Studies on Roll-off-less Polishing of Magnetic Disk Substrate (1st Report)

Change of Substrate Edge Shape in Polishing Process

Abstract

This report deals with the enlarging method of the recording area per a magnetic disk substrate by means of repressing the edge roll-off formed by polishing. The change of the edge shape in polishing process is experimentally examined in detail by measuring the edge shape in the accuracy of nanometer order with WYKO. To clear the formation mechanism of edge shape by polishing, the influence of the revolution of the polisher and the substrate on the edge shape formation is separately investigated and discussed. The edge shape of the substrate after non-electrolytic plating is found to be classified into the roll-up type and the roll-down type. The change of the edge shape in polishing process is divided into the edge roll-up formation type (RUF type) and the edge roll-down enlargement type (RDE type). In case of polishing under only the substrate revolution without polisher revolution and only the polisher revolution without the substrate revolution, the change of the edge shape becomes the RUF type and the RDE type, respectively. The low and high velocity polisher revolution under the normal polishing operation tends to be connected with the RUF type and the RDE type, respectively. The polishing of the RUF type can decrease the roll-down radius width, ΔR_X, of the substrate having the large roll-down, from ΔR_X_??_1.5mm to about 500 μm. for examnle.