Loop Stiffness of Grinding Machine Developed for 450 mm Silicon Wafers

Increasing the wafer diameter from φ300 mm to φ450 mm is required to enhance semiconductor devices productivity. A high-stiffness rotary grinding machine equipped with water hydrostatic bearings was developed for a φ450 mm silicon wafer. The grinding machine has an upper structure consisting of a wheel spindle system and a lower structure consisting of a rotary worktable system. The spindle shaft creates both rotary and axial feeding motion. The upper and lower structures are clamped together rigidly by three kinematic couplings. A higher loop stiffness is required for the grinding machine because grinding the larger wafer requires a higher grinding force. This paper investigates the loop stiffness of the developed wafer grinding machine.