Effect of gallium incorporation on electrical and material characteristics of TiO2 films for high-permittivity dielectric application

In this work, effects of gallium incorporation on electrical and material characterization of TiO2 films were investigated. These 15 nm Ga-doped TiO2 films were grown by supercycle atomic layer deposition (ALD) and then annealed at 500 ºC in O2 ambient. The levels of Ga incorporation to TiO2 films were controlled by the ratio of Ga to Ti cycles during ALD growth. Material characterizations show that the Ga incorporation destabilizes the crystallization of TiO2 films, resulting in amorphous films even after 500 ºC O2 annealing. The bandgap of these Ga-doped TiO2 films were found to monotonically increase with the increased Ga content. Metal-oxide semiconductor capacitors (MOSCAPs) based on p-type Si substrate were fabricated to evaluate the electrical properties of the Ga-doped TiO2 films. Both leakage currents and capacitances were reduced as the Ga content increases. These well-behaved dielectrics under 500 ºC process suggest their great promises for back-end-of-line (BEOL) device applications.