Silicon-CMOS BEOL compatible material systems and processing for on-chip optical interconnect components

Optical interconnects are being actively pursued at smaller length scales in microelectronics to overcome the speed and bandwidth limitations of electrical interconnects. An on-chip implementation of optical interconnects requires the materials and processing to be compatible with the Back End Of the Line (BEOL) silicon Complementary Metal-Oxide Semiconductor (CMOS) transistor technology. This thesis looks at some materials and processing schemes for on-chip passive optical components that satisfy the above compatibility requirements.; Silica xerogel (porous silicon oxide) is used in this work to demonstrate high refractive index contrast waveguides. A binary solvent technique for open bowl, striation-free spin coating with excellent porosity control was developed. Plasma deposited silicon oxide and a hybrid alkoxy-siloxane polymer were used as the core materials. Reduction of the intrinsic stress of the plasma deposited silicon oxide was found to be essential for structural stability. Penetration issues exist for the alkoxy-siloxane polymer/xerogel system, which were overcome with the use of an optically thin silicon oxide capping layer.; This thesis also deals with the fabrication vertically reflecting micro-mirrors. A sacrificial layer based isotropic etching technique was explored to make angular facets for micro-mirror fabrication. The theory of this process is presented followed by numerical simulations and experiments. An isotropic wet etching technique is shown to be a reliable process for the fabrication of flat mirror faces. However, due to penetration of the etchant into the etch-stop/sacrificial material interface, the angle obtained was less than predicted. Various strategies to overcome this problem are presented. A similar penetration related angle decrease was not observed for a plasma etching based process.; The angular facet in the alkoxy-siloxane polymer core that would function as the mirror surface was also fabricated by a pattern transfer method involving transferring the angle from a template to the waveguide using a CF₄/O ₂ based reactive ion etching (RIE). Metallization of the mirror faces was done using a self-aligned technique, which ensures metal deposition only on the angular facet and also eliminates a lithography step. A reflection efficiency of 83% was measured for these micro-mirrors using a prism-coupler based setup.