Effects of Al Precursors on Deposition Selectivity of Atomic Layer Deposition of Al₂O₃ Using Ethanethiol Inhibitor

Abstract

Area-selective atomic layer deposition (AS-ALD) is a promising bottom-up patterning approach for fabricating conformal thin films. One of the current challenges with respect to AS-ALD is the deficiency of the surface inhibitor used for fabricating nanoscale three-dimensional structures. In this study, a vapor-deliverable small inhibitor called ethanethiol (ET) that thermally adsorbs on surfaces was used for the AS-ALD of Al2O3. The inhibitor selectively adsorbed on Co and Cu substrates but not on the SiO2 substrate, allowing for the selective deactivation of Co and Cu substrates in Al2O3 ALD. The use of dimethylaluminum isopropoxide (DMAI) as the Al precursor resulted in better inhibition than the use of trimethylaluminum (TMA). Various experimental and theoretical methods, including water contact angle measurements, spectroscopic ellipsometry, X-ray photoelectron spectroscopy, density functional theory calculations, and Monte Carlo simulations, were used to elucidate the process of AS-ALD using ET. Dimerization of the DMAI precursor is considered to be a governing factor for its high deposition selectivity, while the probability of this phenomenon is very low for the TMA precursor. The current study provides insight into the selectivity of AS-ALD from the perspective of the chemical reaction and an opportunity to improve selectivity via precursor selection.

Role of Precursor Choice on Area-Selective Atomic Layer Deposition

“…The calculated value for Al(CH 3 ) 3 (76.8 kJ/mol) is similar to those of previously reported dimer dissociation energies (76.5−84.5 kJ/mol) for this species. 56,57 Compared to that of Al(C y H 2y+1 ) 3 , the dissociations of the AlCl 3 and Al(CH 3 ) 2 Cl precursors are less favorable, which is attributed to a strong Lewis acid−base interaction of the Al center and the Cl ligand in the Cl-containing precursors. Additionally, Al(C 2 H 5 ) 3 shows a similarly favorable dissociation energy to Al(CH 3 ) 3 , indicative that the strength of the dimer is related to the stability of the Al−X−Al bond (X = Cl for AlCl 3 and Al(CH 3 ) 2 Cl or C for Al(CH 3 ) 3 and Al(C 2 H 5 ) 3 ).…”

Atomic Layer Modulation of Multicomponent Thin Films through Combination of Experimental and Theoretical Approaches

“…The adsorption ratios of both precursors were simulated using a modified algorithm , running on simulation program “R” (version 3.6.1; GUI 1.70; El Capitan build 7684). The SiO 2 substrate was simulated as a single crystalline surface showing a 6-fold ring matrix.…”

Relation between Reactive Surface Sites and Precursor Choice for Area-Selective Atomic Layer Deposition Using Small Molecule Inhibitors

“… 31 In addition, Kim et al reported area-selective Al 2 O 3 ALD on SiO 2 exploiting the selective adsorption of ethanethiol on Co and Cu. 32 Studies by Khan et al and Soethoudt et al have also shown that ALD precursors with inherent selectivity for precursor adsorption can be employed as SMI to achieve area-selective ALD. 36 , 37 …”