JPH09213638A - Method for manufacturing semiconductor thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing semiconductor film whose pressure at a high temperature and high-voltage can be measured and which exhibits a high gauge factor. SOLUTION: Though the gauge factor G becomes larger as the doping concentration becomes low, the conductivity σ tends to be low. When the doping concentration is 1% or more, the gauge factor G becomes small and there is no more merit as pressure-sensing resistive material. On the other hand, when the doping concentration is 0.01% or less, the conductivity σ becomes so low that the semiconductor thin film can hardly be used as a device. Therefore, phosphin flow rate: silane flow rate is in the range of 10<2> -10<4> . The semiconductor thin film needs to be crystallite and not amorphous to obtain a large gauge factor G. Silane flow rate: hydrogen flow rate is more than 1:80 to form crystallite silicon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor thin film used as a pressure sensitive resistance material such as a semiconductor pressure sensor.

[0002]

2. Description of the Related Art Conventionally, a semiconductor pressure sensor has been used for ion implantation of impurities such as boron (B) into the surface of a single crystal silicon substrate.
Along with thermal diffusion to form a piezoresistor, anisotropic etching is performed from the back surface of the substrate with an etchant such as potassium hydroxide (KOH) aqueous solution to form a concave portion in the central portion to form a support portion and a diaphragm. It was produced by doing.

However, in the semiconductor pressure sensor using the single crystal silicon substrate as described above, since the piezoresistor and the substrate are insulated and separated from each other by the pn junction, 150 ° C.
There are problems that the measurement cannot be performed at the above high temperature and that high pressure cannot be measured because silicon is used as the diaphragm.

In order to solve this problem, a semiconductor thin film is formed by decomposing an insulating film such as SiO ₂ on a diaphragm formed of silicon or metal, and the semiconductor thin film is processed to form a piezoresistor. Semiconductor pressure sensors of the type to be manufactured are being studied. As a semiconductor thin film formed on an insulating film in such a semiconductor pressure sensor, silane (Si
Amorphous silicon thin films and microcrystalline silicon thin films formed by plasma CVD using H ₄ ) or disilane (Si ₂ H ₆ ) as a raw material gas have been studied.

[0005]

However, the amorphous silicon thin film generally has a gauge factor of about 10 to 20, which is an order of magnitude smaller than that of single crystal silicon of about 100 to 200.

Therefore, when an amorphous silicon thin film is used as a pressure sensitive resistance material of a semiconductor pressure sensor, there is a problem that the sensor sensitivity becomes small.

Further, even in a microcrystalline silicon thin film which can be expected to have an improved gauge ratio by including a microcrystalline phase in the amorphous phase, the gauge ratio is about 20 to 30, which is a very small value as compared with single crystal silicon. Is.

The present invention has been made in view of the above points, and an object thereof is to manufacture a semiconductor thin film capable of measuring pressure at high temperature and high pressure and having a high gauge factor. To provide a method.

[0009]

According to the first aspect of the present invention,
Silane (SiH ₄ ) as a source gas, hydrogen (H ₂ ) as a dilution gas, and phosphine (P as a doping gas)
In the method for producing a semiconductor thin film by the plasma CVD method using H ₃ ), the flow rate of silane: the flow rate of hydrogen is 1:80 or more, the flow rate of phosphine: the flow rate of silane is 1:10 ² to 1:
It is characterized in that it is in the range of 10 ⁴ .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

= Embodiment 1 = An embodiment of the present invention will be described below. A silicon thin film was formed on a single crystal silicon substrate by the plasma CVD method under the following conditions. Silane (SiH ₄ ) flow rate: Hydrogen (H ₂ ) flow rate 1:80 Phosphine (PH ₃ ) flow rate: Silane (SiH ₄ ) flow rate 1: 1000 Chamber pressure 0.7 Torr Substrate temperature 250 ° C. Discharge power density 0.11 W / cm ² Next, in order to obtain the gauge factor of the silicon thin film formed under the above conditions, the silicon thin film was processed into a size of 1 mm x 0.5 mm using a photolithography process, and a chrome (Cr) electrode was formed on both ends of this. Is formed by a vapor deposition method to form a strain gauge. And 4.4 × 10 in this strain gauge
When the gauge factor G is calculated from the change in resistance value when a strain of ^-4 is applied, it becomes -51.

Second Embodiment A silicon thin film was formed on a single crystal silicon substrate by a plasma CVD method under the following conditions where the doping concentration was lower than that of the first embodiment. Silane (SiH ₄ ) flow rate: Hydrogen (H ₂ ) flow rate 1:80 Phosphine (PH ₃ ) flow rate: Silane (SiH ₄ ) flow rate 1: 10000 Chamber pressure 0.7 Torr Substrate temperature 250 ° C. Discharge power density 0.11 W / cm ² Then, similarly to the case of the first embodiment, the gauge ratio G of the silicon thin film formed under the above conditions is −67.

Here, FIG. 1 shows the first embodiment and the second embodiment.
And doping concentration (phosphine flow rate: silane flow rate)
FIG. 3 is a characteristic diagram showing the relationship between the doping concentration, the gauge factor G, and the conductivity σ of a silicon thin film formed with 1% as 1%. From FIG. 1, as the doping concentration decreases, the gauge factor G increases, but the conductivity σ tends to decrease.

Here, when the doping concentration is 1% or more, the gauge factor G becomes small, and the merit as a pressure-sensitive resistance material is lost, and when the doping concentration is 0.01% or less, the conductivity σ becomes too small and the device. Is difficult to use.

Therefore, the flow rate of phosphine (PH ₃ ): silane (SiH ₄ ) is in the range of 1:10 ² to 1:10 ⁴ .

Further, in order to obtain a high gauge factor G, the semiconductor thin film needs to be in a microcrystalline state rather than an amorphous state. For the formation of microcrystalline silicon, the flow rate of silane (SiH ₄ ): hydrogen ( The flow rate of H ₂ ) must be 1:80 or more.

Further, in order to form microcrystalline silicon, a discharge power density of a certain value or more is required, but if the discharge power density is too high, on the contrary, the effect of etching or the like may hinder microcrystallization. is there.

Therefore, the discharge power density is 0.1 W / cm.
It is desirable that it be ² or more. From Embodiments 1 and 2 and FIG. 1 described above, a semiconductor thin film is formed by a plasma CVD method in the range of silane flow rate: hydrogen flow rate of 1:80 or more and phosphine flow rate: silane flow rate of 1:10 ² to 1:10 ^4. By doing so, when used as a pressure-sensitive resistance material for a semiconductor pressure sensor or the like, it is possible to obtain a semiconductor thin film capable of increasing the sensitivity of the sensor.

[0018]

According to the invention described in claim 1, a semiconductor thin film formed by a plasma CVD method using silane (SiH ₄ ) as a source gas, hydrogen (H ₂ ) as a diluent gas, and phosphine (PH ₃ ) as a doping gas. In the manufacturing method,
Silane flow rate: Hydrogen flow rate is 1:80 or more, and phosphine flow rate: Silane flow rate is in the range of 1:10 ² to 1:10 ⁴ by forming a semiconductor thin film by the plasma CVD method. When used as a material, it is possible to obtain a semiconductor thin film capable of achieving high sensitivity of a sensor, capable of measuring pressure at high temperature and high pressure, and a method for manufacturing a semiconductor thin film having a high gauge factor. Could be provided.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between a doping concentration and a gauge factor and a conductivity of a silicon thin film formed by a plasma CVD method according to an embodiment of the present invention.

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[Procedure amendment]

[Submission date] March 29, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

[0004] To solve this problem, on the diaphragm is formed of silicon, metal or the like, the semiconductor thin film was formed by through the insulating film such as SiO _2, a piezo resistor to processing the semiconductor thin film Semiconductor pressure sensors of the type to be manufactured are being studied. As a semiconductor thin film formed on an insulating film in such a semiconductor pressure sensor, silane (Si
Amorphous silicon thin films and microcrystalline silicon thin films formed by plasma CVD using H ₄ ) or disilane (Si ₂ H ₆ ) as a raw material gas have been studied.

Claims (1)

[Claims] 1. A method for producing a semiconductor thin film by a plasma CVD method using silane (SiH ₄ ) as a source gas, hydrogen (H ₂ ) as a diluent gas, and phosphine (PH ₃ ) as a doping gas. Flow rate is 1:80 or more, phosphine flow rate: Silane flow rate is 1:
The method for producing a semiconductor thin film is in the range of 10 ² to 1:10 ⁴ .