JPH0711535B2 - Semiconductor type acceleration sensor - Google Patents

Description

The present invention relates to a semiconductor type acceleration sensor having a vibrator and a damping liquid in its package.

[Conventional technology]

Conventionally, as a structure generally used to detect vibration, acceleration, etc., a thin diaphragm part on which a semiconductor strain gauge is formed is formed on a semiconductor substrate, and a support which is one thick part is formed. There is known a cantilever-type semiconductor acceleration sensor or the like, which fixes a pressure sensor and uses the other thick portion as a free end to detect a measured force according to a change in resistance value of a semiconductor strain gauge.

The semiconductor type acceleration sensor as described above has an advantage that the strain sensitivity output is large as compared with the metal wire strain gauge, but has a defect that the fracture strength is low and it is weak against impact. Therefore, conventionally, in order to compensate for such a defect, a mechanical stopper is provided to limit the displacement of the free end. For example, "A Batch
-Fabricated Silicon Accelerometer "IEEE Transactio
ns On Electron Devices, Vol.ED−26, No.12, December
In the semiconductor type acceleration sensor shown in 1979,
The free end of the cantilever is sandwiched between two glasses and is hermetically sealed, each of which is provided with a recess to limit displacement of the cantilever. That is, when a shock is applied to the semiconductor type acceleration sensor,
Displacement of the free end is forcibly stopped when the free end comes into contact with the bottom of the recess formed in the glass to prevent damage to the cantilever due to excessive displacement.

[Problems to be solved by the invention]

By the way, in the cantilever type semiconductor acceleration sensor, the characteristics are almost determined by the shape of the cantilever, and the resonance frequency range of the cantilever itself (usually 350
Approximately 400Hz), the output will be several tens of times the output in other frequency ranges. Therefore, for example, when trying to detect the acceleration of a car, etc.,
Since it requires only about 10 Hz or less), in order to cut the relatively high frequency range including the resonance frequency range, by placing the cantilever in the damping liquid such as silicone oil, the damping effect by viscous resistance is used. Damping liquid is used as a mechanical high-cut filter.

Here, the conventional semiconductor acceleration sensor has no problem when the medium around the cantilever is a gas, but when the medium is a damping liquid which is a liquid for the above-mentioned purpose, that is, Assuming that the damping liquid is enclosed in the glass, the damping liquid moves back and forth between the recesses formed in each glass according to the displacement of the free end, but the flow path is formed around the free end. It is only the gap that was made. Therefore, the damping liquid receives a resistance force when passing through the gap,
The effective viscosity becomes a value much larger than the damping factor of the damping liquid itself, and the frequency response of the semiconductor acceleration sensor deteriorates.

Therefore, the present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor type acceleration sensor having an oscillator and a damping liquid in its package and having excellent frequency response.

[Means for solving problems]

In order to achieve the above object, in the first invention of the present application, a pedestal housed in a package is joined with a vibrator part of which is fixed to the pedestal and the other part of which is a free end. In a semiconductor type acceleration sensor in which a damping liquid is enclosed in the package, a recess is provided on a surface of the pedestal facing the free end of the vibrator, and the recess is formed from the recess to the rest of the pedestal. The semiconductor type acceleration sensor is characterized in that it communicates with the inside of the package through a communication passage arranged so as to reach at least one of the surfaces.

According to a second aspect of the present invention, in a semiconductor type acceleration sensor having a vibrator, a part of which is fixed to a pedestal and the other part of which is a free end, and a damping liquid, in which the pedestal has the free end. A recess having a predetermined depth is formed on a surface facing the free end so as to limit displacement toward the pedestal side, and a communication passage reaching the recess to at least one of the other surfaces of the pedestal is formed. The semiconductor-type acceleration device further includes a stopper formed at a predetermined interval with the free end to limit the displacement of the free end in the direction opposite to the pedestal side. It uses a sensor.

[Action]

Further, according to the present invention, a recess is formed in the pedestal facing the free end of the vibrator, and the recess communicates with the inside of the package through the communication passage. Therefore, when the free end is displaced, the damping liquid passes through the communication passage and can freely move between the recess and the outside (inside the package) with almost no resistance.

The displacement of the free end of the vibrator toward the pedestal can be limited according to the depth of the recess. Further, by forming the stopper with a predetermined distance from the free end in the direction opposite to the pedestal side, displacement of the free end in that direction is also limited.

〔Example〕

 The present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 1 is an overall perspective view of an embodiment of the present invention, showing a package before airtight sealing. In the figure, 100 is a stem made of metal such as Kovar, except for a welded portion 101 which is the outer periphery thereof, and a pedestal 6 and a stopper 2 which will be described later.
A convex portion for mounting 00 etc. is formed by pressing, etc., and there are, for example, four through holes for electrical connection to the outside, and the cured glass 500 should be welded to the through holes. The lead terminal 400 is fixed via the glue.
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 which is mounted on the stem 100 and is composed of the cantilever 4a and the base 6 will be described in detail with reference to FIG. First, the top view shown in FIG.
And in the same figure (b) which is the AA line sectional view, 4a
Is a cantilever made of, for example, an N-type silicon single crystal substrate, a thin diaphragm portion 7, a free end 1, and a guard portion 4a arranged around the free end 1 to protect the free end 1.
₁ and a support 8. The scribe for forming the gap 4a ₂ between the free end 1 and the guard 4a ₁ is a cantilever 4a.
Is performed by double-sided etching. For example, the surface of the cantilever 4a to be scribed (upper surface in FIG. 2B) is previously grooved and etched, and then the rear surface is etched when the diaphragm portion 7 is formed. As a result, formation of the diaphragm portion 7 and scribing are performed simultaneously.

A base layer 3b formed by plating or vapor depositing a Ni layer or the like is formed on the surface of a predetermined region of the support 8 and the card portion 4a ₁ , and a pedestal 6 on which the base layer 3b is formed and a solder layer 5b are also interposed. Are glued together. Here, the pedestal 6 which is the main part of this embodiment
In order to allow the cantilever 4a to be displaced according to the acceleration to be measured, a recess 6a ₁ having a predetermined depth is formed on the surface 6a facing the cantilever 4a _{1 as} shown in (c).

The recess 6a ₁ 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 the cantilever 4a.

Multiple points (7 in the figure) on one main surface (adhesive surface) 2 of the free end 1.
A base layer 3a is formed at a location), and a solder layer 5a as a load is bonded via the base layer 3a. Here, by forming the solder layer 5a at a plurality of positions as in this example, it is possible to suppress the sagging and the deviation of the solder as much as possible. Underlayer 3a
And the solder layer 5a are respectively a base layer 3b and the solder layer 5b formed on the surface of the support 8 or the guard portion 4a ₁ can be formed simultaneously in the same process.

In addition, a well-known semiconductor processing technique, for example, P-type impurities such as boron is thermally diffused or ion-implanted into the diaphragm portion 7 or on the diaphragm portion 7 (the former is shown in the figure) to form the diaphragm portion 7. There are four semiconductor strain gauges 9, and there is a wiring layer 1a formed by introducing a P-type impurity at a high concentration, and a wiring member 1 including an Al vapor deposition film or the like.
The semiconductor strain gauges 9 are electrically connected to each other by 1b to form a full bridge. Reference numeral 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 electrically connected by wire bonding a wire wire 300.

Then, in the above sensor element, when acceleration is applied to the free end 1, the diaphragm portion 7 is distorted, the resistance value of the semiconductor strain gauge 9 changes according to the magnitude of the acceleration, and the 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, and it is fixed by bonding the pedestal 6 to the stem 100 with solder.

In FIG. 1, reference numeral 200 designates a stopper, and its shape is, as shown in the perspective view of FIG. Are vertically combined with each other, and the lower surface 203a of the plate member 203 and the upper surface of the cantilever 4a are adjusted to have a predetermined distance. The material is, for example, Kovar,
It is attached to the stem 100 by soldering.

Next, 600 is a shell made of metal such as Kovar,
At the position of the stem 100 opposite the weld 101, the weld 60
1 and the other part has a box shape in which a recess is formed by pressing. 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 sealing is performed by bringing the welded portion 601 and the welded portion 101 into contact with each other and applying mechanical pressure, and by welding the two by energizing the shell 600 and the stem 100. After that, the first in FIG.
As shown in the cross-sectional view taken along the line BB after welding in the figure, for example, an injector 900 having a needle-shaped discharge tip is inserted into a hole 602, and a damping liquid 700 such as silicon oil is supplied in a fixed amount, for example, 70 to 70% of the total volume. About 80% is injected, and the holes 602 and 603 are sealed with solder. In FIG. 6, 800 is the air remaining in the package, and 604 is a partition wall that suppresses the ripple of the damping liquid 700.

So determined according to body embodiment, is formed with a recess 6a ₁ of a predetermined depth in the cantilever 4a and the opposing surface 6a of the base 6, the maximum value of the displacement of a depth of the free end 1 the concave portion 6a ₁ To do. That is, when a strong impact is applied to the semiconductor type acceleration sensor, the displacement of the free end 1 in the downward direction in FIG. 1 (the pedestal 6 side) is forcibly stopped when the free end comes into contact with the bottom of the recess 6a _1. Therefore, breakage of the cantilever 4a due to excessive displacement can be prevented. Then, the concave portion 6a ₁ moves from the end surface 6b to the end surface 6b.
Since it is formed over c, the damping liquid 700 can freely move back and forth according to the displacement of the free end 1 through the escape port 6d shown in FIG. Since the effective viscosity of 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 on the upper portion of the cantilever 4a with a predetermined interval, the displacement of the free end 1 in the upward direction in FIG. 1 is limited, and the cantilever 4a can be reliably prevented from breaking. Further, in the stopper 200, the plate member 203 is arranged only above the free end 1 so as to limit the displacement of the end portion where the displacement of the free end 1 is the largest.
The upper part is almost equal to the free space, there is no element that increases the effective viscosity of the damping liquid 700, and the frequency response of the cantilever 4a is further improved.

The present invention is not limited to the above-described embodiments, and various modifications can be made, for example, as shown below, without departing from the spirit of the present invention.

(1) The recess formed on the surface of the pedestal 6a facing the free end 1 may reach at least one surface other than that surface, for example, as shown in the perspective view of FIG. 4 (a). End face
6c may be reached, or, as shown in the perspective view of FIG. 6 (b), it may reach four end faces that share one side with the face facing the free end 1.

(2) The stoppers 200 may be arranged at a predetermined interval in a direction opposite to the pedestal 6 side when viewed from the free end 1. The shape of the stoppers is as shown in the perspective view of FIG.
It may have a hook shape formed by a plate member 201 perpendicular to 0 and a parallel plate member 203, or may have the same shape as the pedestal 6.

〔The invention's effect〕

As described above, according to the present invention, the damping liquid can freely pass between the recess and the outside through the recess and the communication passage with almost no resistance, so that the effective viscosity of the damping liquid does not increase, Therefore, the frequency response of the vibrator can be improved.

[Brief description of drawings]

FIG. 1 is an overall perspective view of an embodiment of the present invention before airtight sealing, FIG. 2 (a) is a top view of the sensor element in FIG. 1, and FIG. 2 (b) is the same figure (a). A-A in
FIG. 2C is a perspective view of the pedestal in FIG. 1, FIG. 3C is a perspective view of the stopper in FIG. 1, and FIG.
FIGS. 5A and 5B are perspective views showing another example of the shape of the pedestal, and FIG. 5 is a perspective view showing another example of the shape of the stopper.
FIG. 6 is a sectional view taken along line BB of FIG. 1 after welding. 4a ... cantilever, 6 ... pedestal, 6a ₁ ... recess, 100 ...
Stem, 200 …… Stopper, 600 …… Shell, 700 …… Damping fluid.

Claims (4)

[Claims] 1. A semiconductor having a pedestal housed in a package and a vibrator, a part of which is fixed to the pedestal and the other end being a free end, joined to the pedestal, and a damping liquid is enclosed in the package. In the acceleration sensor, a recess is provided on a surface of the pedestal facing the free end of the vibrator, and the recess extends from the recess to at least one of the other surfaces of the pedestal. A semiconductor type acceleration sensor, characterized in that it communicates with the inside of the package through a communication passage arranged in the. 2. The semiconductor according to claim 1, wherein the concave portion is provided with a predetermined depth so as to limit the displacement of the free end toward the pedestal side. Acceleration sensor. 3. A semiconductor acceleration sensor having a vibrator, a part of which is fixed to a pedestal and the other part of which is a free end, and a damping liquid, wherein the pedestal is on the pedestal side of the free end. A recess having a predetermined depth on the surface facing the free end to limit the displacement of the recess to the free end, and the communication path having the recess reaching at least one of the other surfaces of the pedestal. And a stopper formed at a predetermined interval to limit the displacement of the free end in the direction opposite to that of the pedestal side. 4. The semiconductor type acceleration sensor according to claim 3, wherein the stopper has a hook shape.