Methods of Reducing Metal Damager Defect in Back End of Line for Semiconductor in 28Nm Technology

Abstract

As technology keeps shrinking to 28nm and below, airborne molecular contamination has become a critical element of cleanroom management, which would influence the performance of device, but also decrease the yield and productivity in the semiconductor manufacturing process. As we know that in the Fab, wafers are always stored in the Front-Opening-Unified-Pod (FOUP) while waiting for process. The outgassing or contamination distribution within the FOUP has a strong negative impact on wafers. So additional precautions need to be taken to prevent external contamination during FOUP door opening or closing. This study investigated that metal damager defect appeared after the Cu electroplating (ECP) process in M1 feature structure. It was susceptible that Cu seed exposing to atmosphere was easy to be damaged by ambient gas. Here we illustrated two methods to reduce the metal damager defect. Firstly, Annealing process was applied before Buried Seed deposition, which could help remove the outgassing on the surface of wafer. Secondly, using the diffuser FOUP during the process of Via Etch to ECP process, and making sure the copper was in a super pure gas environment. The experiments consistently demonstrated that using diffuser FOUP and simultaneously introducing Annealing before Buried Seed could significantly improve metal damager defect.