Abstract
Within a few years, a 450-mm large wafer will be used to develop next-generation semiconductor devices and to raise volume efficiency. When this occurs, the ″22 nm rule″ will require a site flatness of less than 22 nm across the entire top surface of all wafers. The flatness of less than 0.2 μm has been achieved for a 300-mm wafer using the optimum oscillation-speed control polishing. This paper describes the relation between a grinding profile and the inclination of a grinding wheel for a 450-mm wafer, a flatness degradation of the 450-mm wafer, and a comparison between the grinding profiles and the calculated results, where it was assumed that the moving path of the grinding wheel is accurately transferred to the ground wafer surface including its center portion. The grinding profiles due to the inclination of the grinding wheel were calculated. The flatness of the 450-mm wafer degrades beyond twice for that of the 300-mm wafer under the wheel conditions with the same diameter and inclination. The calculation results were roughly consistent with the experimental results. Good flatness of less than 1 μm over the entire surface was achieved with a precise inclination adjustment method.
