Letter to the Editor
Staff -- Semiconductor International, 10/1/2002
It was interesting to read the article on wet clean technology by the Applied Materials team ("Single-Wafer, Short Cycle Time Wet Clean Technology," July 2002). The authors properly note that the industry-standard RCA clean traces back to work done in 1965. What the authors didn't say, or maybe didn't realize, is that the use of megasonics was also an RCA creation.
The term "megasonic cleaning" was created by the inventors of the technology, Alfred Mayer and Stanley Shwartzman, both of whom worked at RCA's facility in Somerville, N.J. Their original patent (#3,893,869) was issued in 1975, but was filed a year earlier, and the actual work started at least a year before that. Their work was first published in 1979 in a paper titled "Megasonic Cleaning: A New Cleaning and Drying System for Use in Semiconductor Processing," J. Electronic Materials, Vol. 8, p. 855.
I've always found it amusing that most proposed replacements or improvements for RCA clean involve the use of megasonics. It's ironic when people look to improve the 37-year-old RCA clean with the more modern 29-year-old RCA clean using megasonics.
Another element of RCA clean that has always interested me is the way it is referred to in papers published by non-RCA authors. When the original cleaning system was moved to RCA factories, the traveler — the recipe sheet that accompanied each lot — identified the cleaning steps as Standard Clean 1 and Standard Clean 2, abbreviated SC-1 and SC-2. To the best of my knowledge, no RCA author used that nomenclature in literature. However, the published literature, even in technical journals, always refers specifically to SC-1 and SC-2.
My own supposition is that the conduit for the descriptors involves equipment suppliers who were supplied the names by RCA purchasing groups. I have never looked through the published literature to find the first public use of the terms.
Norman Goldsmith
Senior Director, Program Office
Sarnoff Corp.
