Tetraallyltin precursor for plasma enhanced atomic layer deposition of tin oxide: Growth study and material characterization

Abstract

In this letter, the authors report on the application of tetraallyltin (TASn) as an Sn-precursor for plasma enhanced atomic layer deposition (PEALD) of tin oxide (SnO2) thin films. The selection procedure for the TASn precursor is discussed. Tin oxide PEALD growth is shown to be self-limiting with a constant growth-per-cycle of 0.046 ± 0.002 nm/cycle in the substrate temperature (Tsub) range of 50–150 °C. Optical constants, chemical bonding, and electronic properties of as-grown PEALD films were characterized to evaluate the quality of tin oxide film obtained with the TASn precursor. A 21.6 nm tin oxide film grown at Tsub = 50 °C exhibited an indirect optical bandgap (Eg) of 2.94 eV and appeared amorphous from the glancing incidence x-ray diffraction pattern. Binding energy difference ΔBE(O1s, Sn3d5/2) = 43.77 eV and valence band emission in x-ray photoelectron spectroscopy showed that these were near-stoichiometric SnO2 with the relative O:Sn atomic ratio of 1.98 (or SnO1.98). Moreover, room temperature electrical resistivity ρele = 13.1 ± 1.6 mΩ cm, with electron concentration Ne = (3.78 ± 0.79) × 1019 cm−3 and Hall mobility μe = 13.2 ± 2.0 cm2 V−1 s−1, showed that electrical characteristics of the as-grown tin oxide films with the TASn precursor are comparable to those grown using other standard Sn precursors.