#homecmos IRC log for Friday, 2011-07-22

azonenberg_labRunning experiments on evaporated copper now01:04
azonenberg_labFirst step was the "Scotch tape test" on a glass sample, it failed miserably01:05
azonenberg_labalmost complete delamination01:05
azonenberg_labNext will be seeing how it handles HF01:05
azonenberg_labi've heard some people say they think it passivates, others say it will etch01:06
azonenberg_lablekernel: Know anything about the behavior of Cu in HF?01:28
azonenberg_labWill it etch, passivate, not react at all?01:28
CIA-67homecmos r104 | trunk/lithography-tests/labnotes/azonenberg_labnotes.txt | Today's lab notes02:55
azonenberg100x view of evaporated copper on wafer03:10
azonenbergafter spin coating in PR, exposing, developing, and wet etching in SC203:10
azonenbergAfter stripping resist; http://i.imgur.com/WZDVv.jpg03:10
azonenbergColors are a bit off03:10
azonenbergBut the yellow is copper and the background is silicon03:10
azonenbergI wonder if 60 sec in SC2 is too much03:11
azonenbergThe film is very thin, after all03:11
azonenbergMaybe i want to water it down...03:11
azonenbergYeah, its waaay too much03:53
azonenbergEtch Rates for Micromachining Processing - Part II, IEEE MEMS journal03:54
azonenberggives etch rate for a similar FeCl3 based etchant as 3900nm/min03:54
azonenbergI'm using HCl : H2O2 but in PCBs they etched at about the same rate03:54
azonenbergWhich means my film (rough guesstimate 200nm) would be etched throuhg in 5 sec03:54
azonenbergAnd then 12x overetched :P03:55
nathan7azonenberg: :o07:26
LaurencebHF is acid12:40
Laurencebit should etch copper12:41
lekernelLaurenceb, not all acids etch copper, e.g. hydrochloric acid does not13:37
lekernelHF, I don't know13:37
lekernelLaurenceb, also, you have passivation phenomena with some strong acids... for example pure sulfuric acid does not etch copper, but diluted sulfuric acid does (iirc)13:38
lekernelazonenberg: see http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD288458&Location=U2&doc=GetTRDoc.pdf13:39
lekernel"In  the  manufacture  and  storage  of  hydrogen  fluoride  and  its aqueous  solution,  i.e.,  hydrofluoric  acid,  equipment  made  of  copper and  its  alloys  is  used"13:39
lekernelso it most probably does not ;)13:40
bart416For HF storage, just use teflon13:40
lekernelthat's a 1962 document13:40
lekerneland the question isn't how to store HF but whether it can be used to etch copper13:41
nathan7lekernel: In the presence of Cu(2+) it does13:43
nathan7ahem, Cu²z13:43
lekernelHF or HCl?13:44
lekerneland I guess that's a chain reaction?13:44
azonenbergWell thats good because it means i can use evaporated copper as a hardmask for HF etching15:04
azonenbergI just might need a little bit more than i used for this deposition run15:04
azonenbergThis might finally solve my patterning problems15:07
azonenbergSpin coat TaCl5, bake to oxidize15:08
azonenbergEvaporate Cu15:08
azonenbergSpin coat photoresist, develop, wet etch Cu hardmask in dilute SC215:08
azonenbergEtch Ta2O5 through Cu with hot HF15:08
azonenbergStrip Cu in SC215:08
azonenbergEtch Si through Ta2O5 with KOH15:08
azonenbergSo i'd have *three* levels of masking15:09
azonenbergBut in theory it should work15:09
azonenbergMy last run seems to have had adhesion issues with the Cu, thats my only concern15:22
azonenbergWondering if it wasnt pure enough / I didnt clean the surface adequately15:22
azonenbergbut when i tried HF etching a glass substrate with Cu over it, the Cu floated off15:23
azonenbergNot damaged, but it was undercut15:23
bart416Well, HF tends to do that azonenberg16:44
azonenbergbart416: Yeah, i was hoping the Cu would actually mask it16:44
azonenbergNeed to figure out if i just etched too long or what16:44
azonenbergI only need to go down around 100nm16:44
bart416For etching glass I'd just use regular photoresist to be honnest16:55
azonenbergbart416: Doesnt work17:01
azonenbergMy resist allows F- to diffuse through it17:02
bart416auch :(17:02
azonenbergyou get etching of the substrate with intact photoresist over it17:02
azonenbergAt least, thats my working hypothesis17:03
azonenbergall i know for sure is what actually happens17:03
azonenbergnot how17:03
azonenbergSo my newly modified process calls for ten different operations to pattern one bulk-etch mask level into a piece of silicon lol20:00
azonenbergSpin coat TaCl5, bake20:02
azonenbergEvaporate Cu20:02
azonenbergSpin coat photoresist, soft bake20:02
azonenbergExpose, develop, hard bake20:02
azonenbergWet etch Cu in dilute SC220:02
azonenbergStrip PR in acetone20:02
azonenbergWet etch Ta2O5 through Cu with HF20:02
azonenbergStrip Cu in SC220:03
azonenbergWet etch Si in KOH20:03
azonenbergStrip Ta2O5 in HF20:03
azonenbergStandard Clean 2, the second of two cleaning solutions in the RCA clean20:03
azonenberg1 part HCl : 1 part 30% H2O2 : 6 parts water20:03
azonenbergI use a slightly different mixture due to lack of 30% peroxide, i use 1 part conc HCl to 6 parts 3% H2O220:04
azonenbergA little less of an oxidizer but its pretty close, just slightly slower etch rate on some materials20:04
nathan7azonenberg: ebay has 30% H2O220:35
azonenbergnathan7: Not saying it cant be obtained20:36
azonenbergBut i dont have it20:36
azonenbergIt also decomposes fast enough i dont want to order it20:37
nathan7Not terribly fast20:37
nathan7Just keep it in the dark and don't keep it with metal20:37
azonenbergIn any case, cant do too much moe work until sunset in the USA20:39
azonenbergsilly photoresist and my lack of a darkroom...20:39
bart416H202 lasts quite a while if you keep it in the right bottles21:23
bart416As long as you don't expose it to much light and avoid heating it it'll last years21:27
azonenbergbart416: 3% or 30%?21:35
azonenbergAnd i'd use an opaque plastic or brown glass bottle under a shelf21:35
azonenbergat 75F21:35
nathan7Put it in the lab freezer!21:36
azonenbergnathan7: Dont have one (working at least)21:36
bart416put it in a fridge21:36
bart416I mean, it's not like it's really all that toxic21:36
bart416Unless if you intend to drink it21:36
azonenbergOn general principle i keep lab stuff well separated from food / living spaces21:36
nathan7H2O2 is nontoxic21:37
nathan7just oxidising21:37
bart416Just keep it in a labeled teflon bottle21:38
bart416And put it somewhere in a cool cupboard21:38
bart416that's my storage procedure for 10% H202 and up21:38
bart416As long as you stay under 50% that should be safe21:39
azonenberg50%? Lol21:39
azonenbergI'm not working with rocket fule here21:39
bart416It's only qualified as rocket fuel starting from 65% or something like that21:40
azonenbergLol, 50 is still quite possibly explosive21:40
bart416Nah, 50% is still safe if you don't heat it21:40
nathan7or stir it with silver spoons21:44
nathan7or silver powder21:44
nathan7really high-surface area silver powder21:44
nathan7that still gets a nice fizz out of 3%21:44
azonenberglol :P21:45
azonenberghow about 50nm nanopowder? :p21:45
bart416nathan7, don't try to feed it iron either :p21:47
bart416And never ever try to feed it alkali metals21:47
azonenbergAlkali metals...21:47
bart416you know, if you throw a block of potasium in water it reacts violently eh...21:47
azonenbergRubidium plus 50% H2O221:47
nathan7azonenberg: I dissolved 97/3 Sn/Ag solder in HCl(aq)21:48
bart416Now try throwing it in high concentration hydrogen peroxide21:48
bart416I'll stand back a bit :P21:48
bart416Violent is an understatement21:48
bart416Its a damned depth charge >_>21:48
nathan7bart416: better, put a tube to the bottom22:01
nathan7make sure it's dry inside22:01
nathan7and drop the K in22:01
nathan7then quickly remove the tube22:01
nathan7the K will be at the bottom22:01
bart416nathan7, heh we had another method22:02
bart416we put the potasium in a one of those large plastic canisters you can buy chemicals in22:02
azonenbergAnd puncture the lid?22:02
bart416attach a brick to it22:03
bart416attach fireworks with fuses that work under water to the lid22:03
bart416and throw it in the river22:03
azonenbergSo you use a small charge to blow the lid off22:03
nathan7azonenberg: where are you located?22:03
azonenbergnathan7: USA22:03
nathan7azonenberg: Yes, where USA?22:03
azonenbergNear Albany22:03
azonenbergwhy you ask?22:03
nathan7You<->ozonenerd distance22:04
azonenbergWhere's he at?22:04
nathan7ah, that's far22:04
azonenbergYeah, 500 miles ish?22:04
azonenbergmaybe a bit more?22:04
nathan7americaland is big.22:04
bart416I'm bored22:17
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