Topic for #homecmos is now Homebrew CMOS and MEMS foundry design | http://code.google.com/p/homecmos/ | Logs: http://en.qi-hardware.com/homecmos-logs/
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<azonenberg> when B0101 comes back tell her yes, i've considered it
<azonenberg> but have not done any experimental work yet
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<Sync> = 03:00:20 < azonenberg> when B0101 comes back tell her yes, i've considered it
<Sync> = 03:00:24 < azonenberg> but have not done any experimental work yet
<azonenberg> My reading indicates that the OH- is what etches Si
<azonenberg> TMAH is simply a less volatile and metal-free OH- source than NH3OH
<azonenberg> a reflux condenser should reduce evaporation
<azonenberg> and it's not a contact toxin like TMAH is
<azonenberg> By the same token ammonia at a suitable concentration should be usable as a photoresist developer
<Sync> I have to ask about the process we use
<azonenberg> Most people doing metal-free Si etching and PR developing use TMAH
<azonenberg> but we're hoping to find something less toxic for amateur use
<Sync> I'll ask my prof what he'd do
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<drygol> hmm isnt ammonium hydroxide to weak for Si etching ? I mean sodium or potassium hydroxide is waaaay stronger.
<drygol> hmm i think i could run few tests with it
<azonenberg> drygol: I would not use ammonia for through-wafer etch, it'd take forever
<azonenberg> but if you just wanted to put alignment marks in something
<azonenberg> or use it to develop photoresist
<azonenberg> it should do the job
<drygol> oh , got it
<azonenberg> For a deep etch i'd go with TMAH if you needed to be CMOS compatible
<azonenberg> and KOH otherwise
<drygol> i am not an expert , but still ammonium hydroxied is 32% max if i remember correctly , would it be enough ?
<azonenberg> I don't know what the equivalent OH- concentration is vs KOH
<drygol> very strong
<azonenberg> KOH etching at higher concentrations gives smoother surfaces but even 10% (i think it was w/v) gives good results
<drygol> oooh now i got it
<azonenberg> if you dont mind some roughness
<drygol> all the time you are talking about solution of KOH , not melted KOH
<azonenberg> Lol, yes
<drygol> thx for the link , ill go through it in a minute :)
<azonenberg> And this is why i am hoping to avoid TMAH if i can http://www.ncbi.nlm.nih.gov/pubmed/20230335
<Sync> eww
<azonenberg> Low-concentration ammonia seems to be somewhat safer especially if used in a hood
<azonenberg> I mean it's still in the "try not to get it on you" category but not in the "kills you on contact" category :P
<Sync> my ozone cleaner is pretty hardcore at making my flat oxidize my nostrils
<azonenberg> I was under the impression that's a bad thing?
<Sync> yes but it is not too bad
<Sync> but I was amazed how fast it could produce such lots of ozone
<Sync> then again ozone is used to desmell public bathrooms in large quantities
<Sync> so it cannot be all that bad
<azonenberg> by oxidizing all of the VOCs?
<Sync> yup
<azonenberg> interesting
<Sync> so some people think the smell of ozone is "fresh"
<azonenberg> I think of it as "left a strong UV source on too long without ventilation" :p
<Sync> well I have extensive experience with ozone from the teslacoils I built in the past
<B0101> Hmm, I wonder if I can ionize all the air in a cleanbox using electrically charged plates and filter all the dust
<azonenberg> I would just use a HEPA filter
<azonenberg> but thats me
<B0101> If I could remove the dust from the air, I might be able to replicate Czochralski process of growing silicon
* B0101 thinks that she is crazy...
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<Sync> I'd use the silane process for small scale Si growing
<azonenberg> SiH4 isn't the most friendly substance to have around a home lab though
<azonenberg> i try to avoid pyrophoric materials
<Sync> better than phosphine
<Sync> and it is easy to work with
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<lekernel> growing silicon is boring. what about non linear optical crystals? :)
<Sync> azonenberg: do you have resources on using pmma as a photoresist?
<Sync> my prof had not heard about that
<Sync> drygol: it seems that everyone of them works
<drygol> oh good to know , so it pretty much doesn't matter which hydroxide of mentioned you choose , only concentration matters
<Sync> well the concentration only speeds things up from what he said
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<azonenberg> Sync: actually lower concentrations of OH- are faster up to a point
<azonenberg> but lead to rougher etches
<azonenberg> read the paper i linked above
<azonenberg> and pmma is used as an e-beam resist
<azonenberg> i have not looked into the details of it
<Sync> yeah I did at work
<Sync> it seems to work fine
<Sync> you can also use deep UV
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<azonenberg> You can use DUV to expose PMMA? Interesting
<azonenberg> Are we talking like 220nm wavelength or 15nm?