JPH07117553B2 - Method of manufacturing semiconductor 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 a method for manufacturing a microminiaturized semiconductor acceleration sensor using a cantilever beam formed on a semiconductor substrate.

[0002]

2. Description of the Related Art Recently, an ultra-compact semiconductor acceleration sensor formed on a semiconductor substrate has been developed. This semiconductor acceleration sensor is formed on a semiconductor substrate using a thin film technique such as etching, and detects acceleration by detecting a resistance change due to the piezoresistive effect of the semiconductor and a minute capacitance change due to deviation. It is like this. Since these semiconductor acceleration sensors are formed by using the thin film technology as described above, for example, the length of the vibrating portion is 100 μm.
It has an excellent feature that it can be formed in a very small size, about 1 μm in thickness, about 1 μm in size, and about 1 mm square in size of the entire chip, and can be formed on the same substrate as other elements in an integrated circuit. is there. As the semiconductor acceleration sensor as described above, for example, "IEEE Electron Devices, Vol.ED-26, N
o.12, p.1911, Dec. 1979. “A Batch-Fabricated Si
"Licon Accelerometer".

FIG. 2 is a perspective view and a sectional view of the above semiconductor acceleration sensor. In FIG. 2, 21 is an n-type Si substrate, 22 is a Si cantilever, 23 is a Si weight, 24 is the center of gravity of the weight 23, and 25 is a diffusion resistance. In the semiconductor acceleration sensor shown in FIG. 2, when acceleration is applied, Si
The weight 23 is displaced, which causes the Si cantilever beam 22 to be distorted. A diffusion resistance 25 is formed in the vicinity of the support portion of the Si cantilever 22, and when strain occurs in the cantilever, the resistance value of the diffusion resistance 25 changes due to the piezoresistance effect. Acceleration can be detected by detecting the change in the resistance value.

[0004]

However, in the semiconductor acceleration sensor as described above, since the weight 23 is formed by etching one Si substrate 21, the center of gravity of the weight 23 is cantilevered due to its structure. Since the flash 22 deviates from the center of gravity, there is a problem that lateral acceleration sensitivity increases.

Generally, in such a cantilever structure, it is desirable to sense only the required acceleration in the x direction and not have sensitivity to the accelerations in the y and z directions. However, in the conventional semiconductor acceleration sensor, as shown in FIG. 3, the center of gravity 26 of the cantilever beam 22 and the center of gravity 24 of the weight 23 are deviated from each other by h, so that the conventional semiconductor acceleration sensor also has sensitivity to acceleration in the y direction. . This y-direction sensitivity Sy is the normal x-direction sensitivity Sy.
x, the length from the support end of the cantilever 22 to the center of gravity 26 is l
Then, it is given by the following (Formula 1). Sy.apprxeq.Sx.multidot.h / l (Equation 1) It should be noted that the displacement h between the center of gravity 26 of the cantilever beam and the center of gravity 24 of the weight 23 is approximately equal to half the thickness of the weight 23. Therefore, for example, if the thickness of the Si substrate is 1 μm and l = 3 μm, then Sy≈0.1Sx. Therefore, for example, when acceleration of 1G is applied in the y direction, 0.1G in the x direction is applied.
Will be regarded as the acceleration of. As mentioned above,
A semiconductor acceleration sensor that forms a cantilever beam and a semiconductor weight by etching the semiconductor substrate can be formed in a very small size, and can be formed on the same substrate as other elements in an integrated circuit. However, since the cantilever beam and the semiconductor weight are formed by etching one semiconductor substrate, the center of gravity of the cantilever beam and the center of gravity of the weight are displaced from each other, so that unnecessary lateral sensitivity is eliminated. There was a problem of getting bigger.

The present invention has been made in order to solve the problem peculiar to the ultra-compact semiconductor acceleration sensor manufactured by the thin film technology as described above, and has sensitivity only in a necessary direction and is unnecessary. It is an object of the present invention to provide a method of manufacturing a semiconductor acceleration sensor which has no lateral sensitivity.

[0007]

In order to achieve the above object, the present invention is constructed as described in the claims. That is, according to the first aspect of the present invention, by etching the first semiconductor substrate, the cantilever beam and the first semiconductor weight are formed on one surface of the tip portion of the cantilever beam. Then, the second semiconductor substrate is adhered to the other surface of the cantilever through a thin film serving as an etching stopper to form a thin film serving as the etching stopper.
While protecting the first semiconductor substrate by the second
By etching the semiconductor substrate of
A second semiconductor weight having a weight approximately the same as that of the first weight is formed at a position symmetrical to the first weight on the other surface of the cantilever beam, so that the entire center of gravity of the two weights is the cantilever beam. It is configured to manufacture a semiconductor acceleration sensor whose center coincides with the center in the thickness direction.

[0008]

[0009]

1 is a cross-sectional view of a main part of an embodiment of a semiconductor acceleration sensor manufactured by the method of the present invention.
In FIG. 1, 27 is a Si weight, which is made of the same material as the Si weight 23 and has the same weight. Therefore, the total center of gravity 2 of the Si weights 23 and 27 is
8 substantially coincides with the center of gravity of the cantilever beam 22.
By configuring as described above, x originally required
It is possible to realize a semiconductor acceleration sensor having sensitivity only in the direction. In FIG. 1, the same symbols as those in FIG. 2 indicate the same items.

Next, FIG. 4 is a diagram of a first embodiment of the manufacturing method of the present invention, showing a manufacturing process of the semiconductor acceleration sensor of FIG. In FIG. 4, (a) shows the same Si substrate 21 as the conventional structure as shown in FIG. 2, and shows a state in which the Si cantilever beam 22 and the Si weight 23 have already been formed by etching. Next, in (b), a Si substrate 31 having the same thickness as the Si substrate 21 is bonded to the Si substrate 21. In addition, oxide films 32 and 33 are formed in advance on both surfaces of the Si substrate 31. Further, as the adhesive, low melting point glass, epoxy or the like can be used. Next, in (c), a part of the oxide film 33 is removed by photoetching, and the Si weight 2 provided on the upper surface is removed.
Only the oxide film 33 'corresponding to the portion 7 is left. Next, in (d), the Si substrate 31 is etched using the remaining oxide film 33 'as a mask to leave only the portion 31' to be a weight provided on the upper surface. At this time, the lower S
The i-substrate 21 is coated with a resin or the like so as not to be etched. Next, in (e), the oxide film 33 '
By removing the oxide film 32 and the oxide film 32 by etching, the Si weight 27 on the upper surface is formed.

[0011]

[0012]

[0013]

[0014]

[0015]

According As has been described above in the present invention, the semi
By etching the conductive substrate,
A semiconductor acceleration sensor having a weight formed on one surface of the cantilever.
Sensor has sensitivity only to the acceleration in the required direction,
It has good characteristics with no sensitivity to unwanted lateral
The effect of being able to manufacture semiconductor acceleration sensors
The fruit is obtained. Further, in the present invention, a semiconductor etchant is used.
The second technique is applied to the symmetrical position of the first semiconductor weight only with the ching technique.
Since a semiconductor weight is formed, a micro cantilever of the order of μm
Precisely forming a minute weight on the burr at a precise position.
The effect is that it can be easily done .

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a semiconductor acceleration sensor manufactured by a first method of the present invention.

FIG. 2 is a perspective view and a cross-sectional view of a conventional device.

FIG. 3 is a cross-sectional view for explaining the operation of the conventional device.

FIG. 4 is a manufacturing process diagram of the first method of the present invention.

[Explanation of symbols]

 21 ... Si substrate 22 ... Si cantilever 23 ... Si weight 24 ... Weight center of gravity 25 ... Diffusion resistance 26 ... Cantilever center of gravity 27 ... Si weight 28 ... Weight entire center of gravity

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor acceleration sensor, which detects acceleration by detecting a displacement of a cantilever beam having one end supported on a semiconductor substrate, wherein a first semiconductor substrate is etched. A cantilever beam, a step of forming a first semiconductor weight on one surface of a tip portion of the cantilever beam, and the other surface of the cantilever beam or one surface of a second semiconductor substrate.
A step of forming a thin film to serve as an etching stopper, a step of bonding the other surface of the cantilever to the second semiconductor substrate via the thin film to serve as an etching stopper, and the etching stopper. The first by the thin film
By etching the second semiconductor substrate while protecting the semiconductor substrate, a second semiconductor weight having substantially the same weight as the first weight is replaced with the first weight on the other surface of the cantilever. And a step of forming them at symmetrical positions, and manufacturing a semiconductor acceleration sensor, characterized in that the center of gravity of the two weights is aligned with the center of the cantilever in the thickness direction. Method.