JPH0352231A - Cleaning method using pure water - Google Patents

Abstract

PURPOSE:To prevent attachment of particles in air to a body to be cleaned which is lifted up from pure water by discharging the bubbles of carbon dioxide gas from the lower part of the body to be cleaned in the pure water in a container wherein the body to be cleaned is immersed. CONSTITUTION:Bubbles 25 of carbon dioxide gas 24 are discharged at a part lower than an immersed body to be cleaned 1 into pure water 6. The body to be cleaned (semiconductor substrate) 1 is immersed into the pure water 6. Therefore, the carbon dioxide gas is dissolved into the pure water for cleaning the substrate 1, and carbonic acid is formed. The carbonic acid (H2CO3) is decomposed into (+) ions of H and (-) ions of HCO3. Thus, the resistance value of the pure water 6 is decreased. Therefore, static electricity is hard to generate in the substrate 1 in the pure water 6. The negative static electricity of the substrate 1 is offset with the H ions, and the positive static electricity is offset with the HCO3 ions. Therefore, particles in the air are not attached to the substrate which is lifted from the pure water.

Description

[Detailed Description of the Invention] [Summary] In order to improve the method of cleaning various objects to be cleaned made of members charged with static electricity with pure water, fine particles in the air adhere to the objects to be cleaned after being lifted from the pure water. In order to prevent this, the deionized water in the container in which the object to be cleaned is immersed is characterized by emitting carbon dioxide bubbles from below the object to be cleaned.

[Industrial application field]

The present invention relates to a method for cleaning objects to be cleaned, which are statically charged members, with pure water, such as semiconductor substrates, glass masks, substrate holders, etc. used in the manufacture of semiconductor devices, and piezoelectric devices used in the manufacture of vibrators. This invention relates to an improvement in a method for cleaning body substrates, etc. with pure water.

In recent years, as patterns in semiconductor devices have become finer, the problem is how to reduce the amount of fine particles that adhere to semiconductor substrates, glass masks, etc., since this has a significant effect on the yield of products.

[Prior Art] FIG. 2 is an explanatory diagram of a conventional method of cleaning a semiconductor substrate with pure water.

In FIG. 2, l is a semiconductor substrate, 2 is a quartz basket that supports the substrate l, 3 is a cleaning container generally made of quartz, 4 is a stand that supports the basket 2 in the container 3, and 5 is a quartz basket that supports the substrate l. a vibrator that supplies pure water 6 for cleaning the substrate from the bottom;
7 is a pipe for emitting bubbles 9 of nitrogen gas 8 from the lower part of the container 3; 10 is a receiving container for the pure water 6 overflowing from the container 3; and 11 is a drain pipe communicating with the container 10.

In such a cleaning device 12, the pure water 6 emitted from the pipe 5 overflows from the container 3, and the pure water 6 in the container 3
The bubbles 9 of the nitrogen gas 8 emitted from the opening (nozzle) 13 of the pipe 7 become mixed with the bubbles 9 of the nitrogen gas 8 .

Therefore, when the substrate 1 is immersed in the pure water 6 in the container 3, the substrate 1 is cleaned by the pure water 6 flowing upward from the bottom and the bubbles 9 floating in the pure water 6.

However, static electricity is generated on the substrate 1 in the pure water 6 due to friction between the pure water 6 and the bubbles 9, and when the substrate 1 charged with such static electricity is pulled up from the pure water 6, the substrate 1 is exposed to air. fine particles are attached.

Therefore, the cleaning device l2, which extremely dislikes the adhesion of fine particles,
It is used in a draft type clean bench where air that has been purified through a Hepar filter etc. flows.

[Problem to be solved by the invention]

As explained above, the method of preventing fine particles in the air from adhering to the semiconductor substrate l in the conventional pure water cleaning method is a method of reducing the fine particles in the air, which eliminates or reduces the static electricity on the substrate l. It was not meant to be.

Therefore, even if a draft-type clean bench equipped with air purification means is used, the adhesion of fine particles passing through the filter and fine particles floating in the air when the semiconductor substrate l is taken out from the clean bench can be completely prevented. There was a problem that it could not be removed.

An object of the present invention, which was made in view of the above problems, is to remove the object to be cleaned in pure water to prevent the attachment of fine particles.

[Means to solve the problem]

According to the method of the present invention aimed at solving the above-mentioned problems, as shown in FIG. This is a pure water cleaning method characterized by emitting bubbles 25 of carbon dioxide gas 24 from below.

[Effect]

According to the above means, carbon dioxide gas is dissolved in the pure water used to clean the substrate, and carbon dioxide is produced. Such carbonic acid (H2CO,)
is decomposed into + ions of H and one ion of HCO3, which lowers the resistance value of pure water, making it difficult for static electricity to be generated on the substrate in pure water.
Since the static electricity is eliminated by I{Co and ions, fine particles in the air no longer adhere to the substrate that has been pulled out of the pure water.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pure water cleaning apparatus for semiconductor substrates according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of an embodiment in which a semiconductor substrate is cleaned with pure water according to the present invention.

In FIG. 1, in which the same reference numerals are used for parts common to those in FIG.
In place of the radiation pipe 7, a pipe 22 for radiating bubbles 25 of carbon dioxide (Co.) 24 is provided at the bottom of the container 3.

In the cleaning device 2l, 2 is a group ttri. 1 is a quartz basket that supports it; 3 is a cleaning container generally made of quartz;
4 is a stand on which the basket 2 is mounted; 5 is a pipe for supplying pure water 6 for substrate cleaning from the bottom of the container 3; 22 is a pipe for emitting bubbles 25 of carbon dioxide gas 24 from the bottom of the container 3; 10
is a saucer container for pure water 6 that overflowed from container 3,
11 is a drain pipe communicating with the container 10.

In this cleaning device 21, pure water 6 emitted from the pipe 5 overflows from the container 3, and bubbles 25 of carbon dioxide gas 24 emitted from the opening (nozzle) 23 of the pipe 22 are mixed with the pure water 6 in the container 3. Make it.

Then, a part of the bubbles 25 dissolves into the pure water 6 and as shown in the chemical formula below, Hz O + COz → H2C○3 When carbonic acid (H, Co.) is produced, H + ions and H
C.O. 1 by H, Co, which is decomposed into one ion of
The specific resistance of pure water 6, which was about MΩ·m, was 0. 1 MΩ
- Decreases to about m.

As a result, the substrate 1 that has been cleaned by the flow effect of the pure water 6 containing many bubbles 25 becomes less likely to be charged with static electricity because the specific resistance of the pure water 6 is smaller than that of conventional water, and the static electricity generated on the substrate 1 is Since it is erased by + ions of H or one ion of HCO, fine particles in the air will not adhere when the water is pulled up from the low resistivity pure water 6.

Note that in the above embodiments, a semiconductor substrate was explained as the object to be cleaned. However, the method of the present invention is not limited to cleaning semiconductor substrates, and can be applied to components that are charged with static electricity, such as glass masks and substrate holders used in the manufacture of semiconductor devices, and piezoelectric substrates used in the manufacture of vibrators. Moreover, it can be used for various objects to be cleaned that are extremely unfavorable to the attachment of fine particles in the air, and is equally effective as the above-mentioned embodiment.

〔Effect of the invention〕

As explained above, according to the method of the present invention, the specific resistance of pure water used for cleaning is reduced to about 1710, and the carbonic acid ions released by dissolving carbon dioxide gas remove static electricity from the object to be cleaned. Therefore, particles in the air are less likely to adhere to the cleaned object, which has the effect of improving the manufacturing yield of semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, and FIG. 2 is an explanatory diagram of a conventional method. In the figure, ■ is a semiconductor substrate (object to be cleaned), 3 is a cleaning container, 6 is pure water, 21 is a pure water cleaning device, 24 is carbon dioxide gas, 25 is carbon dioxide bubbles,

Claims (1)

[Claims] Bubbles (25) of carbon dioxide gas (24) are emitted from below the immersed object (1) into the pure water (6) in the container (3) in which the object (1) to be cleaned is immersed. A pure water cleaning method characterized by: