ACROSS-WAFER NONUNIFORMITY OF LONG THROW SPUTTER-DEPOSITION

Physical sputter deposition has been used at longer-than-normal cathod e-to-sample distances for semi-directional deposition within high aspe ct ratio features. ''Long throw'' sputter deposition can be advantageo us over other means of directional sputtering, such as collimated sput ter deposition, because of the absence of collimators and related prob lems. However, due to the finite target size and sample geometry, an a symmetry is observed at the wafer edge with a thicker deposit on the i nward-facing walls of trench and via structures compared with the outw ard-facing walls. We have used numerical simulation as well as metal s putter deposition experiments to characterize this asymmetry, which is typically 2-3:1 at the wafer edge. We also discuss how ionized sputte r deposition would alter the deposition profile in the edge region. (C ) 1997 American Vacuum Society. [S0734-211X(97)00405-8].