Structural and electrical characterization of Al_2O_3/HfO_2/Al_2O_3 on strained SiGe

摘要

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 ℃, 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.