Chemical mechanical polishing on GaN using a developed resin-metal plate through the aluminum contact corrosion

To address the issue of non-environmentally friendly polishing fluids in the chemical mechanical polishing (CMP) of single-crystal GaN, a CMP method based on Al metal contact corrosion is proposed. Results from static contact corrosion experiments indicates that a Ga-O corrosion layer formed on the surface of single-crystal GaN in areas are in close contact with Al metal in a Na 2 SO 4 solution. A resin-Al and resin-Cu plates were prepared for the polishing experiments, the polishing effect of resin-Al plate is better than that of resin-Cu plate. Using a resin-Al plate in the Na 2 SO 4 solution, a material removal rate (MRR) of 150–175 nm/h and a surface roughness Ra of 1.3–1.5 nm(measurement area:0.45 × 0.60 mm) were obtained. Upon adding silica sol abrasive to the Na 2 SO 4 solution, the MRR reached 225–240 nm/h and Ra increased to 1.8–2.3 nm. This indicates that while the addition of abrasives enhances mechanical removal, it decreases the contact between the GaN workpiece and the Al metal, thereby weakening the chemical action. The material removal mechanism of single-crystal GaN based on Al metal contact corrosion involves Al metal acting as the anode and losing electrons. Dissolved oxygen (O 2 ) in the solution capturing these electrons to form reactive oxygen species (ROS). These ROS react with H + to generate H 2 O 2 , whose highly unstable O O bonds break down to form hydroxyl radical (•OH). These •OH corrode single-crystal GaN, forming a Ga 2 O 3 corrosion layer, which is then removed mechanically.