High quality optical thin film formation with low energy gas cluster ion beam irradiation

Abstract

O2 gas cluster ion beam (O2-GCIB) assisted depositions were employed to deposit high quality dielectric films (Ta2O5, Nb2O5 and SiO2). The optimum irradiation energy and ion current density for Ta2O5 and Nb2O5 film were 5 to 9 keV and 0.5 mA/cm2, respectively. The Nb2O5/SiO2 films deposited with O2-GCIB irradiation showed very uniform and dense structures without columnar or porous structures. Due to the significant surface roughness improvement effect of GCIB, the interface and top surface of Nb2O5/SiO2 multi-layer were quite flat. The interference filter deposited with O2-GCIB assist deposition was very stable and there was no shift of wavelength before and after environmental tests. As O2-GCIB is equivalently very low-energy ion beam and is able to deposit flat and dense amorphous films at low substrate temperature, it suitable for deposition of multi-layered films where low-energy assisting ions are required.