JPH08136574A - Semiconductor capacity-type accelerometer - Google Patents

Abstract

PURPOSE: To provide a semiconductor capacity-type accelerometer which is of simple structure and can detect an acceleration with high accuracy over a wide range from a low acceleration up to a high acceleration. CONSTITUTION: One pair of acceleration-detection-element parts 10A, 10B are formed on a silicon substrate 1 for a sensor-part body. The size and the mass of beam parts 1b in the acceleration-detection-element parts 10A, 10B are changed at a prescribed rate, the degree of the displacement of load parts 1a in an acceleration is made irregular, and a change in electric capacities regarding the respective acceleration-detection-element parts 10A, 10B is made diverse. Then, the electric capacities regarding the respective acceleration- detection-element parts 10A, 10B are converted separately into voltages by a signal processing circuit, and an acceleration-detection signal is output as a result in which a plurality of voltage-detection signals obtained by comparing respective voltage signals with respective intrinsic threshold values have been ORed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor capacitive acceleration sensor mounted on various devices such as an air bag of an automobile and an attitude control device which require detection of acceleration.

[0002]

2. Description of the Related Art Conventionally, as an example of a sensor section main body in a semiconductor capacitive acceleration sensor of this type, there is a structure shown in FIG. In this sensor unit body, an upper insulating substrate 2 and a lower insulating substrate 3 (usually Pyrex glass or the like are used) are electrostatically bonded to one surface (upper surface) and the other surface (lower surface) of the silicon substrate 1, respectively. It is superposed and joined.

Among these, in a portion near the center of the silicon substrate 1, a predetermined pattern is removed by fine processing such as anisotropic etching to accelerate the beam portion 1b and a load portion 1a extending from the beam portion 1b. The detection element unit 10 is formed. With respect to the acceleration detecting element portion 10, the load portion 1a is a portion that is displaced by the inertial force generated when it is accelerated, and the beam portion 1b is a portion that holds the displaced load portion 1a. Further, in the upper insulating substrate 2 and the lower insulating substrate 3, a storage groove capable of storing the acceleration detecting element unit 10 is formed by removing local portions facing the acceleration detecting element unit 10 to form a step. . Further, an upper fixed electrode 4 is provided on the wall portion of the storage groove in the upper insulating substrate 2 so as to be separated from the surface of the load portion 1a of the acceleration detecting element portion 10 with a predetermined gap (gap). The lower fixed electrode 5 is also provided on the wall portion of the storage groove in the insulating substrate 3 so as to be separated from the surface of the load portion 1a of the acceleration detecting element portion 10 with a predetermined distance. In this sensor part main body, electrostatic capacitances are formed between the load part 1a and the upper fixed electrode 4 and between the load part 1a and the lower fixed electrode 5, respectively.

By the way, the semiconductor capacitive acceleration sensor includes, in addition to such a sensor unit main body, a signal processing circuit for converting an electrostatic capacitance into a frequency or a voltage and outputting an acceleration detection signal. The acceleration G is detected because the electrostatic capacitance changes when the load portion 1a of the acceleration detecting element portion 10 is displaced by the inertial force generated when the semiconductor capacitive acceleration sensor is accelerated. This is performed by outputting the result detected by the signal processing circuit as an acceleration detection signal.

[0005]

In the case of the semiconductor capacitive acceleration sensor described above, since the acceleration detecting element portion in the sensor body is single, the range of the acceleration that can be detected is the beam portion or the load. Dimensions and mass in the section,
It is uniquely determined by the size of the void formed between the load part and the upper fixed electrode or the lower fixed electrode.

For this reason, a semiconductor capacitive acceleration sensor for detecting low acceleration (for example, an attitude control sensor for detecting 1G to 2G acceleration) and a semiconductor capacitive acceleration sensor for detecting high acceleration are provided. (Eg 4
It is significantly different in design from the one for airbag for detecting acceleration of 0G to 50G) and is configured (manufactured) as a separate one.

That is, the conventional semiconductor capacitive acceleration sensor has a drawback that it cannot detect acceleration in a wide range as a single product.

The present invention has been made to solve the above problems, and its technical problem is a semiconductor capacitive type capable of highly accurately detecting acceleration in a wide range from low acceleration to high acceleration with a simple structure. An object is to provide an acceleration sensor.

[0009]

According to the present invention, a plurality of acceleration detecting element portions each having a beam portion and a load portion extending from the beam portion are formed by removing the central portion in a predetermined pattern. The silicon substrates formed adjacent to each other in the vicinity of the silicon substrate are bonded to one surface and the other surface of the silicon substrate, respectively. A pair of insulating substrates formed with a storage groove capable of storing the detection element portion, and a pair of insulating substrates facing the load portions of the plurality of acceleration detection element portions and separated from the surfaces of the load portions. In this way, a semiconductor capacitive acceleration sensor including a plurality of fixed electrodes provided on the wall portions of the respective housing grooves can be obtained.

Further, according to the present invention, in the semiconductor capacitance type acceleration sensor, the plurality of acceleration detection element portions are semiconductor capacitance type acceleration in which the size and mass of the beam portion or the load portion are made to differ by a predetermined ratio. A sensor is obtained.

Further, according to the present invention, in any one of the semiconductor capacitance type acceleration sensors described above, a plurality of capacitance / voltage conversion circuits for converting electric capacitances relating to a plurality of acceleration detection element portions into voltages and outputting voltage signals. And a plurality of voltage comparison circuits that output the voltage detection signal by comparing the voltage value of the voltage signal with its own voltage threshold, and the voltage detection signals from the plurality of voltage comparison circuits are logically added to obtain the acceleration detection signal. A semiconductor capacitive acceleration sensor including a signal processing circuit including an output logical sum addition circuit can be obtained.

[0012]

The semiconductor capacitive acceleration sensor of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a basic structure of a sensor body of a semiconductor capacitive acceleration sensor according to an embodiment of the present invention. FIG. And (b) is a side sectional view thereof.

This sensor unit body also has an upper insulating substrate 2 and a lower insulating substrate 3 on the upper surface and the lower surface of the silicon substrate 1, respectively.
Are superposed and joined by electrostatic joining, etc.,
In the vicinity of the center of the silicon substrate 1, a pair of acceleration detection element portions 10A each including a beam portion 1b and a load portion 1a,
10B are formed adjacent to each other. Regarding each acceleration detection element section 10A, 10B, each beam section 1b
Although the width and the thickness t1 are the same, the length L2 of the beam portion 1b of the acceleration detecting element portion 10A is longer than the length L1 of the beam portion 1b of the acceleration detecting element portion 10B. That is, the beam portions 1b of the acceleration detecting element portions 10A and 10B have different dimensions and masses at a predetermined ratio, and thus the acceleration detecting element portions 10A and 1B.
There is variation in the degree of displacement when the load portion 1a at 0B is accelerated. As a result, the acceleration detecting element unit 10A has high displacement sensitivity and detects low acceleration, and the acceleration detecting element unit 10B has low displacement sensitivity and is used to detect high acceleration.

Further, the upper insulating substrate 2 and the lower insulating substrate 3 are capable of accommodating the acceleration detecting element portions 10A and 10B by removing local portions facing the acceleration detecting element portions 10A and 10B to form steps. A storage groove is formed. Further, upper fixed electrodes 4A and 4B are provided on the wall portion of the storage groove in the upper insulating substrate 2 so as to be spaced apart from the surface of the load portion 1a of the acceleration detection element portions 10A and 10B with a predetermined distance. The lower fixed electrodes 5A and 5B are also provided on the walls of the storage groove in the lower insulating substrate 3 so as to be spaced apart from the surfaces of the load portions 1a of the acceleration detection element portions 10A and 10B at predetermined intervals. There is.

In this sensor unit body, with respect to the acceleration detecting element unit 10A, the load unit 1a and the upper fixed electrode 4 are provided.
Capacitances are respectively formed between A and between the load portion 1a and the lower fixed electrode 5A, and regarding the acceleration detection element portion 10B, between the load portion 1a and the upper fixed electrode 4B and between the load portion 1a and the lower fixed electrode. Capacitance is formed between the electrodes 5B.

When manufacturing such a sensor body,
First, a predetermined number of predetermined patterns are formed on a silicon substrate wafer, which is a base material of the silicon substrate 1, by semiconductor lithography, and then etching is performed by a micro-machining method to remove each predetermined pattern. A predetermined number of a pair of acceleration detection element portions 10A and 10B, which are composed of different beam portions 1b and load portions 1a, are formed.

On the other hand, the upper insulating substrate 2 and the lower insulating substrate 3
After forming a predetermined number of storage groove patterns on a pair of Pyrex glass insulating substrate wafers, which are the base materials of the above, each etching groove is formed to form a step at a depth of several microns to form each storage groove. Then, the fixed electrodes are formed on the walls of the respective storage grooves by sputtering or the like so that one of them becomes the upper fixed electrodes 4A and 4B and the other becomes the lower fixed electrodes 5A and 5B. deep.

Next, a pair of Pyrex glass insulating substrate wafers are electrostatically bonded to the upper and lower surfaces of the silicon substrate wafer to obtain a laminated body, and finally the laminated body is cut by dicing. Then, a predetermined number of sensor unit bodies as shown in FIGS. 1A and 1B may be obtained.

FIG. 2 is a block diagram showing the basic structure of a signal processing circuit applied to such a sensor unit main body.

This signal processing circuit includes an acceleration detecting element section 1
0A, a capacitance / voltage (C / V) conversion circuit 6A that converts the electric capacitance C _A of the acceleration detection element unit 10A into a voltage and outputs a voltage signal, and a voltage from the capacitance / voltage conversion circuit 6A. Comparing the voltage value of the signal with a predetermined specific voltage threshold (threshold voltage value) SL _A , the first
Is connected to a voltage comparison circuit 7A that outputs a voltage detection signal of the acceleration detection element section 10B.
A capacitance / voltage (C / V) conversion circuit 6B that converts the electric capacitance C _B relating to 0B to a voltage and outputs a voltage signal, and a voltage value of the voltage signal from the capacitance / voltage conversion circuit 6B to a predetermined specific voltage. A voltage comparison circuit 7 that outputs a second voltage detection signal by comparing it with a threshold value (threshold voltage value) SL _B.
B, and a logical sum addition circuit 8 which logically sums the first voltage detection signal and the second voltage detection signal and outputs an acceleration detection signal.

The semiconductor capacitive acceleration sensor including this signal processing circuit and the above-mentioned sensor section main body has an acceleration detecting element section 10 according to the magnitude of the inertial force generated when it is accelerated.
A or capacitance C _A or capacitance C _A , C _B changes when load portions 1 a of A or acceleration detection element units 10 A, 10 B are automatically selected and displaced. By outputting the result detected by the circuit as an acceleration detection signal, acceleration detection can be performed with high accuracy for low acceleration and high acceleration.

Specifically, since the inertial force is small at low acceleration, the acceleration detecting element portion 10A having high displacement sensitivity.
Only the load part 1a of 1 is displaced and the electrostatic capacitance C _A is changed.
For this reason, the logical sum addition circuit 8 includes the capacitance / voltage conversion circuit 6
The first voltage detection signal output through A and the voltage comparison circuit 7A is transmitted, and as a result, the logical addition circuit 8 outputs the acceleration detection signal for the acceleration detection element unit 10A for low acceleration.

On the other hand, if the acceleration is high, the inertial force is large, so that the load section 1 of the acceleration detecting element section 10B having low displacement sensitivity.
a is also displaced and the electrostatic capacitance C _B is changed. Therefore, the second voltage detection signal output through the capacitance / voltage conversion circuit 6B and the voltage comparison circuit 7B is transmitted to the logical sum addition circuit 8 together with the first voltage detection signal, and the result From the logical sum addition circuit 8, the acceleration detection element unit 10A for low acceleration and the acceleration detection element unit 10 for high acceleration are
An acceleration detection signal for B is output.

By the way, the structure of the acceleration detecting element portions 10A and 10B in the above-mentioned sensor portion main body is, for example, as shown in FIG.
It can be modified as shown in. That is, also in this sensor part main body, a pair of acceleration detection element parts 10'A and 10'B each including the beam part 1b and the load part 1a are formed adjacent to each other in the vicinity of the center of the silicon substrate 1. Regarding the acceleration detection element portions 10'A and 10'B, the width and thickness t2 of each beam portion 1b are
The lengths are equal, and the vertical and horizontal plane dimensions and mass of the load portion 1a of the acceleration detection element portion 10'A are larger than those of the load portion 1a of the acceleration detection element portion 10'B. Thereby, the acceleration detection element units 10'A, 10 '
The degree of displacement of the load portion 1a in B when being accelerated is varied, and the acceleration detection element portion 10'A is for low acceleration detection and the acceleration detection element portion 10'B is for high acceleration detection.

Incidentally, in the case of this sensor unit main body, the dimension of the load portion 1a of the acceleration detecting element portion 10'A is larger than the dimension of the load portion 1a of the acceleration detecting element portion 10'B. An upper fixed electrode 4'A and a lower fixed electrode 5'A (not shown) having larger dimensions than those in the previous embodiments are provided on the wall of the storage groove of the insulating substrate 3.

Therefore, when manufacturing this sensor unit body, a pair of acceleration detecting element units 10 'comprising the beam unit 1b and the load unit 1a having different dimensions and masses when the respective predetermined patterns are removed from the silicon substrate wafer. A, 10'B are formed in a predetermined number, and the upper fixed electrodes 4'A, 4B are provided on one side of the wall of each storage groove for a pair of insulating substrate wafers of Pyrex glass, and the lower side is provided on the other side. It can be manufactured in the same manner as the above sensor main body except that the fixed electrodes are formed so as to become the fixed electrodes 5'A and 5B.

In each of the above examples, the silicon substrate 1 is used.
The case where a pair of acceleration detection element parts is provided in the vicinity of the center has been described. However, in order to further subdivide the acceleration detection range, three or more acceleration detection element parts each including a beam part and a load part are provided. The number of capacitance / voltage conversion circuits and voltage comparison circuits on the signal processing circuit side may correspond to the number of acceleration detection element units.

[0029]

As described above, according to the semiconductor capacitive acceleration sensor of the present invention, a plurality of acceleration detecting element portions are formed on the silicon substrate of the sensor body, and the beams in the plurality of acceleration detecting element portions are provided. Section or load section is made to have a different size and mass at a predetermined ratio, and the degree of displacement of the load section is varied in the case of acceleration to diversify the change in the electric capacitance of each acceleration detection element section, and Acceleration detection is performed as a result of logical sum addition of multiple voltage detection signals obtained by converting the electric capacitances related to each acceleration detection element unit to a voltage individually by the processing circuit and comparing each voltage signal with its own threshold Since it is configured to output signals, it is possible to detect acceleration in a wide range from low acceleration to high acceleration with a single product with a simple configuration. That.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic configuration of a sensor body in a semiconductor capacitive acceleration sensor according to an embodiment of the present invention,
(A) is a perspective view showing a part of it in a transparent manner and omitting it, and (b) is a side sectional view thereof.

FIG. 2 is a block diagram showing a basic configuration of a signal processing circuit applied to the sensor unit main body shown in FIG.

FIG. 3 is a perspective view showing a basic configuration when a main part of the sensor unit main body shown in FIG. 1 is modified.

FIG. 4 is a side sectional view showing a basic configuration of a sensor unit main body in a conventional semiconductor capacitive acceleration sensor.

[Explanation of symbols]

1 Silicon substrate 1a Load part 1b Beam part 2 Upper insulating substrate 3 Lower insulating substrate 4, 4A, 4B Upper fixed electrode 5, 5A, 5B, 5'A Lower fixed electrode 6A, 6B Capacitance / voltage (C / V) conversion circuit 7A, 7B Voltage comparison circuit 8 OR addition circuit 10, 10A, 10B, 10'A, 10'B Acceleration detection element section

Claims (3)

[Claims] 1. A plurality of acceleration detecting element portions each having a beam portion and a load portion extending from the beam portion are formed adjacent to each other in the central portion by removing the central portion in a predetermined pattern. A storage that can store the silicon substrate and the one surface and the other surface of the silicon substrate, which are superposed on each other and bonded to each other, and local portions facing the plurality of acceleration detection element portions are removed to store the plurality of acceleration detection element portions. A pair of insulating substrates in which a groove is formed and a storage groove of each of the pair of insulating substrates that face the load portions of the plurality of acceleration detecting element portions and are spaced apart from the surfaces of the load portions. A semiconductor capacitive acceleration sensor including a plurality of fixed electrodes provided on a wall. 2. The semiconductor capacitive acceleration sensor according to claim 1, wherein the plurality of acceleration detection element portions are different in size and mass in the beam portion or the load portion at a predetermined ratio. A characteristic semiconductor capacitive acceleration sensor. 3. The semiconductor capacitive acceleration sensor according to claim 1, further comprising: a plurality of capacitance / voltage conversion circuits that convert the electric capacitances of the plurality of acceleration detection element units into voltages and output voltage signals. A plurality of voltage comparison circuits that output a voltage detection signal by comparing the voltage value of the voltage signal with a unique voltage threshold value, and an acceleration detection signal by logically adding the voltage detection signals from the plurality of voltage comparison circuits A semiconductor capacitive acceleration sensor comprising a signal processing circuit including an output logical sum addition circuit.