| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Tuesday Sessions |
| Session TF-TuM |
| Session: | Advanced CVD and ALD Processing, ALD Manufacturing and Spatial-ALD |
| Presenter: | Daniel Higgs, University of Colorado Boulder |
| Authors: | J. Higgs, University of Colorado Boulder S.M. George, University of Colorado at Boulder |
| Correspondent: | Click to Email |
Molecular layer deposition (MLD) is usually restricted by the low vapor pressure of the organic reactants. This low vapor pressure could be especially problematic during spatial MLD when rapid substrate speeds limit the reactant exposure times. To address this problem, we have developed a new spatial MLD reactor. The new spatial MLD reactor is based on a rotating cylinder inside an outer fixed cylinder with dosing, pumping and purging modules. In addition, the spatial MLD reactor and the reactants are both located in an isothermal environment using a custom oven. This isothermal environment avoids any possible cold spots in the apparatus.
We have used the new spatial MLD reactor to deposit a polyamide network polymer on a metalized PET polymer substrate. The polyamide network polymer is derived from trimesoylchloride and m-phenylenediamine. This polyamide network polymer has application as a reverse osmosis membrane for desalination. We observed polyamide MLD growth rate of 4.5 Å/cycle at 115°C. The rotating cylinder can be rotated at up to 200 RPM and achieves substrate speeds up to 3 m/s. This reactor can produce growth rates of up to 14 Å/s. The growth of the polyamide MLD film is linear with number of MLD cycles. We could routinely grow polyamide MLD films with thicknesses of 4000 Å in 5 minutes. Polyamide MLD film growth was confirmed using transmission Fourier transform infrared spectroscopy (FTIR) and microRaman spectroscopy.
In addition to the desalination membrane application, these polyamide network polymer films will be useful for flexible gas diffusion barriers. One major difficulty for ALD gas diffusion barriers on polymers is the presence of particles on the initial polymer substrate. These particles mask the polymer surface during ALD and then “fall off” leaving behind pin-hole defects in the ALD film. One solution is to bury all the particles in a thick MLD film and then perform ALD on the surface of the MLD film. We have recently coated a PEN polymer substrate with a MLD polyamide film with a thickness of ~1 µm. After deposition of a 50 nm Al2O3 ALD gas diffusion barrier film, the number of pin-hole defects in the Al2O3 gas diffusion barrier film reduced by an order of magnitude.