HfO/sub 2/ for strained-Si and strained-SiGe MOSFETs

We report on HfO/sub 2/ gate dielectrics grown by atomic layer deposition (ALD) at 600/spl deg/C on strained-Si and strained-SiGe layers. The strain status in the Si layer remained unaltered after HfO/sub 2/ deposition and an interface state density of /spl sim/1/spl times/10/sup 11/ cm/sup -2/ eV/sup -1/ was obtained for the case of thick HfO/sub 2/ films. The breakdown fields were in the range 2-5 MV/cm, which is high compared to HfO/sub 2/ films grown at higher temperatures. The leakage current was reduced by more than five orders of magnitude for the case of a thin HfO/sub 2/ film with an EOT of 1.25 nm and ultra-thin cap (2.5-3 nm) layers on Si/sub 0.77/Ge/sub 0.23//Si. The carrier transport through these HfO/sub 2/ films was found to follow Frenkel-Poole emission over a wide range of applied gate voltage.