| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF-TuM |
| Session: | Advanced CVD and ALD Processing, ALD Manufacturing and Spatial-ALD |
| Presenter: | Gregory Parsons, North Carolina State University |
| Authors: | G.N. Parsons, North Carolina State University A.H. Brozena, North Carolina State University C.J. Oldham, North Carolina State University |
| Correspondent: | Click to Email |
Although there are few thin film deposition methods which can coat complex substrates, such as fibers and membranes, with as high a degree of conformality as atomic layer deposition (ALD), slow growth rates and other scaling limitations have prevented the industrial application of ALD to these materials.
To increase the speed of thin film deposition, researchers have developed spatial ALD as way to scale up traditional ALD systems. By flowing reactants continuously through alternating channels and moving the substrate beneath these reactant flows, thin films can be deposited at rapid speed. However, current spatial ALD systems are designed for solid or solid-backed substrates, such as silicon wafers. The technique has not yet been demonstrated on porous or fibrous substrates, such as woven or non-woven textiles.
To achieve rapid spatial ALD growth on these kinds of porous materials, we modeled and built a flow-through spatial ALD reactor for roll-to-roll deposition of Al2O3, using non-woven polypropylene fabric as the test substrate. The tool is operated under open atmospheric conditions and does not use expensive vacuum equipment. The reactor’s shower-head design utilizes alternating gas-flows of nitrogen, trimethyl aluminum, and water to produce three complete ALD cycles for a single traversal of the substrate. More ALD cycles can be additively deposited with increasing passes of the substrate. The gases flow through the material and are vented away using a slight negative pressure generated by facility exhaust. With this prototype flow-through spatial ALD reactor, we study how gas flow rates, fabric porosity, and web speed affect self-limiting ALD growth. By monitoring changes to the surface energy of the polypropylene using water contact angle and comparing the spatial ALD coated materials to batch-coated samples, we learn what conditions are necessary to achieve high-throughput, roll-to-roll ALD coatings on porous samples.