Effect of Radical Scavenger and UV Irradiation on Removal of Photoresist and BARC using Water/Ozone in Cu/Low-k Interconnect

Abstract

This study focused on the removal of post-etch photoresist (PR) and bottom anti-reflection coating (BARC) layers using O3 dissolved in H2O at 60 {degree sign}C. A complete removal of the PR layer was achieved with a short rinse in propylene carbonate (PC). However, the k-value of the film as determined using Hg-probe showed an increase of about 0.3 due to the wet process at 60 {degree sign}C for 5 min, and the BARC layer remained on the substrate. Using acetic acid (HAc) 0.5 M, a radical scavenger, as additive resulted in a small reduction in k-value of about 0.2 with respect to the sample processed in the same solution without HAc. Within the range of HAc concentration of 0.01-0.5 M, there was no clear trend and no significant effect in terms of PR removal as a function of HAc concentration, indicating a direct O3 attack of PR. The issue of BARC removal was addressed using UV treatment at 222 nm wavelength.