#homecmos IRC log for Wednesday, 2012-11-14

azonenbergwhen B0101 comes back tell her yes, i've considered it02:00
azonenbergbut have not done any experimental work yet02:00
Sync= 03:00:20 < azonenberg> when B0101 comes back tell her yes, i've considered it06:44
Sync= 03:00:24 < azonenberg> but have not done any experimental work yet06:44
azonenbergMy reading indicates that the OH- is what etches Si06:45
azonenbergTMAH is simply a less volatile and metal-free OH- source than NH3OH06:46
azonenberga reflux condenser should reduce evaporation06:46
azonenbergand it's not a contact toxin like TMAH is06:46
azonenbergBy the same token ammonia at a suitable concentration should be usable as a photoresist developer06:46
SyncI have to ask about the process we use06:52
azonenbergMost people doing metal-free Si etching and PR developing use TMAH07:08
azonenbergbut we're hoping to find something less toxic for amateur use07:08
SyncI'll ask my prof what he'd do07:39
drygolhmm isnt ammonium hydroxide to weak for Si etching ? I mean sodium or potassium hydroxide is waaaay stronger.08:12
drygolhmm i think i could run few tests with it08:12
azonenbergdrygol: I would not use ammonia for through-wafer etch, it'd take forever08:13
azonenbergbut if you just wanted to put alignment marks in something08:14
azonenbergor use it to develop photoresist08:14
azonenbergit should do the job08:14
drygoloh , got it08:14
azonenbergFor a deep etch i'd go with TMAH if you needed to be CMOS compatible08:14
azonenbergand KOH otherwise08:14
drygoli am not an expert , but still ammonium hydroxied is 32% max if i remember correctly , would it be enough ?08:15
azonenbergI don't know what the equivalent OH- concentration is vs KOH08:15
drygolvery strong08:15
azonenbergKOH etching at higher concentrations gives smoother surfaces but even 10% (i think it was w/v) gives good results08:15
drygoloooh now i got it08:16
azonenbergif you dont mind some roughness08:16
drygolall the time you are talking about solution of KOH , not melted KOH08:16
azonenbergRead this paper http://www.sciencedirect.com/science/article/pii/S002626920000015X08:16
azonenbergLol, yes08:16
drygolthx for the link , ill go through it in a minute :)08:16
azonenbergAnd this is why i am hoping to avoid TMAH if i can http://www.ncbi.nlm.nih.gov/pubmed/2023033508:17
azonenbergLow-concentration ammonia seems to be somewhat safer especially if used in a hood08:19
azonenbergI mean it's still in the "try not to get it on you" category but not in the "kills you on contact" category :P08:19
Syncmy ozone cleaner is pretty hardcore at making my flat oxidize my nostrils08:22
azonenbergI was under the impression that's a bad thing?08:26
Syncyes but it is not too bad08:27
Syncbut I was amazed how fast it could produce such lots of ozone08:27
Syncthen again ozone is used to desmell public bathrooms in large quantities08:28
Syncso it cannot be all that bad08:28
azonenbergby oxidizing all of the VOCs?08:28
Syncso some people think the smell of ozone is "fresh"08:29
azonenbergI think of it as "left a strong UV source on too long without ventilation" :p08:34
Syncwell I have extensive experience with ozone from the teslacoils I built in the past08:35
B0101Hmm, I wonder if I can ionize all the air in a cleanbox using electrically charged plates and filter all the dust08:47
azonenbergI would just use a HEPA filter08:49
azonenbergbut thats me08:49
B0101If I could remove the dust from the air, I might be able to replicate Czochralski process of growing silicon08:50
Action: B0101 thinks that she is crazy...08:52
SyncI'd use the silane process for small scale Si growing09:14
azonenbergSiH4 isn't the most friendly substance to have around a home lab though09:17
azonenbergi try to avoid pyrophoric materials09:18
Syncbetter than phosphine09:22
Syncand it is easy to work with09:22
lekernelgrowing silicon is boring. what about non linear optical crystals? :)10:39
Syncazonenberg: do you have resources on using pmma as a photoresist?10:57
Syncmy prof had not heard about that10:57
Syncdrygol: it seems that everyone of them works10:58
drygoloh good to know , so it pretty much doesn't matter which hydroxide of mentioned you choose , only concentration matters11:01
Syncwell the concentration only speeds things up from what he said11:06
Synchttp://i1167.photobucket.com/albums/q625/frontrunners2/SEA1/SEA-824/8_24_2_img0000951A.jpg wow that was some pretty inefficient wafer15:34
azonenbergSync: actually lower concentrations of OH- are faster up to a point16:30
azonenbergbut lead to rougher etches16:30
azonenbergread the paper i linked above16:30
azonenbergand pmma is used as an e-beam resist16:31
azonenbergi have not looked into the details of it16:31
Syncyeah I did at work20:16
Syncit seems to work fine20:16
Syncyou can also use deep UV20:16
azonenbergYou can use DUV to expose PMMA? Interesting23:30
azonenbergAre we talking like 220nm wavelength or 15nm?23:31
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