Unveiling growth mechanisms of PEALD In2O3 thin films with amide-based versus alkyl-based novel indium precursors

Abstract

Indium oxide is currently in the spotlight of the micro-optoelectronics industry because of its high carrier concentration, electrical conductivity, and transmittance in the visible-light region. Among the methods of depositing indium oxide, atomic layer deposition (ALD) has the advantage of thickness control and conformality. In addition, it has high conformality, but a slow deposition rate. Therefore, plasma-enhanced ALD, which uses highly reactive radicals, is receiving attention. ALD is based on a self-limiting reaction. Therefore, the selection of the precursor is important because the ligand that reacts with the surface has a significant influence on the reaction. Herein, DIP-3 and DIP-4, amine/alkyl-based precursors, were developed based on previously used precursors. The growth characteristics of indium oxide deposited through the O₂ plasma-enhanced ALD process using these two precursors differed depending on the precursor used. Alkyl-based DIP-4 resulted in a higher growth rate (∼1 Å per cycle) compared to that of amine-based DIP-3. The difference in the properties is related to the new ligands of the two precursors. DIP-4 was stably adsorbed on the surface with an energy reduction of 173 kJ mol⁻¹, which is greater than that of DIP-3. Owing to its small size and added ligand, DIP-4 covered the substrate surface quickly and accelerated the film growth. The consumption of more hydroxyl groups can lead to the formation of more nuclei, and the coarsening of the crystals based on this phenomenon is associated with an increase in the growth per cycle (GPC).