Effect of alkaline agent on polishing rate of nitrogen-doped Ge2Sb2Te5 film in chemical mechanical polishing

Abstract

For chemical mechanical polishing (CMP), the effect of an alkaline agent, tetramethyl ammonium hydroxide (TMAH), on the polishing rate of nitrogen-doped Ge2Sb2Te5 (NGST) film was investigated. The inclusion of TMAH in a slurry with colloidal silica abrasives produced a smaller surface roughness of the NGST film, as compared to other alkaline agents: NaOH, NH4OH, and KOH. The polishing rate of the NGST film increased with increasing the TMAH concentration up to 0.12 wt % and then decreased as the concentration was increased further. This polishing rate trend correlated with the inverse of the contact angle of TMAH on the NGST film surface after CMP. Thus, the polishing rate of NGST film is associated with the hydrophilicity of the NGST surface during CMP.