Hi every one
I used the e-beam evaporation technique to deposit a layer of 200 nm of copper. However, after the deposition, many black dots (like the pinholes in SiN layer deposited by PECVD) have appeared. Do you have any idea what the problem would be and how to get rid of it?
Vaccum was 5e-6 mTorr, and the deposition rate was 2.5 A/s.
Many thanks for your suggestions in advance.
Milad Shojaeian are you doing any surface cleaning prior to the Cu? One thing I used to do when depositing metal with evaporation is to add a fresh pellet every time so I know that the metal I'm getting is Cu. You could maybe try to decrease the deposition rate to 1-1.5 A/s to see if that helps.
Valentin Bogatu Adam Weidling
Thank you so much for your suggestion. I was suspicious about the pellets and the crucible we have been using. However, I asked some other colleagues using this device, and interestingly, they have the same problem with any metals they are depositing. We investigated those dots with EDX and I am looking forward to hearing what those dots are. I talked to the specialists of the cleanroom and they suggested a complete cleaning of the chamber, including the sealing tubes, pressure gauges and etc.
If the problem is solved I will inform you.
However, do you have any opinion about which crucible would be more beneficial for Cu evaporation? Tungsten or Graphite?
Thank you very much
Hi Milad,
If you can do some microscopy, you can identify if the dots are Cu2S like Valentin said or if they are actual pinholes. If they are pinholes, it typically means you're depositing too quickly. The easiest fix is depositing more slowly, but, if that isn't an option, you can try heating your substrate or adding an ion source for ion-assisted deposition. For some reason, copper likes to form into big blobs instead of a smooth film unless you add some extra energy or deposit really slowly. If you try to lower the rate, you might also experiment with a lower acceleration voltage on your ebeam to try to reduce the amount of large groups of particles that are evaporated. Lesker recommends graphite or molybdenum for the crucible.
Good luck,
Chuck
Use the graphite crucible, you can have also some atomic layers exfoliated. Look at a metaligraphic microscope, this can tell you imediately many about those black dots on the surface of copper.
Dear Milad Shojaeian ,
The black material related to cupper is cupperoxide.
So I assume that you have residual oxygen molecules in your evaporation chamber which reacts with the cu forming trances of cupperoxide.
Th remedy is to inprove the vacuum and you have to preheat the the crucible before the evaporation phase where the high temperature melting prevails.
Best wishes and happy new year.
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