As will be clear from many of our posts on this blog(1, 2, 3), area-selective deposition (ASD) is currently an extremely hot research topic. This is mainly because of its potential application in future nanoelectronics as a solution to the challenge of aligning features at the nanoscale.
After our work on direct-write ALD of Pt , area-selective ALD for the synthesis of core-shell nanoparticle , direct-ALD of In2O3 , and our review paper “The use of atomic layer deposition in advanced nanopatterning” , we have recently published a novel approach for area-selective ALD based on inhibitor molecules in three-step ALD cycles. The article “Area-selective atomic layer deposition of SiO2 using acetylacetone as a chemoselective inhibitor in an ABC-type cycle” has just appeared in ACS Nano .
Novel approach for area-selective ALD as published in ACS Nano . It is published as an open access article.
The approach relies on the blocking of precursor adsorption by small inhibitor molecules (e.g. acetylacetone, methanol), and is inspired on previous work by Yanguas-Gil et al. on inhibitor molecules for the synthesis of doped materials . The idea is to dose inhibitor molecules in step A of the cycle that selectively adsorb on those surfaces on which no growth should occur. The adsorbed inhibitor molecules subsequently block the adsorption of precursor molecules when dosed in step B. Finally, in step C, the inhibitor molecules and the precursor ligands are removed by the co-reactant. The three steps together result in area-selective deposition on those materials on which the inhibitor does not adsorb.
The key features of this approach are:
- It is compatible with plasma-assisted (or ozone-based) ALD. We expect that this can significantly extend the set of materials for which area-selective ALD is achievable.
- It yields more freedom as compared to approaches relying on chemoselective adsorption of precursor molecules. We believe it potentially allows for the tailoring of the substrate-selectivity of ALD growth by the selection of the inhibitor molecule.
- The re-application of the inhibitor molecules during every cycle can be beneficial from a reliability point-of-view (instead of relying on self-assembled monolayers that degrade during the deposition).
The method was demonstrated for selective deposition of SiO2 (by a plasma-assisted ALD process!) on several substrate material combinations. Most prominently, we demonstrated area-selective ALD of SiO2 on a patterned Al2O3/GeO2 sample as is shown in the figure below. Note that this process uniquely distinguishes between different oxide starting surfaces.
TOF-SIMS analysis after SiO2 ABC-type ALD on a GeO2 surface with patterned Al2O3. SiO2 was deposited on GeO2 and not on Al2O3.
To be able to clearly explain the concept of the novel area-selective ALD process, we decided to make a stop motion movie based on nanoblocks. We ordered several boxes of nanoblock models and we put three of our talented graduate students at work. It turned out to be a great team-building event and the final result, made together with Ruben Olislagers of the company Design Al Dente (www.designaldente.nl) can be seen below.
The nanoblocks and the graduate students (from left to right) Sander Vlaanderen, Rick Jongen, and Marc Merkx at work with Ruben Olislagers overseeing the result.
The stop-motion movie
The 3th Area Selective Deposition workshop (ASD2018) will be held April 29 – May 1 2018 at NC State University in Raleigh, North Carolina.
 A. J. M. Mackus, S. A. F. Dielissen, J. J. L. Mulders, and W. M. M. Kessels, Nanopatterning by direct-write atomic layer deposition, Nanoscale 4, 4477 (2012),
 M. J. Weber, A. J. M. Mackus, M. A. Verheijen, C. van der Marel, and W. M. M. Kessels, Supported Core/Shell Bimetallic Nanoparticles Synthesis by Atomic Layer Deposition, Chem. Mater. 24, 2973 (2012), DOI: 10.1021/cm301206e
 A. Mameli, Y. Kuang, M. Aghaee, C. K. Ande, B. Karasulu, M. Creatore, A. J. M. Mackus, W. M. M. Kessels, and F. Roozeboom, Area-selective atomic layer deposition of In2O3:H using a µ-plasma printer for local area activation, Chem. Mater. 29, 921 (2017), DOI: 10.1021/acs.chemmater.6b04469
 A. J. M. Mackus, A. A. Bol, and W. M. M. Kessels, The use of atomic layer deposition in advanced nanopatterning, Nanoscale 6, 10941 (2014), DOI:10.1039/C4NR01954G
 A. Mameli, M. J. M. Merkx, B. Karasulu, F. Roozeboom, W. M. M. Kessels, and A. J. M. Mackus, Area-selective atomic layer deposition of SiO2 using acetylacetone as a chemoselective inhibitor in an ABC-type cycle, ACS Nano 11, 9303 (2017), DOI: 10.1021/acsnano.7b04701
 A. Yanguas-Gil, J. A. Libera, and J. W. Elam, Modulation of the growth per cycle in atomic layer deposition using reversible surface functionalization, Chem. Mater. 25, 4849 (2013), DOI: 10.1021/cm4029098