Water assisted atomic layer deposition of yttrium oxide using tris(<i>N</i>,<i>N</i>′-diisopropyl-2-dimethylamido-guanidinato) yttrium(<scp>iii</scp>): process development, film characterization and functional properties

Abstract

We report a new atomic layer deposition (ALD) process for yttrium oxide (Y₂O₃) thin films using tris(<i>N</i>,<i>N'</i>-diisopropyl-2-dimethylamido-guanidinato) yttrium(iii) [Y(DPDMG)₃] which possesses an optimal reactivity towards water that enabled the growth of high quality thin films. Saturative behavior of the precursor and a constant growth rate of 1.1 Å per cycle confirm the characteristic self-limiting ALD growth in a temperature range from 175 °C to 250 °C. The polycrystalline films in the cubic phase are uniform and smooth with a root mean squared (RMS) roughness of 0.55 nm, while the O/Y ratio of 2.0 reveal oxygen rich layers with low carbon contaminations of around 2 at%. Optical properties determined <i>via</i> UV/Vis measurements revealed the direct optical band gap of 5.56 eV. The valuable intrinsic properties such as a high dielectric constant make Y₂O₃ a promising candidate in microelectronic applications. Thus the electrical characteristics of the ALD grown layers embedded in a metal insulator semiconductor (MIS) capacitor structure were determined which resulted in a dielectric permittivity of 11, low leakage current density (≈10^-7 A cm^-2 at 2 MV cm^-1) and high electrical breakdown fields (4.0-7.5 MV cm^-1). These promising results demonstrate the potential of the new and simple Y₂O₃ ALD process for gate oxide applications.