JPH0618342A - Pressure sensor - Google Patents

Abstract

PURPOSE:To improve durability of metal contact point and reliability as a sensor by forming a concave part in the center of electrically active region where impurity in silicon diaphragm is diffused, and forming a metal contact point in this cocave part. CONSTITUTION:On the back surface (the surface facing to contact metal) of glass 1, a metal thin film 2 is formed. On a silicon diaphragm 3 formed by fabricating monocrystal silicon 5 wafer, an impurity diffusion layer 6 electrically connectable is formed. On the diffusion layer 6 surface in the center of the diaphragm 3, a concave groove is formed and there, a metal contact point 4 is inserted. As the diffusion layer 6 electrically connects the contact point 4 and an aluminum pad 7, an electric signal is fetched out of the pad 7. When pressure is impressed to the sensor for switching, the contact point 4 and surface other than concave part in the diaphragm 3 being in contact flat with the thin film 2. Thus, even with long term pressure impression, collapse and distortion of the set point are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The pressure sensor according to the present invention relates to a semiconductor pressure sensor for detecting tire pressure in the automobile industry.

[0002]

2. Description of the Related Art In a conventional pressure sensor, a metal contact 4 is formed as a convex portion on a silicon diaphragm 3 as shown in FIG. Further, as shown in FIG. 4, it has no metal contact and operates only by the contact between the electrically active region in which impurities are diffused in the silicon diaphragm and the glass side electrode.

[0003]

In the conventional pressure sensor shown in FIG. 3, since the metal contact 4 is projected on the silicon diaphragm 3, it may be deformed by the application of pressure for a long period of time. That is, the metal contact 4 is crushed, and if the metal contact 4 is turned off and then turned on again, switching is delayed by the amount of the crushed metal contact 4. Therefore, in order to turn on the switch, the first ON
A pressure higher than the time pressure is required, and the reliability of the pressure sensor becomes low.

On the other hand, in the pressure sensor of the form as shown in FIG. 4, the problem of contact crushing does not occur, but when the silicon diaphragm 3 having only the impurity diffusion region and the glass side electrode 2 are in contact, a sufficient resistance value is obtained. However, there is a problem in that the stable switch operation cannot be guaranteed.

[0005]

According to the present invention, in order to solve the above problems, a recess is formed in the center of an electrically active region 6 in which impurities are diffused in a silicon diaphragm 3 by a photofabrication technique or the like. The metal contact 4 was formed in the recess. This makes it possible to prevent the metal contact 4 from being crushed or deformed even if a pressure is applied for a long period of time.

[0006]

As described above, by forming contacts with a metal thin film or the like in the recesses in the silicon diaphragm of the pressure sensor, it is possible to prevent the set point from being crushed or deformed. The reliability as a pressure sensor can be improved, and the processing depth of the gap can be reduced because the set point does not project, so that the processing accuracy is improved.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a pressure sensor according to the present invention. However, it is not shown as the actual magnification because it is drawn for easy understanding.

FIG. 2 also corresponds to the present invention, but is an example in which the periphery of the metal contact 4 protruding on the silicon diaphragm 3 is protected by a thin film of polycrystalline silicon 8 or the like. Both of them prevent the problems that the metal contact 4 is crushed or spread in the lateral direction due to the application of pressure.

In FIG. 1, reference numeral 1 denotes glass having a thickness of 300 μm or less. A metal thin film 2 is formed on the back surface of the glass 1 (the surface facing the contact metal). This glass-side metal thin film 2 has a film thickness of several thousand Å. Reference numeral 3 is a silicon diaphragm, 4 is a metal contact insert-formed in the silicon diaphragm 3, and 5 is single crystal silicon. Reference numeral 6 denotes a layer in which impurities are diffused into the single crystal silicon 5, and the metal contact 4 having the impurity diffusion layer 6 inserted therein and the aluminum pad 7 are electrically connected. Then, the electric signal is taken out through the aluminum pad 7. Further, FIG. 5 illustrates a state in which pressure is applied to the pressure sensor according to the present invention to perform switching.

FIG. 6 illustrates a state in which the conventional pressure sensor is switching, and shows a state in which the metal contact 4 is crushed. The above results are shown in FIG. 7, which shows the relationship between the switch pressure and the number of times of use. The curve indicated by the broken line in FIG.
The change of the switch pressure with respect to the number of times of use of the conventional pressure switch shown in FIG. 4 is shown, and the straight line shown by the solid line shows the switch pressure with respect to the number of times of use of the pressure switch of the present invention.

[0011]

As described above, the present invention has a structure in which a concave groove is formed in the center of a silicon diaphragm and a metal contact is inserted in that portion, so that the metal contact and the recess other than the recess in the silicon diaphragm are formed. Since the surfaces are in planar contact with each other, even if a pressure is applied for a long period of time, the set point can be prevented from being crushed or deformed, and the reliability of the pressure sensor can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a pressure sensor according to the present invention.

FIG. 2 is a sectional view of an embodiment of a pressure sensor according to the present invention.

FIG. 3 is a cross-sectional view of a conventional pressure sensor having a metal contact on a silicon diaphragm.

FIG. 4 is a cross-sectional view of a conventional pressure sensor without a metal contact.

FIG. 5 is a cross-sectional view of an embodiment of the pressure sensor according to the present invention, showing a switching state.

FIG. 6 is a cross-sectional view of an example of a conventional pressure sensor, showing a switching state.

FIG. 7 is an explanatory diagram comparing a change in switching point (pressure) between the pressure sensor according to the present invention and a conventional pressure sensor, the number of times of repeated measurement.

[Explanation of symbols]

 1 Glass 2 Metal Thin Film 3 Silicon Diaphragm 4 Metal Contact 5 Single Crystal Silicon 6 Impurity Diffusion Layer 7 Aluminum Pad 8 Polycrystalline Silicon

Claims (2)

[Claims] 1. In a semiconductor pressure sensor, an impurity diffusion layer electrically connectable to an external connection terminal is formed on a diaphragm formed by processing a single crystal silicon wafer, and the impurity diffusion layer of the impurity diffusion layer is formed. A pressure sensor characterized in that a contact electrode made of a metal material is insert-molded in a part, and a switch operation is performed by contact or non-contact with a facing glass-side electrode. 2. A recess is formed in the region of the impurity diffusion layer formed on the silicon diaphragm, and a contact electrode made of a metal material is provided in the recess so as to be flush with the surface of the impurity diffusion layer. The pressure sensor according to claim 1, wherein: