RCA cleaning is for Si wafer but can it be applied also for oxidized Si wafer? I don't want to remove oxides from the wafer. So, what is a better process to clean an oxidized Si wafer?
In RCA process, there are three process. Do the RCA1 and dry the substrates in the fumes of hot propanol.
Hydroflouric acid treatment removes oxygen. But be careful about HF, it is very dangerous acid when diffuses into your skin
You can use degreasing process (Boil your sample in acetone methanol and isopropanol for 10 mins each)
If you want to keep your oxide don't use HF as this removes the oxide layer!
Instead use 2-step RCA cleaning process.
To remove organic material (incl. oils):
- RCA1: NH4OH:H2O2:DI(water) in 1:1:5 ratio on heated plate in suitable beaker
- Rinse for 5 minutes under DI(water).
To remove metal contaminates:
- RCA2: HCl:H2O2:DI(water) in 1:1:10 ratio on heated plate in suitable beaker
- Rinse for 5 minutes under DI(water)
If you also want to remove the oxide, then HF:DI(water) in 1:10 ratio until surface is hydrophobic. This must be done in a non-glass beaker obviously within a fume cupboard, and yes correct protection needs to be worn for dealing with HF as it is EXTREMELY DANGEROUS both in liquid and vapour form.
Cleaning is a very broad term, it all depends on what you want to remove. That said, RCA cleaning is a very general technique that should remove virtually all contaminants. If you follow the steps as described on https://en.wikipedia.org/wiki/RCA_clean, it should in general not be a problem for your oxidized wafers, but it depends a bit on your oxide thickness, because the second step (dilute HF stripping of native oxide) will typically etch a few nm of oxide, depending on the concentration of HF and the immersion time you use. If you don't want that, you can skip that step, but then you will also not remove possible contaminants that might be present in the outer layer of oxide.
Soak the wafer in acetone (warm) for about 10 minutes. Remove the wafer and then soak in methanol for another 5 minutes. Rinse the wafer with deionized water and blow to dry.
never use HF it will remove all oxid . ( you can't control it even with very little amount of diluted HF )
you could rinse like we do:
5min acetone, sonicate (do not let it dry out wiht acetone, keep it wet
5 min rines with water, sonicate
5min IPA sonicate
dry in a clean oven 100 degr. 1 h
I think acetone and alcohol, as has been proposed by many people here, do not remove metal contaminants. So if you want to remove that I think you need more aggressive cleaning.
Also I have to disagree here with P. Bomholt about HF (sorry). 1 wt. % HF aqueous solution at room temperature etches thermal silicon oxide with 3 to 4 nm/min in a very controlled way in our lab, and we even use this for controlled thinning of silcon oxide films that are already only a few tens of nanometres thick.
thanks for you onformstion Pieter, I might use them :-)
but why should there be metal in the oxidized layer ? that was not the question, was it?
That is why I stated in my first answer that 'cleaning' is a very broad term. It all depends on what you want to remove, and that was not specified in the question. So I guess acetone and alcohol are perfect in many cases. However I am used to aggressive cleaning before my wafers go into a furnace, because very small amounts of metallic contaminants would already be catasrophic for the electronic grade silicon devices that are processed in our furnaces.
http://www.bgrchem.com/specifications/A_SPEC_FR_8196.pdf
http://dx.doi.org/10.1109/DTIP.2016.7514895 (first paragraph of section III)
my main point is I don't want my oxide layer to be damaged. using HF etching would definitely damage it. I would rather stick with using just acetone and propanol.
Well I would not call it damage because you remove a very thin layer in a very uniform and controlled way with the dilute HF. But indeed if you do not want that it is probably best to go for acetone and alcohol, or the RCA cleaning without the HF-step.
I wanted to remove the deposited 150 nm Aluminum (after lithography) from my silicon dioxide wafer. I followed the aluminium etch recipe but still there are imprints on the silicon wafer. The silicon dioxide layer thickness is 300 nm. So, HF cleaning will get me a clean and new wafer at the cost of 3-4 nm of oxide layer. But, can piranha cleaning remove the same??
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