Challenges in Etching of OSG Low- K Materials for Dual-Damascene Metallization
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Challenges in Etching of OSG Low- K Materials for Dual-Damascene Metallization Vladimir N. Bliznetsov, Moitreyee Mukherjee-Roy, Leong Yew Wing, Ng Beng Teck 1 , Yew Wee Chuan Institute of Microelectronics, Singapore. 1 National University of Singapore. 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 89º 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. INTRODUCTION Usually during trench etch three basic requirements should be met simultaneously. These are profile control, selectivity to barrier layer and minimal post-etch residues. To achieve these in etching of OSG films is more difficult comparing to conventional SiO2 because of high hydrocarbon content in OSG films. Moreover, if trench stop-layer is not used, additional issues such as microtrenching, across-wafer non-uniformity, microloading, and RIE lag may appear. If selectivity of OSG etching to copper barrier layer on the via bottom is not sufficient (
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