Novel Materials and Processes for Advanced CMOS vol:745 pages:35-40
Materials Research Society Symposium Proceedings
Symposium on Novel Materials and Processes for Advanced CMOS held at the 2002 MRS Fall Meeting location:Boston, MA, USA date:2-4 December 2002
Scaled HfAlxOy/SiO2 stacks down to 1.5 nm EOT have been achieved. Although the 'addition of Al to the HfO2 matrix can be beneficial, it is observed that the benefit of using a Hf-aluminate is compromised if the film has a high Al-content. This is observed in terms of a dielectric constant close to that of pure Al2O3 (similar to 9) and a large amount of negative fixed charge in the film (similar to 10(12) cm(-2)). Using oxygen post deposition anneals we have been able to reduce flatband voltage shifts associated with fixed charge as well as CV hysteresis. In terms of scaling, the benefit of using a high-k material is compromised if a SiO2 layer is also present in the gate stack. Therefore, it is necessary to perform an O-2 PDA at moderate temperatures or in low O-2 partial pressures in order to control the thickness of the interfacial oxide layer.