SELF-CONTROLLED DIFFUSION OF AL IN CU THIN-FILM

A layer of copper with the thickness of 0.5 mu m was sputter deposited on well polished aluminum substrates. The samples were exposed to a l ow pressure weakly ionized RF hydrogen plasma at different conditions. A layer of copper aluminide was formed on the sample at the temperatu re of approximately 250 degrees C. The formation of the aluminide was confirmed with the AES depth profile. The time necessary for formation of the coating depended on the sample temperature. At the maximum tem perature of 250 degrees C it was three minutes, while at 320 degrees C it was 50 s. When the aluminum atoms reached the surface, the tempera ture of samples began to fall thus decreasing further diffusion of Al. This was explained in the terms of the change of the recombination co efficient for the reaction H+H --> H-2. As the temperature of the samp les fell as soon as the formation of the coating was accomplished, the possibility of self controlled formation of thin copper aluminide coa tings is suggested. (C) 1998 Elsevier Science Ltd. All rights reserved .