REFLOW OF COPPER IN AN OXYGEN AMBIENT

In order to investigate the reflow characteristics of copper, copper w as deposited on hole and trench patterns by metal organic chemical vap or deposition and it was annealed in nitrogen and oxygen ambients with the annealing temperatures ranging from 350 to 550 degrees C. Upon an nealing in an oxygen ambient at higher than 450 degrees C, copper was reflowed into the trench patterns whose linewidth and aspect ratio wer e 0.2 mu m and 4:1, respectively. Copper oxide was found with a thickn ess of less than a fifth of the total film thickness. The resistivity of the copper film increased when reflow occurred. It is thought that the reflow of copper in an oxygen ambient takes place because of enhan ced surface diffusion. (C) 1998 American Vacuum Society.