JPH07234238A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To detect with high sensitivity, high accuracy and good responsiveness an acceleration applied to a sensor main body by easily obtaining the very small, accurate sensor main body through micromachining that utilizes semiconductor device manufacturing technology. CONSTITUTION:A semiconductor substrate, on which a recess 3 and a bridge 4 over the recess 3 are etched and in which a heating wire 5 serving as a heat- sensitive resistance element is patterned over the bridge 4, is installed within a closed space inside which gas is sealed.

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 an acceleration applied to a sensor body.

[0002]

2. Description of the Related Art Conventionally, an acceleration sensor has been developed in which the strength of an air flow generated in a case when an acceleration is applied is detected as a change in resistance in a thin film resistance temperature element.

This is because a thin-film resistance temperature element is provided in a case made of synthetic resin together with a temperature compensating temperature element for detecting the temperature of the air in the case so that the air flow generated in the case when acceleration is applied is The state when the temperature element is exposed and the resistance value is changed is electrically detected (see Japanese Patent Laid-Open No. 3-176669).

[0004]

The problem to be solved by the present invention is that in an acceleration sensor in which the strength of the air flow caused by acceleration applied to the sensor body is detected as a change in resistance in the thin film resistance temperature element, The larger the space inside the case is, the worse the response is because it detects the change of the air flow that occurs in the case.However, in the conventional case, there is a limit to miniaturization due to its structure, and the response is small. There is a problem in terms of sex.

Further, in the conventional acceleration sensor, since the change state of the air flow generated in the case is detected, the detection sensitivity changes depending on the position of the thin film resistance temperature element installed in the case, and The tendency becomes more remarkable as the size becomes smaller, and it becomes difficult to position the thin film resistance temperature element in the case.

Further, in the conventional acceleration sensor, only the magnitude of the acceleration applied to the sensor body is detected, and the direction in which the acceleration is applied cannot be detected.

[0007]

According to the present invention, an ultra-compact and precise acceleration sensor can be easily obtained by micromachining utilizing a semiconductor device manufacturing technique, and a sensor body having high sensitivity, high accuracy and good responsiveness can be obtained. In order to be able to detect the acceleration applied to, the semiconductor substrate is provided with a concave portion and a bridge portion corresponding to the concave portion formed by etching, and a heat wire as a heat-sensitive resistance element is patterned on the bridge portion. It is designed to be installed in a closed space filled with gas.

Further, according to the present invention, a pair of heat wires are formed on the bridge portion at a predetermined interval, and a change in heat distribution caused by an acceleration applied to the sensor body is detected by which heat wire. It is possible to detect the acceleration so that the acceleration applied to the sensor body can be detected directionally.

[0009]

1 and 2 show the basic structure of a sensor body in an acceleration sensor according to the present invention, in which a recess 3 and a bridge portion 4 extending over the recess 3 are formed by etching.
Lower semiconductor (Si) substrate 1 in which a heat wire 5 as a heat-sensitive resistance element is formed on the bridge portion 4
And the upper semiconductor (Si) substrate 2 in which the recesses 6 have been formed by etching are joined so that the recesses 3 and 6 of the two are brought into contact with each other, and the chamber 7 formed by bringing the recesses 3 and 6 into contact with each other. It is configured by enclosing an inert gas such as nitrogen or argon inside.

The heat wire 5 is formed by depositing a metal such as Pt which is a material of the heat wire on a silicon substrate which will be the lower semiconductor substrate 1, and then etching the metal material into a predetermined pattern. .

When the silicon substrate is etched to form the recesses 3, the lower portion of the heat wire 5 formed on the silicon substrate is removed by etching to form the bridge portion 4.

Electrode portions 8 made of the same material as the heat wire 5 are pattern-formed on both sides of the bridge portion 4 in the lower semiconductor substrate 1.

In the case of such a configuration, the state when the resistance value is changed by detecting the degree of change in the heat distribution generated in the chamber 7 when the sensor body is subjected to acceleration is detected by the heat wire 5. Is detected electrically, the magnitude of the acceleration at that time can be measured.

Therefore, according to the present invention, by the micromachining process utilizing the manufacturing technique of the semiconductor device,
It is possible to easily manufacture an ultra-small sensor body of the order of several mm with high accuracy, and to detect an acceleration applied to the sensor body with high sensitivity and high responsiveness.

In the present invention, the upper semiconductor substrate 2 serving as the lid of the lower semiconductor substrate 1 is not particularly required, but the lower semiconductor substrate on which the heat wire 5 is formed is installed in the gas sealed space. You may do it.

Further, as the lower substrate 1 on which the heat wire 5 is formed, instead of using a semiconductor substrate, another insulating substrate such as glass may be used. As the lid of the lower semiconductor substrate 1, instead of using the upper semiconductor substrate 2, a substrate made of other material such as glass or metal can be widely used.

3 and 4 show an example of the structure of the sensor main body when the acceleration applied to the sensor main body can be detected directionally. Here, the concave portion 3 and its portion are formed by etching. A bridge portion 4 is formed on the recessed portion 3, a pair of heat wires 51 and 52 are formed on the bridge portion 4 at a predetermined interval, and a heater 9 is provided at an intermediate position between the heat wires 51 and 52.
Lower semiconductor (Si) substrate 1 formed on the bridge portion 10
And the upper conductor (S
i) The substrate 2 is joined so that the concave portions 3 and 6 of the two are abutted with each other, and an inert gas such as nitrogen or argon is sealed in the chamber 7 formed by abutting the concave portions 3 and 6. It consists of:

A pair of heat wires 51 and 52 are formed on a silicon substrate which is the lower semiconductor substrate 1 by using Pt and Mo as refractory metals which are stable at high temperature and which are materials of the heat wires.
It is formed by vapor-depositing a metal such as Ni, Au and Ti and then etching the metal material into a predetermined pattern.

At this time, particularly in order to improve the thermal stability and durability of the heat wires 51, 52, the heat wires 51, 52 are coated with an oxide film made of SiN or the like.

Similarly, the heater 9 is formed by vapor-depositing a heater material on a silicon substrate which will be the lower semiconductor substrate 1, and then etching it into a predetermined pattern.

Then, when the concave portion 3 is formed by etching the silicon substrate, the lower portion of the pair of heat wires 51 and 52 and the lower portion of the heater 9 formed on the silicon substrate are removed by etching. As a result, the bridge portion 4 and the bridge portion 10 are formed.

As an electric circuit section of the acceleration sensor,
As shown in FIG. 5, a bridge circuit 11 in which a pair of heat wires 51 and 52 provided on the sensor body side and reference resistors R1 and R2 are provided on each branch path is configured, and acceleration is applied to the sensor body. The output of the bridge circuit 11 in the unbalanced state is output by the amplifier 12.

In the acceleration sensor thus constructed, when acceleration is applied in the direction indicated by the arrow (or dotted arrow) in FIG. 4, the heat distribution changes in that direction, and the heater changes. One of the heat wires 51 (or the heat wire 52) is exposed to the gas heated by 9 and its resistance value changes.

The unbalanced output of the bridge circuit 11 in accordance with the change in the resistance value of the heat wire 51 (or the heat wire 52) is taken out from the amplifier 12,
From the magnitude of the output, the magnitude of the acceleration applied to the sensor body at that time, and the polarity of the output can detect the direction of the acceleration.

In that case, the thermal conductivity is 0.024 Kcal.
/ M · h · ° C, and the heating value of the heater 9 is 0.01 Kcal / h per 1 mm ^2, the temperature gradient (= heating value / thermal conductivity) in the heater 9 part is 400 ° C / It can be set to about mm, and the heat distribution state in the heater 9 portion becomes sharp and 1
Acceleration can be detected with high sensitivity in a minute space of mm or less.

At this time, if the gas is pressurized to 1 atm or more and enclosed in the chamber 7, the sensitivity is further improved.

According to the present invention, the space for detecting the acceleration in the sensor body can be easily set to several mm (preferably 2 to 3 mm) by the micromachining process using the semiconductor device manufacturing technology, and the sensor can be easily manufactured. Acceleration applied to the main body can be detected with good responsiveness.

Further, according to the present invention, the precision machining of the sensor main body can be easily performed, and the height from the bottom surface is on the center line where the distances from the wall surfaces on both sides in the direction in which the acceleration in the chamber 7 is applied are equal. The heat wires 51 and 52 can be accurately arranged at the same hollow position and symmetrically on both sides of the heater 9 with the heater 9 as the center, and the acceleration applied to the sensor body can be accurately detected with directionality. Will be able to.

In this case, in particular, according to the present invention, it is possible to easily form the heat wires 51, 52 provided in a pair so that their respective resistance values are the same. Therefore, the bridge circuit 11 when acceleration is not applied to the sensor body
The balanced state can be maintained well, and the offset output that causes the detection error can be effectively suppressed.

If it is attempted to manufacture the sensor body without depending on the semiconductor device manufacturing process, there is a limit to downsizing the sensor body, and a pair of heat wires 51, 52 installed in the chamber 7 of the sensor body. It is difficult to maintain the mutual positional relationship between the heater 9 and the heater 9 to a predetermined value, and the accuracy of detecting the acceleration deteriorates.

The present invention is not limited to the above-described embodiment, and for example, as shown in FIG. 6, the heat wires 51 and 52 may be used as a heater without providing a heater. A pair of heat wires 5 installed
It is difficult to maintain the mutual positional relationship between the heaters 1 and 52 and the heater 9 to a predetermined value, and the accuracy of acceleration detection is reduced.

[0032]

As described above, in the acceleration detector according to the present invention, the concave portion and the bridge portion corresponding to the concave portion are formed on the semiconductor substrate by etching, and the heat wire as the heat sensitive resistance element is patterned on the bridge portion. It is designed to be installed in a sealed space in which a gas is enclosed, and it is easy to obtain an ultra-compact and precise acceleration sensor by micromachining using semiconductor device manufacturing technology, and with high sensitivity. It has an advantage that the magnitude of the acceleration applied to the sensor body can be detected with high responsiveness with high accuracy.

In particular, according to the present invention, a pair of heat wires are formed on the bridge portion with a predetermined space therebetween, and a heater is formed between the heat wires to generate heat generated by acceleration of the sensor body. It is possible to see which heat wire is used to detect the change in the distribution, and there is an advantage that the acceleration applied to the sensor body can be detected with directivity.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of an acceleration detector according to the present invention.

FIG. 2 is a plan view of a lower semiconductor substrate in the example.

FIG. 3 is a front sectional view showing another embodiment of the acceleration detector according to the present invention.

FIG. 4 is a plan view of a lower semiconductor substrate in another example.

FIG. 5 is a circuit configuration diagram showing a configuration example of an electric circuit unit of the acceleration sensor.

FIG. 6 is a plan view of a lower semiconductor substrate according to still another embodiment of the present invention.

[Explanation of symbols]

 1 Lower Semiconductor Substrate 2 Upper Semiconductor Substrate 4 Bridge 5 Heat Wire 51 Heat Wire 52 Heat Wire 7 Chamber 8 Electrode 9 Heater

Claims (4)

[Claims] 1. An acceleration sensor in which the degree of change in heat distribution caused by acceleration applied to the sensor body is detected as a change in resistance in a thermosensitive resistance element, wherein a first semiconductor substrate or an insulating substrate is etched. As a result, a concave portion and a bridge portion corresponding to the concave portion are formed, and a heat wire as a heat-sensitive resistance element is patterned on the bridge portion, and the acceleration is formed by installing it in a gas-enclosed sealed space. Sensor. 2. A chamber in which the two recesses are abutted is formed by bonding the second substrate in which the recesses are formed to the first semiconductor substrate or the insulating substrate in which the bridge portion of the heat wire is formed. Thus, the acceleration sensor according to the above-mentioned item 1, wherein gas is enclosed in the chamber. 3. The acceleration sensor according to claim 1, wherein a pair of heat wires are formed on the bridge portion at a predetermined interval, and a heater is formed between the heat wires. 4. The acceleration sensor according to claim 1, wherein a heat wire is used as a heater.