Experimental Study of ALD HfO2 Deposited on Strained Silicon-on-Insulator (sSOI & xsSOI) and SOI

Abstract

4 nm HfO2 films are deposited on silicon-on-insulator (SOI) with various amounts of lattice strain and thickness by atomic layer deposition (ALD). After post deposition annealing (PDA), the samples are studied by Rutherford backscattering spectroscopy (RBS), high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS), and x-ray photoelectron spectroscopy (XPS). The as-deposited HfO2 film shows good stoichiometry and thickness uniformity. HRTEM images show that while HfO2 films on non-strained SOI becomes poly-crystalline after PDA at 600 oC, HfO2 films on strained SOI still keep amorphous. The strain SOI also suppresses the IL growth during PDA. The EELS and XPS results confirm the interdiffusion across the HfO2/Si interface. The XPS data also show that formation of Hf-O-Si bonds depend on the SOI lattice strain and thickness. The SOI thickness is critical to reduce the formation of silicate in the IL.