Area-Selective Atmospheric-Pressure Spatial ALD of SiO2 Using Interleaved Back-Etch Steps Yielding Selectivity > 10 Nanometer

Abstract

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. ----------------------------------------------------------------------------------------------------------------------------------------------------------------