| azonenberg | lekernel: https://www.facebook.com/pages/Lift-off/135686133131491 | 00:21 |
|---|---|---|
| azonenberg | Oh, the interesting things you can find when facebook crawls all of wikipedia looking for fanpages... | 00:22 |
| azonenberg_lab | So I'm prepping samples for an experiment to be done on thursday | 03:02 |
| azonenberg_lab | Any ideas as to how to store microscope coverslips or slides (to be used as substrates for deposition) in a clean environment for a day or two? Preferably padded so i can carry them around | 03:02 |
| azonenberg_lab | Looks like i need more gel boxes o_O running out | 03:11 |
| azonenberg_lab | but i have one left | 03:11 |
| azonenberg_lab | So now i have 17 samples which are going to be coated in 100nm ish of Cu on thursday | 03:59 |
| azonenberg_lab | Four of <100> Si and the rest of glass | 03:59 |
| azonenberg_lab | Next step is to expose some of these guys with simple test patterns so i can do lift-off | 03:59 |
| azonenberg_lab | Trying half-strength photoresist (watered down with acetone) now | 04:51 |
| azonenberg_lab | I'm expecting better resolution and shorter exposues | 04:52 |
| azonenberg_lab | exposures* | 04:52 |
| azonenberg_lab | At the cost of increased permeability | 04:52 |
| CIA-67 | homecmos r102 | trunk/lithography-tests/labnotes/azonenberg_labnotes.txt | Today's lab notes | 05:25 |
| azonenberg | This is getting annoying | 05:46 |
| azonenberg | All of my processes seem to be working decently well (so far) except the KOH isnt playing well | 05:46 |
| azonenberg | Because i cant get hardmask to work | 05:47 |
| azonenberg | I'm starting to wonder if maybe i should just try CMOS | 05:47 |
| Laurenceb | why is hardmask needed? | 11:13 |
| azonenberg | Laurenceb: Because photoresist is attacked by KOH | 14:15 |
| azonenberg | As well as related etchants like NaOH and TMAH | 14:15 |
| Laurenceb | silicon entchants? | 14:18 |
| azonenberg | Laurenceb: Correct | 14:19 |
| Laurenceb | do silicon dioxode etchants eat photoresist? | 14:19 |
| azonenberg | Not exactly | 14:19 |
| azonenberg | But F- ions have a tendency to diffuse through photoresist | 14:20 |
| Laurenceb | how is it done commercially? | 14:20 |
| azonenberg | They dont actually damage it but they appear on the other side | 14:20 |
| Laurenceb | - dioxide etching | 14:20 |
| azonenberg | They normally use fluoride-proof resists | 14:20 |
| azonenberg | Also, the usual mask for silicon etching is silicon nitride | 14:20 |
| azonenberg | Which is deposited by reactive sputtering or LPCVD | 14:21 |
| Laurenceb | i see | 14:21 |
| Laurenceb | i dont understand how spin coating leaves an eavent coat | 14:21 |
| Laurenceb | *even | 14:21 |
| azonenberg | I dont know all of the physics either, you'd think it'd be thinner in the middle and thicker around the rim | 14:22 |
| Laurenceb | yeah | 14:22 |
| azonenberg | I mean, there is frequently a ring around the *very* edge | 14:22 |
| azonenberg | But that due to edge effects (surface tension etc) | 14:22 |
| azonenberg | the thickness in the remaining area is normally extremely even | 14:23 |
| Laurenceb | oh with my aerosol precipitator, we found you could get even a repoducable coats | 14:23 |
| azonenberg | Interesting | 14:23 |
| Laurenceb | as the precipitate was nonconductive and blocked the field | 14:23 |
| Laurenceb | - allowed a static buildup that blocked the field | 14:23 |
| azonenberg | And I think my problem is that my hardmask is soluble in alcohol | 14:23 |
| azonenberg | But so is my photoresist | 14:23 |
| Laurenceb | unfortunately it ended up quite thick | 14:24 |
| azonenberg | So the two are interacting somehow | 14:24 |
| Laurenceb | interesting | 14:24 |
| azonenberg | The resist dissolves slowly, it doesnt disintegrate like it would with say acetone | 14:24 |
| azonenberg | But i think its contaminating the film somehow | 14:24 |
| Laurenceb | i saw some papers on using electrostatic dust precipitation to coat nonconductive surfaces uniformly | 14:24 |
| azonenberg | well i just came up with a very interesting idea | 14:25 |
| azonenberg | Gonna have to prepare some samples tonight to test | 14:25 |
| azonenberg | One is to try using an evaporated metal hardmask to pattern tantalum chloride by a wet etch in alcohol | 14:30 |
| azonenberg | Another one is to use evaporated metal directly as a hardmask for KOH etch (but only certain metals are compatible) | 14:30 |
| azonenberg | And another is to use evaporated metal as a hardmask for etching tantalum oxide | 14:31 |
| azonenberg | And still another is to try something i should have done a long time ago | 14:33 |
| azonenberg | Now that i have ammonia i can synthesize ammonium fluoride and, by extension, buffered oxide etch | 14:33 |
| azonenberg | Which i'm told diffuses through photoresist much less than pure HF | 14:33 |
| azonenberg | gaah, going to be fun going to work today while thinking about this :P | 14:34 |
| Laurenceb | heh | 14:38 |
| azonenberg | My last attempt at buffering HF used NaOH | 14:44 |
| azonenberg | Didnt end well | 14:44 |
| azonenberg | Took the photoresist right off | 14:44 |
| nathan7 | \o/ | 14:45 |
| azonenberg | What, you didnt know the channel existed? Been working here for like two months lol | 14:45 |
| nathan7 | Nope | 14:45 |
| azonenberg | http://code.google.com/p/homecmos/source/browse/trunk/lithography-tests/labnotes/azonenberg_labnotes.txt?spec=svn102&r=102 is my current lab notes if you have any suggestions | 14:45 |
| nathan7 | cool. | 14:46 |
| Laurenceb | before copper was used on commercial fab, was CPM necessary? | 14:47 |
| Laurenceb | i dont see that being practical to do cheaply | 14:50 |
| SolidRaven | What CPM? | 14:50 |
| SolidRaven | Stop the acronyms | 14:50 |
| SolidRaven | They can mean loads of things | 14:50 |
| Laurenceb | surface polishing | 14:51 |
| SolidRaven | The thing about polishing is, you could get an old industrial machine fairly cheaply | 14:53 |
| SolidRaven | You know, for watch making and so on | 14:53 |
| SolidRaven | Those are usually rather precise | 14:53 |
| SolidRaven | So with minor modifications you should be able to get them to the level required to polish a wafer | 14:53 |
| Laurenceb | i was interested in tabletop fab | 14:54 |
| SolidRaven | You somehow see this as a huge machine | 14:55 |
| SolidRaven | It generally isn't | 14:55 |
| SolidRaven | I'm talking about watch making equipment :P | 14:55 |
| SolidRaven | Goes in the same category as those small lathes | 14:56 |
| SolidRaven | That's actually another thing you could use to polish them | 14:56 |
| SolidRaven | Assuming you find a good enough tool | 14:57 |
| SolidRaven | You know Laurenceb a good average lathe will let you go down to 10µm or even smaller | 14:59 |
| SolidRaven | And some of the better CNC lathes can go sub micrometer... | 15:00 |
| SolidRaven | So really, look into it | 15:00 |
| SolidRaven | But don't use the automatic feed of a small lathe if you want precision, too much shocks :( | 15:01 |
| SolidRaven | Actually, now that I think of it | 15:03 |
| SolidRaven | cooling, you'll need that if you use a lathe | 15:03 |
| SolidRaven | Blast it with a jet of nitrogen | 15:03 |
| SolidRaven | So go and get your jewelry lathe that's precise enough | 15:04 |
| SolidRaven | :P | 15:04 |
| Laurenceb | interesting | 15:09 |
| SolidRaven | The reason lathes are generally not used at such precision is the lack of measurement instruments and the lack of need to do so | 15:15 |
| SolidRaven | It's cheaper to work at a precision of 0.1mm than at 0.01 or 0.001mm | 15:15 |
| SolidRaven | But mechanically they're capable of going down to that precision | 15:16 |
| azonenberg_work | Laurenceb: I think you meant CMP | 15:20 |
| azonenberg_work | Not CPM | 15:20 |
| Laurenceb | oops | 15:20 |
| azonenberg_work | And it was still used before copper damascene processing to some extent | 15:20 |
| azonenberg_work | Most submicron aluminum processes use it | 15:21 |
| Laurenceb | interesting | 15:21 |
| azonenberg_work | The reason is that the depth of field of your litho process is less than the thickness of a metal layer | 15:21 |
| azonenberg_work | So you need to have a flat surface for exposing the mask onto | 15:21 |
| azonenberg_work | I was actually expecting to planarize during some of my processing so i bought a quart of 50nm colloidal silica slurry from ted pella | 15:23 |
| azonenberg_work | Havent had a chance to actually try any real processing with it | 15:23 |
| Laurenceb | thats small | 15:26 |
| azonenberg_work | Thats the particle size, it can actually polish to below that | 15:27 |
| azonenberg_work | Probably 10-25nm surface roughness as a guess | 15:27 |
| azonenberg_work | In any case its far better than i need for depositiong 50-100nm (or thicker) films with 5-20um horizontal feature sizes | 15:28 |
| azonenberg_work | Lol so just for the heck of it i was reading up on metal etchants and found a section on platinum | 16:32 |
| azonenberg_work | The two etches they suggest are aqua regia and molten sulfur :P | 16:32 |
| SolidRaven | Not really a shocker | 16:46 |
| SolidRaven | You just listed two of the few things capable of harming platinum | 16:46 |
| azonenberg_work | I'm surprised they didnt just say "effectively indestructible" | 16:46 |
| azonenberg_work | as i dont think either of those etches is very selective :P | 16:47 |
| azonenberg_work | They'll eat almost anything you can try to mask it with | 16:47 |
| SolidRaven | well, aqua regia doesn't harm polymers all that much | 16:47 |
| azonenberg_work | Hmm | 16:48 |
| Action: azonenberg_work gets terrible idea | 16:48 | |
| SolidRaven | + you could use titanium oxides to protect the wafer... | 16:48 |
| azonenberg_work | Does aqua regia eat silicon? | 16:48 |
| SolidRaven | Those are resistant to aqua regia | 16:48 |
| SolidRaven | Not sure | 16:48 |
| SolidRaven | But I doubt it'll be healthy for the other wafer | 16:48 |
| azonenberg_work | I was going to suggest using a platinum or gold hardmask (which i can sputter or even deposit by sol-gel) | 16:49 |
| azonenberg_work | then use aqua regia to etch it through photoresist | 16:49 |
| azonenberg_work | Half jokingly, i dont want to have the stuff around right now (no fume hood) | 16:49 |
| SolidRaven | That'd probably work | 16:49 |
| SolidRaven | I wonder if it harms silicium | 16:49 |
| azonenberg_work | In the meantime what i want to try is making some BOE | 16:49 |
| SolidRaven | Get a silicium crystal and dump it in some aqua regia | 16:49 |
| SolidRaven | The chemistry department should have some spare aqua regia anyway | 16:50 |
| SolidRaven | It's ideal for cleaning things | 16:50 |
| azonenberg_work | If i can get my photoresist to survive a BOE etch then i'm in good shape | 16:50 |
| azonenberg_work | spin coat tantalum oxide and pattern by straightforward wet etch | 16:50 |
| SolidRaven | azonenberg, seriously if you use titanium you could use aqua regia to etch! | 16:58 |
| azonenberg_work | I have no way to deposit titanium | 17:00 |
| azonenberg_work | At least not yet | 17:00 |
| azonenberg_work | I'd need to sputter or evaporate and i dont have the equipment for either atm | 17:00 |
| SolidRaven | You could also use the aqua regia to deposit gold on a surface now that I think about it | 17:02 |
| SolidRaven | But that'd require a (large) current :( | 17:02 |
| azonenberg_work | Lol | 17:03 |
| azonenberg_work | Electroplating gold from aqua regia? Yeah | 17:03 |
| azonenberg_work | Though... | 17:03 |
| azonenberg_work | I could synthesize copper chloride easily enough and electroplate it potentially | 17:03 |
| azonenberg_work | I just dont know if it would give good results | 17:03 |
| azonenberg_work | I also dont think copper would work well as a hardmask | 17:04 |
| --- Thu Jul 21 2011 | 00:00 | |
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