UV-light assist chemical mechanical polishing of GaN with mesh polisher made of chemical durable plastics

摘要

We developed Ultra Violet (UV) light assist polishing system for GaN. A newly developed mesh polisher is set up on silica glass platter. The UV light is irradiated to polishing surface of a GaN substrate directly through a silica platter and the mesh polisher. The UV light which wave length is 365 nm has nearly equal the GaN band gap energy. This UV irradiation assists chemical mechanical polishing by optical chemical reaction with electron excitation. The mesh polisher has 0.2-mm fibre bundles and 0.2 mm gaps. Through this gap, the UV light reach directory to polishing surface very near polishing point. Strong alkali slurry was used for investigating UV assist polishing. Potassium permanganate and potassium peroxodisulfate are also used for oxidizing agent. Ga surface of GaN is polished with silica slurry (70-nm diameter in average). The polishing rate with the mesh polisher made of Vectran was almost same as the rate with SUBA 800 which is commonly used as polisher. The rate in the case of UV irradiation and strong alkali (pH = 14.5) is higher 28 times than that of no UV irradiation and no alkaline agents. The rate of UV irradiation and potassium peroxodisulfate is also 20 times higher than that of no irradiation and agents. It is concluded that UV irradiation, strong alkaline and potassium peroxodisulfate oxidants improve polishing efficiency extremely. It is also revealed that the mesh polisher developed in this study was effective for these polishing.