Fabrication of laser ablation masks by wet etching

Abstract

Tantalum (or hafnium) oxide layers, alternated with silicon oxide layers in a dielectric stack reflector type mask for high power laser ablation, are wet etched at a high temperature with a highly caustic solution, preferably potassium hydroxide, to provide a much increased manufacturing yield in comparison with known processes such as ion milling. High feature density is achieved through the use of a resist which is built in two patterning steps. Preferably, a chromium layer is deposited and covered with an organic resist which is patterned by an optical or electron beam exposure. The chromium is then etched by means of the resist mask to form a resist for the caustic wet etch of the tantalum (or hafnium) oxide either separately or together with silicon oxide layers of the dielectric stack reflector mask to be used in the laser ablation process at high power.