Mechanism studies of Cu RIE for VLSI interconnections

In this paper, an etch mechanism study of a chlorine based Cu RIE is presented. It has been generally accepted that the chlorination of Cu and the volatilization of (CuCl)/sub 3/ are essential steps during RIE of Cu in a chlorine based discharge. The exposure of Cl/sub 2/ to a Cu surface leads to a chlorinated surface layer whose thickness increases with exposure. Based on these results we have investigated the chlorination of Cu in a reactive plasma at elevated temperature. In order to minimize isotropic etching or chlorine residues in the remaining Cu film it is necessary to reduce the thickness of the chlorinated film. One way to do this is to lower the Cl/sub 2/ partial pressure. The influence of the Cl/sub 2/ partial pressure on the Cu chlorination is discussed. AES surface measurements at the etch bottom and the Cu sidewall after RIE interruption have been carried out showing only a very thin chlorinated surface layer.