Experimental study of ALD HfO2 deposited on strained silicon-on-insulator and standard SOI

HfO2 films of 4 nm were deposited by atomic layer deposition on silicon-on-insulator (SOI) substrates with various amounts of intentionally introduced lattice strain and several film thicknesses. After postdeposition annealing (PDA), the samples were studied by Rutherford backscattering spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS), and X-ray photoelectron spectroscopy (XPS). The as-deposited HfO2 film showed a good stoichiometry and thickness uniformity. The strain in strained SOI (sSOI) layers remained after high-temperature PDA at 1100 degrees C. HRTEM images showed that, while HfO2 films on standard nonstrained SOI became polycrystalline after PDA at 600 degrees C, HfO2 films on sSOI remained amorphous. The strain in the sSOI layer also suppressed the interlayer (IL) growth during PDA. The EELS and XPS results confirmed the interdiffusion across the HfO2/Si interface. The XPS data also showed that the formation of Hf-O-Si bonds depends on the SOI lattice strain and thickness. The SOI thickness is critical to reduce the formation of silicate in the IL. (c) 2008 The Electrochemical Society.