I'm trying to deposit aluminum from a boron nitride crucible using an Ebeam evaporator at a pressure of ~5e-6 torr. When the metal melts, it starts boiling and bursts out globules of molten metal inside the chamber in all directions. How can I avoid this problem?
The problem might be that there is air in the form of gas bubble trapped in the Al. First slowly heat and degas the Al. You must heat the Al very slowly to the melting point. This is especially when you fill the crucible for the first time with Al pieces. After this, slow heating of Al bottom is preferred.
Thats possible, but the metal is already in a molten and solidified state. We did evaporate very slowly, still had that problem.
- Yes aluminum tends to splash and climb a lot.
- Try soaking the source for sometime before evaporating them.
- Use beam rastering
Thanks for the answers.
We have tried all the above mentioned techniques, but still facing the same problem.
@Singh: We used a spiral beam. Is there any specific pattern that will help?
I had the same problem when evaporating calcium aluminate and calcium alumino-ferrite. Couldn't find a solution...
Using very low current helped to minimize the bursts but the film formed doesn't have aluminium...
@Ramesh
I used a circular (expanding) beam sweep pattern, controlling the gain of the pattern is useful provided you can see the beam. Are you using any deposition rate controller - like a PID controlled QCM? Preconditioning with sufficient soaking and beam sweep using both visual observation and deposition rate (from QCM) work just fine.
Check the purity of Aluminium material. The contaminants can have their effect on material outgasing.
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