Silicon-on-insulator chip structure with substrate-embedded optical waveguide and method

Abstract

Disclosed is a silicon-on-insulator (SOI) chip structure with a substrate-embedded optical waveguide. Also disclosed is a method for forming the SOI chip structure. In the method, an optical waveguide is formed within a trench in a bulk substrate prior to a wafer bonding process that results in the SOI structure. Subsequently, front-end-of-the-line (FEOL) processing can be performed to form additional optical devices and/or electronic devices in and/or above the silicon layer. By embedding an optical waveguide within the substrate prior to wafer bonding as opposed to forming it during FEOL processing, strict limitations on the dimensions of the core layer of the optical waveguide are avoided. The core layer of the substrate-embedded optical waveguide can be relatively large such that the cut-off wavelength can be relatively long. Thus, such a substrate-embedded optical waveguide brings different functionality to the SOI chip structure as compared to FEOL optical waveguides.