JPH05343380A - Method for cleaning semiconductor substrate - Google Patents

Abstract

PURPOSE:To prevent impurities in pure water used for a final process from attaching to a semiconductor substrate surface by performing a final cleaning process with pure water using pure water of a specific nature. CONSTITUTION:Pure water, HF and HCl are supplied from a pure water supply line 4, an HF supply line 5 and an HCl supply line 6 respectively into a mixing tank 2 to adjust cleaning pure water where HF and HCl contents are in a range of 1 to 100ppm, respectively. Then in a cleaning tank 1, after a semiconductor substrate W is subjected to at least a final process of a series of cleaning processes using chemical, the cleaning pure water is supplied from the mixing tank 2 to a bottom of the cleaning tank 1 to make the cleaning pure water overflow from the cleaning tank 1. Thus impurities in pure water used for the final process can be prevented from attaching to the semiconductor 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.

[0002]

2. Description of the Related Art In manufacturing a semiconductor device, it is necessary to clean a semiconductor substrate between steps. And
In cleaning semiconductor substrates, cleaning treatments using various chemicals are carried out. Usually, as the final step, pure water (including ultrapure water) is used to remove the chemicals attached to the substrates. It is being cleaned.

By the way, it is known that when the surface of a semiconductor substrate is exposed, a natural oxide film having a thickness of several angstroms is formed on the surface of the substrate in pure water.
It is known that this natural oxide film causes the electrical characteristics of the thin film to be deteriorated when a thin film having a thickness of 100 angstroms or less is formed on the surface of the substrate in the subsequent manufacturing process of the semiconductor device.

Therefore, conventionally, there has been considered a method of suppressing the growth of the natural oxide film by containing HF of several ppm to several tens of ppm in pure water.

[0005]

However, when HF is contained in pure water and the surface of the semiconductor substrate is exposed, fine particles and impurity elements in the pure water adhere to the surface of the substrate. However, even if the HF content in pure water is as small as several ppm to several tens of ppm, this problem occurs when the cleaning time is long and contaminates the substrate.

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

[0007]

According to the method of cleaning a semiconductor substrate of the present invention, the final cleaning step with pure water in the cleaning process of a series of semiconductor substrates using chemicals is performed with HF.
It is characterized in that it is performed using pure water containing 1 to 100 ppm and HCl 1 to 100 ppm.

In the above, HF contained in pure water is
It has the property of etching the natural oxide film formed on the surface of the substrate in pure water, but its content is 1 p
If it is less than pm, such an etching action cannot be obtained, and if it exceeds 100 ppm, it remains on the substrate surface after cleaning, which adversely affects the semiconductor device.
It should be selected within the range of -100 ppm.

HCl in pure water has a property of reacting with impurity element ions in pure water to form a salt, but if the content thereof is less than 1 ppm, the above effect cannot be obtained and 100
When it exceeds ppm, it remains on the surface of the substrate after cleaning and adversely affects the semiconductor device, so the content is 1 to 100 pp.
It should be selected within the range of m.

The cleaning of the semiconductor substrate with the pure water containing the above-mentioned amounts of HF and HCl is carried out by, for example, immersing the semiconductor substrate in the pure water placed in a cleaning tank, or by cleaning the semiconductor substrate with the pure water. It is done by spraying water.
The cleaning time by immersion or jetting is preferably about 5 to 10 minutes. In addition, such drying after washing may be performed by vapor drying of isopropyl alcohol,
It is performed by spin drying.

[0011]

[Operation] When pure water contains an impurity element, HC
It is possible to prevent the adhesion of the impurity element to the surface of the semiconductor substrate due to the presence of HF in pure water because a salt is formed by 1 and the impurity element ion. Moreover, the natural oxide film generated in pure water by HF can be removed by etching.

[0012]

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

FIG. 1 shows one specific example of an apparatus used for carrying out the final cleaning treatment with pure water in the cleaning treatment of a series of semiconductor substrates using chemicals, that is, 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). The mixing tank (2) has pure water supply line (4), HF supply line (5) and HCl supply line.
(6) are connected respectively.

The semiconductor substrate cleaning method using this cleaning apparatus is as follows. That is, in the mixing tank (2),
Pure water supply line (4), HF supply line (5) and HCl
Pure water, HF and HCl are supplied from the supply line (6), and the HF content and the HCl content are 1 to 1 respectively.
Prepare pure water for cleaning in the range of 100 ppm. Then, in the cleaning tank (1), the semiconductor substrate (W) is subjected to at least the final processing of a series of cleaning processing using chemicals, and then the connection line (3) is connected from the mixing tank (2). The cleaning pure water is supplied to the bottom of the cleaning tank (1) through the cleaning tank (1), and the cleaning pure water is overflowed from the cleaning tank (1) to replace the cleaning chemical liquid containing the chemicals. Immersion wash in running water. Then the semiconductor substrate
(W) is taken out from the purified 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.

On the silicon substrate (W), NH ₄ OH: H ₂ O
₂ : H ₂ O = 1: 1: 5 cleaning treatment using a mixed cleaning solution, pure water cleaning treatment, HCl: H ₂ O ₂ : H ₂ O = 1:
The cleaning treatment using the 1: 5 mixed cleaning liquid, the cleaning treatment using pure water, and the cleaning treatment using hydrofluoric acid having a concentration of 1% were performed for 10 minutes each. The cleaning treatment using hydrofluoric acid having a concentration of 1% was performed by the dipping method in the cleaning tank (1).

Then, in the mixing tank (2), a pure water supply line
(4), HF supply line (5) and HCl supply line (6)
Pure water, HF, and HCl were respectively supplied from the above to prepare cleaning pure water in which the HF content and the HCl content were each 10 ppm. Then the connection line from the mixing tank (2)
The cleaning pure water is supplied to the bottom of the cleaning tank (1) through (3), and the cleaning pure water is overflowed from the cleaning tank (1) to replace the cleaning chemical liquid containing hydrofluoric acid. The silicon substrate (W) was immersed and washed in running water for 10 minutes. Then, the silicon substrate (W) was taken out from the washed 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, no impurities were attached to the surface and no natural oxide film was formed.

[0019]

As described above, according to the method of manufacturing a semiconductor substrate of the present invention, impurities in pure water used in the final step in the cleaning process of a series of semiconductor substrates using a chemical agent are semiconductor substrates. Contamination of the semiconductor substrate can be prevented by preventing adhesion to the surface. Moreover, the natural oxide film generated on the surface of the semiconductor substrate in pure water can be 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 final cleaning step with pure water in a series of cleaning processing of a semiconductor substrate using a chemical agent,
A method of cleaning a semiconductor substrate, which is performed using pure water containing ˜100 ppm and HCl 1-100 ppm.