JP3433671B2 - 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 formed by processing a semiconductor substrate.

[0002]

2. Description of the Related Art FIG. 4 is a configuration diagram showing a configuration of a conventional acceleration sensor. In this figure, the sensor chip 1 is subjected to anisotropic etching to form a thin support body 3 made of a diaphragm on the back surface, and a mass portion 4 is formed on the central side of the sensor chip 1 and a peripheral edge side is formed on the peripheral edge side. The thick portions 5 are formed respectively. A through groove 6 is formed around the mass portion 4. The mass portion 4 and the thick portion 5 are connected only by the support body 3 formed by the etching process, and the support body 3 supports the mass portion 4 as a cantilever support. Further, gauge resistors 7 are formed on the surface of the support 3, and the gauge resistors 7 are connected to form a Wheatstone bridge circuit.

Glass stoppers 2a and 2b are joined to both sides of the thick portion 5 of the sensor chip 1 by anodic bonding, and the glass stoppers 2a and 2b are provided with recesses 9 respectively, and are connected to the mass portion 4. A gap 8 is formed between the mass portion 4 and the glass stoppers 2a and 2b facing each other. The gap 8 is a swing range of the mass portion 4 when acceleration is applied, and the glass stoppers 2a and 2b are such that the mass portion 4 is excessively displaced in the vertical direction of the acceleration sensor (direction shown by an arrow in FIG. 4 ). It regulates the

Pyrex glass # 7740 or the like is used as the material of the glass stoppers 2a and 2b. These are bonded to both sides of the sensor chip 1 by anodic bonding, and air or oil is sealed inside to form an air damping structure. Is forming. As a result, when the acceleration sensor receives an excessive acceleration, the support body 3 supporting the mass portion 4 is protected from an impact. Similarly, when the mass portion 4 swings excessively, the mass portion 4 touches the glass stoppers 2a and 2b and the movement is restricted, so that the support body 3 is prevented from being broken or damaged.

Next, the operation of this acceleration sensor will be described. Now, when the acceleration α is applied in the direction perpendicular to the acceleration sensor chip 1, a force F = mα is generated in the mass portion 4. This force F causes the support 3 to bend, causing distortion on the surface,
This distortion changes the value of the gauge resistance 7 formed on the surface of the support 3. At this time, if a voltage is externally supplied to the Wheatstone bridge circuit, the gauge resistance 7
The voltage signal proportional to the acceleration is detected to the outside through the wire 12 due to the change in the resistance value of.

[0006]

However, in the acceleration sensor configured as described above, the mass portion 4 is formed by anisotropic etching from the same silicon wafer as the support 3 at the time of manufacture. It was difficult to increase the weight of No. 4 and improve the sensitivity.

Therefore, a structure has been considered in which a glass weight is bonded to the mass portion 4 by anodic bonding to improve the sensitivity of the acceleration sensor (see Japanese Patent Laid-Open No. 5-288770).

However, in anodic bonding, high temperature (about 400
In order to apply a high voltage (about 600 to 1000 V) at (° C.), there was a problem that stress was applied to the support body 3 due to the difference in thermal expansion coefficient between glass and silicon, and strain was generated in the gauge resistance 7. . Therefore, the characteristics of the offset sensitivity during manufacturing are unstable, and the glass and the mass portion 4 are
There is a problem in that the residual stress due to the joining causes the characteristics to change with temperature.

The present invention has been made to solve the above problems, and aims to improve the sensitivity of the acceleration sensor and to provide an acceleration sensor having good temperature characteristics (offset temperature characteristic and sensitivity temperature characteristic). To do.

[0010]

In order to achieve the above object, the invention of claim 1 processes a semiconductor substrate to form a mass portion which is swingably supported by a support, and the support. An acceleration sensor having a sensor chip formed by forming a gauge resistance on the surface of and a stopper provided on both surfaces of the sensor chip to restrict the swing range of the mass part
A plurality of weights made of semiconductor and having the same thickness are arranged at least equidistantly on at least one surface of the mass portion through a low melting point glass thin film.
The by bonding, the thermal expansion coefficient of the sensor chip and the weight are equal, these without distortion occurs in the gauge resistance when bonding, the temperature characteristic of the acceleration sensor is improved, to improve the sensitivity You can Furthermore
In addition, divide the impact applied to the acceleration sensor into multiple weights,
Excessive impact can be mitigated.

According to a second aspect of the present invention, the semiconductor substrate is processed.
Forming a mass part that is swingably supported on the support
And a sensor formed by forming a gauge resistance on the surface of the support
It is provided on both sides of the chip and the sensor chip, and the mass part shakes.
For an acceleration sensor equipped with a stopper that limits the range of motion.
The low melting point glass thin film on at least one side of the mass part.
Join the weights made of semiconductors through at least the weights
Both ends are joined to both ends of the mass part or the peripheral part,
By forming a convex portion on the surface facing the stopper of,
The sensor chip and the weight have the same coefficient of thermal expansion,
There is no strain in the gauge resistance when joining
The temperature characteristics of the acceleration sensor are improved and the sensitivity is improved.
You can go up. In addition, the impact on the acceleration sensor
When it is added, the convex part comes into contact with the glass stopper and
Shock can be mitigated.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 is a sectional view showing the basic structure of the present invention. In addition,
Since the basic configurations of the present embodiment and the embodiments described below are almost the same as those of the conventional example, the common parts are denoted by the same reference numerals and the description thereof will be omitted. Only the characteristic parts will be described.

First , as shown in FIG. 1, the basic structure of this embodiment is that a weight 10 made of a semiconductor (hereinafter referred to as a silicon weight) is provided on at least one surface of a mass portion 4 of a sensor chip 1.
The is obtained by bonding by glass film 11.

Here, the mass portion 4 is formed in such a shape that one side on the side supported by the support 3 is wide and the other side has a narrow end surface, and the silicon weight 10 is formed in the shape of a thin flat plate. ing. Further, the width of the silicon weight 10 joined to the mass portion 4 is formed to be substantially the same as the width of the wide surface of the mass portion 4, and one surface of the silicon weight 10 has a low melting point on the wide surface of the mass portion 4. By bonding with the glass thin film 11, the mass of the mass portion 4 is increased, and the sensitivity of the acceleration sensor is improved.

The low-melting-point glass thin film 11 is made of, for example, lead-based amorphous glass and is formed on a silicon wafer to be the weight 10 to have a thickness of about several μm by an RF sputtering method or the like. The weight 10 and the sensor chip 1 are formed. Over, about 50 ℃ ~ 80 ℃
At the temperature of, the weight 10 side is made a negative electrode and a direct current voltage of several tens of volts is applied to join.

When the silicon weight 10 and the mass portion 4 are bonded in this manner, bonding can be performed at a lower temperature and a lower voltage as compared with the case where conventional glass is anodically bonded to the mass portion 4, and the weight 10 and the sensor chip 1 are bonded. Since the same silicon material is used for the two, the coefficients of thermal expansion are equal and almost no strain occurs during bonding. Therefore, stress is not generated in the gauge resistor 7, and the offset temperature characteristic and the sensitivity temperature characteristic of the acceleration sensor can be improved.

On the other hand, a concave portion 9 is formed in the glass stoppers 2a, 2b facing the silicon weight 10 and the depth of the concave portion 9 is sufficiently deep so that the silicon weight 1 is formed between the concave portion 9 and the mass portion 4.
Enough space is secured for the 0s to be placed. Therefore, even if the silicon weight 10 is bonded to the mass portion 4 as described above, the glass stopper 2a facing the silicon weight 10 is provided.
A constant gap 8 is provided between and, so that the mass portion 4 can swing. The width of the gap 8 is set by changing the depth of the concave portion 9 of the glass stopper 2a, and the swing range of the mass portion 4 can be controlled.

If the acceleration sensor is constructed as described above,
It is possible to increase the weight of the mass portion 4 by the weight of the silicon weight 10, and as a result, it is possible to improve the sensitivity of the acceleration sensor. Furthermore, since the silicon weight 10 and the sensor chip 1 have the same coefficient of thermal expansion, the strain generated when joining them becomes extremely small, and the offset temperature characteristics of the acceleration sensor and the offset temperature characteristics of the acceleration sensor are smaller than those when other conventional weights are used. The sensitivity temperature characteristic is improved.

In this embodiment, as shown in FIG.
To a plurality of silicon heavy Ri 10 having the same thickness, approximately equal
Joined to the mass part 4 via the glass thin film 11 at intervals
Is characterized by. Here, the silicon weight 10 has a uniform thickness.
Excessive acceleration from the outside because there are multiple
When the degree is added in the vertical direction (the direction shown by the arrow in Fig. 2)
In that case, the impact is divided into multiple silicon weights 10.
The impact force is dispersed, and damage to the support 3 can be prevented.
it can.

(Embodiment 2) In the present embodiment, the silicon weight 10 is attached to the silicon weight 10 as shown in FIG.
In addition, the convex portion 19 is provided on the surface facing the glass stopper 2a.
Provided, both ends or the peripheral portion of the silicon weight 10 and the mass portion 4
Are joined by a glass thin film 11. This allows
Glass stopper near the top of the convex portion 19 of the recon weight 10
The gap 8 with 2a becomes narrower and excessive acceleration is applied from the outside.
When crossed, the convex portion 19 of the silicon weight 10 first faces
The glass stopper 2a is in contact with the glass stopper 2a.
Then, at this time, the silicon weight 10 has both ends or a circumference.
The side part is joined to the wide surface of the mass part 4, and the lower center part is
Since it is not joined and a space is provided, silicon weight 1
0 bends, which causes excessive impact on the acceleration sensor.
The attack can be mitigated.

[0021]

According to the invention of claim 1, a sensor chip is formed by processing a semiconductor substrate to form a mass portion swingably supported by a support, and forming a gauge resistance on the surface of the support. And an acceleration sensor having stoppers provided on both sides of the sensor chip for restricting the swinging range of the mass portion, and a plurality of semiconductor sensors having the same thickness formed on at least one surface side of the mass portion with a low melting point glass thin film interposed therebetween. Carved of weight
By joining the sensor chips at equal intervals, the coefficient of thermal expansion of the sensor chip becomes equal to that of the weight, and the gauge resistance is not distorted when joining them, improving the temperature characteristics of the acceleration sensor and improving the sensitivity. There is an effect that can be achieved. In addition, the shock applied to the acceleration sensor
Can be divided into multiple weights to reduce excessive shock.
There is an effect that you can.

According to a second aspect of the present invention, a semiconductor substrate is processed.
Forming a mass part that is swingably supported on the support
And a sensor formed by forming a gauge resistance on the surface of the support
It is provided on both sides of the chip and the sensor chip, and the mass part shakes.
For an acceleration sensor equipped with a stopper that limits the range of motion.
The low melting point glass thin film on at least one side of the mass part.
Join the weights made of semiconductors through at least the weights
Both ends are joined to both ends of the mass part or the peripheral part,
By forming a convex portion on the surface facing the stopper of,
The sensor chip and the weight have the same coefficient of thermal expansion,
There is no strain in the gauge resistance when joining
The temperature characteristics of the acceleration sensor are improved and the sensitivity is improved.
There is an effect that it can improve. Furthermore, the shock
The glass stopper on the acceleration sensor
The effect of being able to contact with
There is a fruit.

[Brief description of drawings]

FIG. 1 is a sectional view showing a basic configuration of the present invention .

FIG. 2 is a cross-sectional view showing the first embodiment.

FIG. 3 is a sectional view showing a second embodiment.

FIG. 4 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

1 sensor chip 2a glass stopper 2b glass stopper 3 support 4 squares 7 gauge resistance 10 silicon weights 11 Glass thin film

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-167888 (JP, A) JP-A-7-146307 (JP, A) JP-A-8-320340 (JP, A) JP-A-8- 122361 (JP, A) JP 9-105760 (JP, A) JP 7-128360 (JP, A) JP 7-306223 (JP, A) JP 7-306224 (JP, A) JP-A-5-273230 (JP, A) JP-A-6-300774 (JP, A) JP-A-3-49267 (JP, A) Practical application 3-1-15862 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01P 15/12 H01L 29/84

Claims (2)

(57) [Claims] 1. A sensor chip formed by processing a semiconductor substrate to form a mass part swingably supported by a support, and forming a gauge resistance on the surface of the support, and on both sides of the sensor chip. In an acceleration sensor provided with a stopper for restricting the swing range of the mass portion , a plurality of weights having the same thickness made of a semiconductor are provided at substantially equal intervals on at least one surface of the mass portion via a low melting point glass thin film. An acceleration sensor characterized by being joined. 2. A semiconductor substrate is processed to be freely swingable on a support.
A mass portion supported by the support and the surface of the support.
A sensor chip formed by forming a gauge resistance on the surface, and a sensor
Provided on both sides of the chip to regulate the swing range of the mass part
In an acceleration sensor having a stopper, at least
From the semiconductor through a low melting point glass thin film on one side of the mass part
The weights are joined, and at least both ends of the weight are
It is joined to both ends or the peripheral part of the and faces the stopper of the weight.
An acceleration sensor characterized in that a convex portion is formed on a surface to be formed .