@article{oh_kim_margavio_parsons_2023, title={Self-Aligned Nanopatterning and Controlled Lateral Growth by Dual-Material Orthogonal Area-Selective Deposition of Poly(3,4-ethylenedioxythiophene) and Tungsten}, volume={35}, ISSN={["1520-5002"]}, url={https://doi.org/10.1021/acs.chemmater.3c00530}, DOI={10.1021/acs.chemmater.3c00530}, abstractNote={Despite recent advances in area-selective deposition (ASD) processes, most studies have focused on single-material ASD. Multi-material ASD processes could provide additional flexibility for fabricating semiconductor devices. In this work, we identify process requirements to sequentially combine two intrinsic ASD processes: (1) poly(3,4-ethylenedioxythiophene) (PEDOT) ASD on SiO2 vs Si–H via oxidative chemical vapor deposition and (2) W ASD on Si–H vs SiO2 via atomic layer deposition. Using ex situ X-ray photoelectron spectroscopy, we show that a preferred orthogonal ASD sequence involves PEDOT ASD on SiO2 vs Si–H, followed by W ASD on Si–H vs PEDOT. We find that the properties of the individual PEDOT and W ASD materials, including resistivity, surface roughness, and growth rate, are affected by the ASD sequence. Furthermore, we successfully demonstrate that orthogonal ASD can be extended to nanoscale starting patterns. The cross-sectional scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy analysis shows that the resulting PEDOT thickness on SiO2 depends on feature geometry and dimension. Finally, we demonstrate the feasibility that the PEDOT layer can control the lateral growth of W onto the non-growth surface.}, number={11}, journal={CHEMISTRY OF MATERIALS}, author={Oh, Hwan and Kim, Jung-Sik and Margavio, Hannah R. M. and Parsons, Gregory N.}, year={2023}, month={May}, pages={4375–4384} }
 @article{kim_oh_parsons_2022, title={Growth behavior and substrate selective deposition of polypyrrole, polythiophene, and polyaniline by oxidative chemical vapor deposition and molecular layer deposition}, volume={40}, ISSN={["1520-8559"]}, url={https://doi.org/10.1116/6.0002036}, DOI={10.1116/6.0002036}, abstractNote={Bottom-up self-aligned area-selective deposition (ASD) plays an important role in patterning of advanced electronic devices. Specifically, ASD of organic materials can be utilized for nucleation inhibitors, sacrificial layers, and air-gap materials for next-generation nanoscale processing. This work introduces fundamental growth behavior of various conjugated polymers including polypyrrole, polythiophene, and polyaniline via oxidative molecular layer deposition and chemical vapor deposition. Effects of process parameters on film properties are described, and ASD behavior of different polymers are quantitatively characterized. These findings expand fundamental understanding of conjugated polymer deposition and provide new perspectives for ASD of organic thin films.}, number={6}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, author={Kim, Jung-Sik and Oh, Hwan and Parsons, Gregory N.}, year={2022}, month={Dec} }
 @article{gu_lee_corkery_miao_kim_yuan_xu_dai_parsons_kevrekidis_et al._2022, title={Modeling of deposit formation in mesoporous substrates via atomic layer deposition: Insights from pore-scale simulation}, volume={9}, ISSN={["1547-5905"]}, url={https://doi.org/10.1002/aic.17889}, DOI={10.1002/aic.17889}, abstractNote={Abstract}, journal={AICHE JOURNAL}, author={Gu, Hao and Lee, Dennis T. and Corkery, Peter and Miao, Yurun and Kim, Jung-Sik and Yuan, Yuchen and Xu, Zhen-liang and Dai, Gance and Parsons, Gregory N. and Kevrekidis, Ioannis G. and et al.}, year={2022}, month={Sep} }
 @article{song_kim_margavio_parsons_2021, title={Multimaterial Self-Aligned Nanopatterning by Simultaneous Adjacent Thin Film Deposition and Etching}, volume={15}, ISSN={["1936-086X"]}, url={https://doi.org/10.1021/acsnano.1c04086}, DOI={10.1021/acsnano.1c04086}, abstractNote={Printed component sizes in electronic circuits are approaching 10 nm, but inherent variability in feature alignment during photolithography poses a fundamental barrier for continued device scaling. Deposition-based self-aligned patterning is being introduced, but nuclei defects remain an overarching problem. This work introduces low-temperature chemically self-aligned film growth via simultaneous thin film deposition and etching in adjacent regions on a nanopatterned surface. During deposition, nucleation defects are avoided in nongrowth regions because deposition reactants are locally consumed via sacrificial etching. For a range of materials and process conditions, thermodynamic modeling confirms that deposition and etching are both energetically favorable. We demonstrate nanoscale patterning of tungsten at 220 °C with simultaneous etching of TiO2. Area selective deposition (ASD) of the sacrificial TiO2 layer produces an orthogonal sequence for self-aligned patterning of two materials on one starting pattern, i.e., TiO2 ASD on SiO2 followed by W ASD on Si-H. Experiments also show capacity for self-aligned dielectric patterning via favorable deposition of AlF3 on Al2O3 at 240 °C with simultaneous atomic layer etching of sacrificial ZnO. Simultaneous deposition and etching provides opportunities for low-temperature bottom-up self-aligned patterning for electronic and other nanoscale systems.}, number={7}, journal={ACS NANO}, publisher={American Chemical Society (ACS)}, author={Song, Seung Keun and Kim, Jung-Sik and Margavio, Hannah R. M. and Parsons, Gregory N.}, year={2021}, month={Jul}, pages={12276–12285} }
 @article{kim_parsons_2021, title={Nanopatterned Area-Selective Vapor Deposition of PEDOT on SiO2 vs Si-H: Improved Selectivity Using Chemical Vapor Deposition vs Molecular Layer Deposition}, volume={33}, ISSN={["1520-5002"]}, url={https://doi.org/10.1021/acs.chemmater.1c02842}, DOI={10.1021/acs.chemmater.1c02842}, abstractNote={Area-selective deposition (ASD) of polymers is expected to be useful for self-aligned patterning of nucleation inhibitors, sacrificial layers, and air-gap materials during future bottom-up nanoscale materials fabrication. This work describes a simple, rapid, and effective method to achieve inherent ASD of poly(3,4-ethylenedioxythiophene) (PEDOT) on SiO2 vs hydrogen-terminated silicon (Si-H) substrates via molecular layer deposition (MLD) and chemical vapor deposition (CVD) using 3,4-ethylenedioxythiophene (EDOT) as a reactive monomer and SbCl5 as an oxidant for polymerization. Film thickness measured by spectroscopic ellipsometry indicates the MLD process can obtain ∼35 nm of deposition with a selectivity of 90%, i.e., tS=0.90 ≈ 35 nm, which is better than many other reports of inorganic or organic material ASD. Furthermore, we show that under CVD conditions, the selectivity is further improved, i.e., tS=0.90 ≈ 55.4 nm and that CVD can achieve ASD at an overall rate more than 100 times faster than MLD for the same ASD thickness, allowing 30 nm of ASD to be achieved in less than 10 s of process time. The selective growth of PEDOT on SiO2 vs Si-H is ascribed to the localized reduction of the SbCl5 on the Si-H surface, thereby inhibiting EDOT polymerization in that region. The high selectivity allows us to observe and analyze lateral "mushroom" overgrowth and compare ASD growth rates on blanket vs patterned wafers. Overall, results suggest that CVD may have distinct advantages over MLD or atomic layer deposition (ALD) for other ASD applications.}, number={23}, journal={CHEMISTRY OF MATERIALS}, publisher={American Chemical Society (ACS)}, author={Kim, Jung-Sik and Parsons, Gregory N.}, year={2021}, month={Dec}, pages={9221–9230} }
 @article{volk_kim_jamir_dickey_parsons_2021, title={Oxidative molecular layer deposition of PEDOT using volatile antimony(V) chloride oxidant}, volume={39}, ISSN={["1520-8559"]}, url={https://doi.org/10.1116/6.0000791}, DOI={10.1116/6.0000791}, abstractNote={Molecular layer deposition and chemical vapor deposition are emerging and promising techniques for the incorporation of high-performance conductive polymers into high surface area devices, such as sintered tantalum anodes for electrolytic capacitors. Until recently, vapor-phase synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) has relied on solid reactants which require relatively high temperatures and complex dosing schemes for sequential layer-by-layer processes. This work introduces a facile and high-performing layer-by-layer oxidative molecular layer deposition (oMLD) scheme using the volatile liquid oxidant antimony(V) chloride (SbCl5) to deposit PEDOT thin films. Effects of reactor parameters on PEDOT film characteristics are described, and the necessary foundation for future studies aiming to understand the nucleation and growth of layer-by-layer oMLD PEDOT is detailed.}, number={3}, journal={JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A}, publisher={American Vacuum Society}, author={Volk, Amanda A. and Kim, Jung-Sik and Jamir, Jovenal and Dickey, Elizabeth C. and Parsons, Gregory N.}, year={2021}, month={May} }
 @article{saare_song_kim_parsons_2020, title={Effect of reactant dosing on selectivity during area-selective deposition of TiO2 via integrated atomic layer deposition and atomic layer etching}, volume={128}, ISSN={["1089-7550"]}, url={https://doi.org/10.1063/5.0013552}, DOI={10.1063/5.0013552}, abstractNote={A key hallmark of atomic layer deposition (ALD) is that it proceeds via self-limiting reactions. For a good ALD process, long reactant exposure times beyond that required for saturation on planar substrates can be useful, for example, to achieve conformal growth on high aspect ratio nanoscale trenches, while maintaining consistent deposition across large-area surfaces. Area-selective deposition (ASD) is becoming an enabling process for nanoscale pattern modification on advanced nanoelectronic devices. Herein, we demonstrate that during area-selective ALD, achieved by direct coupling of ALD and thermal atomic layer etching (ALE), excess reactant exposure can have a substantially detrimental influence on the extent of selectivity. As an example system, we study ASD of TiO2 on hydroxylated SiO2 (Si–OH) vs hydrogen-terminated (100) Si (Si–H) using TiCl4/H2O for ALD and WF6/BCl3 for ALE. Using in situ spectroscopic ellipsometry and ex situ x-ray photoelectron spectroscopy, we show that unwanted nucleation can be minimized by limiting the water exposure during the ALD steps. Longer exposures markedly increased the rate of nucleation and growth on the desired non-growth region, thereby degrading selectivity. Specifically, transmission electron microscopy analysis demonstrated that near-saturated H2O doses enabled 32.7 nm thick TiO2 patterns at selectivity threshold S > 0.9 on patterned Si/SiO2 substrates. The correlation between selectivity and reactant exposure serves to increase fundamental insights into the effects of sub-saturated self-limiting surface reactions on the quality and effectiveness of ASD processes and methods.}, number={10}, journal={JOURNAL OF APPLIED PHYSICS}, author={Saare, Holger and Song, Seung Keun and Kim, Jung-Sik and Parsons, Gregory N.}, year={2020}, month={Sep} }