Optical film formation with O/sub 2/ cluster ion assisted deposition

Formation of high-quality optical films is increasingly important due to the rapid progress of optical components. These films must be durable, dense and very flat. We have developed a noble film formation process by cluster ion assisted deposition. Unique characteristics of cluster ion bombardment have been found such that it is applicable for various industrial applications that cannot be achieved by conventional ion beam processing (Yamada et al, 2000). Cluster ions can transport thousands of atoms per ion with very low energy and realize dense energy deposition within a very localized region, which enhances the chemical reaction between clusters and target atoms near its surface (Toyoda et al, 1997). Furthermore, cluster ions exhibit a surface smoothing effect due to lateral sputtering effects. These properties are useful for the formation of high quality thin films. In this work, we focused on optical thin films such as Ta/sub 2/O/sub 5/, TiO/sub 2/ and SiO/sub 2/. We have fabricated Ta/sub 2/O/sub 5//SiO/sub 2/ multi-layer structures with O/sub 2/ cluster ion assisted deposition and studied the quality of these optical films by AFM observations, environmental tests and various optical measurements.