Chemical Mechanical Polishing of Selective Epitaxial Grown Germanium on Silicon

Germanium (Ge) waveguides selectively grown on Silicon (Si) in oxide trenches are chemical mechanical polished (CMP) using a mixture of commercial CMP slurries with H2O2 and deionized (DI) water dilution at a pH value of around 3. The abrasive concentration reduction due to dilution effectively lowers the Ge removal rate. Pattern density effects are also studied and show a lower removal rate with higher pattern density. Two commercial slurries are used for the Ge CMP. The W2000 based slurry is more suitable for blanket Ge films or Ge waveguides with high pattern density, delivering a moderate removal rate (200 nm/min to 600 nm/min) and minimal dishing with good time control. The G1000 based slurry works better for Ge waveguides with low pattern density. We achieved only 10 nm dishing during 60s over-polishing due to the lower Ge dissolution rate compared to the W2000 based slurries. (C) 2013 The Electrochemical Society. All rights reserved.