Mechanistic and Experimental Investigations on Ultraviolet-Electro-Magnetic Multifield-Coupling Colloid Jet Machining of Gallium Nitride.

In response to the demand for ultrasmooth surfaces of gallium nitride (wurtzite structure) in the microelectronics field, this paper proposes a method of UV(Ultraviolet)-E(Electro)-M(Magnetic) multifield coupling colloid jet machining to achieve efficient removal of microprotrusions on the surface of gallium nitride (GaN) workpieces. In this paper, material removal models for multifield-coupled nanoparticle colloid jet machining with microprotrusions and micropits are respectively established, and the distribution characteristics of the fluid dynamic pressure field, electric field, and magnetic field at the microprotrusions and micropits on the workpiece surface during the multifield-coupled nanoparticle colloid jet machining process are compared and analyzed. The experiments of photocatalytic degradation of methyl orange and adsorption experiments verify the enhancement effect of the applied electric field and magnetic field on the photocatalytic performance of the polishing liquid and the adsorption degree of nanoparticles on the workpiece surface. The optimal combination of process parameters is obtained through multifactor experiments. Using the optimized process parameters, a GaN workpiece with an original surface roughness (measurement range 10 × 10 μm) Sa of 0.949 nm is polished by UV field, UV-E field, and UV-E-M multifield-coupled nanoparticle colloid jet. The comparison results of the microscopic morphology and surface roughness of the workpiece surface after polishing show that the multifield-coupled nanoparticle colloid jet machining has a better removal effect on the microprotrusions on the workpiece surface and reduces the surface roughness of GaN to Sa 0.122 nm.