Abstract
The interfacial integrity of a gate stack featuring a polycrystalline SiGe gate, an ultrathin Al 2O 3/HfO 2/Al 2O 3 nano-laminate and a strained-SiGe surface-channel is examined for full transistor fabrication and characterization. The high-κ dielectric nano-laminate is prepared by means of atomic layer deposition, and the SiGe channel and gate by chemical vapor deposition. After full transistor-processing including a rapid thermal processing step at 930 °C, the 3 nm thick HfO 2 film becomes polycrystalline whereas the Al 2O 3 films about 0.5 nm thick remain in the amorphous state, according to analyses using high-resolution and energy-filtering transmission electron microscopy. No interfacial reaction is observable between the HfO 2 film and the SiGe gate or channel, since both interfaces are flat and the two Al 2O 3 films remain continuous. Well-behaving gate leakage and capacitance characteristics of the transistors are found. An enhanced channel hole mobility compared to the Si universal curve is obtained.
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