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The Role of HO2− in SC-1 Cleaning Solutions

Published online by Cambridge University Press:  10 February 2011

Steven Verhaverbeke ,
Jennifer W. Parker  and
Chris F. McConnell
Steven Verhaverbeke
Affiliation:
CFM Technologies Inc., 1336 Enterprise Drive, West Chester, PA 19380
Jennifer W. Parker
Affiliation:
CFM Technologies Inc., 1336 Enterprise Drive, West Chester, PA 19380
Chris F. McConnell
Affiliation:
CFM Technologies Inc., 1336 Enterprise Drive, West Chester, PA 19380
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The RCA Standard Clean, developed by W. Kern and D. Puotinen in 1965 and disclosed in 1970 [1] is extremely effective at removing contamination from silicon surfaces and is the defacto industry standard.[2]. The RCA clean consists of two sequential steps: the Standard Clean 1 (SC-1) followed by the Standard Clean 2 (SC-2). The SC-1 solution, consisting of a mixture of ammonium-hydroxide, hydrogen-peroxide, and water, is the most efficient particle removing agent found to date. This mixture is also referred to as the Ammonium- Hydroxide/Hydrogen-Peroxide Mixture (APM). In the past, SC-1 solutions had the tendency to deposit metals on the surface of the wafers, and consequently treatment with the SC-2 mixture was necessary to remove metals. Ultra-clean chemicals minimize the need for SC-2 processing. SC-I solutions facilitate particle removal by etching the wafer underneath the particles; thereby loosening the particles, so that mechanical forces can readily remove the particles from the wafer surface. The ammonium hydroxide in the solution steadily etches silicon dioxide at the boundary between the oxide and the aqueous solution (i.e., the wafer surface). The hydrogen peroxide in SC-I serves to protect the surface from attack by OH" by re-growing a protective oxide directly on the silicon surface (i.e., at the silicon/oxide interface). If sufficient hydrogen peroxide is not present in the solution, the silicon will be aniostropically etched and surface roughening will quickly occur. On the other hand, hydrogen peroxide readily dissociates and forms water and oxygen. If the concentration of the resulting oxygen is too high, bubbles will appear in the solution. The gas liquid interfaces that result from the bubble formation act as a “getter” for particles that can re-deposit on the wafer surface if a bubble comes in contact with the wafer.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 477 , 1997 , 47
Copyright
Copyright © Materials Research Society 1997

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References

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