JP3117581B2 - Manufacturing method of semiconductor acceleration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mechanical deformation applied to resistance element portion of a semiconductor in response to the acceleration to be detected, a method of manufacturing a semiconductor acceleration sensor for detecting a change in electrical resistance.

[0002]

2. Description of the Related Art As an acceleration sensor using a semiconductor,
A sensor has been proposed in which a resistive element is formed on a diaphragm formed on a semiconductor substrate, mechanical deformation is caused in the resistive element by an acceleration to be detected, and the mechanical deformation is detected as a change in electric resistance. . Such a semiconductor acceleration sensor is disclosed in, for example, JP-A-3-2535.

FIG. 4 is a partially cutaway perspective view showing an example of a conventional semiconductor acceleration sensor. Referring to FIG. 4, a diaphragm portion 2 having a thickness of several tens of μm is formed on a silicon sensor chip 1 made of an n-type silicon substrate by circular etching. A mass 3 is formed at the center of the silicon sensor chip 1, and the mass 3 has a truncated cone shape. Around the diaphragm 2,
A rim portion 4 is formed. The rim portion 4 and the silicon pedestal 8 are overlapped and bonded by eutectic bonding.

A concave portion is formed at the center of the silicon pedestal 8 so that the gap portion 7 is formed below the mass portion 3. The silicon pedestal 8 is adhered and fixed to the metal stem 9 with an epoxy resin adhesive 10.

In the diaphragm portion 2 of the silicon sensor chip 1, four p-type piezoresistive resistance element portions 14 are formed by diffusing a dopant. The aluminum wiring 6 is connected to these resistance element portions 14.
On the surface of the silicon sensor chip 1 on which the resistance element section 14 and the aluminum wiring 6 are formed, a silicon dioxide film 5 is formed as a protective film.

A plurality of poles 12 are provided at predetermined positions near the silicon sensor chip 1.
A gold wire 11 is provided between the upper part of the second and the aluminum wiring 6, and the aluminum wiring 6 and the pole 12 are electrically connected. An insulating glass 13 is provided at a portion where the pole 12 is attached to the metal stem 9.

The silicon sensor chip 1 in the state shown in FIG.
A cap is placed on the upper part of the device to complete a semiconductor acceleration sensor element.

[0008]

FIG. 5 is a diagram showing the relationship between the temperature and the offset output of the conventional semiconductor acceleration sensor element shown in FIG. As shown in FIG. 5, there is a considerable difference around 40 ° C. between the graph locus when the temperature is raised from the low temperature side and the graph locus when the temperature is lowered from the high temperature side, and there is thermal hysteresis.

Such thermal hysteresis may be caused by the appearance of residual stress in the diaphragm due to heating or cooling, or may be caused by the combination of a semiconductor acceleration sensor pellet combining a silicon sensor chip and a silicon pedestal, and a metal stem / adhesive. This is considered to be due to the fact that stress was generated in the diaphragm due to the difference in thermal expansion. These thermal hysteresis causes a measurement error at the time of measuring the acceleration, so that it is necessary to reduce the thermal hysteresis as much as possible.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor acceleration sensor in which no residual stress remains in a diaphragm portion of a silicon sensor chip and stress generated in the diaphragm portion can be reduced.
It is an object of the present invention to provide a method for manufacturing a semiconductor .

[0011]

According to the present invention, there is provided a manufacturing method comprising:
A diaphragm is formed around the mass provided in the center
And a rim is provided around the diaphragm.
Recon sensor chip is fixed on the substrate and semiconductor acceleration
This is a method of manufacturing a sensor,
An adhesive layer is provided in the area on the substrate corresponding to the rim,
The area on the board corresponding to the lower part of the consensus chip mass
Spacer is provided in the area, silicon sensor by adhesive layer
After bonding the chip and substrate, remove the spacer.
It is characterized by. The semiconductor acceleration sensor obtained by the manufacturing method of the present invention has, for example, a structure in which a rim portion of a silicon sensor chip is bonded to a substrate via an adhesive layer, and an adhesive forming the adhesive layer Is characterized in that a ceramic adhesive is used for a ceramic substrate and a metal substrate, and a rubber adhesive containing a filler is used for a resin substrate.

In a preferred embodiment of the present invention, a recess is formed in the center of the substrate so that a gap is formed below the mass of the silicon sensor chip. In the present invention, a ceramic adhesive is used for the ceramic substrate and the metal substrate. The ceramic adhesive is an adhesive containing ceramic particles such as alumina, zirconia, or magnesia, and forms an adhesive layer having a coefficient of thermal expansion of 6.4 to 12.6 × 10 ⁻⁶ / ° C. Are preferred.

The ceramic substrate used in the present invention includes fine ceramic materials such as alumina, mullite, zirconia and silicon nitride. The material of the resin substrate used in the present invention is PP
Heat-resistant engineering plastics such as S (polyphenylene sulfide) and PBT (thermoplastic polyester resin obtained by polymerization of terephthalic acid and 1,4-butanediol) are exemplified.

The material of the metal substrate is SPCC
(Cold rolling steel), Fe-Ni alloy (compounding ratio 58:42)
And Ni-Au plating on the surface to perform spot welding.

In the present invention, a rubber adhesive containing filler is used for the resin substrate. Examples of the fillers include fillers such as silica, glass, and alumina, and silica fillers are particularly preferable. The rubber component of the rubber adhesive is not particularly limited, but silicon rubber is particularly preferable. Silicon rubber has a thermal expansion coefficient of 3.0 ×
It is about 10 ⁻⁴ / ° C., and a filler is contained to reduce this. By including the filler, the coefficient of thermal expansion can be reduced to about half. The content of the filler is preferably 5% by weight or less.

According to the manufacturing method of the present invention, an adhesive layer is provided in a region on a substrate corresponding to a rim portion of a silicon sensor chip,
It is characterized in that a spacer is provided in a region on the substrate corresponding to a portion below the mass portion of the silicon sensor chip, and after the silicon sensor chip and the substrate are bonded by an adhesive layer, the spacer is removed.

In the manufacturing method of the present invention, as the adhesive used for the adhesive layer for bonding the rim portion of the silicon sensor chip to the substrate, the adhesive used in the above-described semiconductor acceleration sensor of the present invention can be used.

In the manufacturing method of the present invention, the spacer provided in the region on the substrate corresponding to the lower portion of the mass portion of the silicon sensor chip is preferably a spacer which can be easily removed after bonding the silicon sensor chip and the substrate. Those which can be removed by dissolving in a solvent or those which can be removed by thermal decomposition by heating are preferable. Such include cyanoacrylate adhesives and nitrocellulose adhesives. These adhesives can be easily swelled and dissolved with a solvent such as acetone after bonding the rim portion of the silicon sensor chip to the substrate. Furthermore, at temperatures above 100 ° C., cyanoacrylate adhesives rapidly lose their adhesive strength and have a very small adhesive area, so they begin to peel off spontaneously. When further heated, it melts at about 180 ° C., and when it reaches 230 ° C. or higher, it is thermally decomposed. When further heated, carbonization of the adhesive residue proceeds and disappears. Similarly,
The nitrocellulose adhesive is also thermally decomposed at 200 ° C., causing carbonization and disappearing.

[0019]

[Action]

[0020]

[0021]

According to the manufacturing method of the present invention, the spacer is provided in the region on the substrate corresponding to the lower portion of the mass portion of the silicon sensor chip. By providing such a spacer, it is possible to prevent the occurrence of residual stress in the diaphragm due to the weight of the mass.

[0023]

1 is a partially cutaway sectional view showing a semiconductor acceleration sensor according to an embodiment of the present invention. Referring to FIG. 1, a silicon sensor chip 2 made of an n-type silicon substrate
In FIG. 1, a diaphragm portion 22 having a thickness of several tens of μm is formed by being etched in an annular shape. Since the diaphragm portion 22 is formed in an annular shape by etching, a mass portion 23 is formed at a central portion surrounded by the diaphragm portion 22. The diaphragm portion 22 is provided with four piezoresistive resistance element portions 28. The resistance element portion 24 is formed as a p-type piezoresistance by diffusing a dopant. The aluminum wiring 26 is electrically connected to the resistance element portion 28. On the surface of the silicon sensor chip 21 on which the resistance element portion 28 and the aluminum wiring 26 are formed, a silicon dioxide film 25 as a protective film is formed.

Rim 24 of silicon sensor chip 21
Are bonded to a ceramic substrate 31 made of alumina via a ceramic adhesive layer 30. At the center of the ceramic substrate 31, a step portion 31a is formed. The formation of the step portion 31a allows the silicon sensor chip 2
A gap portion 27 is formed between the first mass portion 23 and the lower end surface. In the step 31a, a through hole 32 is provided.
Are formed.

An external connection terminal 33 formed on the outer periphery of the ceramic substrate 31 is connected to a gold wire 29 from the aluminum wiring 26 of the silicon sensor chip 21. A semiconductor acceleration sensor element can be obtained by placing a cover over the silicon sensor chip 21 in the state shown in FIG.

FIG. 2 is a sectional view showing a manufacturing process of the semiconductor acceleration sensor shown in FIG. First, a ceramic substrate 31 as shown in FIG. 2A is prepared. A step 31a is formed at the center of the ceramic substrate 31,
It has a step of about 10 μm.

Next, referring to FIG. 2B, a ceramic adhesive is applied to a region of the ceramic substrate 31 corresponding to the rim portion of the silicon sensor chip, and a ceramic adhesive layer 3 is formed.
0 is formed. Further, a cyanoacrylate adhesive is applied to a region of the ceramic substrate 31 corresponding to the mass portion of the silicon sensor chip so as to have a thickness of about 40 μm to form a spacer 34. The thickness of the ceramic adhesive layer 30 is formed to be about 30 μm.

Referring to FIG. 2C, next, the rim portion 24 of the silicon sensor chip 21 is placed on the ceramic adhesive layer 30, and the silicon sensor chip 21 is placed on the spacer 34.
Silicon sensor chip 2 so that the mass 23 of
1 is placed on a ceramic substrate 31. At this time, since the spacer 34 is provided below the mass portion 23,
The generation of stress in the diaphragm portion 22 due to the weight of the mass portion 23 can be prevented. Therefore, the silicon sensor chip 2 is set with the diaphragm portion 22 being flat.
1 can be bonded to the ceramic substrate 31. In this state, the ceramic adhesive layer 30 was cured by drying at 100 ° C. for 120 minutes. Next, acetone was injected into the through hole 32 to dissolve the cyanoacrylate adhesive in the spacer 34, and the dissolved adhesive was discharged to the outside from the through hole 32.

Referring to FIG. 2D, the through holes 32
Was turned upside down, the ceramic substrate 31 was reversed, and heated to 370 ° C. in this state, and this temperature was maintained for 60 minutes. As a result, the remaining cyanoacrylate adhesive was completely removed, and a gap 27 was formed between the mass 23 of the silicon sensor chip 21 and the center of the ceramic substrate 31. The vaporized gas generated when the cyanoacrylate adhesive was thermally decomposed was discharged to the outside through the through-hole 32.

As described above, a semiconductor acceleration sensor as shown in FIG. 1 can be obtained. In the above embodiment,
Although a cyanoacrylate adhesive is used as the spacer 34, a semiconductor acceleration sensor according to the present invention can be manufactured in the same manner when a nitrocellulose adhesive is used.

FIG. 3 is a partially cutaway perspective view showing a semiconductor acceleration sensor of another embodiment according to the present invention. Referring to FIG. 3, silicon sensor chip 21 has the same structure as that of the embodiment shown in FIG. The rim portion 24 of the silicon sensor chip 21
It is bonded to a resin substrate 41 made of PPS resin by a silicone rubber adhesive layer 40. A silica filler having a particle size of about 20 μm is mixed in the silicone rubber adhesive layer 40. A through-hole 42 is formed in an inner region of the PPS resin substrate 41 which is bonded with the silicone rubber adhesive layer 40. The through holes 42 are formed to release gas generated from the silicone rubber adhesive layer 40.
The gold wire 29 is connected between the metal terminal 43 provided on the PPS resin substrate 41 and the aluminum wiring 26.

In the semiconductor acceleration sensor of the embodiment shown in FIG. 3, since the silicon rubber adhesive layer 40 having rubber elasticity is provided between the PPS resin substrate 41 and the silicon sensor chip 21, the PPS resin substrate 41 The stress based on the difference in the coefficient of thermal expansion of the sensor chip 21 can be reduced and absorbed by the silicone rubber adhesive layer 40. Therefore, the thermal hysteresis characteristics can be improved. Further, since the silicon sensor chip 21 is provided directly on the PPS resin substrate 41 via the adhesive layer, the manufacturing process can be further simplified.

[0033]

【The invention's effect】

According to the manufacturing method of the present invention, a spacer is provided in a region on the substrate corresponding to a portion below the mass portion of the silicon sensor chip, and the rim portion of the silicon sensor chip and the substrate are bonded by an adhesive layer. After the bonding, the spacer is removed. Since the spacer is provided at the time of bonding, generation of residual stress in the diaphragm portion due to the weight of the mass portion can be prevented, and characteristics of thermal hysteresis based on the residual stress can be improved.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing one embodiment according to the present invention.

FIG. 2 is a sectional view showing a step of manufacturing the embodiment shown in FIG. 1;

FIG. 3 is a partially cutaway perspective view showing another embodiment according to the present invention.

FIG. 4 is a partially cutaway perspective view showing an example of a conventional semiconductor acceleration sensor.

FIG. 5 is a diagram showing a relationship between temperature and offset output characteristics in a conventional semiconductor acceleration sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 ... Silicon sensor chip 22 ... Diaphragm part 23 ... Mass part 24 ... Rim part 25 ... Silicon dioxide film 26 ... Aluminum wiring 27 ... Gap part 28 ... Resistance element part 29 ... Gold wire 30 ... Ceramic adhesive layer 31 ... Ceramic substrate 31a ... Step portion 32... Through hole 33... External connection terminal 40... Filler-containing silicone rubber adhesive layer 41... PPS resin substrate 42.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tadashi Kobayashi 5-4-1, Higashi 5-chome, Hanyu City, Saitama Prefecture Inside the Akebono Brake Central Research Institute Co., Ltd. (56) References JP-A-4-274005 (JP, A) JP-A-63-233342 (JP, A) JP-A-5-119057 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01P 15/12 H01L 29/84

Claims (1)

(57) [Claims] 1. A semiconductor acceleration sensor is manufactured by fixing a silicon sensor chip having a diaphragm provided around a mass provided at a central portion and having a rim provided around the diaphragm on a substrate. A method comprising: providing an adhesive layer in a region on a substrate corresponding to a rim portion of the silicon sensor chip; providing a spacer in a region on the substrate corresponding to a region below a mass portion of the silicon sensor chip; A method for manufacturing a semiconductor acceleration sensor, comprising removing a spacer after bonding a silicon sensor chip and a substrate with a layer.