Correlation between polishing pad’s properties and material removal during full-aperture polishing

Polishing pad plays a vital role in the fabrication of large flat optical elements during full-aperture polishing. Material removal rate (MRR) and material removal distribution (MRD) describe the material removal process from the point of the global average removal rate and the spatial distribution of removed material, respectively. The pad's mechanical property characterized by compression modulus and morphological characteristic indicated by material ratio curve are used to qualitatively clarify the degression of MRR at different rough polishing stage. Moreover, the novel MRD model is proposed to quantitatively correlate the pad's mechanical and morphological characteristic with MRD. The radial surface profile predicted by MRD model meets well with the experimental results. Furthermore, the influence of pad viscoelastic property is used to explain the generation of additional MRD in experiment at the edge of workpiece.