[labnetwork] Advice on mitigating spitting during indium thermal evaporation

[Joseph E. Palmer]

Hello all,

I’m reaching out for advice on mitigating spitting during thermal 
evaporation of indium.

We are evaporating In from a resistively heated crucible setup (Mo 
crucible with a surrounding resistive heater), targeting deposition 
rates of ~30 Å/s for bump-bonding applications. Our typical run pressure 
is ~1×10⁻⁵ Torr.

We perform a pre-melt with a slow ramp, but are still seeing 
intermittent spitting during deposition, leading to particulates and 
film defects.

At this point, I’m trying to better understand the dominant mechanism 
(e.g., oxide skin rupture, trapped gas, or localized overheating) and 
what process changes are most effective in suppressing it.

If anyone has experience with indium evaporation and would be willing to 
share insights or discuss offline, I would greatly appreciate it.

Thank you in advance,

-- 
Joseph E. Palmer
Chief of Operations for the MNFC
PMI, Princeton University
Contact:
Office: 609-258-4706
Cell: 609-731-8962