Development of Evaluation Method of Pad Surface Characteristics Based on Contact Image Analysis Using Image Rotation Prism

Polishing is generally used in fabricating high-quality silicon wafers. Polishing efficiency and accuracy depend not only on the pad surface characteristics but also the actual conditions of contact between the wafer and the pad. Furthermore, the pad surface characteristics are affected by the dressing conditions. Currently, no effective quantitative methods or parameters for pad surface evaluation have been established. In this study, we propose a technique based of contact image analysis using an image rotation prism; we also discuss the effect of dressing conditions on the following parameters; (1) contact ratio, (2) number of contact points, (3) spacing of contact points and (4) spatial FFT results of a contact image. These parameters were found to be effective for evaluating pad surface conditions.