Improvement in Wet Etch of TiW Fusible links in AlCu/TiW/PtSi Metallization for 0.8μm BICMOS

Abstract

AbstractIn our 0.8μm BICMOS process flow, TiW fusible links are defined by concentrated H2O2 wet etching. Our investigation to improve uniformity, reproducibility and reliability of TiW wet etching showed that in our etch system, the flow characteristics were the most critical. There is a tradeoff between TiW residues between metal lines and the amount of undercut of the TiW fuses: longer etch times to remove residues result in more undercut. With improved flow dynamics and optimum etch time, we achieved less residue and lower undercut. Results of the pre-etch treatment which reduces lot-to-lot induction time variation were encouraging. When the AlCu/TiW/PtSi metal stack resided on a P+/N junction, we observed an enhanced etching of the TiW due to a photovoltaic effect.