Thermal stability and scalability of Zr-aluminate-based high-k gate stacks

It is demonstrated that a narrow composition range exists in the ZrAl_xO_y mixed oxide system between 25 and 50 mol% Al₂O₃, where the crystallization temperature exceeds 950°C and at the same time the k-values remain larger than 12. In this composition range, enhanced thermal stability for better integration of the ZrAl_xO_y gate dielectric in a conventional poly-Si device process is observed. It is also shown that thin interfacial oxides strongly enhance the electrical stability while allowing for thickness scaling down to ∼1 nm, providing gate leakage current reductions of two to three orders of magnitude.