Scaling the gate dielectric

The gate dielectric is arguably the biggest challenge facing the physical scaling of the MOSFET. The alternatives to continued scaling of SiO2 include radical departures from standard process flows and very challenging new materials issues. In the short term, the industry continues to pursue improvements to the reliability and tunneling performance of silicon-dioxide. New data on reliability suggests that SiO2 as thin as 1.6nm may achieve acceptable reliability in the field. Beyond SiO2, there is no material which has yet demonstrated comparable reliability or interface-state-density. The most promising approach involves using sandwiched high-k materials, with thin SiO2 at both interfaces. Either Ta2O5 or TiO2 may be suitable in structures of this type.