Deposition of Silicon Dioxide Films Using the Helicon Diffusion Reactor for Integrated Optics Applications

Existing optical fibre and fibre-device fabrication techniques have been complemented recently by the development of new processes for the fabrication of planar optical waveguides and devices. These processes rely on new forms of plasma reactors and diagnostic systems which allow in-situ control of optical parameters such as refractive index. These plasma processing systems allow the fabrication of optical devices which are not readily feasible in fibre technology, and allow the fabrication of very compact and highly complex optical circuitry which can be produced on a single photonic chip. They also offer the potential to integrate photonic devices with semiconductor sources and detectors to realise a compact, hybrid photonic-optoelectronic chip, complete with fibre pig-tailing. Because of their compactness and potential low cost, these types of photonic chips are attractive components for future high-capacity optical telecommunications and other networks now being planned as part of the information super highway. The paper presents the physical constraints and design rules for the fabrication of the devices, and the research carried out using a helicon plasma reactor to grow the thick films of silica necessary for the waveguides. From the start, the reactor was designed to process substrates at low temperatures to allow the integration with other optical and electronic components on the same wafer. Hence a considerable amount of research was carried out on the relation between the plasma parameters and the physical properties of the films deposited. The last section of the paper describes the fabrication of an actual device; a 1:8 splitter, and its characteristics.