Tunable optical and electrical properties of thermal and plasma-enhanced atomic layer deposited Si-rich SixTi1-xO2 thin films

Ternary dielectrics with varying composition formed by alloying two binary oxides can enable tunable optical and electrical properties for advanced technological applications. Atomic layer deposition (ALD) gives precise control over ternary dielectric composition through the ability to finely tune the precursor pulsing ratio. This work presents ALD development of Si-rich SixTi1-xO2 dielectrics with varying composition (x), along with spectroscopic and electrical characterization of their properties. Stoichiometry of the SixTi1-xO2 films was determined using X-ray photoelectron spectroscopy. Their composition-dependent refractive index, energy bandgap, and reflectance show promise for diverse optical applications ranging from anti-reflective coatings in photovoltaics to optical waveguides. This work also reports a first comparative study of SixTi1-xO2 films prepared by thermal (T-) and plasma-enhanced (PE-) ALD with varying Si composition and deposition temperatures. Deposition rates of 0.67-0.92 angstrom /cycle were obtained for SixTi1-xO2 films with x=0.5-0.91 deposited using PE-ALD at 250 degrees C, which were higher than that of T-ALD at 200 degrees C (0.42-0.05 angstrom /cycle). PE-ALD also exhibited a high deposition rate of 0.81 angstrom /cycle for SixTi1-xO2 film with x=0.91 at a low growth temperature of 150 degrees C. The PE-ALD Si-rich silica-titania films show substantially lower (100x) leakage current densities than the thermally deposited films, along with higher breakdown fields for decreasing deposition temperature. A dielectric constant as low as similar to 5 was achieved for PE-ALD SixTi1-xO2 films with high Si (x=0.91) content.

Automated summary

Ternary dielectrics formed by alloying two binary oxides can achieve tunable optical and electrical properties through precise control of composition using atomic layer deposition (ALD). Si-rich SixTi1-xO2 films with varied composition were successfully fabricated using ALD, showing promising characteristics for diverse optical applications. Plasma-enhanced ALD exhibited higher deposition rates and lower leakage current densities compared to thermally deposited films, with potential for achieving dielectric constants as low as 5.