JPH0516653B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a semiconductor thin film, which is a silicon thin film.

[Conventional technology]

In general, the field of use of integrated circuits (hereinafter referred to as IC) is not limited to electronic devices, but also extends to a wide range of non-electronic devices, and as the field of use of integrated circuits expands, the development of IC technology is also rapid. Recently, ICs have become more dense, faster, and smaller, and for example, bipolar ICs and C-MOS ICs are being actively developed.

However, these bipolar or C-
When manufacturing MOS type ICs, epitaxial substrates are used to obtain ICs with good characteristics. In this case, an important issue is how to minimize autodoping and solid-phase diffusion of impurities, and as a countermeasure, epitaxial growth in a low-temperature process of semiconductor thin films such as silicon has been proposed. For example, there is a method described on page 79 of the October 1985 issue of Nikkei Microdevices, a magazine published by Nikkei McGraw-Hill, which describes the method of processing semiconductor substrates placed in a reduced pressure processing furnace. The surface of a single-crystal silicon substrate is cleaned by argon plasma sputtering as a pretreatment, and then a silicon thin film is vapor-phase epitaxially grown on the cleaned substrate surface at a relatively low temperature by thermal decomposition of monosilane. .

[Problem that the invention seeks to solve]

However, in this case, when placing the substrate in the processing furnace, the inside of the processing furnace is exposed to the atmosphere, and even if the inside of the processing furnace is evacuated and depressurized using a pressure reducing means, the oxygen inside the processing furnace cannot be completely removed. Oxygen molecules remain attached to the walls of the processing furnace and the substrate surface, and this residual oxygen is incorporated into the silicon thin film that grows on the substrate surface, inducing crystal defects in the silicon thin film and causing monolayer formation. The defect density is approximately twice that of a crystalline silicon substrate, causing an increase in leakage current of the pn junction of the device to be formed, and the resistivity of the silicon thin film formed is only about 30Ω cm, which is a high resistivity problem. There is a problem that a silicon thin film cannot be obtained.

Therefore, the technical object of the present invention is to significantly reduce the amount of oxygen taken into the growing silicon thin film and to form a high resistivity silicon thin film with few crystal defects at a low temperature.

[Means for solving problems]

This invention has been made with the above-mentioned points in mind. A semiconductor substrate is disposed in a reduced pressure processing furnace that is evacuated and depressurized by a pressure reduction means, and a silicon thin film is vapor phase epitaxially grown on the substrate. In the method for forming a semiconductor thin film, the method includes a step of removing oxygen in the furnace by a reaction between silane gas introduced into the furnace and residual oxygen, and a step of depositing on the surface of the substrate by the reaction of the silane gas and oxygen. The method includes the steps of: cleaning the substrate surface by removing deposits by argon plasma sputtering; and growing a silicon thin film on the cleaned substrate surface by vapor phase epitaxial growth by thermal decomposition of monosilane. This is a method for forming a semiconductor thin film.

[Effect]

Therefore, in the present invention, when growing a silicon thin film on the surface of a semiconductor substrate by vapor phase epitaxial growth, silane gas that easily combines with oxygen is introduced into a reduced pressure processing furnace to remove residual oxygen in the processing furnace. After the deposits deposited on the substrate surface due to the reaction between silane gas and oxygen are removed by argon plasma sputtering and the substrate surface is cleaned, a silicon thin film is formed on the substrate surface by thermal decomposition of monosilane.

At this time, the reaction between the silane gas and the residual oxygen removes most of the residual oxygen that had adhered to the inner walls of the processing furnace, the substrate surface, etc., and the amount of oxygen incorporated into the growing silicon thin film is greatly reduced. A silicon thin film with specific resistance is formed, and a silicon thin film with good film quality is obtained.

〔Example〕

Next, the present invention will be described in detail with reference to drawings showing one embodiment thereof.

The drawing shows a forming apparatus, in which 1 is a quartz tube as a reduced-pressure processing furnace, 2 is a pressure reducing means connected to the right end of the quartz tube 1 to exhaust and reduce the pressure inside the quartz tube 1, and 3 is the left side of the quartz tube 1. A lid body with a sealed opening, 4 a mounting table installed approximately at the center of the quartz tube 1, 5 a single crystal silicon substrate placed on the mounting table 4, and 6 an approximately central portion of the quartz tube 1. an infrared lamp disposed outside and heating the mounting table 4 and the substrate 5 to a predetermined temperature;
Reference numeral 7 denotes a gas introduction tube that extends through the lid body 3 and has its right end inserted into the quartz tube 1; 8 is wound around the outside of the left end of the quartz tube 1, and a high-frequency current from a high-frequency power source 9 is passed through the gas introduction tube; A high frequency coil that converts the argon gas introduced into the quartz tube 1 through the introduction tube 7 into plasma, 10 a DC power supply that applies a negative bias voltage to the substrate 5 via the mounting table 4, and 11 a thermocouple. It is inserted through the lid body 3 and into the quartz tube 1,
The temperatures of the mounting table 4 and the substrate 5 are detected.

When forming a silicon thin film on the surface of the substrate 5 using the above-mentioned apparatus, the inside of the quartz tube 1 is evacuated and depressurized to 1×10 ^-6 Torr by the pressure reducing means 2, and the substrate 5 is placed on the mounting table 4 by the lamp 6 at a pressure of 700 Torr. After heating to ~900°C, -
Apply a bias voltage of 300V and
Ar gas was introduced into the quartz tube 1 at a flow rate of cc/min,
The pressure inside the quartz tube 1 is stabilized at 0.1 Torr.

Furthermore, a high frequency power of 13.56 MHz and 50 W is applied to the coil 8 from the power source 9 to turn the Ar gas in the quartz tube 1 into plasma, and after cleaning the surface of the substrate 5 for 5 minutes by Ar plasma sputtering, the DC power source The bias application by 10 and the power supply to the coil 8 by the power supply 9 are stopped, and monosilane gas [SiH ₄ ] is introduced into the quartz tube 1 from the introduction tube 7 instead of Ar gas, and the gettering of residual oxygen by SiH ₄ , that is, SiH The residual oxygen adhering to the inner wall of the quartz tube 1 and the substrate 5 is removed by the reaction between ₄ and the residual oxygen.

Next, deposits deposited on the surface of the substrate 5 due to the reaction between SiH ₄ and oxygen are removed by Ar plasma sputtering similar to the Ar plasma sputtering described above, and the surface of the substrate 5 is cleaned.
Thereafter, SiH ₄ is again introduced from the introduction pipe 7 in place of the Ar gas, and by thermal decomposition of the SiH ₄ , a silicon [Si] thin film with a predetermined thickness is grown by vapor phase epitaxial growth on the surface of the cleaned substrate 5.

At this time, the oxygen concentration, defect density, and specific resistance of the Si thin film formed on the surface of the substrate 5 were measured and found to be 5×10 ¹⁸ cm ^-3 , 6×10 ⁴ cm ^-3 , and 100 Ω・cm, respectively. The oxygen concentration, defect density, and specific resistance of the Si thin film formed by the conventional method were 4.
×10 ¹⁹ cm ^-3 , 1 × 10 ⁵ cm ^-3 , 30Ω・cm, whereas the oxygen concentration decreased by almost an order of magnitude, and the defect density of crystal defects induced by oxygen in the film was also approximately halved. As a result, a high resistivity Si thin film with few crystal defects can be obtained.

In addition, in the above embodiment, the quartz tube ₁ was
However, it is of course possible to getter the residual oxygen using a higher-order silane gas [SinH _2o+2 ; n≧2] such as disilane gas [Si ₂ H ₆ ]. .

〔Effect of the invention〕

As described above, according to the method for forming a semiconductor thin film of the present invention, the residual oxygen adhering to the inner wall of the quartz tube 1, the surface of the substrate 5, etc. is removed by the reaction between the silane gas and the residual oxygen, so that the semiconductor thin film grows. Oxygen taken into the Si thin film can be significantly reduced.
High resistivity Si thin film with few crystal defects at 700-900℃
It can be formed at low temperatures such as
It is possible to obtain a Si thin film and manufacture ICs with excellent characteristics, making it extremely advantageous as an IC manufacturing technology.

[Brief explanation of the drawing]

The drawing shows 1 of the method for forming a semiconductor thin film of the present invention.
FIG. 3 is a partially cutaway front view of the embodiment. 1...quartz tube, 2...pressure reduction means, 5...substrate.

Claims (1)

[Claims] 1. In a method for forming a semiconductor thin film, in which a semiconductor substrate is disposed in a reduced pressure processing furnace that is evacuated and depressurized by a pressure reduction means, and a silicon thin film is formed on the substrate by vapor phase epitaxial growth, a step of removing oxygen in the furnace by a reaction between the silane gas and residual oxygen; and a step of removing deposits deposited on the substrate surface due to the reaction of the silane gas and oxygen by argon plasma sputtering to remove the substrate surface. 1. A method for forming a semiconductor thin film, comprising the steps of: cleaning the surface of the substrate; and vapor-phase epitaxial growth of a silicon thin film on the surface of the cleaned substrate by thermal decomposition of monosilane.