Copper Catalysis Effect Investigation for TiW Etch Process on Patterned Wafers

Abstract

The use of various H2O2 based chemistries for TiW etch was studied on single wafer and wet bench tools. The focus of the investigation was put on the different behaviors of these chemicals on blanket and patterned wafers. The results of the etch rate tests showed much higher values on the wafers where copper was exposed, leading to the hypothesis that the etch rate on TiW should be driven by the catalysis effect of the transition metal on the H2O2 decomposition reaction. Additional optical inspections, ToF SIMS, SEM and TEM analyses were carried out to confirm this hypothesis and find the best conditions in terms of morphology for RDL applications. Finally, the collected data were also used to evaluate the process cycle time and cost of ownership.