Methods for improving ion beam etching uniformity of large-sized DOEs

Abstract

DOE is often produced by lithography and ion beam etching. The etching depth error directly affects the diffraction performance of DOE. The uniformity of ion beam etching depth is particularly important for large-sized DOEs in that errors by ion beam etching uniformity would result in an obvious aberrant spot of intensity in the focal area of DOE, which consumedly reduces the uniformity of target field in uniform illumination. On the basis of the KZ-400 ion beam etching equipment the method of improving DOE ion beam etching uniformity is investigated. The step-by-step method is used to improve the uniformity of ion beam etching, in which the etching time and location are adjusted. Experimental result shows that in the range of 190mm along the major axis of ion beam source the etching uniformity of DOE increases from ±5% to ±1.3%.