Effect of the stack layer on the electrical properties of Ta2O5 gate dielectrics deposited on strained-Si0.82Ge0.18 substrates

Stacked SiO2/Ta2O5 and Si2ON2/Ta2O5 films have been deposited on strained-Si0.82Ge0.18 layers at a low temperature in a microwave plasma using O2, NO and tantalum pentaethoxide. The stacked films are compared on the basis of electrical parameters determined using high-frequency capacitance–voltage and current–voltage characteristics, before and after the electrical stressing of the metal–insulator–semiconductor capacitor structures. With the help of constraint theory, we explain the chemical bonding issues at various interfaces (such as substrate–dielectric and dielectric–dielectric) in the plasma-grown oxides and stacked high-k dielectrics. In this paper, we show that the stacked Si2ON2/Ta2O5 films are superior to SiO2/Ta2O5 structures due to the enhanced incorporation of nitrogen.