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

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 μA/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.