Research Laboratory, Hitachi, Ltd. (72) Masahiro Matsumoto 7-chome, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1-1 Inside Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Akihiko Saito 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory Co., Ltd. (72) Inventor Norio Ichikawa Hitachinaka, Ibaraki 2477 Takaba Inside Hitachi Car Engineering Co., Ltd. (72) Inventor Junichi Horie 2520 Takaji, Hitachinaka-shi, Ibaraki Prefecture Automotive Equipment Division, Hitachi, Ltd. (72) Terumi Nakazawa In-house Takaba, Hitachinaka-shi, Ibaraki 2520 Inside the Automotive Equipment Division of Hitachi, Ltd.

Claims (12)

[Claims] 1. A doubly supported beam fixed to a substrate surface, a movable electrode supported by the doubly supported beam with a gap with respect to the substrate and displaceable in a direction parallel to the substrate surface,
A fixed electrode provided on the substrate in opposition to the movable electrode, including a side electrode provided on a side of the movable electrode and protruding from the surface of the substrate, wherein the movable electrode and the fixed electrode A capacitance-type acceleration sensor, wherein a change in facing area is detected as a change in capacitance. 2. The capacitance type acceleration sensor according to claim 1, wherein a ratio L2 of a half length L2 of the doubly supported beam and a length L1 of the movable electrode fixed to the doubly supported beam.
/ L1 is 0.8-2.2. 3. The capacitance type acceleration sensor according to claim 1, wherein a ratio h / d of the thickness h of the movable electrode to the gap d is 1.2 to 3.4. Capacitive acceleration sensor. 4. The capacitance type acceleration sensor according to claim 1, wherein the fixed electrode includes a first electrode and a second electrode, and the movable electrode and the first electrode. The facing area with the electrode and the facing area with the movable electrode and the second electrode have a relationship that when one increases due to the displacement of the movable electrode, the other decreases, and the movable electrode and the first A capacitance type acceleration sensor which detects a difference between capacitance between electrodes and capacitance between the movable electrode and the second electrode. 5. A doubly-supported beam fixed to a bottom surface of a concave portion formed by engraving a substrate surface, and supported by the doubly-supported beam with a gap with respect to the substrate, and displaceable in a direction parallel to the substrate surface. Movable electrode, comprising a fixed electrode provided on the substrate with a gap on the side of the movable electrode,
A capacitance type acceleration sensor, wherein a change in a gap distance between the movable electrode and the fixed electrode is detected as a change in capacitance. 6. A capacitance type acceleration sensor according to claim 5, wherein a ratio L2 / L of a half length L2 of said doubly supported beam and a length L1 at which said movable electrode is fixed to said doubly supported beam.
1. A capacitance type acceleration sensor, wherein 1 is 0.8 to 2.2. 7. A doubly-supported beam fixed to a substrate surface, a movable electrode supported by the doubly-supported beam with a gap with respect to the substrate and displaceable in a direction parallel to the substrate surface,
A fixed electrode protruding from the substrate surface with a gap on a side of the movable electrode, and detecting a change in a gap distance between the movable electrode and the fixed electrode as a change in capacitance. Capacitive acceleration sensor. 8. The capacitance type acceleration sensor according to claim 7, wherein a ratio of a half length L2 of the doubly supported beam to a length L1 at which the movable electrode is fixed to the doubly supported beam is 0. 8
To 2.2, a capacitance-type acceleration sensor. 9. A doubly supported beam fixed to a substrate surface, a movable electrode supported by the doubly supported beam with a gap with respect to the substrate and displaceable in a direction parallel to the substrate surface,
A fixed electrode provided on the substrate in opposition to the movable electrode, including a side electrode provided on a side of the movable electrode and protruding from the surface of the substrate, wherein the movable electrode and the fixed electrode A method of manufacturing a capacitance-type acceleration sensor that detects a change in facing area as a change in capacitance,
(A) forming a first film for a mask on a single crystal silicon substrate; and (b) forming a pattern on the first film;
Doping the substrate with impurities using the film on which the pattern is formed as a mask, and forming the fixed electrode on the substrate; and (c) removing the first film, and then forming a second film for the mask. Forming a film, (d) forming a hole serving as an anchor portion of the doubly supported beam and a hole to which the side electrode is coupled in the second film, and (e) forming polycrystalline silicon thereon. Forming a film, conducting the polycrystalline silicon film for conductivity, forming a third film for a mask thereon, and (f) processing the polycrystalline silicon film into the third film And (g) etching the polycrystalline silicon film using the film on which the pattern is formed as a mask, the doubly supported beam, the movable electrode coupled to the doubly supported beam, and Forming a side electrode; and (h) Method for producing the polycrystalline capacitive acceleration sensor for removing the second layer located below the silicon film, comprising a. 10. A doubly-supported beam fixed to a substrate surface, a movable electrode supported by the doubly-supported beam with an air gap and displaceable in a direction parallel to the substrate surface, and the movable electrode A fixed electrode provided on the substrate so as to face, and a side electrode provided on the side of the movable electrode and protruding from the surface of the substrate, and having a facing area between the movable electrode and the fixed electrode. A method for manufacturing a capacitance type acceleration sensor for detecting a change as a change in capacitance, comprising the steps of: (a) forming a polycrystalline silicon film on a substrate, subjecting the polycrystalline silicon film to a conductive treatment, Forming a first film for a mask thereon, and (b) forming a pattern on the first film, etching the polycrystalline silicon film using the film on which the pattern is formed as a mask, Form a fixed electrode (C) removing the first film, and then forming a second film for a mask;
(D) forming, in the second film, a hole serving as an anchor portion of the doubly supported beam and a hole to which the side electrode is coupled; and (e) forming a polycrystalline silicon film thereon, A step of forming a third film for a mask thereon after conducting the conductive treatment of the crystalline silicon film, and (f) a step of forming a pattern for processing the polycrystalline silicon film on the third film (G) etching the polycrystalline silicon film using the film on which the pattern is formed as a mask to form the doubly supported beam, the movable electrode and the side electrode coupled to the doubly supported beam; And (h) removing the second film located below the polycrystalline silicon film. 11. A doubly-supported beam fixed to a bottom surface of a concave portion formed by engraving a substrate surface, and supported by the doubly-supported beam with a gap with respect to the substrate and displaceable in a direction parallel to the substrate surface. A movable electrode, a fixed electrode provided on the substrate with a gap on the side of the movable electrode, a capacitance type for detecting a change in the gap distance between the movable electrode and the fixed electrode as a change in capacitance A method for manufacturing an acceleration sensor, comprising: (a) forming a first film for a mask on a single crystal silicon substrate; and (b) forming a pattern on the first film, wherein the pattern is formed. Doping the substrate with impurities using a film as a mask to form the fixed electrode on the substrate; and (c) removing the first film;
(D) forming a second film for a mask after that;
Forming a pattern on the second film, etching the substrate and the fixed electrode using the pattern as a mask, and exposing the fixed electrode on a side surface of a groove formed in the substrate; Laminating an electric insulating film and a third film for a mask thereon, (f) forming a hole in the third film as an anchor portion of the doubly supported beam, and (g).
Forming a polycrystalline silicon film thereon, conducting the polycrystalline silicon film and then forming a fourth film for a mask thereon, and (h) forming the polycrystalline silicon film on the fourth film. Forming a pattern for processing the crystalline silicon film; and (i) etching the polycrystalline silicon film using the film on which the pattern is formed as a mask;
(J) removing the third film located between the polycrystalline silicon film and the electrical insulating film. 12. A double-supported beam fixed to a substrate surface, a movable electrode supported by the double-supported beam with a gap with respect to the substrate and displaceable in a direction parallel to the substrate surface, and the movable electrode A method for manufacturing a capacitance type acceleration sensor, comprising: a fixed electrode protruding from the surface of the substrate with a gap on a side thereof, and detecting a change in a gap distance between the movable electrode and the fixed electrode as a change in capacitance. And
(A) forming a wiring for the fixed electrode on a substrate;
(B) a step of depositing an oxide film on a substrate; (c) a step of etching the oxide film so that a vertical wall of the oxide film is positioned on the wiring; and (d) a step of etching the oxide film. Forming the fixed electrode on the vertical wall so as to be connected to the wiring; (e) laminating an electric insulating film and a first film for a mask on the substrate; Forming a hole in the first film on the electrical insulating film, which serves as an anchor portion of the doubly supported beam; and (g) forming a polycrystalline silicon film thereon and subjecting the polycrystalline silicon film to a conductive treatment. Forming a second film for a mask thereon,
(H) forming a pattern for processing the polycrystalline silicon film on the second film; and (i) etching the polycrystalline silicon film using the film on which the pattern is formed as a mask. (J) a step of removing the first film located between the polycrystalline silicon film and the electric / electrical insulating film.