Thin Lu2O3 and Yb2O3 layers grown on Si using Atomic Layer Deposition (ALD) were studied with x-ray photoelectron spectroscopy (XPS) and low energy ion spectroscopy (LEIS). Our results show that ALD grown Lu2O3 and Yb2O3 films subsequently annealed in N2 are polycrystalline, and that their oxygen" subsystems" are very sensitive to further heat treatments in various atmospheres. In particular, it is evident that two chemically nonequivalent oxygen states are present in the oxides at equilibrium conditions. The one with the higher binding energy (BE0i. v «531.8 eV) is loosely bound, desorbs from the subsurface region upon vacuum annealing at T> 300 C, and reappears upon annealing in O2 (T= 500 C, PO2= 10-1 Torr). ALD can provide a variety of Lu silicates, depending on precursor combination and growth conditions. As grown ultrathin (< 5 nm) continuous Lu2Oi and Yb^ O3 films on Si exhibit an interfacial layer from~ 1 to 3 nm thick and a hydroxide layer on top. Upon annealing in N2, both components of the stacks transform into amorphous silicates. In situ XPS and LEIS analyses show that ultrathin Lu silicate films are further stable on Si at least up to T= 900oC, while for ultrathin Yb silicate layers the valence band structure appears sensitive to the annealing environment, and the Yb silicates eventually decompose and desorb from the surface upon vacuum annealing at T= 900 C.
Springer Science & Business Media
27 Jan 2006
Defects in HIgh-k Gate Dielectric Stacks: Nano-Electronic Semiconductor Devices