Effect of Fe-complex catalysts on passivation layer and hydroxyl radical generation during tungsten chemical mechanical planarization

This study investigates the effect of Fe-complex catalysts in improving tungsten chemical mechanical planarization (CMP) by enhancing material removal rate (MRR) and surface quality. EDTA-Fe and citrate-Fe (CTA-Fe) were evaluated against ferric nitrate (Fe(NO₃) ₃) as reference. The catalysts’ ability to generate hydroxyl radicals via the Fenton reaction and form a tungsten passivation layer (WO₃) was evaluated. Results showed CTA-Fe achieved the best CMP performance with an MRR of 766.5 Å/min and a surface roughness (R_a) of 2.51 nm, attributed to continuous hydroxyl radical generation and efficient WO₃ layer formation. EDTA-Fe exhibited superior performance in static etch rate (SER) due to rapid initial passivation layer formation but showed lower CMP efficiency with an MRR of 304.4 Å/min and a R_a of 5.49 nm. In addition, Fe-complex catalysts were found to leave less residual iron contamination after CMP compared to Fe(NO₃)₃. This study elucidates the critical role of hydroxyl radical generation in improving tungsten CMP performance and demonstrates the potential of Fe-complex catalysts for advanced semiconductor manufacturing process.