JPH03248577A - Pressure sensor - Google Patents

Abstract

PURPOSE:To miniaturize a device, and to improve a gauge factor by forming a plurality of strain resistors onto a surface having strain characteristics in the same direction while forming these strain resistors by N-type resistance layers and P-type resistance layers. CONSTITUTION:An N-type silicon layer 14 constituting a strain resistor R2(R3) and a P-type silicon layer 15 constituting a strain resistor R1(R4) are formed on a surface 13 having strain characteristics in the same direction as the film section 12 of a diaphragm 11. These silicon layers 14, 15 are bridge-connected while an electrode 16 for supplying electric power is shaped in a pattern form, and a conductive wire for leading out an output is connected to the electrode 16 while a protective film 17 covering the silicon layers 14, 15 and the electrode 16 is formed. Consequently, one of the resistance of the N-type resistance layer 14 and the resistance of the P-type resistance layer 15, which are bridge- connected, is increased and the other is reduced to strain in the same direction as the pressure-receiving section of the diaphragm 11, thus obtaining a high gauge factor. Accordingly, a device can be miniaturized and the gauge factor improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a pressure sensor using a semiconductor diaphragm.

[Conventional technology]

A conventional pressure sensor of this type is disclosed in Japanese Patent Application Laid-Open No. 1-199476.
As disclosed in the above publication, a strain resistance pattern is formed by bridge connection on the surface of the membrane part that becomes the pressure receiving part of the diaphragm, and the deformation of the diaphragm in response to pressure is caused by a piezoresistance effect that changes the resistance of the strain resistance. It is designed to detect pressure by converting it into For example, as shown in FIG. 5, a polysilicon layer 3 serving as a strain resistance is formed in a pattern on the surface of the membrane portion 2 of the diaphragm l, and the polysilicon layer 3 is connected by bridges and bridges for power supply. The electrode 4 is formed in a pattern, a conductive wire (not shown) for output extraction is connected to the electrode 4, and a protective film 5 is formed to cover the polysilicon layer 3 and the electrode 4. , an example of its manufacturing method will be explained with reference to FIG.

First, as shown in FIG. 6(A), silicon nitride (SiN), silicon oxide (
In addition to forming an insulating film (not shown) such as SiOz), an amorphous silicon film 3a is formed by plasma CVD.
6(B), the surface of the amorphous silicon film 3a is crystallized by laser annealing to form a polysilicon film 3b, and then, as shown in FIG. 6(C).
As shown in FIG. 6(D), the polysilicon film 3b is patterned by etching to form a pattern of the polysilicon layer 3 that serves as a strain resistor, and then an aluminum film is formed by vacuum evaporation as shown in FIG. 6(D). 4a or an aluminum alloy film is vapor deposited, and the aluminum film 4a is patterned by etching as shown in FIG. 6(E) to form an electrode 4 consisting of an aluminum film pattern, and then as shown in FIG. 6(F).
As shown in FIG. 3, connection of conductive wires (not shown) and formation of a protective film 5 made of silicon nitride (SiN) or the like are performed. In this case, the plurality of polysilicon layers 3 are resistors R+, Rz, Rx, R4 shown in the bridge circuit of FIG.
These are bridge-connected using an electrode pattern.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, the resistance change characteristics of the polysilicon layer 3 forming each of the strain resistances R1 to R4 are the same and the resistance increases with elongation. A detection output is obtained by forming a polysilicon layer 3 in a portion of the film portion 2 which serves as a portion having a different strain direction. In other words, the polysilicon layer 3 constituting the resistors R, , R, is formed in the portion 2a that generates tensile strain when receiving pressure, and the resistors R2, R4 are formed in the portion 2b that generates shrinkage strain.
A polysilicon layer 3 is formed to obtain unbalance when receiving pressure.

However, forming a plurality of polysilicon layers 3 serving as strain resistance in film parts with different strain directions requires a large space in the sensor part of the pressure sensor, hinders miniaturization, and increases the amount of strain in different directions. Since it is difficult to do so, there is a problem that the gauge factor is also low.

Therefore, an object of the present invention is to provide a pressure sensor that can be downsized and have an improved gauge factor.

[Means to solve the problem]

The present invention provides a pressure sensor that detects pressure by forming a plurality of strain resistors on the surface of a pressure receiving part of a diaphragm by bridge connection and converting deformation of the diaphragm according to pressure into a resistance change of the strain resistors. The strain resistors are formed on a surface having strain characteristics in the same direction, and these strain resistors are formed by an n-type resistance layer and a p-type resistance layer.

[Effect]

The present invention deals with distortion in the same direction of the pressure receiving part of the diaphragm.
A high gauge factor can be obtained by increasing one of the resistances of the bridge-connected n-type resistance layer and the resistance of the P-type resistance layer and decreasing the other.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, the n-type 9937 layer 14 forming the strain resistance Rz (Rs) in FIG. 5 and the strain resistance R, (R , ) are formed, and these silicon layers 14 and 15 are bridge-connected, and an electrode 16 for power supply is formed in a pattern, and a conductive wire for output output is connected to this electrode 16. (not shown), and a protective film 17 is formed to cover the silicon layers 14 and 15 and the electrodes 16. In FIG. 2, two n-type 9937 layers 14 forming Rt and Rx and two P-type silicon layers 15 forming RI and Ra are formed on a surface 13 having strain characteristics in the same direction, and bridged by an electrode 16. A connected state is schematically shown. in this case,
The n-type 9937 layer 14 is made of amorphous silicon (a-Si
), polysilicon (P-St), microcrystalline silicon (μc-Si), etc., doped with phosphorus as an impurity, and has the characteristic that resistance decreases when tensile strain occurs. Furthermore, the P-type silicon layer 15 is made of amorphous silicon (a-5i), polysilicon (P-Si), microcrystalline silicon (μc-Si), etc. doped with poron as an impurity, and when tensile strain occurs. It has the property of increasing resistance.

FIG. 3 shows an example of a manufacturing method. First, amorphous silicon 1118 is formed on the surface of the diaphragm 11 by plasma CVD method as shown in FIG.
As shown in FIG. 3(B), a resist layer 19 is formed on the surface of the amorphous silicon film 18, leaving a portion where the n-type 9937 layer 14 will be formed, and then a resist layer 19 is formed on the surface of the amorphous silicon film 18, as shown in FIG. 3(C). An n-type 9937 layer 1 is formed by diffusing phosphorus ions into a portion of the amorphous silicon layer 18 that does not have a resist layer 19 using an ion implantation method using gas (PH3) as a raw material gas.
4, and then a resist layer 19 is formed as shown in FIG. 3(D).
A resist layer 20 is formed leaving a portion where the P-type silicon layer 15 will be formed, and then a resist layer 20 is formed as shown in FIG. 3(E).
A P-type silicon layer 15 is formed by diffusing boron ions into the amorphous silicon layer 18 in a portion not having the resist layer 20 by an ion implantation method using a poran gas such as diborane (B, H, ) as a raw material gas, as shown in FIG. Then, the resist layer 20 and the amorphous silicon layer 18 are removed if necessary, and the electrodes 16, protective film 17, etc. are formed by an appropriate method.

In this case, the amorphous silicon film 18 is doped with impurities, but a polysilicon film or a microcrystalline silicon film is formed and doped with impurities in the same process to make it n-type.

P-type silicon layers 14 and 15 may also be formed.

As shown in the schematic explanatory diagram of FIG. 3, strain resistances R, , R are provided on the surface 13 having strain characteristics in the same direction.

Since it forms the n-type 9937 layer 14 that constitutes R1 and the P-type silicon layer 15 that constitutes R1 and R4, when tensile strain occurs on the surface 13, the resistance of the n-type 9937 layer 14 increases, and conversely, Since the resistance of the P-type silicon layer 15 decreases,
A good unbalanced state of the bridge circuit can be obtained and a high gauge factor can be obtained.

In this way, in the above embodiment, the silicon layer 14 forming R2-R4 is formed on the surface 13 having strain characteristics in the same direction.
．． 15 can be formed, the sensor section has a small space, and the pressure sensor can be downsized. In addition, membrane part 1
2 in the same direction, the resistance of some of the strain resistors Rl-Ra that make up the Brifuji circuit increases, and conversely, the other resistances decrease, so the difference in these resistances increases, and along with this, The gauge factor increases and the accuracy of the pressure sensor improves.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, the Brifuji circuit can be applied to appropriate types,
In addition, in FIG. 5, R+ and Ra are n-type resistance layers, RLR3
It can be changed as appropriate, such as by forming it in a P-type resistance layer.The point is that if at least one resistor is n-type, the others are p-type, and conversely, if at least one resistor is p-type, the others are n-type.
Just make it into a mold.

〔Effect of the invention〕

The present invention provides a pressure sensor that detects pressure by forming a plurality of strain resistors on the surface of a pressure receiving part of a diaphragm by bridge connection and converting deformation of the diaphragm according to pressure into a resistance change of the strain resistors. The strain resistors are formed on a surface having strain characteristics in the same direction, and these strain resistors are formed by an n-type resistance layer and a p-type resistance layer, and it is possible to reduce the size and improve the gauge factor. Can provide pressure sensors.

[Brief explanation of drawings]

1 to 4 show one embodiment of the present invention, FIG. 1 is a schematic explanatory diagram showing a pressure sensor, FIG. 2 is a schematic explanatory diagram showing a bridge-connected resistance layer pattern, and FIG. A)～(
E) is a schematic diagram showing the manufacturing process, Figure 4 is a schematic diagram showing the pressure receiving state, Figure 5 is a schematic diagram showing the conventional pressure sensor, and Figures 6 (A) to (F) are the conventional pressure sensors. FIG. 7 is a general bridge circuit diagram, and FIG. 8 is a schematic diagram showing a conventional pressure receiving state. 11 - Diaphragm 13 - Surface 14 - N-type silicon layer (n-type resistance layer)

Claims (1)

[Claims] (1) A pressure sensor that detects pressure by forming a plurality of strain resistances on the surface of a pressure receiving part of a diaphragm by bridge connection and converting deformation of the diaphragm according to pressure into a resistance change of the strain resistance. A pressure sensor characterized in that strain resistors are formed on a surface having strain characteristics in the same direction, and these strain resistors are formed of an n-type resistance layer and a p-type resistance layer.