Multistep Si(100) Terraced Structure by one Photo Mask for Microlens

Abstract

The preparation method of multistep Si(100) terraced structure by one photo mask has been proposed. Firstly, silicon nitride or oxide is deposited on the Si(100) substrate as the etching mask of Si(100) in KOH solution. Then, the pattern of the photo mask is transferred to the etching mask by the standard lithography and etching process. The pattern design is very important for the formation of multistep Si(100) terraced structure. In the application of n-step diffractive lens with the same step height, the widths [b_n] and intervals [a_n] of the masked areas of the photo-mask pattern are decided under an arithmetic relation. Finally, the multistep Si(100) structure is formed during the KOH anisotropic etching process. Eight-level Si(100) terraced structure has been achieved. It will simplify the conventional process, in which m masks are necessary for 2^m-step microlens, and reduces the cost.