I have a nanochannel with a top and bottom surfaces silicon nitride. I found a note that says "Hydrolysis of stoichiometric silicon nitride to evolve ammonia is known to occur for films exposed to liquid- and vapour-phase water [ Si3N4 + 6H2O->3SiO2 + 4NH3]. But it doesn't say at what condition this would occur. I am wondering whether I need to consider this phenomena for my nanochannel case as well.
Thank you!
Top 1-2 nm of a silicon nitride film will usually be converted in storage to oxide, by hydrolysis (mostly) or by oxidation. Keeping the wafer under dry nitrogen slows the process a lot but it's hard to entirely eliminate it. Unless your film is very fresh you have to assume it has some surface oxide and consider removing it by treatment with dilute HF (0.5% HF for one minute is usually enough).
Emanuel Cooper Thank you so much. I appreciate the recommendation.
I am actually using water and other buffer solutions in the nanochannels, and I wonder after HF surface treatment when I again flow my liquids such as water, would the hydrolysis and/or oxidation occur again? or is HF alter the surface property permanently?
Thank you
HF solution treatment of a silicon surface turns it moderately hydrophobic, because of an Si-H film forming on the surface. See (if you can get access)
A study of the ionic route for hydrogen terminations... DOI: 10.1016/s0169-4332(98)00182-2 (Cerofolini, Applied Surface Science 133, 108 (1998).
This film is not stable in the long run. It will typically be replaced by the usual Si-OH within minutes or hours, depending on the exposure conditions. It may be hard to figure out exactly what happens in your nanochannels, but the next best thing is to examine flat coupons of the same material with the same treatment sequence and see how fast they convert from hydrophobic to hydrophilic by measuring contact angle of water droplets. (The difference is stark enough that a qualitative assessment can actually be done visually, without instrumentation.)
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