Dual mask pattern transfer techniques for fabrication of lenslet arrays

Abstract

A method for forming lenslets of a solid-state imager, includes providing a first etch-stop layer on a spacer layer formed on a substrate or layer(s) on a substrate; providing a patterned first photosensitive resin layer to form a first mask pattern; performing an etch transfer of the first mask pattern to the first photosensitive resin layer to form a first etch-stop mask pattern, and removing the first photosensitive resin layer; providing a transparent lenslet-forming layer on the spacer layer. The method further includes forming a second etch-stop layer on the transparent lenslet-forming layer to form a second mask pattern and patterning a second photosensitive resin layer on the second etch-stop layer wherein the second mask pattern corresponds to the lenslet array to be formed and wherein the lenslet array defined by the second mask pattern is aligned to the array of open regions of the first etch-stop mask pattern; transferring by etching the pattern of the second photosensitive resin layer to the second etch-stop layer to form a second etch-stop mask pattern; anisotropically plasma etching the transparent lenslet-forming layer according to the second etch-stop mask pattern; anisotropically plasma etching the spacer layer according to the first etch-stop mask pattern; isotropically etching to remove remaining portions of the first etch-stop layer forming the first etch-stop mask and portions of the second etch-stop layer forming the second etch-stop mask; and thermally reflowing the patterned transparent lenslet-forming layer to form the lenslets on the solid-state imager.