Abstract:
During the CMP of titanium nitride (TiN) blade electrodes for phase-change memory (PCM), silica-based slurries are employed to remove excess dielectric layers. However, the TiN surface is susceptible to oxidation, forming a high-resistance oxide layer that adversely affects device performance. This study addresses post-polishing surface oxidation through process optimization, without modifying the slurry formulation. Polishing experiments were conducted to investigate the influence of mechanical action on the oxide layer. The results confirm that TiN removal during CMP follows an oxidation-removal cyclic mechanism, wherein mechanical removal critically controls the oxide layer. Following optimization, the resistivity of the TiN thin film decreased from
2510.3 μΩ·cm to 238.0 μΩ·cm, representing a 90.5% reduction. The optimized process was further validated on patterned wafers. The surface oxide layer thickness on TiN patterned-wafer electrodes decreased from 2.17 nm to 1.09 nm, a 49.8% reduction. Under identical optimized conditions, the oxide layer thickness on polished TiN blade electrode patterned wafers was 1.09 nm, which is 17.4% lower than the 1.32 nm observed on TiN thin film wafers. Consequently, it is inferred that the resistivity reduction for the polished TiN blade electrode patterned wafers also exceeds 90.5%. This study provides a viable optimization strategy for the CMP of blade electrodes in phase-change memory, offering a reference for improving device yield.