Atomic Layer Epitaxy Growth of Tantalum Oxide Thin Films from Ta ( OC 2 H 5 ) 5 and H 2 O

Abstract

The deposition of thin films by atomic layer epitaxy (ALE) was investigated in the temperature range of 150 to 450°C using and water as precursors. Because of the thermal self‐decomposition of the self‐limiting ALE growth was achieved only below 350°C. All the films grown were amorphous as examined by x‐ray diffraction analysis. The films grown at 250 and 325°C were stoichiometric within the accuracy of Rutherford backscattering spectrometry and contained 4 and 0.6 atom percent (a/o) hydrogen as determined by nuclear reaction analysis, respectively. Except for the outermost surface, the content of carbon residues was below 3 a/o as analyzed by x‐ray photoelectron spectroscopy. The films exhibited smooth surfaces as observed by scanning electron microscopy and relatively uniform thicknesses with 7% deviation in the gas flow direction. The refractive index of the films increased with deposition temperature stabilizing at 2.23 at temperatures higher than 300°C. The permittivities for the films grown at 250 and 325°C were 21 and 25, respectively, and leakage current densities at 1 MV/cm electric field were 4.0 and 2.3 mA/cm², respectively.