Effects of annealing temperature on the characteristics of silicate/HfO2 insulator formed on the p-Si/Si0.8Ge0.2 and p-Si/Si0.8Ge0.2/intrinsic-Si (20Ã ) substrates

We successfully deposited the reliable silicate/HfO2 insulator films on both p-Si/Si0.8Ge0.2 and p-Si/Si0.8Ge0.2/intrinsic-Si substrates via the oxidation and annealing of thin Hf film deposited by rf-magnetron sputtering. The oxidation of Hf metal films results in the electrically stable silicate/HfO2 stacked layers. The silicate films (i.e., a layer of Hf-Si-Ge-O) were formed between the HfO2 film and the p-Si/Si0.8Ge0.2 substrate. We found that the Ge segregation is suppressed by the insertion of a 2-nm-thick Si-overlayer on the Si0.8Ge0.2 substrate, resulting in better electrical properties than those obtained from the samples without the Si-overlayer. High-temperature annealing at 700 °C causes the diffusion of Ge into the silicate/HfO2 stacked insulator films only for the samples without the Si-overlayer. In addition, 700 °C annealing results in the formation of a thin SiOx layer at the silicate-Si0.8Ge0.2 substrate regardless of the presence of the Si-overlayer.