A novel technique of fabricating rear 45° micromirror for stacked die optical interconnect

Abstract

This paper presents a novel technique of fabricating rear 45° micromirror which is located on the upper die to direct a vertical optical beam from the bottom die to propagate horizontally in the upper die. The fabrication of the 45° micromirror is based on anisotropic wet etching on (100) crystalline silicon surface. By using surfactant NCW-1002 in low concentration TMAH (2.5% to 10%) smooth (110) 45° micromirrors can be fabricated. Together with a suitable orientation of the back side etch window, this 45° micromirror provides the framework for fabricating the rear 45° micromirror.