Effects of annealing on the electrical properties of TiO2 films deposited on Ge-rich SiGe substrates

Titanium oxide (TiO2) high-k dielectric layers were deposited on the Si0.3Ge0.7 substrates by plasma enhanced chemical vapor deposition (PECVD) at low temperature (150 degrees C). To study the effects of annealing on the electrical properties, the TiO2 films were annealed in pure nitrogen ambient in the temperature range of 400-600 degrees C. Good electrical performance for the gate dielectrics was observed for the dielectric films annealed up to 500 degrees C, in terms of interface state density, leakage current, and charge trapping properties. Annealing at 600 degrees C is found to degrade the electrical properties due to Ge segregation and subsequent diffusion into the TiO2 layer. Schottky emission was found to be the dominant leakage current conduction mechanism in PECVD TiO2 films. (c) 2006 American Institute of Physics.