We have a thermal evaporator which can go up to 40V and 300 Amps. The problem we are facing is, tungsten or Tantalum boats that we are using always face overflow, and we run out of material so we can't coat the desired thickness (180 nm sometimes). Putting too much pellets would not help and Al will also over flow in this case. I was thinking boat geometry type might help. Have you guys used any covered boats or really deep boats to avoid overflow? The boat we are using right now has a "deep" pocket (1/4") and over flow still happens with 0.5 gram pellet.
Dear Ehsan,
I strongly suggest you to use 5" tungsten filaments instead of crucible. It will increase the surface area drastically and this most probably will prevent overflow. If you use this kind of filaments you will need to use wire aluminum with high purity.
All the best.
Aluminium is wettable metal, can easily make alloy with tungsten. So we prefer rapid evaporation rather than changing tungsten boat. Evaporate Al immediately after melting by increasing power
I've tried many and the best without any doubt are the intermetallic crucibles. For instance, evc9intspl01
Thank you all.
Ahmet, you mentioned rapid evaporation. Isn't that bad for the device? I thought Al can penetrate through the layers and cause shorting.
Erkan, Can you please let me know the brand of filament and wires you have used?
Rafael, These crucibles looks exactly as what might help. I checked the price and they are expensive. How many times they can be used?
It is not sputtering Al particles do not carry high momentum. I think rapid evaporation will not affect to device property
In our case the crucubles last around ten evaporations. However, you always need to prevent aluminum spills. If that happen the thermal box will be damaged.
Dear Ehsan,
Hope every thing is okay with you and with our colleagues in the discussion.
In order to save aluminum you can keep the wafers nearer to source, then you may not need to use a large quantity of aluminum and normal boat may be sufficient to accommodate the melt. If you have multiple source evaporator you can load them with aluminum too and successively evaporate aluminum from them. Otherwise the last solution to use a customized boat with large and deep well. The boat is made from tungsten sheet.
wish you success
Please use the graphite core ceramic-coated Al boat for a constant rate, and it lasts for a minimum of 40 depositions. You can easily find it on the Angstrom Engineering website.
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