JPH05343379A - Method for cleaning semiconductor substrate - Google Patents

Abstract

PURPOSE:To prevent contamination of a semiconductor substrate caused by impurities in a natural oxide film by cleaning the substrate using cleaning fluid comprising sulfuric acid, hydrogen peroxide solution and hydrochloric acid which has been raised in temperature. CONSTITUTION:Sulfuric acid, hydrogen peroxide solution and hydrochloric acid are supplied from a sulfuric acid supply line 6, a hydrogen peroxide supply line 7 and a hydrochloric acid supply line 8 respectively into a mixing tank 2 to adjust cleaning fluid. Then the cleaning fluid is fed into a cleaning tank 1 and heated by a heater. Then by soaking a semiconductor substrate W for 5 to 10 minutes in the cleaning fluid in the cleaning tank 1, the semiconductor substrate W is subjected to cleaning treatment for removing organic substances on the surface of the substrate W. Thus impurities during cleaning can be prevented from being taken into a natural oxide film formed on the substrate surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a semiconductor substrate for the purpose of removing organic substances such as photoresist in the process of manufacturing a semiconductor device such as a semiconductor integrated circuit.

[0002]

2. Description of the Related Art Conventionally, as a method of cleaning a semiconductor substrate for the purpose of removing such organic substances, a method of using a cleaning solution containing a mixture of sulfuric acid and hydrogen peroxide solution heated to 90 to 150 ° C. It has been known.

[0003]

However, it has become clear that the conventional method has the following problems. That is, in the cleaning solution, a natural oxide film having a thickness of about 10 angstroms is formed on the surface of the semiconductor substrate. When the cleaning solution contains an impurity element, the impurity element causes the natural oxide film to grow. There is a possibility that the semiconductor substrate will be taken in and that the semiconductor substrate will be contaminated.

An object of the present invention is to provide a method of cleaning a semiconductor substrate which solves the above problems.

[0005]

A method of cleaning a semiconductor substrate according to the present invention comprises cleaning a semiconductor substrate using a cleaning liquid which is composed of a mixture of sulfuric acid, hydrogen peroxide solution and hydrochloric acid and is heated and heated. It is a feature.

The mixing ratio of sulfuric acid, hydrogen peroxide solution and hydrochloric acid in the above cleaning solution is 1 volume of sulfuric acid,
Hydrogen peroxide water 0.1-0.25, hydrochloric acid 0.01-0.1
It is preferable that The reason is that the organic substances can be most effectively removed at such a mixing ratio. It is preferable to use sulfuric acid, hydrogen peroxide solution and hydrochloric acid having a concentration of 98%, 30% and 35%, respectively.

The temperature of the cleaning solution used is 90 to 15
It is preferably in the range of 0 ° C. The reason is that if the temperature of the cleaning liquid is lower than 90 ° C., a sufficient cleaning effect cannot be obtained, and if it exceeds 150 ° C., the surface of the semiconductor substrate tends to be roughened.

The cleaning of the semiconductor substrate using the above-mentioned cleaning liquid is performed, for example, by immersing the semiconductor substrate in the cleaning liquid contained in a cleaning tank or by spraying the cleaning liquid on the semiconductor substrate. The cleaning time by immersion or jetting is preferably about 5 to 10 minutes.

After the cleaning with the cleaning liquid, pure water (including ultrapure water) is used to perform a pure water rinse. The pure water rinsing is performed, for example, by immersing the semiconductor substrate in pure water placed in a cleaning tank or by spraying the pure water on the semiconductor substrate. The pure water rinsing time by the immersion or jetting is preferably about 5 to 10 minutes. Drying after such a rinse with pure water is performed by vapor drying of isopropyl alcohol or spin drying, for example.

[0010]

[Function] When the cleaning liquid contains an impurity element, a salt is formed by hydrochloric acid and the impurity element ion, and the impurity element is taken into the natural oxide film due to the presence of sulfuric acid and hydrogen peroxide solution. Is prevented.

[0011]

EXAMPLES Next, examples of the present invention will be described.

FIG. 1 shows one embodiment of the apparatus used to carry out the method of the present invention. In FIG. 1, the cleaning apparatus comprises a cleaning tank (1) and a mixing tank (2) connected to the bottom of the cleaning tank (1) via a connection line (3). A pure water supply line (4) and a drain line (5) are connected to the bottom of the cleaning tank (1). Further, the cleaning tank (1) is provided with a heating device (not shown) for heating the cleaning liquid therein. A sulfuric acid supply line (6), a hydrogen peroxide solution supply line (7) and a hydrochloric acid supply line (8) are connected to the mixing tank (2), respectively.

The semiconductor substrate cleaning method using this cleaning apparatus is as follows. That is, in the mixing tank (2),
Sulfuric acid, hydrogen peroxide solution and hydrochloric acid are supplied from the sulfuric acid supply line (6), the hydrogen peroxide solution supply line (7) and the hydrochloric acid supply line (8), respectively, and the mixing ratio of these is based on 1 volume of sulfuric acid. A cleaning solution is prepared in the range of 0.1 to 0.25 hydrogen peroxide solution and 0.01 to 0.1 hydrochloric acid. Then, this cleaning liquid is fed into the cleaning tank (1) through the connection line (3) and heated to 90 to 150 ° C. by a heating device. Next, in the cleaning solution in the cleaning tank (1), the semiconductor substrate
By dipping (W) for 5-10 minutes, the semiconductor substrate
The (W) is subjected to a cleaning treatment for removing organic substances on its surface. Then, after draining the cleaning liquid in the cleaning tank (1) from the drain line (5), pure water is supplied from the pure water supply line (4) to the bottom of the cleaning tank (1) to clean this pure water. The cleaning liquid is replaced by overflowing from the tank (1), thereby rinsing the semiconductor substrate (W) in running water. Finally,
The semiconductor substrate (W) is taken out from pure water and dried. Thus, the semiconductor substrate (W) is cleaned.

Next, a more specific embodiment of the present invention will be described.

This concrete example is carried out by using the apparatus shown in FIG.

In the mixing tank (2), sulfuric acid, hydrogen peroxide solution and hydrochloric acid are mixed from the sulfuric acid supply line (6), the hydrogen peroxide solution supply line (7) and the hydrochloric acid supply line (8) at a mixing ratio of these. A cleaning solution was prepared by supplying the cleaning solution at a volume ratio of 1: 0.25: 0.025. Then, this cleaning liquid was fed into the cleaning tank (1) through the connection line (3). Next, heat the cleaning liquid in the cleaning tank (1) to 100 ° C with a heating device,
The silicon substrate (W) was immersed in a heated cleaning liquid for 10 minutes to perform a cleaning treatment for removing organic substances on the surface of the silicon substrate (W).

Then, after the cleaning liquid in the cleaning tank (1) is drained from the drain line (5), the cleaning tank is drained from the pure water supply line (4).
Pure water was supplied to the bottom of (1), and the pure water was allowed to overflow from the cleaning tank (1) to replace it with the above cleaning solution, whereby the silicon substrate (W) was rinsed in running water for 10 minutes. Then, the silicon substrate (W) was taken out from pure water and dried with a vapor of isopropyl alcohol. Thus, the silicon substrate (W) was washed.
When the surface of this silicon substrate (W) was inspected, a natural oxide film with a thickness of 20 Å was formed on the surface, but no impurities were contained in it.

[0018]

As described above, according to the method of manufacturing a semiconductor substrate of the present invention, impurities in the cleaning liquid are prevented from being taken into the natural oxide film formed on the surface of the substrate during the cleaning process. It Therefore, contamination of the substrate due to impurities in the natural oxide film is prevented. Moreover, organic substances on the surface of the semiconductor substrate can be reliably removed.

[Brief description of drawings]

FIG. 1 is a diagram showing a specific example of an apparatus used for carrying out a method for cleaning a semiconductor substrate according to the present invention.

[Explanation of symbols]

 W semiconductor substrate

Claims (1)

[Claims] 1. A method of cleaning a semiconductor substrate, which comprises cleaning a semiconductor substrate using a cleaning liquid which is composed of a mixture of sulfuric acid, hydrogen peroxide solution and hydrochloric acid and heated and heated.