Fabrication of stair-case profiles with high aspect raitos for bazed diffractive optical elements

摘要

A nove method for the fabrication of four level sructures using mutiple electorn beam exposures using very thin (50-80 nm) resist layers is presented. The patterns of the two exposre steps are stored in 20 nm thick metal ayers by rective ion etching (RIE) and ift-off. By stepwise etching into the underlying substrate, a stair-case profile can be obtained. The overlay of the ithogrpahy eves to an accuracy of some tens of nanometers is done using regisration of alignment jmarks. The method has been successfuly applied to the paterning of silicon which is suited for the manfuacure of x-ray opticla components, and of quartz which cna be used for visible light DOEs.