Clean Mode Al Etch Process Development for Defect Reduction

Clean mode chamber condition controlling provides a good method to improve Al etch defect performance. In the same time, it brings significant difference of physical performance such as CD, side wall, corrosion etc. In this study, in order to maintain clean chamber condition, Wafer-less Auto Clean(WAC) is introduced to clean out by-products deposition and optimized to achieve stable particle performance during full MTBC(mean time between clean). To compensate process shift because of chamber condition change, Al etch process and PR strip process are optimized. Cl2/BCl3 ratio, bias power and Cl2 gas flow in DARC step were found having significant impact on CD controlling. PR strip process adjusting has been proved to have great help to enlarge corrosion process window. One question that different Cl2/BCl3 ratio affect plasma sustaining when etching through TiN/Al interface was found during this study and need further efforts to find out the detail mechanism.