Surface Acidity-Induced Inherently Selective Atomic Layer Deposition of Tantalum Oxide on Dielectrics

Abstract

Selective deposition shows a great perspective for the downscaling of nanoelectronics. In this work, inherently selective atomic layer deposition (ALD) of tantalum oxide was studied on a series of oxide substrates. The Ta2O5 films linearly grow on acidic oxides of MnO2, SiO2, and Ta2O5, while there are long nucleation delays on basic oxides such as Al2O3 and HfO2. The inherent selectivity is induced through acidity differences which influence the reaction path, and the H-transfer reaction is a key factor. The Ta­(OEt)5 precursor with alkaline ligands tends to chemically adsorb on acidic SiO2 surfaces through H-transfer reaction between surface hydroxyls and precursor molecules. Through H-transfer reaction, the ligands of the Ta­(OEt)5 precursor are dissociated into ethanol molecules and the remaining intermediates are strongly chemisorbed on the surface, initiating the following nucleation. However, it is hard to nucleate on basic Al2O3 and HfO2 substrates because the H-transfer reaction is blocked. Moreover, robust selectivity only exists within the ALD temperature window, which highlights that tuning deposition temperature is also an effective way to amplify selectivity. The obstruction of H-transfer reaction on basic oxides provides a new strategy for inherently selective ALD, which will expand the selective toolbox of nanofabrication for next-generation nanoelectronic applications.

Self-aligned patterning of tantalum oxide on Cu/SiO2 through redox-coupled inherently selective atomic layer deposition

“…5 and 6 ), indicating that smooth film was obtained. For the ABC-type ALD, it was found that the growth rate of Ta 2 O 5 on Al 2 O 3 and HfO 2 was lower than that on SiO 2 , which confirmed the occurrence of previously reported surface acidity-induced selective deposition 55 . A total of 10 s purge time was sufficient to remove excess precursors and by-products.…”

Substrate-Dependent Area-Selective Atomic Layer Deposition of Noble Metals from Metal β-Diketonate Precursors

“…Hacac exhibits primarily acidic characteristics and therefore preferentially bonds with more basic surfaces, such as Al 2 O 3 , ZrO 2 , and HfO 2 , rather than the acidic SiO 2 . According to the literature, 25,45,46 copper oxides have comparable or even lower surface acidity values than the above-mentioned metal oxides, and native oxide covered Cu is therefore expected to bond strongly with Hacac. The adsorbed molecules passivate the substrate surfaces and thereby prevent the ALD growth, which is proposed to be a mechanism for the current observation of selective growth of Ir on native SiO 2 over Cu.…”

Selection Criteria for Small-Molecule Inhibitors in Area-Selective Atomic Layer Deposition: Fundamental Surface Chemistry Considerations

“…A similar approach can be taken in matching the SMI with a specific substrate, as was illustrated by Li et al in evaluating tantalum oxide deposition on acidic (MnO 2 , SiO 2 , Ta 2 O 5 ) and basic (Al 2 O 3 and HfO 2 ) oxide surfaces. 54 Nevertheless, for any series of chemically similar or homologously different substituents in SMIs, the role of steric effects clearly offers a great handle for using bulkier precursors to improve the selectivity, provided that changing the precursor does not affect all of the other constraints.…”

“…Thus, a different measure has to be involved to evaluate the role of electronic factors, as is summarized in the same Figure in panels B and D using the charge of surface hydrogen atom to be transferred to an amino group in the attachment reaction or a measure of surface acidity/basicity. A similar approach can be taken in matching the SMI with a specific substrate, as was illustrated by Li et al in evaluating tantalum oxide deposition on acidic (MnO 2 , SiO 2 , Ta 2 O 5 ) and basic (Al 2 O 3 and HfO 2 ) oxide surfaces …”