DLTS of ALD HfO2 on s-Si/SiGe/Si: Effects of s-Si Thickness and Surface Nitridation

Abstract

MOS capacitors have been used as depth-dependent probing tools for MOS-DLTS studies of ALD HfO2 on s-Si/SiGe/Si composite samples. Surface nitridation prior to HfO¬2 deposition was carried out to improve the HfO2/s-Si interface by suppressing hafnium silicate interlayer formation. The overall effects of nitridation on the HfO2/s-Si interface and the s-Si/SiGe bulk region with different strained Si layer thicknesses were studied. The relationship between DLTS peak amplitude and pulsing time indicates the emission source in bulk region is related with Ge decorated dislocations and in the interface region it originates from the HfO2/s-Si interface. In the s-Si/SiGe bulk region, nitridation reduces the trap concentration and shifts trap energy level toward mid-gap. For the interface, nitridation shifts trap energy level toward valence band and reduces hole capture cross section significantly.