JPH0289313A - Cleaning nethod for silicon substrate surface - Google Patents

Abstract

PURPOSE:To suppress diffusion of impurity and pollution by forming atomic hydrogen through bringing hydrogen gas in contact with a filament and by removing a silicon oxide film coated on the substrate surface using the atomic hydrogen. CONSTITUTION:An Si substrate 2 is heated to 800 deg.C by a substrate heater 4, and a current is supplied to a tungsten filament 5 from a power supply 6, and the temperature of the filament is set at 2000 deg.C. Then, H2 is introduced into a vacuum vessel 1 through an H2 introduction tube at a flow rate of about 0.1cc/min. In case where the filament temperature is at 2000 deg.C, about 0.1% of molecular hydrogen is thermally dissociated into atomic hydrogen. Therefore, in this case, hydrogen atoms are formed at 5.4X10<15>/sec. If the pressure in the vacuum vessel 1 is kept at the order of 10<-5>Torr, the mean free path of the residual hydrogen is about 5m, so that the formed atomic hydrogens can reach the surface of the Si substrate 2 without even one collision. Thus, SiO2 is removed from the surface of the Si substrate 2 and the surface is cleaned.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for cleaning the surface of a silicon (Si) substrate as a pretreatment when epitaxially growing Si on the substrate.

The purpose is to lower the substrate temperature during substrate cleaning and to suppress the diffusion of impurities and contamination into the substrate.

A silicon substrate and a heated filament are placed apart in a vacuum container, hydrogen gas is brought into contact with the filament to generate atomic hydrogen, and the silicon oxide film deposited on the substrate surface is removed by the atomic hydrogen. Configure to remove.

[Industrial application field]

The present invention relates to a method for cleaning a substrate surface as a pretreatment when epitaxially growing Si on a Si substrate.

[Conventional technology]

The conventional method for cleaning a Si substrate before epitaxial growth is to put a thin Si oxide film formed when the substrate is chemically cleaned into a growth chamber as a protective film, and raise the substrate temperature to about 1000°C in a hydrogen gas atmosphere. The Si oxide film is removed.

The reaction in this case is shown by the following formula.

let→2 II, +1) SiO□
+2H-5iO↑+H! 0↑, (2) In such a substrate surface cleaning method, the substrate temperature is as high as 1000° C., so it is necessary to lower the temperature. The reason for this is to suppress impurity diffusion into the substrate and reduce contamination from the device.

What prevents the substrate temperature from lowering with this cleaning method is (
1) This is the reaction of formula. That is, this is because the above temperature of 1000° C. is required to generate atomic hydrogen near the substrate surface.

[Problem to be solved by the invention]

As mentioned above, it is important to reduce the substrate temperature without reducing the effectiveness of cleaning the substrate.

An object of the present invention is to reduce the substrate temperature during substrate cleaning to suppress diffusion of impurities and contamination to the substrate.

[Means to solve the problem]

To solve the above problem, a silicon substrate and a heated filament are placed apart in a vacuum container, hydrogen gas is brought into contact with the filament to generate atomic hydrogen, and the atomic hydrogen is deposited on the surface of the substrate. This is achieved by a method for cleaning the surface of a silicon substrate, which is characterized by removing the silicon oxide film that is present on the surface of the silicon substrate.

[Effect]

The present invention brings hydrogen gas H, into contact with a high-temperature filament, thermally decomposes it, and generates atomic hydrogen H.
The generated ■ is transported to the substrate surface to reduce the Si oxide film formed on the substrate surface.

The reaction at that time is according to the above formula (2). That is, SiOx
+2H-SiO↑+Ih01. (2) According to the present invention, it is not necessary to raise the substrate temperature to a high temperature in order to generate atomic hydrogen as in the conventional method, and the substrate temperature is the temperature at which SiO in equation (2) separates from the substrate surface. It is enough.

A temperature of 800° C. is sufficient, and the temperature is lower than that of the conventional method.

〔Example〕

The figure is a schematic diagram of an apparatus for explaining an embodiment of the present invention.

In the figure, 1 is a vacuum container, 2 is a Si substrate, 3 is a substrate holder, 4 is a heater for heating the substrate, 5 is a tungsten filament for H2 decomposition, 6 is a power source for heating the filament, 7 is H, an introduction tube, and 8 is a filament. The cover 9 is an exhaust port.

Substrate 2 and ■2 Tungsten filament J for disassembly The distance of 5 is about 30 cra.

First, a Si substrate 2 on which a 5in2 film with a thickness of about 10 layers has been formed by chemical cleaning (for example, etching with nitric acid, hydrogen peroxide, etc.) is held on a substrate holder 3 in a vacuum container 1.

Next, from the exhaust port 9, the pressure inside the vacuum container 1 is increased to 1×1O-
Evacuate to 9 Torr or less.

Next, the substrate heating heater 4 heats the Si substrate 2 by 80°C.
Heat to 0°C.

Next, a current is applied to the tungsten filament 5 from the power source 6, and the temperature of the filament is set to 2000°C.

Next, 2 is introduced into the vacuum vessel 1 through the +OX introduction pipe 7 at a flow rate of about 0.1 cc/min.

When the temperature of the filament is 2000° C., one molecule of hydrogen H3 thermally dissociates into about 0.1% atomic hydrogen)1. Therefore, in this case, 11 of ec will be generated into 15.4×10” pieces.

With hydrogen introduced, the pressure inside the vacuum vessel l is increased to 10-'
If maintained at Torr level, the mean free path of residual hydrogen is approximately 5
IIl, the generated H does not even have a single collision (S
The surface of the i-substrate 2 can be reached.

Then, the reaction of formula (2) occurs on the St substrate 2.

The SiO2 is removed and a clean surface is obtained.

〔Effect of the invention〕

As explained above, according to the present invention, atomic hydrogen is generated not at the substrate but at a filament position distant from the substrate, so there is no need to heat the substrate itself to a high temperature. Therefore, the substrate temperature can be lowered, impurity diffusion into the substrate is suppressed, and contamination from the device is reduced.

Compared to the conventional example, the temperature can be lowered by approximately 200℃.

As a result, the impurity diffusion constant becomes approximately two orders of magnitude smaller.

It becomes possible to form shallow junctions in the epitaxial layer grown on the substrate, making it easier to speed up and integrate devices.

[Brief explanation of the drawing]

The figure is a schematic diagram of an apparatus for explaining an embodiment of the present invention. In fig. 1 is a vacuum container, 2 is an St substrate. 3 is a substrate holder, and 4 is a heater for heating the substrate. 5 is a tungsten filament for H8 decomposition. 6 is a power supply for heating the filament. 7 is the Ht inlet pipe, 8 is the filament cover 9 is the exhaust port 4, and the infrared fork diagram.

Claims (1)

[Claims] A silicon substrate and a heated filament are placed apart in a vacuum container, hydrogen gas is brought into contact with the filament to generate atomic hydrogen, and the silicon oxide film deposited on the substrate surface is removed by the atomic hydrogen. 1. A method of cleaning a silicon substrate surface, the method comprising: removing the surface of a silicon substrate;