Ultrathin high-k gate dielectric films on strained-si/sige heterolayers

We have investigated the deposition of alternative gate dielectrics i.e., high dielectric constant (high-k) materials such as ZrO₂ and TiO₂ on strained-Si on relaxed SiGe and strained-SiGe layers. The strained-Si heterolayers generally acquire a high defect density during heteroepitaxy and also the high-k gate dielectric films are prone to point defects. These defects play an important role in determining the electrical properties of the deposited films and their reliability. Basic understanding of the physical and chemical nature of these defects may help to alleviate the reliability problems. In this paper, the nature of several point defects and trap centers created from both strained-Si substrates and high-k gate dielectrics itself has been studied in detail. Magnetic resonance technique has been used to study the chemical nature of the defects present at the interface and dielectric trapping defects present in strained-Si/high-k metal-insulator-semiconductor (MIS) capacitors. The physical nature and the quantification of the trapping/detrapping centers have also been studied under stressing (in both constant current and voltage modes). Time-dependent dielectric breakdown (TDDB) characteristics have been measured to study the reliability of the MIS capacitors.