Development of rotary table grinding machine for large diameter Si wafers (2nd report: Performance investigation of wheel spindle designed to govern infeed motion)

Si wafer diameter tends to be increased from 300 mm to 450 mm in order to increase semiconductor device productivity. To this end, the authors developed a rotary grinding machine with high stiffness, equipped with water hydrostatic bearings. This grinding spindle is designed to govern infeed motion of the grinding wheel. This study investigates the basic design and performance of the grinding spindle system. This system itself is composed of a constant pressure water hydrostatic bearing as a radial bearing and a magnetic actuator as a thrust bearing. The magnetic actuator combine the infeed device and the thrust bearing. The measured results show that the static stiffness, Ks, is 1.06 kN/μm, the natural frequency is 353 Hz, and the positioning accuracy is 0.2 μm. These results meet the performance requirements necessary to grind φ450 mm Si wafer.