Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Physical deformation
Patent
1996-10-29
1999-03-09
Chaudhuri, Olik
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Physical deformation
257417, 438 50, 438 53, H01L 2982
Patent
active
058805095
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a highly reliable semiconductor pressure sensor having good accuracy and sensitivity, whose measuring diaphragm is composed of an epitaxially grown single silicon crystal, and to its manufacturing method.
BACKGROUND OF THE INVENTION
FIG. 1 shows a drawing illustrating the essential part of the configuration which has been used so far. Such a configuration is shown, for example, in "Fine-grained Polysilicon and its Application to Planar Pressure Transducers," by H. Guckel, et al., TRANSDUCERS '89 PROCEEDINGS Vol. 2, pp.346 to 351.
In FIG. 1,
Number 11 shows a silicon substrate, 12 a measuring diaphragm made of polysilicon forming air gap chamber 13 together with the silicon substrate. Number 14 shows a piezo-resistance strain gage formed on the surface of measuring diaphragm 12. Number 15 shows a connecting hole provided in measuring diaphragm 12 and connects air gap chamber 13 to the outside. Number 16 shows a polysilicon thin film which fills connecting hole 15.
In this configuration, air gap chamber 13 is constructed by forming a solid part corresponding to air gap chamber 13 with silicon oxide film, then removing silicon oxide film using selective etching from connecting hole 15 which connects air gap chamber 13 to the outside, and filling connecting hole 15 with polysilicon thin film 16 formed by reduced-pressure chemical vapor deposition (CVD). The adoption of a reduced-pressure CVD retains air gap chamber 13 as a virtually sufficient vacuum for the reference pressure for the absolute pressure sensor.
However, in such equipment, is composed of polysilicon, the stiffness of the measuring diaphragm changes due to heat treatment. measuring diaphragm 12, its sensitivity becomes low.
The present invention intends to solve these problems.
Although it is not easy to form single crystals of silicon on silicon oxide film, in recent years, a good silicon-on-insulation (SOI) wafer has become available because of the development of semiconductor processing techniques.
The present invention has been contrived by paying attention to such a situation. The purpose of this invention is to provide a highly reliable semiconductor pressure sensor having good accuracy and sensitivity and its manufacturing method, whose measuring diaphragm is composed of epitaxially grown single silicon crystals.
SUMMARY OF THE INVENTION
In order to achieve this purpose, the present invention adopts: substrate; a closed air gap chamber having a predetermined narrow gap which backs up an overpressure application to a diaphragm provided with the single crystal silicon substrate and forming a measuring diaphragm made by epitaxial growth; and a strain detection element incorporated in the above-described measuring diaphragm composed of a single crystal. air gap chamber is incorporated within a single crystal silicon substrate, wherein the following processes are included: wafer by photo-lithography leaving the required portions of them, surface of the above-described SOI wafer to form a measuring diaphragm, diaphragm, on the above SOI surface side, etching through the above connecting hole, and
In the above configuration, the SOI silicon and insulation film of the SOI wafer are removed by photo-lithography leaving the required portions. An epitaxial growth layer is made on the SOI surface side of the SOI wafer to form the measuring diaphragm. The strain detection element is formed on the measuring diaphragm. A connecting hole reaching the insulation film is formed on the SOI surface side. The insulation film is removed by selective etching through the connecting hole. Finally, the connecting hole is filled with a thin film.
As a result, since a semiconductor pressure sensor can be entirely constructed with single crystal silicon, than polysilicon materials can be constructed.
Therefore, the present invention can offer a highly reliable semiconductor pressure sensor with excellent accuracy and sensitivity composed of epitaxially grown single silicon crystals.
BRIEF DESCRIPTION OF
REFERENCES:
patent: 4993143 (1991-02-01), Sidner et al.
patent: 5242863 (1993-09-01), Xiang-Zheng et al.
patent: 5369544 (1994-11-01), Mastrangelo
Ikeda Kyoichi
Kudo Takahiro
Watanabe Tatsuya
Chaudhuri Olik
Wille Douglas A.
Yokogawa Electric Corporation
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