Characteristics and mechanism of etch process sensitivity to chamber surface condition

Process variation with chamber surface condition in high density plasma rea ctors can seriously affect the process performance and productivity of devi ce manufacturing. In this work, the impact of chamber surface coating on po lycrystalline-silicon (polysilicon) gate etching with Cl-2- and HBr-based p lasma has been studied. The dependence of process sensitivity to surface co ating on various processing conditions has been characterized and the mecha nism of process shift has been analyzed. Based on the experimental results, the root cause of process sensitivity has been attributed to the change of surface recombination rate of free radicals on different chamber surfaces which leads to a variation in reactive neutral density. Under a certain dis charge condition, the Cl and Br densities in a clean chamber with anodized aluminum and alumina surfaces are >60% lower than those in a seasoned chamb er with silicon oxide deposition, resulting in lower polysilicon and oxide etch rate in the former case. In general, the process sensitivity to chambe r surface condition depends on process regime and is higher for those proce sses where etching is more chemical in nature, such as processes at higher pressure and with Cl-2-based chemistry. Processes with higher oxygen concen tration and higher source power are also more sensitive due to the accelera ting surface oxidation of polysilicon surface in a clean chamber. Approache s to reduce the effect of process sensitivity have been discussed. (C) 2001 American Vacuum Society.