Study on the process parameters of UV photocatalytic chemical mechanical polishing for single-crystal AlN

Single-crystal aluminum nitride (AlN) has a wide band gap and high thermal conductivity, and is a promising 3th generation semiconductor material. However, single-crystal AlN is characterised by its hardness, good wear resistance and chemical inertness, which collectively present significant challenges in achieving both high efficiency and high-quality polishing. In this paper, the focus is on the processing of single-crystal AlN using chemical mechanical polishing based on UV photocatalysis. The study explores the influence of reaction parameters, including H₂O₂ concentration, TiO₂ concentration, and light intensity, on the concentration of OH. Furthermore, the influence of chemical reaction parameters (H₂O₂ concentration, TiO₂ concentration, light intensity, lighting methods) and mechanical process parameters (abrasive grain size, abrasive concentration, polishing pressure, polishing pad speed) on the processing of single-crystal AlN and the polishing mechanism were studied through single-factor polishing experiments. The findings indicate a robust correlation between the material removal rate (MRR) of single-crystal AlN and the concentration of OH, with both exhibiting an initial increase followed by a subsequent decrease in response to increasing H₂O₂ concentration, TiO₂ concentration, and light intensity. The material removal rate of single-crystal AlN is increased by increasing the abrasive grain size, abrasive concentration, polishing pressure and polishing pad speed. As the H₂O₂ concentration, TiO₂ concentration, light intensity, abrasive grain size, abrasive concentration, polishing pressure and polishing pad speed increased, the surface roughness of single-crystal AlN first decreased and then increased. In the UV photocatalytic reaction, AlN reacts with OH or H₂O to form a corrosion layer (Al₂O₃, AlOOH and Al(OH)₃), which is then removed by the mechanical action of the abrasive, exposing a new single-crystal AlN surface on which corrosion and mechanical removal continue to occur. This paper provides more evidence for the application of UV photocatalytic technology in the field of single-crystal AlN polishing.