| --- Tue Aug 21 2012 | 00:00 | |
| nmz787 | anyone here? | 03:36 |
|---|---|---|
| azonenberg | Yep | 03:43 |
| azonenberg | It's been slow lately but i'm still working on it | 03:43 |
| azonenberg | was machining some microscope tube parts just a few minutes ago | 03:43 |
| nmz787 | so i think i mentioned I was interested in making microfluidics | 03:45 |
| nmz787 | and was trying to build a laser CNC to cut silicone | 03:45 |
| nmz787 | but I'm wondering how far people here have come | 03:46 |
| nmz787 | basically trying to do cost-benefit analysis before putting money down | 03:46 |
| azonenberg | Not sure, my focus personally is mostly on lithography | 03:46 |
| nmz787 | (for my own project) | 03:46 |
| azonenberg | i started out doing IC reverse engineering with a friend | 03:46 |
| azonenberg | then started to realize the basics looked simple enough maybe i could do it | 03:46 |
| nmz787 | did you build a lithography setup for yourself? | 03:47 |
| azonenberg | i've gotten patterning at 20um design rules by projection using totally homebrewed setups but i'm going to break down and buy professionally printed masks i think | 03:47 |
| nmz787 | do you have a reducer for the mask? | 03:48 |
| azonenberg | I've used a microscope objective but my FOV is super limited as a result | 03:48 |
| azonenberg | my new plan calls for doing contact masks 1:1 scale on 2-inch wafers | 03:48 |
| azonenberg | laserlab.com makes 8000DPI (12.5um design rule, 3.125um lambda) masks for under $100 each | 03:48 |
| azonenberg | on plastic film | 03:48 |
| nmz787 | aren;t masks like $500-800 even at academic prices? | 03:48 |
| azonenberg | Thats for chrome on glass | 03:48 |
| nmz787 | electron beam ethced quartz | 03:48 |
| azonenberg | film is a lot cheaper | 03:49 |
| nmz787 | yeah | 03:49 |
| nmz787 | whats the tradeoff? | 03:49 |
| azonenberg | Less resolution, less rigidity. less thermal stability | 03:49 |
| azonenberg | e-beam masks can be deep submicron features | 03:49 |
| azonenberg | plastic limits you to a few um | 03:49 |
| nmz787 | how do you make those? | 03:49 |
| nmz787 | the film ones | 03:49 |
| azonenberg | Photographic film, pretty much | 03:49 |
| azonenberg | direct write with a UV laser on an x-y table | 03:49 |
| azonenberg | I'd be buying them, $80ish for a 10x16 inch sheet is a great price | 03:50 |
| nmz787 | hmm, so you'd need a CNC | 03:50 |
| azonenberg | considering you can cut that up and get a full mask set | 03:50 |
| azonenberg | you can fit 10+ 2-inch wafer masks on that sheet | 03:50 |
| azonenberg | with enough margin to hold in an aligner | 03:50 |
| nmz787 | would you build or buy an XY table? | 03:51 |
| azonenberg | For mask making, neither - like i said i'm going to just buy professional masks | 03:51 |
| nmz787 | from where? | 03:51 |
| azonenberg | laserlab.com | 03:52 |
| nmz787 | you wouldn't happen to be in NYC area? | 03:52 |
| azonenberg | Upstate, actually - near albany | 03:52 |
| nmz787 | hmm, I was up in Rochester for a while, but been in NYC for ~2months | 03:53 |
| azonenberg | Ah, nice | 03:53 |
| nmz787 | I have friends in Albany though | 03:53 |
| azonenberg | i see | 03:53 |
| azonenberg | i'm right across the river (RPI) | 03:53 |
| nmz787 | so are you effectively buying the film from laserlab.com? | 03:54 |
| nmz787 | or credits from them? | 03:54 |
| nmz787 | i don't see BYO-film | 03:54 |
| azonenberg | Yeah, you buy the film | 03:54 |
| azonenberg | from them | 03:54 |
| azonenberg | You email the GDS and pay, a day or so later the mask shows up at your front door | 03:55 |
| azonenberg | i havent ordered from them for this project but a group i consulted for used them for a low-res MEMS mask | 03:55 |
| nmz787 | seems pretty reasonable | 03:56 |
| nmz787 | could effectively cut out the laser CNC in my setup, if I can figure out lithography | 03:57 |
| nmz787 | i've made some transistors in a lab i audited once | 03:57 |
| nmz787 | but that used a stepper | 03:57 |
| azonenberg | lol | 03:57 |
| azonenberg | Yeah, i intend to start with contact litho and then make an H-line stepper in the future | 03:57 |
| nmz787 | what's H line? | 03:58 |
| azonenberg | that will be a much bigger project and most likely wait until i have a full time job | 03:58 |
| azonenberg | mercury vapor H line | 03:58 |
| azonenberg | the wavelength | 03:58 |
| azonenberg | 405nm | 03:58 |
| nmz787 | using it for mono light for interferometric positioning? | 03:58 |
| azonenberg | alternatively I-line, 365nm | 03:58 |
| azonenberg | No, the exposure wavelength | 03:58 |
| nmz787 | ah | 03:58 |
| azonenberg | Either of those is a pissibility | 03:59 |
| nmz787 | where would you get the gear? | 03:59 |
| nmz787 | the stepper? | 03:59 |
| azonenberg | Make it from scratch | 03:59 |
| azonenberg | i mean i'd buy leadscrews and piezos etc | 03:59 |
| azonenberg | probably use encoders for rough positioning and interferometers for fine | 03:59 |
| nmz787 | hmm, and still order the masks? | 03:59 |
| nmz787 | oh, is that how they'd do it | 03:59 |
| azonenberg | That's a long-term project | 04:00 |
| azonenberg | first step is to do contact litho | 04:00 |
| nmz787 | see i got confused after the interferometer and thinking of how much vibration the whole system would have | 04:00 |
| nmz787 | and then needing an optical vibe dampened table | 04:00 |
| azonenberg | i would definitely use a vibration dampening table if i went that far | 04:00 |
| azonenberg | at 1um features its not that bad | 04:00 |
| nmz787 | but I'm only aiming for <10 micron sized features now | 04:01 |
| azonenberg | Even that is a bit tricky | 04:01 |
| nmz787 | hmm | 04:01 |
| nmz787 | cool | 04:01 |
| azonenberg | smallest i've done reliably with my homebrew setup was 20, i hit 5 experimentally | 04:01 |
| nmz787 | so maybe I can try this laserlab.com and contact lith | 04:01 |
| azonenberg | but most of that was my cheap objective i was using | 04:01 |
| nmz787 | that was you making your own masks though, right? | 04:01 |
| azonenberg | i was using inkjet or laser pinted 200um masks | 04:01 |
| azonenberg | then reducing with a horribly hacked setup | 04:01 |
| azonenberg | contact litho with professional masks should give good results | 04:02 |
| nmz787 | sure, so contact should be fine with the professional film masks | 04:02 |
| nmz787 | cool | 04:02 |
| azonenberg | thats the plan | 04:02 |
| nmz787 | so is it actually in contact, or separated slightly? | 04:02 |
| nmz787 | i imagine the photoresin is liquid or tacky | 04:02 |
| azonenberg | No | 04:03 |
| azonenberg | you bake off the solvent first | 04:03 |
| azonenberg | its quite solid | 04:03 |
| azonenberg | Normally you bring the wafer into contact, back off a micron or so, then align | 04:03 |
| azonenberg | then bring into full contact for exposure | 04:03 |
| nmz787 | are there any chemistries that are suited to home/home-business? | 04:05 |
| azonenberg | for photoresist? | 04:05 |
| nmz787 | i'd just be doing soft-lithography | 04:05 |
| azonenberg | i dont know as much about fluidic stuff | 04:05 |
| azonenberg | DNQ-novolac can be obtained for PCBs from injectorall.com | 04:05 |
| azonenberg | the solvent is a little nasty so you probably want exhaust in the area you're actually coating | 04:06 |
| nmz787 | where you expose the resist, develop and clean off, then pour silicon on top, cure, peel off | 04:06 |
| azonenberg | once dried its pretty harmless | 04:06 |
| nmz787 | silicone* | 04:06 |
| azonenberg | the developer is dilute NaOH / KOH / TMAH or, hypothetically but not tested, dilute ammonia | 04:06 |
| nmz787 | hmm | 04:07 |
| azonenberg | and i dont know anything about microfluidic patterning of silicone or polymers in general | 04:07 |
| azonenberg | i've always coated it over a metal layer, then etched | 04:07 |
| nmz787 | hmm, well thanks for the site links | 04:08 |
| nmz787 | this page says 'emulsion side' | 04:11 |
| nmz787 | http://www.laserlab.com/phototool_type.php | 04:11 |
| azonenberg | Yeah | 04:11 |
| nmz787 | does that mean it may have a 3D surface patterned on it? | 04:11 |
| azonenberg | The film is a solid plastic base with a photosensitive later on top | 04:12 |
| azonenberg | layer* | 04:12 |
| azonenberg | you typically want that layer against your wafer to avoid diffraction around it | 04:12 |
| azonenberg | rather than having the plastic in between | 04:12 |
| azonenberg | In most cases you want a PD mask | 04:13 |
| azonenberg | VPD is the ordering code at 8000 DPI | 04:13 |
| nmz787 | i'm wondering if I can just pour silicone on top of that | 04:14 |
| azonenberg | on top of the resist? | 04:15 |
| azonenberg | i dont know anything about patterning silicone but you could potentially do a lift-off type process | 04:15 |
| azonenberg | coat a glass substrate with photoresist | 04:15 |
| azonenberg | expose all of the areas you do not want channels | 04:15 |
| azonenberg | develop, now your channels are high spots where there's resist and background is low spots | 04:16 |
| azonenberg | then coat silicone over the glass | 04:16 |
| azonenberg | after it cures, peel off the glass plate | 04:16 |
| azonenberg | and remove the resist with a solvent | 04:16 |
| nmz787 | ya | 04:24 |
| nmz787 | but i was saying pouring it on the film from laserlab | 04:25 |
| nmz787 | if its already 3D | 04:25 |
| azonenberg | Oh | 04:25 |
| azonenberg | no, odds are its not | 04:25 |
| azonenberg | its just reacting internally | 04:25 |
| azonenberg | also, you dont want to screw up your mask in the event of a process defect :P | 04:25 |
| nmz787 | yeah | 04:26 |
| nmz787 | what if the resist peels off the glass when you start peeling off the silicone? | 04:26 |
| azonenberg | Doesnt matter | 04:28 |
| azonenberg | you just wash it off with a solvent | 04:28 |
| azonenberg | i dont think acetone eats PDMS | 04:28 |
| nmz787 | i'm not sure | 04:29 |
| --- Wed Aug 22 2012 | 00:00 | |
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