JPH0447763B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the structure of a strain sensor that converts strain generated in, for example, a structure into an electrical signal and extracts it.

Description of the Prior Art Conventionally, strain gauges have been widely used as means for detecting strain occurring in, for example, structures. FIG. 1 is a schematic cross-sectional view showing an example of the use of a conventional strain gauge. The strain gauge 1 has a structure in which a strain-sensitive resistor 3 made of, for example, metal foil or filament-like thin metal wire is fixed on a plastic substrate 2 made of, for example, polyester. The strain is detected as an electrical signal by utilizing the change in the electrical resistance of the strain-sensitive resistor 3 made of metal foil or thin metal wire. In the structure shown in Figure 1,
The strain gauge 1 is bonded and fixed onto the detection target member 4 with an adhesive 5, so that the strain generated in the detection target member 4 is transferred to the strain sensitive resistor 3 via the adhesive 5 and the plastic substrate 2. communicated. When the strain-sensitive resistor 3 is distorted, its electrical resistance value changes, and this is taken out by the lead wires 6a, 6b.

By the way, as mentioned above, the conventional strain gauge 1 is
Since it is used by being bonded to the detection target member 4 using the adhesive 5, if the detection target member 4 repeatedly vibrates or is subjected to external vibrations or shocks, the adhesive 5 may There was a problem that the strain gauge 1 would peel off from the detection target member 4 due to deterioration and a decrease in adhesive strength. Also, 80
When used in a high temperature environment of .degree. C. or higher, the adhesive 5 softens, so that even if strain occurs in the detection target member 4, the strain cannot be accurately detected.

Furthermore, since the conventional strain gauge 1 is bonded and fixed to the detection target member 4 with the adhesive 5, it is necessary to apply the adhesive 5 evenly and evenly in order to perform accurate strain detection. Another problem was that this work required considerable skill.

Purpose of the Invention In view of the above-mentioned problems, the purpose of the present invention is to ensure that the strain-sensitive resistor does not peel off even when subjected to repeated external vibrations and shocks, and that the strain-sensitive resistor is used at high temperatures of 80°C or higher. It is an object of the present invention to provide a strain sensor that can be used repeatedly even if the strain sensor is used even when the strain sensor is used, has a strain-sensitive resistor that exhibits a good strain-to-electrical resistance conversion effect, and can perform highly reliable strain detection.

Structure of the Invention A strain sensor according to the present invention includes a strain receiving structural member, a multilayer thin film layer, and a plurality of electrode layers.
The strain-receiving structural member generates strain in response to applied force. The multilayer thin film layer is applied directly onto the strain-receiving structural member.
The semiconductor device is formed by vapor deposition and includes a plurality of semiconductor layers. The electrode layer is formed on the outermost layer of the multilayer thin film layer.
The strain receiving structural member is made of a conductive material. The outermost layer of the multilayer thin film layer is a strain-sensitive resistive layer whose electrical resistance changes according to strain. The plurality of semiconductor layers constitute a diode between the electrode layer and the strain receiving structure member.

That is, in the present invention, a diode is formed between an electrode layer and a strain-receiving structural member, and an insulating layer having high electrical resistance is formed between the electrode layer and the strain-receiving structural member by utilizing the rectifying effect of the diode. can be formed.
Thereby, the outermost layer of the multilayer thin film layer, which becomes the strain-sensitive resistor, exhibits a good strain-to-electrical resistance conversion effect. As a result, the reliability of strain detection by the strain-sensitive resistor is improved. Furthermore, the present invention solves the problems of conventional strain gauges by forming a multilayer thin film layer, including a strain-sensitive resistive layer, over the strain-receiving structure without the use of an adhesive.

Other features of the invention will become clear from the following description of the embodiments.

DESCRIPTION OF EMBODIMENTS FIG. 2 is a front sectional view for explaining an embodiment of the present invention. In this embodiment, the strain of a detection target member 14 made of metal is measured, but here the detection target member 14 itself becomes a strain-receiving structural member. That is, a multilayer thin film layer 17 made of amorphous silicon is closely formed on the detection target member 14 as a strain-receiving structural member by vapor deposition methods such as chemical vapor deposition and physical vapor deposition, or other thin film forming means.

The multilayer thin film layer 17 includes n-i-p in order from the outermost layer.
It has a structure in which semiconductor layers 17a, 17b, and 17c of conductive type are stacked. Note that the multilayer thin film layer 17
may be constructed by stacking pin conductivity type semiconductor layers in order from the outermost layer. Multilayer thin film layer 1
On the outermost layer 17a of No. 7, lead wires 16a, 16
Extracting electrodes 21a and 21b are formed for connecting the terminals b. Note that the electrodes 21a, 21b and the outermost layer 17a may be covered with a synthetic resin layer for moisture proofing.

In the strain sensor of this embodiment, the outermost layer 17a of the multilayer thin film layer 17 is an n-type or p-type semiconductor strain-sensitive resistor, and when strain is transmitted from the strain-receiving structural member 14, its resistance value changes. However, this change in resistance value is transmitted to the lead wires 16a and 16a through the electrodes 21a and 21b.
16b. By the way, multilayer thin film layer 1
7 is, as mentioned above, n-i-p in order from the outermost layer.
or p-i-n conductive type semiconductor thin film layer 17
Since it is formed by laminating the electrodes 21a, 17b, and 17c, a diode is formed between the electrodes 21a, 21b and the strain receiving structure member 14. Therefore, the electrical insulation between the outermost semiconductor layer 17a, which serves as a strain-sensitive resistor, and the strain-receiving structure member 14 can be significantly improved compared to the rectifying performance of a diode, and therefore, the reliability is excellent. distortion detection can be performed. This will be explained with reference to FIG. 3, which is a schematic equivalent circuit of the embodiment shown in FIG. 2, and FIG. 4, which is a circuit diagram showing the state of use. In addition, Figures 3 and 4
In the figure, the resistances of the electrodes 21a, 21b and the strain-receiving structure member 14 in FIG. 2 are approximated to 0, and are omitted from the drawing.

In FIG. 3, R indicates the resistance of the strain-sensitive resistor 17a between the electrodes 21a and 21b, a and b indicate the lead wires 16a and 16b, and 22 and 23 respectively,
A diode formed between the electrodes 21a, 21b and the strain receiving structure member 14 is shown. When using the strain sensor of this embodiment having the circuit configuration shown in FIG. 3, one side of the external power source E is set at the same potential as the strain receiving structural member 14, as shown in FIG. Therefore, as is clear from FIG. 4, the diode 22
Since a voltage is applied in the opposite direction to the diaphragm, it is as if a resistor with an extremely high resistance value is connected between the a-end and the diaphragm, and the b-end is short-circuited to the strain-receiving structural member 14. , resistance R is the strain receiving structural member 14
It can be seen that the material is not affected by the effects of heat, exhibits a good resistance effect against the external power source E, and has excellent reliability as a strain-sensitive resistor.

According to the experiments conducted by the inventors of the present application, when the electrical resistivity of the outermost layer 17a that forms the strain-sensitive resistor is 1×10 ² Ωcm or less, the sensitivity of strain-resistance changes is extremely high, and the outermost layer 17a that forms the strain-sensitive resistor has an extremely high sensitivity. It has been found that when an electrical signal is taken out from the outer layer 17a, a highly sensitive strain sensor with low resistance and suppressed noise can be obtained.

In addition, the multilayer thin film layer 17 is doped with a P-type silicon layer 1 with a thickness of 500 Å by plasma CVD method.
Then, in the same equipment, an i-type silicon layer 17b with an electrical resistivity of 2×10 ⁶ Ωcm and a thickness of 0.5 μm is formed without doping with impurities, and further doped with phosphorus to have an electrical resistivity of 3×10 Ωcm. By forming the ^-1 Ωcm n-type silicon layer 17a with a thickness of 1μ,
Create 2 x 2 mm electrodes 2 with a 2 mm spacing.
When 1a and 21b were formed, the interelectrode resistance was
It was 3.2kΩ. This value is almost the same as the resistance value of the outermost layer 17a, and it can be seen that the resistance of other members between the electrodes 21a and 21b can be ignored.

By the way, in the embodiment shown in FIG. 2, the multilayer thin film layer 17 formed on the strain receiving structural member 14 is n
-i-p type or p-i-n type silicon layer 17
Since it is constructed by laminating layers a, 17b, and 17c, the same main component (Si)-based material can be used, and the films can be formed continuously in the same thin film forming equipment, and Since it is formed by a thin film forming means such as vapor deposition, uniformity in film quality can also be ensured. Therefore, it is possible to realize an inexpensive strain sensor with little individual difference. In addition, since it is formed directly on the strain-receiving structural member 14, there is no need to use the adhesive 5 as in the conventional strain gauge 1 shown in FIG. It is also possible to effectively solve problems in use under high temperatures, and it is possible to obtain a strain sensor that can be used over a wide temperature range.

In the embodiment shown in FIG. 2, the multilayer thin film layer 17 is of n-i-p type or p-type in order from the outermost layer.
Although it is constructed by laminating silicon layers of i-n type conductivity, layers of other conductivity types may be laminated as long as they can form a diode, or the multilayer thin film layer 17 may be formed of other materials. may be configured. For example, n-i type silicon layers may be laminated in order from the outermost layer. In this case, an i-type silicon layer is directly formed on the strain-receiving structure member, and then an n-type silicon layer is formed in close contact with the electrode 21a. , 21b and the strain receiving structural member 14, or a shot barrier diode may be formed between the strain receiving structural member 14.
A thin film insulating layer such as Al ₂ O ₃ , SiO ₂ or insulating carbon is closely formed on top, and an i-type silicon layer and then an n-type silicon layer are successively closely formed on this thin film insulation.
It is also possible to adopt an MIS (Metal-Insulator-Semiconductor) structure and form a diode between the electrodes 21a, 21b and the strain receiving structure member 14.

Further, the material of each layer constituting the multilayer thin film layer 17 is not limited to silicon, but also germanium, carbon (diamond), gallium-arsenic, etc.
Various semiconductor materials can be used, such as gallium-phosphide.

In the embodiment shown in FIG. 2, the detection target member 14 as a strain-receiving structural member is made of a conductive material, but the strain-receiving structure member 14 may be made of an insulating material. There is no need to use the rectifying effect of a diode, and the multilayer thin film layer 1
It goes without saying that strain can be accurately detected by the strain-sensitive resistor present in the outermost layer of 7.

FIG. 5 is a longitudinal sectional view showing a pressure sensor to which the embodiment shown in FIG. 2 is applied. Pressure sensor 31
The main body 34 includes a cylindrical member 33 having an introduction hole 32 into which a fluid whose pressure is to be detected is taken in, and a main body 34 to which the cylindrical member 33 is screwed. A strain receiving structure member 35 is provided. The above-described multilayer thin film layer 17 is formed on the strain receiving structure member 35 by direct vapor deposition, and electrodes 21a and 21b are formed on the multilayer thin film layer 17. Electrode 2
A moisture-proof layer 25 made of synthetic resin is formed above the moisture-proof layer 1a, 21b, and the lead wires 16a, 16b drawn upward from the moisture-proof layer 25 are connected to the support 36.
The pressure sensor 31 is drawn out through an opening 38 of a disk 37 fixed to the inner surface of the pressure sensor 31, a resin mold layer 39, and an opening 41 of a cap 40. Therefore, even if an external force is applied to the lead wires 16a and 16b, since they are fixed in the resin mold layer 39, this external force is received by the resin mold layer 39 and does not affect the strain sensor portion.

In the pressure sensor 31 shown in FIG.
Based on the strain transmitted to the lead wires 16a, 16
b is detected as a change in electrical resistance. Thus, the embodiment shown in FIG.
It is particularly advantageous when configured as a dedicated sensor, such as. This is because the multilayer thin film layer 17 can be formed in advance on the strain receiving structure member 35 by a thin film forming means such as vapor deposition.

In the embodiment shown in FIG. 2, two electrodes 21a and 21b are provided as the plurality of electrodes, but the present invention is not limited to this. Three or more arbitrary electrodes may be formed, and each electrode and the strain receiving A diode may be configured between the structural member. For example, as shown in the schematic circuit diagram in FIG. 6, four electrodes may be formed to form a bridge, to which an external power source E may be connected. In FIG. 6, 61, 62, 63, 64 indicate the outermost layer of the multilayer thin film layer that becomes the strain-sensitive resistor, and 65, 6
6, 67, and 68 indicate diodes formed between each electrode and the strain receiving structure member. As is clear from FIG. 6, since a voltage is applied in the opposite direction to the diodes 65...68, the c, d, and e ends are in a state where a high resistance is connected between them and the strain-receiving structural member, and f Although the ends are short-circuited, the resistors 61, 62, 63, and 64 are not affected by the strain-sensitive structural members, exhibit good resistance to the external power source E, and function as highly reliable strain-sensitive resistors. I understand that.

Effects of the Invention As described above, according to the present invention, a multilayer thin film layer including a strain-sensitive resistance layer as the outermost layer is directly formed by vapor deposition on a strain-receiving structural member that generates strain. The adhesive layer that was previously used can be omitted. Therefore, even if external vibrations or shocks are repeatedly applied, the multilayer thin film layer including the strain-sensitive resistance layer will not peel off from the strain-sensitive structural member.
Further, even when used at high temperatures of 80°C or higher, it can be used repeatedly, and a highly reliable strain sensor can be obtained.

Further, the strain-receiving structure member is made of a conductive material, and a plurality of semiconductor layers forming a multilayer thin film layer constitutes a diode between the electrode layer and the strain-receiving structure member. This multilayer thin film layer including a plurality of semiconductor layers is formed directly on the strain receiving structure member. Therefore, even if an insulating layer with extremely high electrical resistivity is not formed between the strain-sensitive structural member and the region that becomes the strain-sensitive resistor, a path passing only through the strain-sensitive resistive layer between the electrode layers can be created from the strain-sensitive structural member. Can be reliably insulated. That is, a diode is formed between the electrode layer and the strain receiving structural member,
By utilizing the rectifying effect of the diode, an insulating layer having high electrical resistance can be formed between the electrode layer and the strain receiving structure member. As a result, the outermost layer of the multilayer thin film layer serving as the strain-sensitive resistor exhibits a good strain-to-electrical resistance conversion effect. As a result, the reliability of strain detection by the strain-sensitive resistor is improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of the use of a conventional strain gauge. FIG. 2 is a schematic cross-sectional view showing one embodiment of the present invention. FIG. 3 is an equivalent circuit diagram of the embodiment shown in FIG. 2. Figure 4 shows
FIG. 3 is an equivalent circuit diagram showing a state in which the embodiment shown in FIG. 2 is connected to an external power source. FIG. 5 is a vertical sectional view showing a specific structure of a pressure sensor to which the embodiment shown in FIG. 2 is applied. FIG. 6 is an equivalent circuit diagram of still another embodiment of the present invention. In the figure, 14, 35, 51 are strain receiving structural members, 17 is a multilayer thin film layer, 17a, 61, 62, 6
3 and 64 are strain-sensitive resistive thin film layers that are the outermost layers of the multilayer thin film layer; 21a and 21b are electrodes; 22, 23, and 6
5, 66, 67, 68 are diodes.

Claims (1)

[Scope of Claims] 1. A strain-receiving structural member that generates strain in response to applied force; and a strain-receiving structural member formed directly on the strain-receiving structural member by vapor deposition,
and a multilayer thin film layer including a plurality of semiconductor layers, and a plurality of electrode layers formed on the outermost layer of the multilayer thin film layer, the strain receiving structural member is made of a conductive material, and the multilayer thin film layer is made of a conductive material. A strain sensor, wherein the outermost layer is a strain-sensitive resistance layer whose electrical resistance changes according to the strain, and the plurality of semiconductor layers constitute a diode between the electrode layer and the strain-sensitive structural member. 2. The strain sensor according to claim 1, wherein the multilayer thin film layer is a multilayer thin film layer of an n-i-p semiconductor. 3. The strain sensor according to claim 1, wherein the multilayer thin film layer is a multilayer thin film layer of a pin type semiconductor. 4. The strain sensor according to claim 1, wherein the multilayer thin film layer is a n-i type semiconductor layer, and forms a shot barrier diode between the electrode layer and the strain receiving structural member. . 5. The multilayer thin film layer is composed of a multilayer thin film layer of an n-i type semiconductor, and the i type semiconductor layer of the multilayer thin film layer is formed in close contact with the strain receiving structural member via a thin film insulating layer. The strain sensor according to the range 1 above.