Brushing – scrubbing – and general cleaning – Machines – Wiping
Reexamination Certificate
1999-07-27
2001-10-30
Till, Terrence R. (Department: 1744)
Brushing, scrubbing, and general cleaning
Machines
Wiping
C015S077000
Reexamination Certificate
active
06308361
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cleaning apparatus, and more particularly to a cleaning apparatus suitable for cleaning substrates that require a high degree of cleanliness, such as semiconductor wafers, glass substrates, or liquid crystal displays.
2. Description of the Prior Art
As semiconductor devices have become more highly integrated in recently years, circuit interconnections on semiconductor substrates become finer and the distance between those circuit interconnections have become smaller. When semiconductor substrates are processed, small particles such as particles of semiconductor material, dust particles, or crystalline protrusive particles often tend to be attached to the semiconductor substrates being processed. If a particle greater than the distance between interconnections exists on a semiconductor substrate, then the particle will short-circuit interconnections on the semiconductor substrate. Therefore, any undesirable particles on a semiconductor substrate have to be sufficiently smaller than the distance between interconnections on the semiconductor substrate. Such problem and requirement hold true for the processing of other substrates, including a glass substrate to be used as a mask, a liquid crystal panel, and so on. To meet the above requirement, there have been practiced various cleaning procedures for removing fine particles or submicron particles from semiconductor substrates.
For example, as cleaning processes for cleaning semiconductor substrates which have been polished to a high degree of cleanliness, one practice has been to use a brush or a sponge to scrub a surface of a semiconductor substrate. This process is called a scrubbing cleaning process. Another practice has been a cavitation jet cleaning process in which high-pressure water (high speed jet stream) is projected onto the substrate to generate bubbles by cavitation. This process requires that low-pressure water should be supplied to the outer circumference of the high-pressure water to generate bubbles by cavitation.
Although the scrubbing cleaning process is effective in removing contaminants attached to the surface of the substrate, it is not always effective in removing fine particles deposited in fine grooves of the substrate surface. Further, as the amount of fine particles attached to the cleaning member increases, the particles are often reattached to the current substrate or the subsequent substrates in subsequent cleaning operations.
The cavitation jet cleaning process, on the other hand, is effective in removing fine particles deposited in the fine grooves formed in the substrate surface. However, the cavitation jet cleaning process requires that cleaning liquid should be supplied in two layers including an inner high-pressure layer and an outer low-pressure layer surrounding the inner high-pressure layer, resulting in a complicated structure. Thus, this process requires a large amount of cleaning liquid. In addition, the contaminants firmly attached to the substrate surface are difficult to be removed therefrom.
The above problems hold true for other cleaning processes. While most cleaning processes can satisfactorily clean either the substrate surface or the fine grooves in the substrate, none of them can satisfactorily clean both of the substrate surface and the fine grooves. For this reason, cleaning of semiconductor substrates has conventionally been performed in multiple steps or processes.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a cleaning apparatus which can simultaneously clean both of a surface of a substrate and fine grooves in the substrate surface to a high degree of cleanliness and can prevent particles removed from the substrate from being reattached to the substrate.
According to one aspect of the present invention, there is provided a cleaning apparatus for cleaning a substrate. The apparatus comprises a holding device for holding the substrate, and a cleaning unit capable of slidably contacting the surface of the substrate. The cleaning unit comprises a nozzle for ejecting high-pressure cleaning liquid onto the substrate. A cleaning member surrounds the nozzle and contacts the surface of the substrate.
With the above structure, the lower end surface of the cleaning member contacts the surface of the substrate and is capable of sliding on the surface of the substrate, while supplying the cleaning liquid from the nozzle to the surface of the substrate. Therefore, the cleaning apparatus simultaneously performs a scrubbing cleaning and a high-pressure liquid cleaning of the substrate to thus effectively remove fine particles attached to the surface of the substrate and deposited in grooves formed in the surface of the substrate. The cleaning member forms a cover around the high-pressure cleaning liquid to prevent the cleaning liquid from absorbing static electricity or gas in the atmosphere. The cleaning member is a self-cleaning type in which the cleaning liquid supplied from the interior of the cleaning member prevents particles or other contaminants from building up on the cleaning member, thus reducing the chance of resoiling the current substrate or subsequent substrates to be cleaned.
The cleaning member is preferably fixed to the forward end of the swing arm that swings across the substrate while the holding device is rotated, and hence the amount of relative movement between the substrate and the cleaning member is large. Ultrapure water is preferably used as a cleaning liquid, and the cleaning member is made of material having a flexible property and a water absorbing property.
In a preferred aspect of the present invention, the cleaning liquid is ejected from the nozzle to the substrate at a pressure ranging from 5 to 10 MPa. With this arrangement, the cleaning member absorbs and holds the cleaning liquid therein, and an inner high-speed stream and an outer low-speed stream surrounding the inner high-speed are created. The great speed difference at the boundary face of these two streams generates cavitation bubbles that improve the cleaning ability of the cleaning liquid to remove particles.
According to another aspect of the present invention, there is provided a cleaning apparatus for cleaning a substrate, comprising a nozzle for ejecting high-pressure cleaning liquid onto the substrate and a hollow member surrounding the nozzle. The hollow member and the substrate define a space for storing the cleaning liquid ejected from the nozzle, and the high-pressure cleaning liquid ejected from the nozzle passes through the cleaning liquid stored in the space and impinges upon the surface of the substrate.
With the above structure, high-pressure cleaning liquid is ejected from the nozzle to the substrate, and thus the space defined by the hollow member and the substrate is filled with the cleaning liquid. The high-pressure cleaning liquid ejected from the nozzle passes through the cleaning liquid having static pressure and stored in the space, and hence a large speed difference exists at the boundary face where the high-pressure cleaning liquid ejected from the nozzle and the cleaning liquid having static pressure contact with each other. As a result, cavitation bubbles are generated.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.
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Ito Kenya
Matsuda Naoki
Shirakashi Mitsuhiko
Ebara Corporation
Till Terrence R.
Wenderoth , Lind & Ponack, L.L.P.
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