Application of an abrasive-free Cu slurry for MEMS devices

For the fabrication of large conducting copper structures > 100 µm for RF-MEMS devices, a recently developed abrasive-free Cu slurry, intentionally designed for advanced 32/22 nm nodes, has been investigated. Due to a strong chemical nature, a pronounced down force dependence, a high removal rate, and very high selectivities to Ti, TiN and TEOS, excellent planarization efficiency together with very low dishing could be achieved. The observed results are compared to those obtained by using 2 conventional abrasive-based Cu slurries. In combination with an optimized barrier removal step, final dishing values < 50 nm across 300 µm wide structures are obtained.