I did the fabrication process in attached figure.
1 - Preparing chromium mask using lift off process of thickness ~60nm on amorphous silicon of height ~300nm.
2 - Perform inductive coupled plasma reactive ion etching using CHF3 chemistry to etch amorphous silicon.
Then, perform 8min, 150W, 75sccm O2 plasma cleaning to remove by-product polymers.
3 - Remove chromium hard mask using chromium etchant, which etch chromium and chromium oxide.
The problem is in problem 2. The by-product polymers cover the profile of silicon pillars and chromium prevent chromium from being etched.
Do you know, how I can remove by-product polymer from chromium surface to be etched?
Thank you
Hi Omar, the etchant is a solution supposed to come from all sides not from the top only so Cr is supposed to be etched. you can simply check that by deposition of Cr on bare Si and etch it without lift off process - just to check that ur etchant solution works-.
However, if the by products are residues of PR you can further get rid of them by dissolving it in acetone.
Hi Mai,
I have tested Cr etchant using Cr blanket film on bare silicon and etch rate is ~100nm/min.
I use long time O2 plasma cleaning, but could not remove the by-product surround Cr mask.
Were you able to solve the problem Omar? What kind of by-product are you referring to? Are they islands-shaped?
Yes, you will not be able to remove it. You need to dip into HF in order to get rid of the layer that is formed over the CR. I do not remember what my recipe was, but something like 30-60 second BOE etch was enough for me, I guess %10 HF. You need to choose a BOE concentration and find the time required. Then the CR etchant will work. Yes, HF will etch quartz too! Good luck.
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