Can anyone tell me whether the dry etching (ICP plasma ) can damage the CVD graphene which is buried under the uniform 25 nm Al2O3 layer? Can the plasma penetrate into the graphene covered by 25 nm Al2O3 and damage the graphene?
Hi. I have done this and I did not find any effect in Raman as well as in electrical transport. But if the sample has some resist hanging around and plasma power is such high that it affects on the resist then you may find some shift in the Raman peaks or Dirac point. Other than this there will not be any physical damage to graphene.
Hi Abhay,
Thanks for your kind response. Let me express myself clearly about my problem. When I said, damage, I wanted to mean the graphene quality is degraded which could be verified by the Raman D peak. Attached please find the measured spectra.
Please note that the gas I use is CHF3 and ICP power 700 W during the dry etching.
I would appreciate very much if you would have more comments on it.
I see. I want to know few more things.
1. How you deposit Al2O3? Is it ALD water or plasma process and at what temperature?
2. Did you use seed layer before deposition?
3. Does the top Raman spectra measured after depositing the oxide or after?
4. Any RF power is used?
As per my experience, 700W ICP and 150W RF are very high for graphene even if the process will be carried out at 1C. Also there is a also a finite probability of local deformations generated during ALD oxide growth. Recently I learned that these processes will not affect on graphene if it is capped with h-BN.
Thanks, Abhay.
Let me answer your questions:
1. ALD thermal process using water and TMA precursors at 200C
2. Yes, I used 5 nm Al layer on top of graphene prior to depositing Al2O3 layer
3. After every single step I performed, I measured the Raman spectrum to confirm that there is no damage/degradattion. On after the dry etching I observed a strong D band peak.
4. ICP power = 700 W and RIE power = 100 W.
Also there is a also a finite probability of local deformations generated during ALD oxide growth.
---But it is very less likely because I measured the Raman spectrum after Al2O3 deposition and I did not observe any degradation.
As per my experience, 700W ICP and 150W RF are very high for graphene even if the process will be carried out at 1C.
---Perhaps this is the case. What do you think?
Ok. Then the damage due to ALD oxide growth is definitely discarded. The only cause left is the plasma process. Try to do your process at lower powers and longer time. like use 450W ICP and
Hello,
Shamsul, what did you use as mask for etching process? Did you etch Al2O3?
Abhay, which gases did you use for etching Al2O3?
I have issues with plasma etching too. Then, I cover graphene devices with Al2O3(80 nm with 2nm seed layer). I etched Al2O3(80nm) and SiO2 (285 nm) by Cl2, BCl3 and O2, C4F8 for back gate. After, very large gate leakage currents were observed. I use thick photoresist (3um) as mask. I don't understand why large gate leakage is observed. Can anyone suggest the reason and how can I solve this issue?
Thank you,
Salamat
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