Abstract

A reduction of the surface roughness (R_a) to less than 1 Å is required in various applications such as hard-disk and optical-disk processing. R_a is formally defined as the arithmetic average of the absolute values of the surface height deviations from the best-fitting plane. Although chemical-mechanical polishing (CMP) has been used to flatten the surfaces [1], it is generally limited to reducing R_a to about 2 Å because the polishing pad roughness is as large as 10 m, and the polishing-particle diameters in the slurry are as large as 100 nm. We therefore developed a new polishing method that uses near-field etching based on an autonomous phonon-assisted process, which does not use any polishing pad, with which we obtained ultra-flat silica surface with angstrom-scale average roughness (see Fig. 1) [2,3]. Since this technique is a non-contact method without a polishing pad, it can be applied not only to flat substrates but also to three-dimensional substrates that have convex or concave surfaces, such as micro-lenses, optical-disk, and the inner wall surface of cylinders. Furthermore, this method is also compatible with mass-production.

© 2011 Optical Society of America