| azonenberg | when B0101 comes back tell her yes, i've considered it | 02:00 |
|---|---|---|
| azonenberg | but have not done any experimental work yet | 02:00 |
| Sync | = 03:00:20 < azonenberg> when B0101 comes back tell her yes, i've considered it | 06:44 |
| Sync | = 03:00:24 < azonenberg> but have not done any experimental work yet | 06:44 |
| azonenberg | My reading indicates that the OH- is what etches Si | 06:45 |
| azonenberg | TMAH is simply a less volatile and metal-free OH- source than NH3OH | 06:46 |
| azonenberg | a reflux condenser should reduce evaporation | 06:46 |
| azonenberg | and it's not a contact toxin like TMAH is | 06:46 |
| azonenberg | By the same token ammonia at a suitable concentration should be usable as a photoresist developer | 06:46 |
| Sync | I have to ask about the process we use | 06:52 |
| azonenberg | Most people doing metal-free Si etching and PR developing use TMAH | 07:08 |
| azonenberg | but we're hoping to find something less toxic for amateur use | 07:08 |
| Sync | I'll ask my prof what he'd do | 07:39 |
| drygol | hmm isnt ammonium hydroxide to weak for Si etching ? I mean sodium or potassium hydroxide is waaaay stronger. | 08:12 |
| drygol | hmm i think i could run few tests with it | 08:12 |
| azonenberg | drygol: I would not use ammonia for through-wafer etch, it'd take forever | 08:13 |
| azonenberg | but if you just wanted to put alignment marks in something | 08:14 |
| azonenberg | or use it to develop photoresist | 08:14 |
| azonenberg | it should do the job | 08:14 |
| drygol | oh , got it | 08:14 |
| azonenberg | For a deep etch i'd go with TMAH if you needed to be CMOS compatible | 08:14 |
| azonenberg | and KOH otherwise | 08:14 |
| drygol | i am not an expert , but still ammonium hydroxied is 32% max if i remember correctly , would it be enough ? | 08:15 |
| azonenberg | I don't know what the equivalent OH- concentration is vs KOH | 08:15 |
| drygol | very strong | 08:15 |
| azonenberg | KOH etching at higher concentrations gives smoother surfaces but even 10% (i think it was w/v) gives good results | 08:15 |
| drygol | oooh now i got it | 08:16 |
| azonenberg | if you dont mind some roughness | 08:16 |
| drygol | all the time you are talking about solution of KOH , not melted KOH | 08:16 |
| azonenberg | Read this paper http://www.sciencedirect.com/science/article/pii/S002626920000015X | 08:16 |
| azonenberg | Lol, yes | 08:16 |
| drygol | thx for the link , ill go through it in a minute :) | 08:16 |
| azonenberg | And this is why i am hoping to avoid TMAH if i can http://www.ncbi.nlm.nih.gov/pubmed/20230335 | 08:17 |
| Sync | eww | 08:18 |
| azonenberg | Low-concentration ammonia seems to be somewhat safer especially if used in a hood | 08:19 |
| 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 | 08:19 |
| Sync | my ozone cleaner is pretty hardcore at making my flat oxidize my nostrils | 08:22 |
| azonenberg | I was under the impression that's a bad thing? | 08:26 |
| Sync | yes but it is not too bad | 08:27 |
| Sync | but I was amazed how fast it could produce such lots of ozone | 08:27 |
| Sync | then again ozone is used to desmell public bathrooms in large quantities | 08:28 |
| Sync | so it cannot be all that bad | 08:28 |
| azonenberg | by oxidizing all of the VOCs? | 08:28 |
| Sync | yup | 08:28 |
| azonenberg | interesting | 08:28 |
| Sync | so some people think the smell of ozone is "fresh" | 08:29 |
| azonenberg | I think of it as "left a strong UV source on too long without ventilation" :p | 08:34 |
| Sync | well I have extensive experience with ozone from the teslacoils I built in the past | 08:35 |
| B0101 | Hmm, I wonder if I can ionize all the air in a cleanbox using electrically charged plates and filter all the dust | 08:47 |
| azonenberg | I would just use a HEPA filter | 08:49 |
| azonenberg | but thats me | 08:49 |
| B0101 | If I could remove the dust from the air, I might be able to replicate Czochralski process of growing silicon | 08:50 |
| Action: B0101 thinks that she is crazy... | 08:52 | |
| Sync | I'd use the silane process for small scale Si growing | 09:14 |
| azonenberg | SiH4 isn't the most friendly substance to have around a home lab though | 09:17 |
| azonenberg | i try to avoid pyrophoric materials | 09:18 |
| Sync | better than phosphine | 09:22 |
| Sync | and it is easy to work with | 09:22 |
| lekernel | growing silicon is boring. what about non linear optical crystals? :) | 10:39 |
| Sync | azonenberg: do you have resources on using pmma as a photoresist? | 10:57 |
| Sync | my prof had not heard about that | 10:57 |
| Sync | drygol: it seems that everyone of them works | 10:58 |
| drygol | oh good to know , so it pretty much doesn't matter which hydroxide of mentioned you choose , only concentration matters | 11:01 |
| Sync | well the concentration only speeds things up from what he said | 11:06 |
| Sync | http://i1167.photobucket.com/albums/q625/frontrunners2/SEA1/SEA-824/8_24_2_img0000951A.jpg wow that was some pretty inefficient wafer | 15:34 |
| azonenberg | Sync: actually lower concentrations of OH- are faster up to a point | 16:30 |
| azonenberg | but lead to rougher etches | 16:30 |
| azonenberg | read the paper i linked above | 16:30 |
| azonenberg | and pmma is used as an e-beam resist | 16:31 |
| azonenberg | i have not looked into the details of it | 16:31 |
| Sync | yeah I did at work | 20:16 |
| Sync | it seems to work fine | 20:16 |
| Sync | you can also use deep UV | 20:16 |
| azonenberg | You can use DUV to expose PMMA? Interesting | 23:30 |
| azonenberg | Are we talking like 220nm wavelength or 15nm? | 23:31 |
| --- Thu Nov 15 2012 | 00:00 | |
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