AVS 59th Annual International Symposium and Exhibition
    Thin Film Wednesday Sessions
       Session TF-WeM

Paper TF-WeM1
Optimizing a Spatial Atomic Layer Deposition Cell for High Throughput, Low Temperature, Roll-to-Roll Applications

Wednesday, October 31, 2012, 8:00 am, Room 10

Session: Thin Films for Encapsulation, Packaging, and Biomedical Devices
Presenter: M.J. Dalberth, Cambridge Nanotech, Inc.
Authors: M.J. Dalberth, Cambridge Nanotech, Inc.
L. Lecordier, Cambridge Nanotech, Inc.
M.J. Sershen, Cambridge Nanotech, Inc.
M. Ruffo, Cambridge Nanotech, Inc.
R. Coutu, Cambridge Nanotech, Inc.
G. Sundaram, Cambridge Nanotech, Inc.
J.S. Becker, Cambridge Nanotech, Inc.
Correspondent: Click to Email
Atomic layer deposition (ALD) has established itself as a technique capable of producing uniform, dense, pin-hole free films with extremely fine thickness control. The surface reactions involved in many ALD processes are thermally active at temperatures less than 200˚C which makes it attractive for emerging applications coating substrates with a limited thermal budget- for example, a barrier layer for organic photovoltaics on a flexible substrate. Many of these applications demand high throughput, however, and traditional ALD is too slow due to its temporally spaced pulses of reactant A and reactant B, and its need for a vacuum system requiring time consuming evacuation. Spatial ALD replaces the temporal separation of reactants with their spatial separation by confining them to separate gas channels in a deposition cell. Plus, it’s a process that takes place at atmospheric pressure and can eliminate system evacuation times. In spatial ALD, the substrate and cell move relative to one another, and the number of A/B channels determines the thickness of material deposited. At speeds of 10m/min or more, equivalent throughput of 2000-4000 wafers can potentially be achieved with equivalent cycle time << 0.1s/Å. As of today, Cambridge Nanotech has implemented two 150 mm x 150 mm cells based on two and six-cycle designs. 150mm Si wafer and PEN/PET substrates were processed using TMA and water at atmospheric pressure, 100-120˚C, 10m/min speed and 0.1-0.5 mm gap size between cell and substrate. The impact of key process metrics on process performance such as GPC or uniformity was evaluated, including reactant dosage, temperature or stage velocity. Not surprisingly, the ability to maintain the spatial confinement of TMA and water in order to limit parasitic CVD-like reactions (which induces higher GPC and particle formation) is shown to be critically dependent on gap size and flow rate for the inert gas barriers. Data showing the impact of different cell designs (e.g., orifice distribution and size) on wafer- and process-scale metrics will also be discussed. While development on new cells is continuing, the data taken so far support the outlook that spatial ALD could be a key technology for rapid deposition of functional layers in high throughput applications.