Silica Titania Optical Thick Film by Multi-spinning Sol-gel process

Abstract

Sol-gel process has been used for producing high purity and homogenous optical thin films. A high quality, crack free optical thin film and low processing cost are key success factor for optical applications especially in planar waveguides technology. However, film cracks always occur in the silica and silicate base thin films as the thickness of thin film reached above 1m by multi-spinning sol-gel process. Proper handling and consistence conditions was studied using the silica-10% titania sol deposited on silicon wafer substrate. The dry gel silica-10% titania thin film was heat-treated at 680°C using Rapid Thermal Annealing (RTA) furnace. The Rapid Thermal Annealing (RTA) furnace was designed in-house by modifying tube furnace and the required heating rate was set manually. Under controlled deposition conditions in 10K clean room, crack free film ~2micron thick have been succesfully fabricated. However, lack of control in the deposition process can generate dust from excess sol-gel sol during spinning process and then contributes to point of stress in the thin film and cause formation of spider web crack pattern.