Atomic layer deposition of dielectric Y2O3 thin films from a homoleptic yttrium formamidinate precursor and water

We report the application of tris(N,N '-diisopropyl-formamidinato)yttrium(iii) [Y(DPfAMD)(3)] as a promising precursor in a water-assisted thermal atomic layer deposition (ALD) process for the fabrication of high quality Y2O3 thin films in a wide temperature range of 150 degrees C to 325 degrees C. This precursor exhibits distinct advantages such as improved chemical and thermal stability over the existing Y2O3 ALD precursors including the homoleptic and closely related yttrium tris-amidinate [Y(DPAMD)(3)] and tris-guanidinate [Y(DPDMG)(3)], leading to excellent thin film characteristics. Smooth, homogeneous, and polycrystalline (fcc) Y2O3 thin films were deposited at 300 degrees C with a growth rate of 1.36 angstrom per cycle. At this temperature, contamination levels of C and N were under the detectable limits of nuclear reaction analysis (NRA), while X-ray photoelectron spectroscopy (XPS) measurements confirmed the high purity and stoichiometry of the thin films. From the electrical characterization of metal-insulator-semiconductor (MIS) devices, a permittivity of 13.9 at 1 MHz could be obtained, while the electric breakdown field is in the range of 4.2 and 6.1 MV cm(-1). Furthermore, an interface trap density of 1.25 x 10(11) cm(-2) and low leakage current density around 10(-7) A cm(-2) at 2 MV cm(-1) are determined, which satisfies the requirements of gate oxides for complementary metal-oxide-semiconductor (CMOS) based applications.