Experimental study on characteristic of ultrathin sapphire wafer polishing with Layer Stacked Clamping (LSC) method

Abstract

Ultrathin sapphire wafer is of great significance in the semiconductor field. In order to explore the effective clamping method of ultrathin sapphire wafer in double-side polishing, this paper studied the characteristic of Layer stacked clamping (LSC) method on polishing ultrathin sapphire wafer with double-side polishing machine. A self-made friction force test platform was built for learning the friction force between sapphire wafer and baseplate with different baseplate (stainless steel, cast iron, aluminum alloy) and different baseplate surface roughness (Ra 3.6 nm, 68.2 nm, 210.1 nm, 517.9 nm). Single factor polishing experiments were carried out on baseplate with different flatness (PV value 5.3 µm, 9.8 µm, 19.9 µm, 29.7 µm) and different thicknesses (0.082 mm, 0.104 mm, 0.119 mm). The double-side polishing experiments were carried out to compare the polishing performance on the ultrathin sapphire polishing between LSC method and traditional paraffin bonding method. The results show that the friction force of stainless steel and iron increase under the adsorption of droplets. Stainless steel performs higher friction force and is more suitable for making the baseplate. The inner fringe of limiter was cut off by the edge of the sapphire wafer and a slope was thereby formed. According to polishing results, LSC method has higher processing efficiency per unit time. The surface roughness, flatness and material removal rate are better than paraffin bonding. Finally, a smooth surface with surface roughness (Ra) 1.3 nm and flatness (PV) 0.988 µm was obtained with LSC method.