Thick-film doped-oxide deposition processes for applications in planar lightwave circuit fabrication

Abstract

Plasma Enhanced Chemical Vapour Deposition (PECVD) was used in the development of silica layers for use in planar lightwave circuit fabrication. These high-rate (>200nm/min) processes are tailored specifically for the thick-film (5-15pm) films required for these applications A GeH4 addition to the process was used to deposit the Core layer, controlling the core-clad refiactive index (RI) difference in the range of 0.2%-1.65%. Un-doped Si02 and Ge-doped Si02 films up to l o p have been deposited on to 4" Si <loo> wafers. The 'as deposited' and 'annealed' film properties: film uniformity, RI, RI uniformity and stress have been compared. The upper Cladding layer in an optical planar waveguide is typically formed using Boron and Phosphorus doped films (BPSG) which provides the necessary reflow characteristics.Refiactive index uniformity of fo.0003 across 4" silicon wafers was achieved on all films after annealing. The core layer was shown to be capable of producing optical losses of <O. ldB/cm when processed into a waveguide.