Area-Selective Atmospheric-Pressure Spatial ALD of SiO2 Using Interleaved Back-Etch Steps Yielding Selectivity > 10 Nanometer
Authors: Mameli Alfredo , Roozeboom Fred , Poodt Paul 
Published: February 2020

Area-selective atomic layer deposition (AS-ALD) has great potential in reducing cost by maskless device manufacturing of patterned layers. Still, in this new bottom-up approach the selectivities currently obtained for film growth on patterned growth areas vs. that on the non-growth areas are often very limited. Also the substrate throughput values for conventional low-pressure ALD is too low for industrial acceptance (1,2). In this work we present a process for AS-ALD of SiO2 using intermittent plasma etch-back steps to increase the selectivity above 10 nm film thickness (3). In addition, the deposition process itself is performed in a spatial ALD reactor at atmospheric pressure which allows for achieving high throughput (4).
AS-ALD of SiO2 on a substrate with pre-patterned SiO2 and ZnO areas was demonstrated using a chemo-selective inhibitor that chemisorbs preferentially on the non-growth area (ZnO) while allowing the deposition of SiO2 on the growth area (SiO2). In order to maximize the process selectivity, a blanket fluorocarbon plasma etch-back step was interleaved after every 110 ALD cycles. This way, selective SiO2 deposition up to ~ 30 nm film thickness was demonstrated (Fig. 1). Furthermore, X-ray Photoelectron Spectroscopy was carried out to verify the selectivity of the process: no Si was detected (detection limit 0.3 at. %) on the non-growth area, demonstrating the high selectivity of the process.
The process presented here combines selective inhibitor chemisorption, plasma-based spatial ALD with high deposition rates and plasma etch-back steps to correct for selectivity loss. This approach is compatible with roll-to-roll and sheet-to-sheet concepts and can therefore enable high-throughput AS-ALD on large-area and flexible substrates.
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References

1. 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, 9303-9311 (2017).
2. F. S. Minaye Hashemi, C. Prasittichai and S. F. Bent, ‘Self-Correcting Process for High Quality Patterning by Atomic Layer Deposition’, ACS Nano, 9, 8710-8717 (2015).
3. R. Vallat, R. Gassilloud, B. Eychenne and C. Vallée, ‘Selective deposition of Ta2O5 by adding
plasma etching super-cycles in plasma-enhanced atomic layer deposition steps’, J. Vac. Sc. Technol. A, 35, 01B104 (2017).
4. P. Poodt, A. Lankhorst, F. Roozeboom, C. Spee, D. Maas and A. Vermeer, ‘High-speed atomic layer deposition of aluminum oxide layers for solar cell passivation’, Adv. Mater., 22, 3564-3567 (2010).
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*Presenting author: F. Roozeboom (f.roozeboom@tue.nl ; fred.roozeboom@tno.nl)

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Figure 1