CMOS-Compatible Fabrication, Micromachining, and Bonding Strategies for Silicon Photonics

The adoption of optical technologies by high-volume consumer markets is severely limited by the cost and complexity of manufacturing complete optical transceiver systems. This is in large part because "boutique" semiconductor fabrication processes are required for III-V lasers, modulators, and photodetectors; furthermore, precision bonding and painstaking assembly are needed to integrate or assemble such dissimilar devices and materials together. On the other hand, 200mm and 300mm silicon process technology has been bringing ever-increasing computing power to the masses by relentless cost reduction for several decades. Intel's silicon photonics program aims to marry this CMOS infrastructure and recent developments in MEMS manufacturing with the burgeoning field of microphotonics to make low cost, high-speed optical links ubiquitous. In this paper, we will provide an overview of several aspects of silicon photonics technology development in a CMOS fabrication line. First, we will describe fabrication strategies from the MEMS industry for micromachining silicon to create passive optical devices such as mirrors, waveguides, and facets, as well as alignment features. Second, we will discuss some of the challenges of fabricating hybrid III-V lasers on silicon, including such aspects as hybrid integration of InP-based materials with silicon using various bonding methods, etching of InP films, and contact formation using CMOS-compatible metals.