Removal of Photoresist and BARC in Cu BEOL using an All-wet Process

Abstract

Wet removal of post-etch photoresist (PR) and bottom anti-reflective coating (BARC) was studied using "multi functional" cleaning solutions based on BASFs tool box. For blanket wafer, Fourier-transform infrared (FTIR) data showed that both PR and BARC layers were completely removed at a megasonic power of 10 W for 2 min. For patterned structure, the plasma used for opening of the BARC layer and metal hard mask resulted in the formation of fluorine- and titanium-containing species in the PR crust. Cross-sectional secondary electron microscopy (SEM) and X-ray photoemission spectroscopy (XPS) data indicated that complete removal of post-etch PR can be achieved under experimental conditions typical for single wafer processing. Subsequent patterning of porous low-k layer showed good low-k profile. Wet processes using solvent-based chemistry followed by a bake at 350 {degree sign}C for 1 min at low pressure was found to have no detrimental impact on k-value degradation.