Advanced Analysis of Silicon Insulator Interface Traps in MOSFET's with SiO2 and with HfO2 as gate dielectrics

One of the points which is not clarified yet concerning the Si-SiO2 interface in conventional state-of-the-art (S-A) MOS devices is the properties and the nature of the trap remaining electrically active after forming gas annealing. In this paper, it is shown that in such devices, in a large region in the central part of the silicon energy gap, only two distributions of traps are probed using charge pumping. One coy-responds to donor-like traps while the other is composed of acceptor-like traps. They are located in the lower and upper halves of the silicon bandgap, respectively. It is also demonstrated that both trap types are not independent, but correspond to the same amphoteric defects. As these traps are likely located at the interface, i.e. are not distributed in depth toward the oxide bulk, they have the properties of the Si(100)-SiO2 interface P-b0 center. The question as to whether these traps are P-b0 centers is dealt with. As the electron spin resonance (ESR) sensitivity does not allow to probe Si-SiO2 interface traps in S-A fully processed MOSFET's, this is done with regard to the literature in that field. Then devices using HfO2 as gate dielectric are studied. Two traps distributions also dominate at the Si-SiO2 interface. Their properties are the same as those in S-A MOS devices, supporting that the traps are the same. However, with regard to S-A MOSFET's, their trap density, the distribution of their trap concentration in energy, D-it(E), as well as at a given energy, that of their time constants are different. Finally, a method for extracting the interface trap density, D-it, from the slope of the CP curves is proposed.