JPH08107217A - Semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE: To relieve film stress, and reduce the warp of a beam part of an acceleration sensor, by laying a Ti based wiring durable to etching solution, instead of A wiring, in the wiring part of a semiconductor acceleration sensor. CONSTITUTION: In a part of an Si substrate, a diffusion resistor 4 is formed, on the resistor 4, an SiO2 oxide film 5 is formed, and a Ti film 8 is formed. Since Ti is a metal durable to etching, a protective film is not necessary to be formed on the whole surface of the Ti wiring 8. Nitride film passivation 7 is formed in the uppermost part of only the contact part of the Ti wiring part 8 and the diffusion resistor 4. That is, the cantilever part of an acceleration sensor of the Ti wiring 8 is constituted as a two-layered structure of an oxide film 5 and the Ti wiring 8. As compared with the conventional Al wiring of three-layered structure, film stress can be relieved. Thereby the warp of the beam part of the acceleration sensor can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-compact semiconductor acceleration sensor for detecting acceleration formed on a semiconductor substrate.

[0002]

2. Description of the Related Art FIG. 1 shows the structure of an acceleration sensor according to the present invention. The acceleration sensor bends the cantilever 2 when the weight 3 receives a certain force, and the diffusion resistance 4 attached near the base of the beam.
Receives a stress according to the amount of deflection, and the resistance value changes due to the stress. The change in the resistance value is electrically taken out as an output.

A process chart of a conventional acceleration sensor is shown in FIG. When anisotropically etching a semiconductor substrate as shown in FIG. 5G to form a cantilever of a cantilever as shown in FIG. 1, Si is used as shown in FIG.
Etching is performed from the back side,
When the substrate is penetrated, the etching solution penetrates into the wiring portion, so a nitride film 7 for protecting the Al wiring is formed on the Al wiring 6 as shown in FIG. 5 (g). There is a need. FIG. 4 shows a cross-sectional view (along A--B in FIG. 1) of the beam of the Al wiring 6 which is conventionally used. In FIG. 4, since the wiring part of the acceleration sensor uses the Al wiring 6 which is generally used in the IC process, the film structure of the Si substrate on the beam is such that the SiO ₂ oxide film 5 and Al which are insulating films are formed on Si.
The wiring 6 and the nitride film 7 for protecting the Al wiring have a three-layer film structure.

[0004]

However, in the past, the above-mentioned A
When a cantilever acceleration sensor having a 1-wiring / three-layer film structure is formed, distortion occurs in each layer film due to the difference in thermal expansion coefficient of each layer film, and the film stress causes warpage in the beam portion. It was

In order to solve such a conventional problem, an object of the present invention is to replace the Al wiring and the nitride film for protecting the Al wiring with Si only in the contact portion of the Ti wiring and the diffusion resistance portion and in the vicinity thereof. By forming a nitride film for preventing liquid infiltration into the structure, film stress is reduced and warpage of the beam portion of the acceleration sensor is reduced.

[0006]

In order to solve the above problems, in the wiring portion, a Ti-based wiring that can withstand an etching solution is laid in place of the Al wiring, so that a protective film required for the conventional Al wiring is provided. It becomes possible to omit the nitride film of the above, and by changing the above-mentioned three-layer film structure to a two-layer film structure of an oxide film and Ti wiring, it is possible to reduce the warpage as much as the film stress applied to the nitride film is eliminated. did. Further, at the contact portion between the Ti wiring portion and the diffusion resistance portion of the acceleration sensor, a nitride film is formed only on the contact portion in order to prevent the liquid intrusion due to the film step, so that the T
It is designed to prevent disconnection of i wiring.

[0007]

In the semiconductor acceleration sensor configured as described above, most of the nitride film as the protective film can be omitted, and the film structure is changed from the conventional three-layer film structure to the two-layer film structure. Thereby, the film stress due to the difference in the thermal expansion coefficient of each layer film is reduced, and the warp of the beam portion of the acceleration sensor is reduced.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of the cantilever acceleration sensor. In FIG. 1, a cantilever 2 and a weight portion 3 are formed on a Si substrate 1. A diffusion resistance 4 is formed near the base of the beam that supports the weight. Further, a metal wiring is formed on the upper surface of the cantilever 2. A partial sectional view of the conventional Al is shown in FIG. 4, and a case of Ti of the present invention is shown in FIG.

FIG. 5 shows a process chart of a conventional Al wiring acceleration sensor for comparison with the present invention. In (a), the oxide film 5, which is an insulating film, is formed on the upper surface of the Si substrate 1,
An oxide film 5 and a nitride film 7 are formed on the lower surface. Ion implantation is performed to form the diffusion resistance 4 on the upper surface of the Si substrate (b), patterning is performed on the upper surface of the Si substrate and the lower surface of the Si substrate (c), and the Al wiring 6 is formed in (d).
And a nitride film 7 is formed to protect the Al wiring. Then, in (e), gap etching for the beam thickness and patterning of the nitride film 7 are performed, and the upper glass 9 for joining as a stopper and for protecting the pad portion 10 is joined (f) and (g). Etching is performed from the lower surface side of the Si substrate 1, the etching liquid penetrates the Si substrate 1,
It penetrates between the upper surface and the upper surface glass 9. Finally, the lower surface glass 11 as a stopper is bonded to the lower surface of the Si substrate (h).

FIG. 3 shows a process chart of the Ti wiring acceleration sensor of the present invention. 5 (e), the nitride film 7 is patterned so as to cover the entire Al wiring, but in FIG. 3 (e), the nitride film 7 is formed only on the contact portion and its vicinity. It is the point that is patterned.

FIG. 4 is a sectional view of a diffusion resistance portion in the Al wiring of the beam portion of the conventional acceleration sensor. Si
A diffusion resistance 4 is formed on a part of the substrate 1, an SiO ₂ oxide film 5 is formed on the diffusion resistance 4, an Al wiring 6 is formed, and a nitride film 7 for protecting the Al wiring by an etching solution is formed on the uppermost portion. And has a three-layer film structure in total.

Similarly, FIG. 2 is a sectional view of a diffusion resistance portion in the Ti wiring of the beam portion of the acceleration sensor of the present invention. A diffusion resistor 4 is formed on a part of the Si substrate 1,
There is a SiO ₂ oxide film 5 on top of it, and Ti wiring
Are formed. Further, since Ti is a metal that can withstand the etching solution, it is not necessary to form a protective film on the entire surface of the Ti wiring portion, and the nitride film passivation 7 is formed only on the contact portion between the Ti wiring portion and the diffusion resistance portion at the uppermost portion. Has been done.

That is, the cantilever portion of the Ti wiring acceleration sensor has a two-layer film structure of the oxide film 5 and the Ti wiring 8.
The film stress can be reduced as compared with the conventional Al wiring having a three-layer film structure. Therefore, it is possible to reduce the warp of the beam portion of the acceleration sensor.

[0014]

As described above, according to the present invention, in the wiring portion of the acceleration sensor, the conventional three-layer film structure of Al wiring is changed to the two-layer film structure of Ti wiring. This has the effect of reducing the sensitivity of acceleration applied to other axes. Further, there is an effect of increasing durability by reducing the warpage.

[Brief description of drawings]

FIG. 1 is a perspective view of an acceleration sensor according to the present invention.

FIG. 2 is a cross-sectional explanatory view of a Ti wiring portion of the present invention.

FIG. 3 is a process chart of the present invention.

FIG. 4 is a cross-sectional explanatory view of an Al wiring portion of a conventional method.

FIG. 5 is a process chart of a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Si substrate 2 Cantilever 3 Weight part 4 Diffusion resistance 5 Oxide film 6 Al wiring 7 Nitride film 8 Ti wiring 9 Top glass 10 Pad part 11 Bottom glass

Claims (2)

[Claims] 1. A diffusion resistance is formed in the vicinity of the root of a beam that is formed on a semiconductor substrate and supports a weight portion. By detecting a change in resistance value that occurs in the diffusion resistance according to the displacement of the beam, A semiconductor acceleration sensor for detecting acceleration, wherein a titanium-based metal is used for a wiring portion of the semiconductor acceleration sensor. 2. The semiconductor acceleration sensor according to claim 1, wherein a nitride film is formed in a contact portion between the wiring portion of the semiconductor acceleration sensor and the diffusion resistance portion and in the vicinity of the contact portion.