Abstract
To integrate Silicon-Germanium (SiGe) into future CMOS devices, it is essential to deposit very thin high-k dielectrics on SiGe surfaces with low density interfacial defects. In this study, Al2O3/HfO2 nanolaminate (HfO2 layers incorporated with Al2O3 monolayers) gate stacks were deposited by atomic layer deposition (ALD) using HfCl4 and H2O precursors. Electrical properties of the interfaces were quantified by capacitance-voltage (C–V) spectroscopy. Interfaces of nanolaminate stacks were found to have 2x smaller density of interface traps (Dit) than pure HfO2 gate stacks. Cross sectional TEM with Energy-dispersive X-ray spectroscopy (EDS) showed that an SiOx rich interlayer was formed between the nanolaminate and the Si0.7Ge0.3(001) substrate. The SiOx interlayer contains almost no Ge indicating that the HfCl4/TMA nanolaminate deposition reduced the GeOx in the interface. Furthermore, the SiGe surface was enriched in Ge from 30% to ~70% consistent with the HfCl4/TMA nanolaminate process reducing and redepositing Ge on the SiGe surface.
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