Surface preparation and interfacial stability of high-k dielectrics deposited by atomic layer chemical vapor deposition

The effects of various interface preparations on atomic layer chemical vapor deposition (ALCVD) deposited Al₂O₃ and ZrO₂ dielectrics properties were investigated by X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), medium energy ion scattering (MEIS) and transmission electron microscopy (TEM). H-terminated Si, SiO₂ and SiO_xN_y surfaces were used as substrates upon which the dielectric was deposited. Thermal annealing of SiO₂ in NH₃ forms an oxynitride; subsequent deposition of a ZrO₂/Al₂O₃ bi-layer stack resulted in a capacitor structure with an equivalent oxide thickness (EOT) of ∼ 0.8 nm and a leakage current of 3 × 10^-4 A/cm² at -1 + V_fb. This is in contrast to capacitor structures grown on H-terminated Si where high leakage was found. The growth of additional interfacial SiO₂ during processing, a critical problem in nano-electronic device applications, is temperature dependent with ZrO₂ exhibiting a higher oxygen permeability than Al₂O₃. Use of a polysilicon cap was shown to be effective at blocking oxygen absorption and transport through the high-k dielectrics, with stability up to 1100°C.