JPS62242830A - Pressure detector - Google Patents

Abstract

PURPOSE:To mass-produce small-sized chips and to detect high proof pressure by making a diaphragm of metal with superior proof strength and constituting a semiconductor strain gauge while a chip is in a metallic wafer state. CONSTITUTION:Metal or copal is cut into a square wafer of, for example, 50-150mm in side length and 0.2-1.0mm in plate thickness, the surface is polished and cleaned, and an oxide layer is formed after a heat treatment. Then, an insulating layer is formed thereupon, polysilicon is filed to proper impurity density, and an annealing treatment, patterning, and etching are carried out to form four polysilicon strain gauges 13a-13d. Metal which form electrodes is vapor-deposited to form the electrodes 14 and the water is cut to the size of a chip 11. Then the chip 11 is fixed to a body 10 with a brazing material 20, and ceramic substrate 16 is fitted; and a wire 15 is bonded, and a post 19 is stood, thus obtaining a sensing element. Consequently, chips of small size are mass-produced and high proof pressure can be detected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a pressure detector using a pressure conversion element for converting the pressure of a fluid such as oil or gas into voltage, and particularly relates to a pressure sensor that converts the pressure of a fluid such as oil or gas into voltage. The present invention relates to a pressure detector suitable for detecting.

[Conventional technology]

Generally, when detecting high pressure, a pressure gauge using a Bourdon tube or a pressure gauge using a metal foil gauge is used. The former has a simple configuration and can provide stable output, but has the disadvantage of being large in size, while the latter is good for use as a measuring instrument because the sensitivity of the metal foil gauge is low and the circuit processing is difficult, but it is suitable for use as a measuring instrument. Droplet drift becomes a problem when used constantly as a detection sensor.

In addition, pressure detectors using semiconductor gauges are known as highly sensitive pressure detectors (for example, Utility Model Application No. 55-4761
5, Utility Model Application Publication No. 56-96344). These are generally intended to detect low pressure fluids around atmospheric pressure, and for this purpose a thin diaphragm portion is formed by etching one side of a semiconductor wafer. In order to achieve a high withstand voltage as the purpose of the present invention, it is necessary to thicken the semiconductor wafer that serves as the diaphragm, and if the thickness of the silicon plate is determined to ensure detectable sensitivity, stress will be generated around the diaphragm. If concentrated, there is a risk of destruction considering the strength of silicon (bending strength 7 to 35 kg/ant), and the thickness must be sufficiently thick to avoid destruction. A detector could not be realized.

In addition, as described in Japanese Utility Model Publication No. 60-168037, a pressure detector in which an amorphous silicon gauge is formed on a metal diaphragm, Japanese Patent Publication No. 56-43489
As described in the above publication, a pressure sensor has been proposed in which a strain gauge is formed on a metal diaphragm with an insulating layer interposed therebetween. In the case of metal, it is stronger than silicon, so it seems possible to realize a pressure detector with high withstand pressure, but in the case of the one described in the above publication, for example, it is necessary to evaporate or etch the metal diaphragm one by one on top of the metal diaphragm. ,
In either case, the size of the diaphragm becomes large, and moreover, it is not suitable for mass production.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide a pressure sensor that can be mass-produced, has a small chip that serves as a diaphragm, and has a high withstand pressure.

[Means for solving problems]

The present invention uses a metal with a small coefficient of thermal expansion and excellent strength to make a chip that becomes a diaphragm, and this chip is obtained by forming a semiconductor strain gauge on a metal wafer and then cutting it. It is designed to be tightly fixed by welding or the like.

[Effect]

In the pressure detector of the present invention, the diaphragm facing the fluid to be detected is made of a metal with excellent strength, and the chip that becomes the diaphragm is a semiconductor strain gauge in the form of a metal wafer. , the chip can be made smaller, suitable for mass production, and can detect high pressure.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention shown in the drawings will be described. 1st
The figure is a longitudinal cross-sectional view of essential parts showing the configuration of one embodiment of the pressure detector according to the present invention, in which 1 is a sensing element for detecting pressure, 2 is a housing, and this housing 2 is provided with a thread 2b. It is designed to be attached to an object to be detected (not shown). The end 1a of the sensing element 1 and the end 2a of the housing 2 are closely fixed by electric welding or the like. 3 is a processing circuit for processing and outputting the signal of the sensing element 1. 4
is a first lead wire for electrically connecting the sensing element 1 and the processing circuit 3. 5 is a sealing resin for sealing the upper part of the housing 2. Reference numeral 6 denotes a ring for pressing the sealing resin 5, which is driven into the housing 2 and fixed therein. 7 is mold resin for sealing. 8 is a second lead wire for taking out signals from the processing circuit 3 to the outside, and is tightly fixed to the sealing resin 5 to maintain airtightness. 2(A) and 2(B) are diagrams showing details of the sensing element 1, and FIG. 2(A)
is a plan view seen from above, and Figure 2 (B) is a longitudinal cross-sectional view.
0 is the body of a sensing element 1 made of metal, the end 1a is a projection, and the center has a circular hole 10 with a diameter.
A is provided. 1) is a chip made of metal, 1
Reference numeral 2 denotes an insulating film made of 5in2 or the like formed on this chip 1), and is an insulating film that is compatible with metal and polysilicon. 13 is a polysilicon strain gauge, and as shown in the figure, there are four strain gauges 13a1) 3bs 13C%.
13d. 14 is an electrode made of a metal thin film, and four electrodes 14a, 14b, 14c, 14
d, whereby the strain gauge 13 has a full bridge configuration. 15 is a wire installed on each of the electrodes. 16 is a substrate made of ceramics. 17 is a bottle for fixing the substrate 16 to the body 10. Reference numeral 18 is an electrode receiver printed with conductive paste and fired, and reference numeral 19 is a fixed post that receives the electrode. The electrode 14, wire 15, electrode receiver 18, and post 19 are in a conductive state.

Next, referring to the manufacturing method of the chip 1), FIG. 5 is a flowchart showing the manufacturing process of the chip 1). First, a metal such as Kovar is cut out and processed into a square shape having sides of 50 to 150 m. The plate thickness is 0.2 to 1. O
A wafer of mm is used. The surface of this wafer is polished to a surface roughness of, for example, lμ or less, and cleaned, and then heat treated to form an oxide layer on the surface. On top of that, an insulating layer of about 0.5 to 1.0 μm is formed using a method such as SiO□ sputtering, and then polysilicon is deposited on top of the insulating layer at an appropriate impurity concentration (for example, B is 1Q20c, -1 degree)
A film is formed so as to have the following properties, annealing treatment using a laser or the like is performed, patterning is performed in a photolithography process, and four polysilicon gauges are formed by etching. Next, a metal that will become an electrode is formed into a film by vapor deposition or sputtering, followed by patterning and etching to form an electrode.

Cut this into chip size pieces. This chip is fixed to the brazing material 2o rebody, a ceramic substrate 16 is attached, a wire 15 is pounded, and a post 19 is erected to serve as a sensing element.

Next, the operation of the pressure detector of the present invention having the above structure will be explained. When fluid pressure is applied to the sensing element l, 1) the part of the body lo corresponding to the circular hole 10a becomes a fixed circular diaphragm and becomes distorted, and the strain gauges 13a and 13C receive tensile stress. The resistance value increases, while compressive stress is applied to the strain gauges 13b and 13d, causing the resistance value to decrease. 4 strain gauges 13a to 13d
has a full bridge configuration, so for example, the electrode 14
A constant voltage E is applied between electrodes 14b and 14c, and
If a voltage between 4d and 4d is used as an output, an output corresponding to a change in fluid pressure can be obtained. After this output is amplified by the processing circuit 3 and subjected to temperature compensation, it is outputted to the outside from the 217th node, %I8.

3(A) and 3(B) show the configuration of another embodiment of the pressure detector according to the present invention, FIG. 3(A) is a plan view, and FIG.
B) is a longitudinal sectional view in which the chip 1) has a recess in the center and has a structure in which the chip and the body are integrated, so that the process of joining the body and the chip can be omitted. The rest of the structure is the same as that of the embodiment shown in FIG.

Note that FIG. 4 shows the back side of the wafer. In this embodiment, the end 1a of the chip 1) has a square shape, so the end 2a of the housing 2 also has a square shape. do.

〔Effect of the invention〕

As described above, in the pressure detector of the present invention, the diaphragm facing the fluid to be detected is made of a metal with excellent strength, and the chip that becomes the diaphragm is a semiconductor strain gauge in the form of a metal wafer. I did it like this,
This has the great effect of making the chip smaller, suitable for mass production, and realizing a pressure detector with high withstand pressure.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a main part showing the configuration of an embodiment of the pressure detector according to the present invention, and FIGS. 3(A) and 3(B) are a plan view and a longitudinal sectional view showing details of another embodiment of the sensing element in the pressure sensor of the present invention, and FIG. a simplified diagram showing an embodiment of a metal wafer in an inventive pressure detector;
FIG. 5 is a flowchart of the manufacturing process of the chip in the pressure sensor of the present invention. ■...Sensing element, 2...Housing. 3... Processing circuit, IQ... Body, 1)... Chip, 12... Insulating film, 13... Strain gauge, 14...
- Electrode, 16... Substrate, 13a, 13b, 13c, 1
3d...Strain gauge.

Claims (5)

[Claims] (1) A sensing element that detects pressure using a semiconductor strain gauge, a housing that is closely fixed to the sensing element, a processing circuit that is connected to the semiconductor strain gauge and amplifies its signal and performs temperature compensation, and this processing circuit. The sensing element is made of metal and has a recess in its central part, this recess becomes a diaphragm, and the semiconductor gauge is connected to the opposite side of the recess via an insulating film. A pressure detector characterized by having a plurality of . (2) The pressure detector according to claim 1, wherein the sensing element is comprised of a metal chip of uniform thickness closely fixed to one side of a metal body having a hole in the center. . (3) The pressure detector according to claim 1, wherein the sensing element is formed by integrally processing a concave portion that becomes a diaphragm from a uniform metal. (4) The first aspect of the present invention is characterized in that the surface of the sensing element opposite to the recessed portion is subjected to oxidation treatment.
Pressure detector described in Section. (5) The metal of the sensing element has a coefficient of thermal expansion of 2.5×10^-^6°C^-^1 to 6.0×10^-
The pressure sensor according to claim 1, characterized in that the temperature is ^6°C^-^1.