A study of post-etch wet clean on electrical and reliability performance of Cu/low k interconnections

Integration of Cu with low k dielectrics has gained wide acceptance for 130 nm and beyond technology nodes at back-end-of-line (BEOL) interconnection in order to reduce both the RC delay and parasitic capacitance. Wet clean is one of the critical steps to remove post plasma etch residues. In this paper, the impacts of wet clean process after etching of (a) via, (b) metal 2 trench and (c) Cu cap of dual damascene structure on electrical performance of 130 nm Cu/CVD low k SiOCH metallization were explored and discussed. Electrical yields and dielectric breakdown strength of interconnects from the use of batch spray and single wafer processing systems of wet clean were also compared. We observed that electrical yields of interconnects were considerably dependant on optimized processing conditions (temperature, time, and mega-sonic power) and appropriate wet clean chemistry. The use of fluoride-based mixture of wet clean chemical for all three post-etch clean is very effective in cleaning the via and trench line before Ta barrier/Cu seed deposition. As a result, we successfully integrated double level Cu/CVD low k BEOL interconnection with excellent electrical and reliability performance.