We recently had an issue where molecules with melting point ~300C were accidentally annealed at high temperature for a long time in a UHV chamber and now the chamber seems to be covered with the molecules. The chamber with base pressure in low 10^-10 to high 10^-11 was in pressure on the order of 10^-8 torr due to the sublimated molecules for a couple of hours. The whole chamber has the color of that molecular powder. We tried baking the chamber ~150C for about a week, but that didn't get rid of the molecules and the chamber is of the same color as before the bake.
What's the best solution to getting rid of these deposited molecules? This is a huge concern as we are worried that these might cause contamination issues.
This seems very problematic. I gues you cannot bake it at higher temperture.
Another way is to use plasma inside the chamber. Install some magnetron and start the plasma arc in whole volume of chamber. Plasma can clean it.
Be ceraful and good luck
Maybe you can try to insert hot gas, such as nitrogen. In this case you don't have to heat up the whole system but the surface inside could reach a temperature high enough to get rid of the molecules.
Well, if the etching solutions of my preposters don't work, you'll have to swallow the bitterest pill of them all, disassemble your chamber and use metal polish or a sandblaster on it. That's nasty, but sometimes it happens.
Derek Oh
It seems like, while 150°C is not good enough and if the higher temperature is not possible of baking. You can try to introduce some reactive gas, that can be pumped through ions pumps and turbos, such as low concentration H2 i order to form water and remove it sequential steps of gas exposure and bake out.
What is the contamination anyway ?
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