Shigeru Semura

Inductively Coupled Plasma-Enhanced Chemical Vapor Deposition of SiO2 and GeO2?SiO2 Films for Optical Waveguides Using Tetraethylorthosilicate and Tetramethylgermanium

SiO2 and GeO2–SiO2 films have been deposited by employing inductively coupled plasma-enhanced chemical vapor deposition (ICP-CVD) from tetraethylorthosilicate (TEOS) and oxygen discharge using tetramethylgermanium (TMGe) as a dopant. A pure SiO2 film deposited with TEOS:O2 at a flow rate ratio of 17% and an operating pressure of 5 Pa showed a low wet-etching rate of 114 nm/min approaching that of a thermally grown oxide. Ge doped SiO2 films were deposited at various TMGe flow rates, and it was found that Ge was incorporated into the film as a replacement for Si. The refractive index of the film is in proportion to the Ge content in the film. Fourier transform infrared (FTIR) analysis confirmed that there were few O–H and C–H defects in the films. Optical waveguides were fabricated using ICP-CVD and reactive ion etching (RIE). A propagation loss of 0.027 dB/cm at 1.55 µm was achieved for the optical waveguide by using GeO2–SiO2 film as the core layer.