Etch-free low loss silicon waveguides using hydrogen silsesquioxane oxidation masks

Maziar P Nezhad,Aleksandar Simic,Yeshaiahu Fainman,Olesya Bondarenko,Mercedeh Khajavikhan

doi:10.1364/oe.19.018827

Abstract

An etch-free fabrication technique for creating low loss silicon waveguides in the silicon-on-insulator material system is proposed and demonstrated. The approach consists of local oxidation of a silicon-on-insulator chip covered with a e-beam patterned hydrogen silsesquioxane mask. A single oxidation step converts hydrogen silsesquioxane to a glass-like compound and simultaneously defines the waveguides, bypassing the need for any wet or dry etching steps. The spectral response of ring resonators fabricated using this technique was used to characterize the waveguide losses. Intrinsic Q-factors as high as 1.57 × 10(6), corresponding to a waveguide loss of 0.35 dB/cm, were measured.

Highlights

Silicon based photonic technology has seen tremendous growth in the past decade [1]
An etch-free fabrication technique for creating low loss silicon waveguides in the silicon-on-insulator material system is proposed and demonstrated
The approach consists of local oxidation of a silicon-oninsulator chip covered with a e-beam patterned hydrogen silsesquioxane mask

Summary

Introduction

The availability of the Silicon-On-Insulator (SOI) material system as a convenient waveguiding platform for fabricating planar photonic circuits has been a major factor in this growth. Most fabrication approaches rely on a plasma etching step which can have detrimental effects on the loss characteristics of the waveguide. Local oxidation of silicon (LOCOS) using a variety of mask materials has been proposed as an alternative fabrication approach to create low loss waveguides [2,3,4]. The main advantage of using LOCOS is that instead of etching the silicon layer directly, only the mask is etched and subsequently the pattern is transferred into silicon using oxidation. The shared commonality in all of these approaches is the need for a plasma or wet etch step to define and pattern the mask. In addition to improving the loss characteristics of the resultant waveguides, the approach simplifies the overall fabrication process considerably, which can result in a distinct economic advantage of this fabrication technique

Waveguide fabrication

Waveguide loss measurements