Atomic Layer Deposition of In2O3 and Ammonolysis into Inn

Indium Nitride is a narrow-band gap semi-conductor that is useful in solar cells and high-speed electronics. Thin films of InN can be deposited with CVD and PVD methods, but these techniques require high temperatures and cannot fill high-aspect-ratio vias. Our approach is to use Atomic Layer Deposition (ALD), a technique based on self-limiting surface reactions, to deposit InN with precise thickness control and mild process conditions. Since there is no direct method to deposit InN with ALD, we propose a two step process where we first deposit In2O3 with ALD and then convert it into InN by ammonolysis. Conformal films of In2O3 are deposited on nanoparticles using sequential exposures of In(CH3)3 and water at 175°C. Self-limiting behavior of both reagents is observed with in-situ FTIR spectroscopy and the In2O3 grows at 0.52Å/cycle. XPS analysis confirms the oxidation state of Indium to be In3+ with a stoichiometry ratio of 2:3.18 In:O. These films were subsequently converted into InN when heated to 450°C in an ammonia atmosphere. The presence of nitrogen is confirmed by Auger spectroscopy, but the ammonolysis roughens the original film as observed by transmission electron microscopy.