JPS6379073A - Semiconductor type acceleration sensor - Google Patents

Abstract

PURPOSE:To prevent the damage of a vibrator due to excessive displacement, by constituting the title sensor so that the free end of the vibrator is limited in its displacement to a pedestal side corresponding to the depth of the recessed part formed to a pedestal. CONSTITUTION:A cantilever 4a composed of an N-type silicon single crystal plate is constituted of a membrane like diaphragm part 7, a free end 1, a guard part 4a1 arranged in order to protect the free end 1 and a support 8. A recessed past 6a1 having a predetermined depth is formed to the surface 6a opposed to the lever 4a of a pedestal 6 and the depth of the recessed part 6a1 determines the max. value of the displacement of the free end 1. That is, when strong impact is applied to semiconductor type acceleration sensor, the displacement of the free end 1 in a downward direction (on the side of the pedestal 6) is forcibly stopped at the point of time when the free end 1 contacts with the bottom part of the recessed part 6a1 and, therefore, the damage of the lever 4a due to excessive displacement can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor acceleration sensor that includes a vibrator and a damping liquid in its package.

[Conventional technology]

Conventionally, the structure generally used to detect vibrations, acceleration, etc. is to form a thin diaphragm part on a semiconductor substrate, on which a semiconductor strain gauge is formed, and one thick part, which is a support. A cantilever-type semiconductor acceleration sensor is known that detects a force to be measured according to a change in the resistance value of a semiconductor strain gauge by fixing the sensor and using the other thick part as a free end.

The semiconductor acceleration sensor described above has the advantage of having a large strain sensitivity output compared to a metal wire strain meter, but has the disadvantage of having low breaking strength and being susceptible to impact. Conventionally, in order to compensate for such drawbacks, a mechanical stopper is provided to limit the displacement of the free end. For example, “A B
atch-F abri-cated S 1lic
on Accelerometer"IEEE T r
ansac-tions On Electron D
evices, Vol, ED-26+N112.
In the semiconductor acceleration sensor shown in December 1979, the free end of the cantilever is sandwiched between two glasses and hermetically sealed, and each glass has a recess formed to limit the displacement of the cantilever. has been done. In other words, when a shock is applied to the semiconductor acceleration sensor, the displacement of the free end is forcibly stopped when the free end contacts the bottom of the recess formed in the glass, thereby preventing damage to the cantilever due to excessive displacement. It is prevented.

[Problem that the invention seeks to solve]

By the way, the characteristics of a cantilever type semiconductor acceleration sensor are almost determined by the shape of the cantilever, and the resonance frequency range of the cantilever itself (usually 35
(approximately 0 to 400 Hz), the output is several tens of times higher than the output in other frequency ranges. Therefore, for example, when trying to detect the acceleration of a car, etc., the low frequency range (
Normally, only about 1011z or less) is required, so in order to cut relatively high frequency ranges including the resonance frequency range, a cantilever is placed in a damping liquid such as silicone oil to utilize the damping effect due to viscous resistance force. The damping liquid is used as a mechanical high-cut filter.

Here, there is no problem with conventional semiconductor acceleration sensors when the medium surrounding the cantilever is gas, but when the medium is a liquid damping liquid for the purpose described above, in other words, when the medium surrounding the cantilever is a gas, Assuming that the damping liquid is sealed in a sealed glass, the damping liquid will move back and forth between the recesses formed in each glass according to the displacement of the free end, but the flow path will be formed around the free end. There is only one gap. Therefore, the damping fluid will be subjected to a resistance force when passing through the gear.
The effective viscosity thereof is much larger than the damping factor of the damping liquid itself, which deteriorates the frequency response of the semiconductor acceleration sensor.

Therefore, the present invention has been made in view of the above points, and includes a vibrator and a damping liquid in its package,
The purpose is to provide a semiconductor acceleration sensor with excellent frequency response.

[Means for solving problems]

In order to achieve the above object, the first invention of the present application provides a vibrator, a part of which is fixed to a pedestal and the other part is a free end;
In a semiconductor acceleration sensor including a damping liquid in a package, the pedestal has a recess of a predetermined depth on a surface facing the free end to limit displacement of the free end, and the recess The present invention employs a semiconductor acceleration sensor characterized in that the semiconductor acceleration sensor is formed so as to reach at least one surface of the base and other surfaces.

Further, in a second aspect of the invention, in a semiconductor acceleration sensor comprising a vibrator with a part fixed to a pedestal and the other part a free end, and a damping liquid in a package, the pedestal is fixed to the free end. A recess of a predetermined depth is provided on a surface facing the free end in order to limit displacement toward the pedestal, and the recess is formed to reach at least one of the other surfaces of the pedestal. and a stopper formed at a predetermined distance from the free end to limit displacement of the free end in a direction opposite to the pedestal side. ing.

[Effect]

According to the present invention, the displacement of the free end of the vibrator toward the pedestal is restricted depending on the depth of the recess formed in the pedestal. In addition, when the free end is displaced, the damping liquid passes through the recess and connects the recess and the outside with almost no resistance because the recess reaches the other surface outside the chamfer that faces the free end. You can come and go freely.

Furthermore, by forming a stopper at a predetermined distance from the free end in the direction opposite to the pedestal side, displacement of the free end in the half direction is also restricted.

〔Example〕

Hereinafter, the present invention will be explained using embodiments shown in the drawings.

FIG. 1 is an overall perspective view of an embodiment of the present invention, showing the package before it is hermetically sealed. In the figure, 100
is a stem made of metal such as Kovar, and except for the welded part 101 on its outer periphery, a convex part on which a pedestal 6, a stopper 200, etc., which will be described later, is mounted is formed by press working, etc. For example, 4 to make electrical connections.
There are two through holes, and the hard glass 5 is inserted into the through holes.
A lead terminal 400 is interposed and fixed by welding 00. The lead terminal 400 and the stem 100 are electrically insulated by a hard glass 500, and the hard glass 500 is interposed with good airtightness.

Next, the sensor element mounted on the stem 100 and consisting of the cantilever 4a and the pedestal 6 will be described in detail using FIG. 2. First, in the top view shown in FIG. 2+a) and the cross-sectional view taken along the line A-A in FIG. , free end l,
It consists of a guard part 4a+ arranged around the free end 1 to protect the free end 1, and a support body 8. Incidentally, the scribing to form the gap 4az between the free end 1 and the guard portion 4a is performed by etching both sides of the cantilever 4a. The formation of the diaphragm part 7 and the scribing are performed simultaneously by performing trench etching on the upper surface of the wafer in advance, and then etching from the back surface during the formation of the diaphragm part 7.

The surfaces of predetermined areas of the support body 8 and the guard portion 4a are coated with N.
A base layer 3b is formed by plating or vapor depositing an i-layer, etc., and the base layer 6 and the solder J, on which the base layer 3b is also formed, are formed.
It is bonded via W5b.

Here, the pedestal 6, which is the main part of this embodiment, is equipped with a cantilever 4a (see FIG.
As shown in C), the surface 6 facing the cantilever 4a+
A recess 6a+ having a predetermined depth is formed in a.

Further, the recess 6a+ is formed from one end surface 6b to the other end surface 6C. The material of the pedestal 6 is preferably silicon in order to match the coefficient of thermal expansion with that of the cantilever 4a.

There are multiple locations on the permanent surface (adhesive surface) 2 of the free end 1 (7 in the figure).
A base layer 3a is formed at the base layer 3a.
A solder layer 5a serving as a load is bonded via the solder layer 5a. Here, by forming the solder layer 5a at a plurality of locations as in this example, it is possible to suppress solder dripping and deviation as much as possible. still,
The base layer 3a and the solder layer 5a are connected to the support 8 or the guard part 4.
．． The base layer 3b and the solder layer 5b formed on the surface of aI can be formed at the same time and in the same process.

Also, inside the diaphragm part 7 or on the diaphragm part 7 (
The figure shows four semiconductor strain gauges 9 formed by introducing a P-type impurity such as boron into the diaphragm part 7 by thermal diffusion or ion implantation using a known semiconductor processing technique 4+j. The semiconductor strain gauges 9 are electrically connected to each other by a wiring layer lla formed by introducing P-type impurities at a high concentration and a wiring member 11b made of an A1 vapor deposited film, etc., forming a full bridge. There is. still,
10 is a protective film such as a silicon oxide film, and the pad portion of the wiring member 11b and the lead terminal 400 are connected to the wire wire 30.
Electrical connection is made by wire bonding 0.

In the sensor element described above, when acceleration is applied to the free end 1, strain is generated in the diaphragm portion 7, and the abrasive resistance value of the semiconductor strain gauge 9 changes depending on the magnitude of the acceleration, and a voltage is applied to the bridge circuit in advance. By doing so, an unbalanced voltage is generated as a bridge output, and the acceleration to be detected is detected according to the voltage value.
It is fixed by gluing the pedestal 6 to the pedestal 6.

In FIG. 1, 200 is a stopper whose shape is perpendicular to the stem 100, as shown in the perspective view of FIG.
The two plates 201 and 202 and the plate 203 parallel to the stem 100, in other words, parallel to the cantilever 4a, are assembled perpendicularly to each other, and the lower surface 203a of the plate 203 and the upper surface of the cantilever 4a are arranged in a predetermined manner. It is adjusted to have an interval. The material thereof is, for example, Kovar, and it is bonded to the stem 100 with solder.

Next, 600 is a shell made of metal such as Kovar, which also has a welded part 601 at a position opposite to the welded part 101 of the stem 100, and the other parts are box-shaped with depressions formed by press working. There is. Further, the shell 600 is formed with a hole 602 for injecting a damping liquid after hermetically sealing and a hole 603 for letting air escape at that time. The hermetic seal is made between the welded portion 601 and the welded portion 101.
While applying mechanical pressure by contacting the shell 600
This is done by welding the two together by applying electricity between the stem 100 and the stem 100. After that, B- after welding in FIG. 1 of FIG.
As shown in the cross-sectional view taken along line B, a syringe 900 with a needle-shaped discharge tip is inserted into the hole 602, and a certain amount of damping liquid 700 such as silicone oil is applied, for example, 70 to 70% of the total volume.
After about 80% injection, the holes 602 and 603 are sealed with solder. In addition, in FIG. 6, 800 is the air remaining in the package, and 604 is the damping liquid 700.
It is a partition wall that suppresses the ripples of the water.

Therefore, according to this embodiment, a recess 6a+ of a predetermined depth is formed in the surface 6a of the pedestal 6 facing the cantilever 4a, and the depth of the recess 6a+ determines the maximum displacement of the free end 1. In other words, when a strong impact is applied to the semiconductor acceleration sensor, the downward displacement of the free end 1 in FIG. 1 (towards the pedestal 6) is forcibly stopped when the free end contacts the bottom of the recess 5a Therefore, destruction of the cantilever 4a due to excessive displacement can be prevented. Since the recess 5a is formed from the end surface 6b to the end surface 6C, the damping liquid 700 freely passes through the escape port 6d shown in FIG. 1 according to the displacement of the free end 1 with almost no resistance. Since the effective viscosity of the damping liquid 700 is given only by the damping factor of the damping liquid itself, the frequency response of the cantilever 4a is improved.

Further, since the stoppers 200 are formed at the upper part of the cantilever 4a at a predetermined interval, the displacement of the free end 1 in the upward direction in FIG. 1 is also restricted, thereby reliably preventing the cantilever 4a from breaking. Also, the stopper 200 has the free end 1
In order to limit the displacement of the end portion where the displacement is the largest, the plate member 203 is placed only above that portion, so the upper part of the cantilever 4a is almost equal to free space, and there are no elements that increase the effective viscosity of the damping liquid 700. Therefore, the frequency response of the cantilever 43 is further improved.

It should be noted that the present invention is not limited to the above-mentioned embodiments (although various modifications can be made, for example, as shown below) without departing from the spirit thereof.

(1) The recess formed on the surface facing the free end 1 of the pedestal 6a only needs to reach at least one surface outside the chamfer, for example, as shown in the perspective view of FIG. 4(a). It may reach only the end surface 6C, or it may reach four end surfaces that share one side of the surface facing the free end 1, as shown in the perspective view of FIG.

(2) The stopper 200 may be disposed at a predetermined interval in the direction opposite to the pedestal 6 side when viewed from the free end 1, and its shape is similar to that of the stem 10 as shown in the perspective view of FIG.
It may be a hook-shaped thing formed by a plate material 201 perpendicular to 0 and a parallel plate material 203, or it may have the same shape as the pedestal 6.

〔Effect of the invention〕

As described above, according to the present invention, the displacement of the free end of the vibrator toward the pedestal is limited according to the depth of the four parts formed on the pedestal, so damage to the vibrator due to excessive displacement is prevented. It can be prevented. Further, since the damping liquid can pass through the recess and freely move between the recess and the outside with almost no resistance, the effective viscosity of the damping liquid does not increase, and therefore the frequency response of the vibrator can be improved.

Furthermore, by forming a stopper at a predetermined distance from the free end in the direction opposite to the pedestal side, the displacement of the free end in that direction is also restricted, which has the effect of more reliably preventing damage to the vibrator. .

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the entire embodiment of the present invention before hermetic sealing, FIG. 2 fa) is a top view of the sensor element in FIG. 1, and FIG. -A
Line sectional view, Figure 2 fc) is a perspective view of the pedestal in Figure 1, Figure 3 is a perspective view of the stopper in Figure 1, and Figures 4 (a) and (b) are other examples of the shape of the pedestal. A perspective view showing
Fig. 5 is a perspective view showing another example of the shape of the stopper;
The figure is a sectional view taken along the line B-B after welding in FIG. 1. 4a...cantilever, 6...pedestal, 6a,...
・Concavity. 100... Stem, 200... Stopper, 600
... Shell, 700... Damping fluid.

Claims (3)

[Claims] (1) In a semiconductor acceleration sensor that includes a vibrator with a part fixed to a pedestal and the other part as a free end, and a damping liquid in a package, the pedestal is configured to limit displacement of the free end. A semiconductor type acceleration device having a recessed portion of a predetermined depth on a surface facing the free end, and the recessed portion is formed to reach at least one of the pedestal and the other surface. sensor. (2) In a semiconductor acceleration sensor that includes a vibrator with a part fixed to a pedestal and the other part as a free end, and a damping liquid in a package, the pedestal has the free end connected to the pedestal side. a recess of a predetermined depth is provided on a surface facing the free end in order to limit displacement, and the recess is formed to reach at least one of the other surfaces of the pedestal; The semiconductor acceleration sensor further includes a stopper formed at a predetermined distance from the free end to limit displacement of the free end in a direction opposite to the pedestal side. (3) The semiconductor acceleration sensor according to claim 2, wherein the stopper has a hook-like shape.