Reactive pulsed laser deposition of high-<i>k</i> silicon dioxide and silicon oxynitride thin films for gate-dielectric applications

Abstract

We have successfully developed two reactive pulsed laser deposition (PLD) processes for the growth of high-k SiO2 and SiOxNy thin films. At a KrF laser intensity of 3×108 W/cm2, both SiO2 and SiOxNy films have been deposited by ablating a silicon target in a reactive gas atmosphere (O2 and O2/N2 mixture, respectively) on both Si (100) and Pt-coated Si substrates. Two key issues are presented here, namely (i) the effect of the deposition temperature (Td in the 20–450 °C range) and (ii) the effect of the N incorporation (in the 0.3–20 at. % concentration range) on the microstructure and electrical properties of PLD SiO2 and SiOxNy thin films, respectively. For the PLD-SiO2 films, 300 °C has been identified as the optimal deposition temperature that yields stoichiometric ([O]/[Si]≈1.9), hydrogen-free films with a low local disorder, a highly dense microstructure and a dielectric constant (k) higher than that quoted for thermally grown SiO2. On the other hand, the PLD SiOxNy films containing 20 at. % of N have exhibited a dielectric constant as high as ∼7. A rather good agreement is obtained between the k values deduced from the Poole–Frenkel emission (PFE) model and those obtained from direct impedance measurements, confirming thereby that the PFE remains the predominant conduction mechanism in the PLD SiOxNy films.