ANALYSIS OF SIDEWALL BUILDUP DURING TRILEVEL RESIST ETCHING OF METAL

Sidewall buildup formed during trilevel resist etching of a layered me tal was analyzed for individual etch steps using Auger electron and mi cro-Raman spectroscopy. Thick sidewall buildup was formed during the d ry SOG strip in a fluorine-containing plasma and found to consist of t he oxide forms of sputtered anti-reflective TiN, TiFx, and CFx polymer s. From the sidewall buildup observed after the metal etch, resist str ip, and wet cleaning, Ti, N, O, and Si AES peaks were identified and T i-O and N-O bonds were detected implying that this buildup is mainly c omposed of the oxide forms of TiN and sputtered BPSG during the metal overetch. We propose that the reduction of sidewall buildup can be ach ieved by maintaining the plasma self-DC bias as low as possible during the bottom resist etch, SOG strip, and metal overetch and employing a carbonless fluorine plasma during the SOG strip. (C) 1997 Elsevier Sc ience B.V.