Highly Conductive and Conformal InN by Plasma-Enhanced Atomic Layer Deposition on amorphous SiO2 substrate Using a Liquid Heteroleptic Indium Precursor and NH3 Plasma

Abstract

Indium nitride (InN) thin films were deposited by plasma-enhanced atomic layer deposition (PEALD) using (N,N′-di-tert-butylacetimidamido)dimethylindium (DBADMIn) and NH3 plasma. By systematically tuning the plasma chemistry, pulse timing, and deposition temperature, we identified a self-limiting growth regime and established a clear ALD window between 175 and 275 °C, where the growth per cycle remained nearly constant at ≈ 0.56Å/cycle. Within this window, the films were dense (6.20g/cm3) with smooth surfaces and a polycrystalline wurtzite structure, showing preferential contributions from the (100), (002), and (101) reflections. Conformal deposition was confirmed on patterned features, yielding step coverages of ~91% (sidewall/top) and ~86% (bottom/top) for 100-nm-wide trenches with an aspect ratio of 2.5. Combined Rutherford backscattering spectrometry (RBS) and time-of-flight elastic recoil detection (ToF-ERD) analyses indicated an In-rich average composition (In:N ≈ 1.47) with residual O and H contents. XPS and air-exposure-dependent sheet-resistance analyses suggest that the oxygen contribution is associated not only with possible donor-type O incorporation but also with native surface oxidation and/or minor amorphous InON, InOx phases. Hall measurements revealed degenerate n-type transport with n ≈ 1 × 1021cm–3, μ ≈ 5.4 cm2/V·s, and ρ ≈ 1000 μΩ·cm, while optical spectra exhibited an apparent band gap of ≈ 2.1eV consistent with a Moss–Burstein shift. Overall, this work demonstrates a reproducible PEALD route to conductive and conformal InN on thermally grown amorphous SiO2 using a liquid, thermally stable indium precursor, and highlights plasma chemistry as a key handle for tuning phase formation and electrical properties.