I'm going to make an aluminum hole array with a 100nm scale. The thickness of aluminum is 150nm and I'm trying to dry-etch aluminum with a thickness of 150nm using ZEP520A mask which is a positive electron beam resist. After spin coating of ZEP520A with a thickness of 500nm on Al 150nm and masking a mask through electron beam exposure patterning, dry etching is performed using Cl2, BCl3 gas. Several attempts were made, but holes were created in some places, and holes were not created in some places, so the hole array was not created uniformly. I think the ZEP520A mask can not act as a mask because of the gas used in the etching process, for example, reaction with gases in etching process. Is there anyone who can advise? Thank you.
Hi Sir,
you do not give too many details, so the solution relies on your further work. The gas mixture should be capable to etch aluminium incl. its usual native oxide on top. Since there is no sidewall protection in the gas mixture, you must hope that the decomposition products of the resist are helping to get a good etch profile
If I understand you rightly, the etch result is locally inhomogeneous such that you are obtaining only some percentage of the number of desired holes.
Are you sure that the resist did not flow into the non-holes?
Are you sure that the Al is of consistent quality?
Do the non-holes correspond with very large resist areas nearby?
If so, you may have a local loading effect in that abundant resist is eatin up the etchant species.
Heinrich
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