JP3345695B2 - Acceleration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor for detecting acceleration applied to a sensor body.

[0002]

2. Description of the Related Art Conventionally, acceleration sensors have been developed in which the strength of airflow generated in a case due to the application of acceleration is detected as a change in resistance in a thin-film resistance temperature element.

[0003] A thin-film resistance temperature element is provided in a case made of a synthetic resin together with a temperature element for temperature compensation for detecting the temperature of air in the case. The state when the resistance value changes when the temperature element is exposed is electrically detected (see Japanese Patent Application Laid-Open No. 3-176669).

[0004]

The problem to be solved is that in an acceleration sensor in which the strength of the airflow generated by the application of acceleration to the sensor body is taken as a change in the resistance of the thin-film resistance temperature element, the problem is not solved. The response is worse as the space inside the case is larger because it is to detect the change of airflow generated in the case. However, the conventional one has a limit in miniaturization due to its structure. There is a problem in terms of gender.

Further, in the conventional acceleration sensor, since the change state of the airflow 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. The tendency becomes remarkable as the size is reduced, 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, but the direction in which the acceleration is applied cannot be detected.

[0007]

According to the present invention, a sensor body is provided.
The degree of change in the heat distribution caused by acceleration
As perceived as a change in resistance in a thermosensitive resistor
In the acceleration sensors, the readily obtain ultra compact and accurate acceleration sensor by micromachining using technology for manufacturing a semiconductor device, for detecting an acceleration applied to good response sensor body with high sensitivity and precision in order to be able, Contact recess by etching
And a first bridge portion over the recess is formed.
A pair of heat wires as a thermal resistance element on the bridge portion 1
Pattern is formed, and a heater is placed between the heat wires.
The heater is patterned on top so that
The first semiconductor substrate having the second bridge portion formed thereon or
An edge substrate and a second half having a recess formed by etching.
A conductive substrate or an insulating substrate;
By joining each semiconductor substrate or insulating substrate,
So that a chamber is formed in which the recesses of the
Gas is sealed in the room .

In this case, in particular, in the present invention, the first bridge
When forming a pair of heat wires at a predetermined interval
In both cases, the heater formed on the second bridge is
Between the heat wires
The acceleration of the sensor body is
The change in heat distribution caused by the heat
By detecting what is detected by the wire, the sensor
Detects acceleration applied to the main unit with high sensitivity with directionality
Have to be able to .

[0009]

1 and 2 show a basic structure of a sensor main body in an acceleration sensor according to the present invention, wherein a concave portion 3 is formed by etching and a bridge portion 4 covering the concave portion 3. FIG.
Is formed, and a lower semiconductor (Si) substrate 1 on which a heat wire 5 as a thermal resistance element is formed on a bridge portion 4 thereof.
And the upper semiconductor (Si) substrate 2 on which the concave portions 6 are formed by etching so that the concave portions 3 and 6 of the two are brought into contact with each other, and a chamber 7 formed by bringing the concave portions 3 and 6 into contact with each other. It is configured by filling an inert gas such as nitrogen or argon therein.

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

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

On both sides of the bridge portion 4 of the lower semiconductor substrate 1, electrode portions 8 made of the same material as the heat wire 5 are formed by patterning.

In the above-described configuration, the degree of change in the heat distribution generated in the chamber 7 when acceleration is applied to the sensor body is detected by the heat wire 5 and the state when the resistance value changes. Is electrically detected, the magnitude of the acceleration at that time can be measured.

Thus, according to the present invention, the micromachining process utilizing the semiconductor device manufacturing technology allows
An ultra-small sensor body of the order of several millimeters can be easily manufactured with high precision, and the acceleration applied to the sensor body can be detected with high sensitivity and responsiveness.

In the present invention, the upper semiconductor substrate 2 serving as a lid of the lower semiconductor substrate 1 is not particularly required, and the lower semiconductor substrate on which the heat wires 5 are formed is installed in a gas-tight space. You may make it.

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

FIGS. 3 and 4 show an example of the configuration of the sensor main body when the acceleration applied to the sensor main body can be detected in a directional manner. Here, the recess 3 is formed by etching. A bridge 4 is formed over the recess 3, a pair of heat wires 51 and 52 are formed on the bridge 4 at a predetermined interval, and a heater 9 is provided at an intermediate position between the heat wires 51 and 52.
Is a lower semiconductor (Si) substrate 1 formed on a bridge 10
And the upper conductor (S
i) The substrate 2 is joined so that the concave portions 3 and 6 thereof are brought into contact with each other, and an inert gas such as nitrogen or argon is sealed in a chamber 7 formed by bringing the concave portions 3 and 6 into contact with each other. It is constituted by that.

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

At this time, when it is desired to improve the thermal stability and durability of the heat wires 51 and 52, the heat wires 51 and 52 are coated with an oxide film made of SiN or the like.

Similarly, the heater 9 is formed by depositing a heater material on a silicon substrate to 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 portions 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. Thereby, the bridge portion 4 and the bridge portion 10 are formed.

Further, as an electric circuit portion of the acceleration sensor,
As shown in FIG. 5, a bridge circuit 11 is provided in which a pair of heat wires 51 and 52 provided on the sensor body side and reference resistors R1 and R2 are provided in respective branches, and acceleration is applied to the sensor body. The unbalanced output of the bridge circuit 11 is output by the amplifier 12.

In the acceleration sensor configured as described above, when acceleration is applied in a direction indicated by an arrow (or a dotted arrow) in FIG. The one heated wire 51 (or heated wire 52) is exposed to the gas heated by 9 and its resistance value changes.

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

In this case, the thermal conductivity is 0.024 Kcal
/ M · h · ° C. and the heating value of the heater 9 is set to 0.01 Kcal / h per 1 mm ^2, the temperature gradient (= heating value / thermal conductivity) in the heater 9 portion is 400 ° C./h. mm, and the state of heat distribution in the heater 9 becomes abrupt.
It is possible to detect acceleration with high sensitivity in a minute space of less than mm.

At this time, if the gas is sealed in the chamber 7 in a state where the gas is pressurized to 1 atm or more, the sensitivity is further improved.

According to the present invention, the space for detecting acceleration in the sensor body can be easily reduced to the order of several mm (preferably, 2 to 3 mm) by micromachining processing utilizing a semiconductor device manufacturing technique. The acceleration applied to the main body can be detected with good responsiveness.

According to the present invention, the precision processing of the sensor main body can be easily performed, and the height from the bottom surface on the center line where the distance from the wall surface on both sides to the direction in which the acceleration is applied in the chamber 7 is 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 at the center, and the acceleration applied to the sensor main body can be accurately detected with directionality. Will be able to do it.

In this case, in particular, according to the present invention, it is possible to easily form the heat wires 51 and 52 provided as a pair so as to make the respective resistance values uniform. Therefore, the bridge circuit 11 when no acceleration is applied to the sensor body
Can be kept in a good balance, and the offset output which causes a detection error can be effectively suppressed.

If the sensor body is to be manufactured without using the semiconductor device manufacturing process, the size reduction of the sensor body is naturally limited, and a pair of heat wires 51 and 52 installed in the chamber 7 of the sensor body. It is difficult to maintain the mutual positional relationship of the heater 9 and the heater 9 at a predetermined value, and the accuracy of acceleration detection is reduced.

The present invention is not limited to the above-described embodiment. For example, as shown in FIG. 6, a configuration may be adopted in which the heat wires 51 and 52 are used as heaters without providing a heater. A pair of heat wires 5 to be installed
It is difficult to maintain the mutual positional relationship between the heaters 1 and 52 and the heater 9 at 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 second portion over the concave portion are etched.
A first bridge is formed, and a heat-sensitive resistor is provided on the first bridge.
A pair of heat wires as elements are pattern-formed,
So that the heater is placed between the heat wires,
The heater forms a second bridge with a pattern.
Etching with the first semiconductor substrate or insulating substrate
A second semiconductor substrate or an insulating substrate having a more concave portion formed
The first and second semiconductor substrates or insulating
By joining the substrates, the two recesses are brought together
A small chamber is formed, and a gas is sealed in the chamber. A micro-machining process using a semiconductor device manufacturing technology enables an ultra-small and precise acceleration sensor to be easily formed. In addition, there is an advantage that the magnitude of the acceleration applied to the sensor body can be detected with high sensitivity and responsiveness with high accuracy.

At this time, in particular, in the present invention, the first bridge portion
When forming a pair of heat wires at a predetermined interval
In both cases, the heater formed on the second bridge is
Between the heat wires
Since the cloth condition is set to be abrupt,
What is the change in heat distribution caused by acceleration?
By detecting what is detected by the heat wire
And the acceleration applied to the sensor body is highly sensitive with directionality.
This has the advantage that it can be detected in

[Brief description of the drawings]

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

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

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 embodiment.

FIG. 5 is a circuit configuration diagram illustrating 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]

 DESCRIPTION OF SYMBOLS 1 Lower semiconductor substrate 2 Upper semiconductor substrate 4 Bridge part 5 Heat wire 51 Heat wire 52 Heat wire 7 Room 8 Electrode part 9 Heater

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-2026 (JP, A) JP-A-5-52862 (JP, A) JP-A-4-369481 (JP, A) 369482 (JP, A) JP-A-2-240573 (JP, A) JP-A-62-236967 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 15/00-15 / 03 G01P 9/00 G01C 19/00 H01C 7/02 H01L 21/822 H01L 27/04

Claims (4)

(57) [Claims] 1. A acceleration sensor so as to capture the extent of the change in the thermal distribution caused by acceleration applied to the sensor body as a change in resistance in the thermosensitive resistor elements, first according to the recesses and the recesses thereof by etching
Bridge portion is formed, and a heat-sensitive resistor is formed on the first bridge portion.
A pair of heat wires as a child are patterned and
So that the heater is located between the heat wires
A second bridge portion formed by pattern formation of the heater is formed.
Etching with the first semiconductor substrate or the insulating substrate
A second semiconductor substrate or an insulating substrate having a recess formed therein;
Consists, first and second respective semiconductor base plate or an insulating group
By joining the plates, both recesses were butted together
An acceleration sensor constituted by forming a chamber and filling gas in the chamber . 2. A chamber in which the two concave portions are joined by joining the second substrate having the concave portions to the first semiconductor substrate or the insulating substrate having the bridge portion of the heat wire. 2. The acceleration sensor according to claim 1, wherein a gas is sealed in the room as described above. 3. The acceleration sensor according to claim 1, wherein a pair of heat wires are formed at predetermined intervals on the bridge portion, and a heater is formed between the heat wires. 4. The acceleration sensor according to claim 1, wherein a heat wire is used for the heater.