Indium Oxide Atomic Layer Deposition Facilitated by the Synergy between Oxygen and Water

This paper explores the atomic layer deposition (ALD) of indium oxide (In 2 O 3 ) films using cyclopentadienyl indium (InCp) and combinations of both molecular oxygen and water as the co-reactants. When either O 2 or H 2 O were used individually as the oxygen source the In 2 O 3 growth was negligible over the temperature range 100−250 °C. However, when oxygen and water were used in combination either as a simultaneous exposure or supplied sequentially, In 2 O 3 films were deposited at growth rates of 1.0−1.6 Å/cycle over the full range of deposition temperatures. In situ quadrupole mass spectrometry and quartz crystal microbalance measurements revealed that water serves the function of releasing ligands from the surface while oxygen performs the role of oxidizing the indium. Since both processes are necessary for sustained growth, both O 2 and H 2 O are required for the In 2 O 3 ALD. The electrical resistivity, mobility, and carrier concentration of the In 2 O 3 films varied dramatically with both the deposition temperature and co-reactant sequence and correlated to a crystallization occurring at ∼140 °C observed by X-ray diffraction and scanning electron microscopy. Using this new process we successfully deposited ALD In 2 O 3 films over large area substrates (12 in. × 18 in.) with very high uniformity in thickness and resistivity.