FABRICATION OF BURIED-CHANNEL WAVE-GUIDES ON SILICON SUBSTRATES USINGSPIN-ON GLASS

A new process for the deposition of thick (= 10-mum) films of silica a nd titania-doped silica on silicon substrates is described. Films are built up by repetitive operation of a simple process cycle in which a layer of sol-gel material is deposited by spin coating, then densified by rapid thermal annealing. Stress-free layers are obtained through c areful choice of the anneal temperature. Bilayer structures suitable f or waveguide fabrication may also be constructed by performing two suc cessive deposition runs using sol-gel precursors with different titani a concentrations. These bilayers may be patterned topographically into ridges by using reactive ion etching, and the ridges may be planarize d by applying additional layers of sol-gel material to form buried cha nnel waveguides.