The effect of KOH and KOH/IPA etching on the surface roughness of the silicon mold to be used for polymer waveguide imprinting

Abstract

We reports on an experimental result on a wet chemical etching of silicon for the fabrication of a mold template to be used in the embossing of optical waveguide. The silicon wafers we etched with its sidewall inclined to 45° and vertical to the bottom by using the anisotropic etching characteristics of the crystalline silicon. The results show that the surface roughness of the etched (100) and (110) planes is very much dependent on the etching condition such as the etchant concentration and etching temperature. The etched surface roughness is reduced by about 10 times from 34.5nm to 3.05nm in the (100) plane etching by changing the etching condition from 10M KOH solution at 80°C to 18M KOH solution at 40°C. For the (110) plane, the etched roughness is reduced dramatically from 115.75nm to 9.05nm by changing the etching condition from IPA saturated 5M KOH solution at 80°C to 1.25M KOH at 40°C.