Effects of annealing temperature on the characteristics of silicate/ HfO₂ insulator formed on the p-Si/Si_0.8 Ge_0.2 and p-Si/Si_0.8Ge_0.2/intrinsic-Si (20Å) substrates

We successfully deposited the reliable silicate/HfO₂ insulator films on both p-Si/Si_0.8Ge_0.2 and p-Si/Si_0.8Ge_0.2/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/Si_0.8Ge_0.2 substrate. We found that the Ge segregation is suppressed by the insertion of a 2-nm-thick Si-overlayer on the Si_0.8Ge_0.2 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 SiO_x layer at the silicate-Si_0.8Ge_0.2 substrate regardless of the presence of the Si-overlayer.