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

O
₂
gas cluster ion beam (O
₂
-GCIB) assisted depositions were employed to deposit high quality dielectric films (Ta
₂
O
₅
, Nb
₂
O
₅
and SiO
₂
). The optimum irradiation energy and ion current density for Ta
₂
O
₅
and Nb
₂
O
₅
film were 5 to 9 keV and 0.5 μA/cm
²
, respectively. The Nb
₂
O
₅
/SiO
₂
films deposited with O
₂
-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 Nb
₂
O
₅
/SiO
₂
multi-layer were quite flat. The interference filter deposited with O
₂
-GCIB assist deposition was very stable and there was no shift of wavelength before and after environmental tests. As O
₂
-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.