Plasma-enhanced chemical vapor deposition of TiO2 thin films for dielectric applications

Amorphous TiO2 thin films were formed by plasma-enhanced chemical vapor deposition (PECVD) from mixtures of titanium IV isopropoxide (Ti(O-i-C3H7)4) and oxygen. The deposition rate was found to be weakly activated, with an apparent activation energy of 4.5 kJ/mol. The deposition rate increased with equivalence ratio and decreased with plasma power. This dependence on atomic oxygen density was consistent with behavior observed in other metal oxide PECVD systems. Metal-insulator-silicon devices were fabricated, and characterized using capacitance–voltage measurements. The apparent dielectric constant of the TiO2 thin films increased from 15 to 82 with film thickness. The observed variations were consistent with the formation of an interfacial SiO2 layer. Assuming that a TiO2/SiO2 bilayer behaves as two capacitors in series, an intrinsic TiO2 dielectric constant of 82 ± 10 and an interfacial SiO2 layer thickness of 3 ± 1 nm were extracted from electrical measurements.