Optimization of saw-tooth surface planarization for ultra-low blaze angle gratings for ALS-U

摘要

Planarization is important in many areas of nanostructure fabrication. Here we describe a new process for planarization saw-tooth surface of blazed gratings used for the monochromatization of light, but the applications should be much wider. Such gratings consist of relatively wide and very shallow triangular grooves with slanted facets which are machined with nanometer accuracy. The process of making such gratings includes planarization of a relatively coarse saw-tooth surface with micron deep grooves following by a plasma etch which provides reduction of the facet angle and hence groove depth by a factor of 10 -100. To achieve high quality of the final grating the planarization step should provide a flat surface over the grating facets with sub-nanometer level planarity. We investigated planarization of coarse saw-tooth surfaces with a groove width of 10 μm and a facet angle of 4° by a polymer coating spun on the grating. The optimized planarization procedure provides 100% planarization even on these highly structured surfaces.