Improvement in the asymmetric Vfb shift of poly-Si/HfSiON/Si by inserting oxygen diffusion barrier layers into the interfaces

1. Introduction Hf-based materials are good candidates of high-k gate dielec-trics for low power consumption CMOS-LSIs. However, the asymmetric flatband voltage (Vfb) shift has been widely reported at poly-Si/Hf-based systems [1-5]. This phenomenon results in high Vth of FETs and makes the applicability of these gate insu-lators to commercial LSIs difficult. In our previous study, we demonstrated that the thick SiO 2 insertion into poly-Si/HfSiON interface improves the anomalous Vfb shift, although the value of Vfb recovery is as small as 0.15 V [6]. In this study, we discuss the design of the interfacial barrier layer for improving the asymmetric Vfb shift at poly-Si/Hf-based dielectrics/Si systems. We find that the Vfb recovery is critically dependent on the preparation process of the barrier layer. In addition , by separating HfSiO spatially from both poly-Si and Si-substrate with rather thick SiO 2 , the ideal Vfb values for n + and p