Fine thickness control of amorphous silicon by wet-etching for low loss wire waveguide

Isotropic wet-etching without surface roughening was applied to an a-Si:H film with nanometer-scale thickness controllability. Record ~1.2 dB/cm low propagation loss was obtained in an etched wire waveguide, being comparable to those of SOI waveguides.

I. Introduction

By partly replacing metallic wirings of the inter/inner-chips in LSIs by optical waveguides, speed-up of signal transmission and energy-saving are expected. In particular, waveguides using hydrogenated amorphous silicon (a-Si:H) materials are promising, because a-Si:H can have small material absorption loss in near-infrared by growth under proper conditions and can be formed at low temperatures enabling the device fabrication on the electric circuit layers. In addition, a-Si:H waveguides have an attractive promise of 3-D wiring possibility. So far, several groups have reported the fabrication ability of high quality wire waveguides with a-Si:H material [1]–[3].