Silicon germanium (SiGe) channels are being developed for CMOS technology due to their high intrinsic carrier mobility. The superior properties of SiGe can be utilized only if SiGe-high k interfaces with a low interface defect density (Dit) can be fabricated. Germanium oxide (GeOx) is known to be the source of interface defects and by selective reduction, selective removal of GeOx, or selective formation of interfacial silicon oxide (SiOx), low-defect interfaces can be formed. Previously, ozone has been employed to form a GeO2 rich interlayer on high Ge content SiGe to passivate the interface (1). In this work, a new method, selective oxidation with ozone nano laminate, was employed; in this method, ozone pulses are dispersed evenly within the HfO2 during ALD HfO2 deposition. Optimized ozone pulsing between 5nm thick HfO2 oxide layers reduced the defect density by 60% compared to standard HfO2 ALD on the same samples. With the ozone nanolaminate and optimized forming gas anneal, an interface defect density of Dit=5x1011 eV-1cm2 with accumulation capacitance of 1.75uF/cm2 was demonstrated for the HfO2/Si0.7Ge0.3 interface. The distribution of the defect density across the band gap was calculated according to full interface state model and integrated Dit of <1x1011 eV-1cm2 was obtained. High resolution STEM images shows thin interface and Si enriched composition compared to the bulk was observed in STEM-EELS and EDS analysis. The data demonstrates that dry selective oxidation can be used to form the SiOx layer required to passivate Si0.7Ge0.3(001).
Ando et al, IEEE ELECTRON DEVICE LETTERS, VOL. 38, NO. 3, MARCH 2017