Engineering High-k/SiGe Interface with ALD Oxide for Selective GeOx Reduction

Suppression of electronic defects induced by GeOx at the high-k gate oxide/SiGe interface is critical for implementation of high-mobility SiGe channels in complementary metal–oxide–semiconductor (CMOS) technology. Theoretical and experimental studies have shown that a low defect density interface can be formed with an SiOx-rich interlayer on SiGe. Experimental studies in the literature indicate a better interface formation with Al2O3 in contrast to HfO2 on SiGe; however, the mechanism behind this is not well understood. In this study, the mechanism of forming a low defect density interface between Al2O3/SiGe is investigated using atomic layer deposited (ALD) Al2O3 insertion into or on top of ALD HfO2 gate oxides. To elucidate the mechanism, correlations are made between the defect density determined by impedance measurements and the chemical and physical structures of the interface determined by high-resolution scanning transmission electron microscopy and electron energy loss spectroscopy. The compositio...