Challenges in Etching of OSG Low- K Materials for Dual-Damascene Metallization

Abstract

Issues associated with trench etching in low-k OSG (organosilicate glass) films for dual damascene applications and in particular for “via-first” integration scheme were the focus of this study. As a result of designed experiment in dipole ring magnet (DRM) etcher with C4F8/N2/Ar gas mixture the trench process was established with sidewall profile 89° and flat bottom. Selectivity obtained was enough to pursue etch processes using planarizing BARC (bottom antireflective coating) for additional via bottom protection. BARC fill in vias and BARC opening time were tuned to reduce generation of polymers during etch. Effective combination of dry /wet clean recipes was developed for removal of post-RIE (reactive ion etching) residues without significant changes in OSG k-value. Optimized processes were successfully used for creating dual damascene structure complying with integration requirements for 0.13 μm design rules.