蓝宝石CMP工艺中粗糙度的控制技术

Sapphire is the main substrate for the third generation semiconductor materials-GaN. The surface quality directly affects device performance. In this paper, chemical mechanical polishing (CMP) of sapphire substrate is studied, several factors which influence the CMP quality are analyzed, and the mechanism of CMP model is discussed. Small size (20~30nm) and low dispersion silica sol is used as abrasive, which can avoid scratches caused by abrasive granules with uneven diameter. The complex surfactant of the slurry can reduce the surface tension and accelerate the mass transfer of the reactant and reaction product effectively, which can accelerate the reaction and lead to better concave-convex selectivity and low roughness. We also find that the mass transfer is related with the temperature, the higher the temperature, the faster the transmission speed. So the removal rate is higher. By controlling the polishing temperature, the roughness can reach 0.2nm and the perfect sapphire surface is achieved.