I'm having issues with sputter deposition on thin polymer films. We deposit a small amount of metal to a UV-cured acrylic urethane film (10 um thick) but the metal film shows cracking which is probably due to outgassing.
What would be the best way to prevent the outgassing? Should normal oven with mild temperatures (c.a. 70 C) be enough or is it best to use vacuum oven just before the deposition? Are there any guidelines how long the substrate should be in the oven?
Degassing is very often a problem when sputtering on a polymer. You can indeed try to degass by curing in a normal convention oven or using a vacuum oven. Be aware that wehn you have done this you might still get cracks. There is a huge difference in expansion coefficient between most polymers and metals. During deposition the substrate (polymer) will get hot and will expand, which might lead to cracks of the metal later on. It is important you cool the substrate during sputtering.
It is best to use a vacuum oven before the deposition. Keep the polymer film in high vacuum and heat the substrate or the holder at mild temperatures for some time in the sputter deposition system itself before you deposit the metal.
Thanks Peter and Nikesh,
Peter, how should I cool the substrate? Should I stop the sputtering and let the substrate cool for a few minutes? If I deposit, say 100nm, should the steps be something like 10nm?
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