Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Patent
1997-07-25
1999-09-21
Warden, Jill
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
134 1, 134 13, 134 26, B08B 600, B08B 300
Patent
active
059548851
DESCRIPTION:
BRIEF SUMMARY
TECHNOLOGICAL FIELD
The present invention relates to a cleaning method, and more specifically to a method of cleaning a semiconductor substrate.
BACKGROUND TECHNOLOGY
A process of cleaning a semiconductor substrate is one of the most important processes in a semiconductor device production process, and its importance has been increasingly higher as performance and a degree of integration in semiconductor device have also been becoming higher.
Conventionally, sulfuric acid, chloric acid, ammonia, hydrogen peroxide, hydrofruolic acid, or a mixture thereof have been used for removing impurities adhering to a surface of a semiconductor substrate. But it has been found as a result of a research conducted by the present inventors that the impurities can not completely be removed with these chemicals, and also that a surface of a semiconductor is corroded by these chemicals and minute irregularities are generated on the surface, and it has been confirmed that these phenomena give effects to device characteristics such as mobility of carrier and insulating performance of an oxide film formed on the surface. Accordingly, it has been desired to develop a cleaning method enabling complete removal of impurities without giving any damage to the semiconductor substrate for production of semiconductor devices with higher performance.
In addition, as the cleaning method based on the conventional technology required a long time and the cleaning steps are very complicated, and also as a vast quantity of chemicals or ultra-pure water is used, the cost is very large, and large scale facilities are required, so that price reduction of semiconductor devices has been prevented.
To solve the problems as described above, it is an object of the present invention to provide a cleaning method with extremely excellent cleaning effect which enables reduction in a quantity of chemicals and ultra-pure water used for cleaning and also which give no damage to a semiconductor substrate.
DISCLOSURE OF THE INVENTION
The cleaning method according to the present invention comprises a first step of removing organic materials, metal, particles adhering to a substrate with ultra-pure water containing ozone; a second step of removing metal or particles adhering to the substrate by irradiating megasonic to a chemical comprising ultra-pure water containing hydrofluoric acid in a cleaning bath; a third step of removing the chemical used in the second step, and a fourth step of cleaning the substrate by irradiating megasonic to the ultra-pure water in the cleaning bath.
Gasses result therein should preferably be removed from the ultra-pure water used in the second step and/or the fourth step.
All the first to fourth steps are performed under a room temperature. Further, the third step is characterized in that the chemical is removed by showering or spraying ultra-pure water.
The present invention is advantageously applied to a case where the ultra-pure water used in the second step contains hydrofluoric acid, hydrogen peroxide, or a surfactant.
It is preferable that the second and/or the fourth step are based on a system in which ultra-pure water in a cleaning bath withdrawn keeping a flow of the ultra-pure water therein at a constant speed and that megasonic is irradiated from a top of the cleaning bath. Especially, a frequency of the megasonic should preferably be in a range from 0.8 to 10 MHz.
It is desirable that the first to fourth steps described above are carried out in an inactive atmosphere with the purity of 99.9999 or more, and also it is desirable that concentration of ozone in the ultra-pure water containing ozone therein is in a range from 2 to 10 ppm.
With the present invention, impurities adhering to a semiconductor substrate such as organic materials, metal, or particles can be removed. Further when cleaning is performed according to the present invention, minute irregularities are not generated on the surface at all. The reason is presumably as described below.
At first, by using ultra-pure water with ozone added therein in the
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Kern, Handbook of Semiconductor Wafer Cleaning Technology, 1993, pp. 24, 84, 85, 122, 141, 144, 145, 393, 400-402.
Knuth Randall J.
Warden Jill
Wilkins Yolanda E.
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