JPH0615986B2 - Manufacturing method of semiconductor type acceleration sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor acceleration sensor, and more particularly to a package in which a vibrator and a damping liquid are enclosed.

[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.

In such a semiconductor type acceleration sensor, the characteristics are almost determined by the shape of the cantilever, and the resonance frequency range of the cantilever itself (usually 350 to 400).
At about Hz), the output will be several tens of times the output in other frequency ranges. Therefore, for example, in order to detect the acceleration of an automobile, etc., only a low frequency range (usually about 10 Hz or less) is required. Therefore, in order to cut a relatively high frequency range including a resonance frequency range, silicon oil, etc. The damping liquid was used as a mechanical high-cut filter by utilizing the damping effect of viscous resistance force by arranging the cantilever in the damping liquid.

[Problems to be solved by the invention]

However, in the case of packaging the cantilever arranged in the damping liquid as described above, conventionally, for example, the support of the cantilever is fixed to a container having a recess,
In addition, a damping liquid is enclosed and the lid is screwed. Therefore, when the semiconductor type acceleration sensor packaged in this way is adopted in a place where operating environment conditions are severe, such as for automobiles, a wide range of temperature conditions (approximately -40 to 100 ° C.) and damping liquid due to it are adopted. Due to the expansion and contraction of the liquid, there is a possibility that the highly fluid damping liquid may leak to the outside through the gap between the container and the lid.

Therefore, the present invention has been made in view of the above points, and an object thereof is to perform packaging with high airtightness so that the damping liquid does not leak even under severe operating environment conditions.

[Means for solving problems]

The present invention relates to a step of fixing a lead terminal with a glass interposed in a through hole of a metal base having a through hole, and fixing a vibrator having a semiconductor strain gauge, a part of which is a free end, to the metal base. In addition, the step of electrically connecting the semiconductor strain gauge and the lead terminal to each other, and the metal cap and the metal base along the entire circumference in a state where the vibrator is provided in a package including the metal cap and the metal base. Projection welding and sealing a predetermined amount of damping liquid and air in the package.

〔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 the first embodiment of the present invention,
It represents before airtight sealing. In the figure, 100 is a stem made of metal such as Kovar, which is the metal base according to the present invention. The stem 100 is the outer periphery of the welded portion 10.
1 except for a pedestal 6 described later, a convex portion for mounting a stopper 200 and the like are formed by press working,
In addition, for example, four through holes are provided for making an electrical connection with the outside, and the lead terminal 400 is fixed by interposing the hard glass 500 by welding to the through holes. The hard glass 5 is used for the lead terminal 400 and the stem 100.
It is electrically insulated by 00 and hard glass 5
00 intervenes with good airtightness.

Next, a sensor element that is mounted on the stem 100 and that includes the cantilever 4a and the pedestal 6 will be described in detail with reference to FIG. In FIG. 2 (a), which is a top view and FIG. 2 (b), which is a sectional view taken along the line AA, 4a is a cantilever made of, for example, an N-type silicon single crystal substrate, and has a thin diaphragm portion 7, Free end 1, Free end 1
Guard part 4a arranged around the free end 1 to protect the
₁ and the support 8. The free end 1 and the guard portion 4a
Scribing for forming a gap 4a ₂ with ₁ is performed by the double-sided etching of the cantilever 4a, for example, pre Mizohoriri etching the surface of the portion to be scribed cantilever 4a (the upper surface in FIG. 2 (b)) Then, the diaphragm portion 7 is formed and scribed at the same time by etching from the back surface when the diaphragm portion 7 is subsequently formed.

Ni is formed on the surface of a predetermined region of the support 8 and the guard portion 4a _1.
A base layer 3b is formed by plating or vapor-depositing a layer or the like, and the base layer 3b and the pedestal 6 on which the base layer 3b is also formed are bonded via the solder layer 5b. The pedestal 6 is provided with a recess 6a having a predetermined depth so that the cantilever 4a can be displaced according to the acceleration to be measured. The depth of the recess 6a determines the maximum value of the displacement of the free end 1, and serves as a mechanical stopper for the downward displacement of the free end 1 in FIG. 2 (b) when a strong impact is applied. The working cantilever 4a is prevented from bursting. Further, as the material of the pedestal 6, silicon is desirable in order to match the thermal expansion coefficient with the cantilever 4a, and the shape thereof is such that the concave portion 6a is formed from one end surface 6b to the other end surface 6c as shown in FIG. Has been done. By forming the pedestal in such a shape, the damping liquid can freely flow in and out through the recess 6a of the pedestal 6, and the frequency response of the cantilever 4a can be improved.

Multiple points (7 in the figure) on one main surface (adhesive surface) 2 of the free end 1.
Base layer 3a is formed on the
The solder layer 5a as a load is bonded via the. 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. still,
The base layer 3a and the solder layer 5a are the support 8 or the guard portion 4
The underlayer 3b and the solder layer 5b formed on the surface of a ₁ can be formed simultaneously in the same process.

Further, a well-known semiconductor processing technique, for example, P-type impurities such as boron is introduced into the diaphragm portion 7 by thermal diffusion or ion implantation into the diaphragm portion 7 or the diaphragm portion 7 (the former is shown in the drawing) to form the dime diaphragm portion 7. There are four semiconductor strain gauges 9, and each semiconductor strain gauge 9 is electrically connected to each other by a wiring layer 11a formed by introducing a P-type impurity at a high concentration and a wiring member 11b made of an A1 vapor deposition film or the like. Connected to form a full bridge. 1
0 is a protective film such as a silicon oxide film, and the wiring member 1
The pad portion 1b and the lead terminal 400 are the wire wire 300.
Are electrically connected by wire bonding.

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 fridge circuit in advance. The unbalanced voltage is generated as a bridge output by detecting the voltage, and the acceleration to be detected is detected according to the voltage value.
It is fixed by adhering the pedestal 6 to.

In FIG. 1, reference numeral 200 denotes a stopper, and the pedestal 6 is a mechanical stopper in the downward displacement of the free end 1 of the cantilever 4a, whereas it serves as a stopper in the upward displacement. That is, the stopper 200 and the cantilever 4a are formed so as to have a predetermined gap. The material is, for example, Kovar,
It is bonded to the stem 100 with solder.

Next, 600 is a shell made of metal such as Kovar, which is the metal cap referred to in the present invention. The shell 600 also has a welded portion 601 at a position opposed to the welded portion 101 of the stem 100, and the other portion has a box shape in which a recess is formed by press working. 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.

Next, a process of performing airtight sealing on the main part of this embodiment will be described. Although not shown in FIG. 1, as shown in the partial sectional view of FIG.
In the surface of shell No. 1 on the shell 600 side, for example, a projection 101a having a triangular cross section is present over the entire circumference. By energizing between the shell 600 and the stem 100 while adding the
It locally flows from 1a in a short time, and the two are welded by the Joule heat generated at that time. Although the above description is about general projection resistance welding, projection resistance welding by capacitor welding may be used, for example.

After the shell 600 and the stem 100 are welded, for example, an injector 900 having a needle-shaped discharge tip is inserted into the hole 602 as shown in the sectional view taken along the line BB of FIG. 4 after the welding. Damping liquid 700 such as silicone oil
Is injected in a fixed amount, for example, about 70 to 80% of the total volume.
At that time, the air existing in the shell 600 escapes to the outside through the hole 603 described with reference to FIG. 1, but the remaining air 800 is enclosed with the damping liquid 700 as it is. After injecting the damping liquid 700, the injector 900 is removed and the holes 602 and 603 are sealed with solder. As shown in the figure, a recess is formed in the hole 602, and the solder remains in the recess (not shown but also formed in the hole 603). Also, shell 6
A partition wall 604 is formed at 00 to suppress the ripple of the damping liquid 700. Then, the hermetically sealed semiconductor type acceleration sensor is assembled with the arrow direction in the drawing as the upward direction.

Therefore, according to this embodiment, the shell 600 and the stem 1 are improved by using an improved metal hermetic package which is usually used for packaging of power transistors and the like.
00 is hermetically sealed by electric resistance welding. Since this electric resistance welding is performed in a short time and hardly heats the vicinity of the sensor element, the sensor element is not adversely affected and the welded portion is not affected. Since the strain is small and the sealing strength is strong, the damping liquid 700 is packaged with high airtightness without leaking. Further, since the temperature of the damping liquid does not rise so much, it is possible to prevent the hard glass 500 from bursting.
When projection resistance welding is performed, the package can withstand an internal pressure of about 6 atmospheres, and since a small amount of air 800 is enclosed, it is sufficient for expansion and contraction of the damping liquid 700 due to wide temperature changes. Can bear.

Next, a second embodiment of the present invention will be described in which the injection amount of the damping liquid into the package can be confirmed. FIG. 5 (a) is a perspective view of the whole, and FIG. 5 (b) is a cross-sectional view of the main part thereof. In the figure, the shell 600 has a window 60 which is a through hole.
5, a transparent member 606 made of, for example, quartz glass is adhered from the inside with good airtightness by welding or the like so as to cover the entire window portion 605. Here, the amount of damping liquid 700 to be injected into the package is usually controlled by a discharge device or the like to inject a fixed amount, but if the amount of damping liquid 700 is not appropriate due to some reason, If air bubbles remain in the vicinity of the element, the characteristics of the semiconductor acceleration sensor will be seriously affected. However, according to the present embodiment, such a situation can be avoided by looking into the package through the window 605. There is an effect that it can be confirmed in advance and can be dealt with. The fifth
For the sake of simplicity, the stopper 200, the lead terminal 400, etc. are not shown in the figure, but the same ones as in FIG. 1 are applicable. In addition, when the partition wall 604 as described with reference to FIG. 4 is formed in this example, the transparent member 606 becomes an obstacle, but the side wall of the shell 600 is used.
It can be formed by a method such as forming on the 0 side. In addition, a scale or the like may be formed on the transparent member 606 in order to easily confirm the amount.

Next, a third embodiment of the present invention will be described for the purpose of improving stability against temperature and resistance to EMI (electromagnetic interference). The feature of this embodiment is that a sensor output amplifier circuit 900 is installed in the package as shown in the schematic sectional view of FIG. Usually, the electric signal output from the cantilever 4a is very weak, such as several mV or less, and the circuit for amplifying the signal is arranged outside the package.
A thermal gradient is apt to occur between the cantilever 4a and the amplification / processing circuit, and in order to detect it more accurately, the thermal gradient must be corrected according to the temperature. Since the amplifier circuit 900 is arranged, there is almost no thermal gradient with the cantilever 4a, and it is stable against temperature. Further, since the package is made of metal, it is excellent in EMI resistance, and since the signal amplified in the package is output to the outside of the package, there is an effect that it is hardly affected by EMI. The output processing circuit only needs to include at least an amplifier circuit, and other processing circuits may be arranged in the package. Further, in FIG. 6, the same components as those shown in the figure are designated by the same reference numerals, and the description thereof will be omitted.

The present invention is not limited to the above-mentioned three embodiments, and various modifications can be made without departing from the spirit of the invention.

For example, in the above embodiment, since the displacement of the free end 1 is limited,
Although the recess 6a is formed in the pedestal 6 and the stopper 200 is provided, the structure without them may be used.
Further, a load other than solder may be adhered to the solder layer 5a in order to increase inertia and further enhance precision sensitivity.

〔The invention's effect〕

As described above, according to the present invention, since the metal cap and the metal base are projection-welded and hermetically sealed, the damping liquid does not leak even under severe operating environment conditions, and the glass for fixing the lead terminal is used. There is an effect that it is possible to provide a semiconductor type acceleration sensor having a highly airtight package that is not destroyed.

[Brief description of drawings]

FIG. 1 is a perspective view of the whole first 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 ( FIG. 2 (c) is a cross-sectional view taken along the line AA in FIG.
FIG. 4 is a partial sectional view of the embodiment shown in FIG. 1, FIG. 4 is a sectional view taken along the line BB of FIG. 1 after welding, and FIG. 5 (a) is a whole view of the second embodiment of the present invention. Fig. 5 (b) is a perspective view
FIG. 6A is a schematic sectional view of a third embodiment of the present invention. 1 ... Free end, 4a ... Cantilever, 6 ... Pedestal, 8
…… Support, 100 …… Stem, 600 …… Shell, 7
00 ... Damping liquid.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chiaki Mizuno 1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd. (72) Inventor Masato Imai 1-1-cho, Showa-cho, Kariya city, Aichi prefecture Nidec Incorporated (56) References JP 59-158566 (JP, A) JP 54-36771 (JP, A) JP 55-166014 (JP, A)

Claims (5)

[Claims] 1. A step of fixing a lead terminal by interposing glass in the through hole of a metal base having a through hole, and a vibrator having a semiconductor strain gauge, a part of which is a free end, on the metal base. Fixing and electrically connecting the semiconductor strain gauge and the lead terminal, and fully connecting the metal cap and the metal base with the vibrator provided in a package including the metal cap and the metal base. And a step of sealing a predetermined amount of damping liquid and air in the package after projection welding over the circumference. 2. The metal cap is provided with a hole for injecting the damping liquid and a hole for allowing the air in the package to escape during the injection. The method of manufacturing a semiconductor type acceleration sensor according to claim 1, wherein the holes are utilized after the projection welding. 3. The method of manufacturing a semiconductor type acceleration sensor according to claim 1, wherein the metal cap has a partition wall for suppressing the ripple of the damping liquid. 4. The metal cap has a window part in a part thereof, and a transparent member is adhered so as to cover at least the window part. A method for manufacturing the semiconductor type acceleration sensor according to 1. 5. The package according to claim 1, further comprising an output processing circuit having at least an amplifier circuit for amplifying a signal value output from the vibrator.
Item 8. A method of manufacturing a semiconductor type acceleration sensor according to any one of items.