<azonenberg>
It's been slow lately but i'm still working on it
<azonenberg>
was machining some microscope tube parts just a few minutes ago
<nmz787>
so i think i mentioned I was interested in making microfluidics
<nmz787>
and was trying to build a laser CNC to cut silicone
<nmz787>
but I'm wondering how far people here have come
<nmz787>
basically trying to do cost-benefit analysis before putting money down
<azonenberg>
Not sure, my focus personally is mostly on lithography
<nmz787>
(for my own project)
<azonenberg>
i started out doing IC reverse engineering with a friend
<azonenberg>
then started to realize the basics looked simple enough maybe i could do it
<nmz787>
did you build a lithography setup for yourself?
<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
<nmz787>
do you have a reducer for the mask?
<azonenberg>
I've used a microscope objective but my FOV is super limited as a result
<azonenberg>
my new plan calls for doing contact masks 1:1 scale on 2-inch wafers
<azonenberg>
laserlab.com makes 8000DPI (12.5um design rule, 3.125um lambda) masks for under $100 each
<azonenberg>
on plastic film
<nmz787>
aren;t masks like $500-800 even at academic prices?
<azonenberg>
Thats for chrome on glass
<nmz787>
electron beam ethced quartz
<azonenberg>
film is a lot cheaper
<nmz787>
yeah
<nmz787>
whats the tradeoff?
<azonenberg>
Less resolution, less rigidity. less thermal stability
<azonenberg>
e-beam masks can be deep submicron features
<azonenberg>
plastic limits you to a few um
<nmz787>
how do you make those?
<nmz787>
the film ones
<azonenberg>
Photographic film, pretty much
<azonenberg>
direct write with a UV laser on an x-y table
<azonenberg>
I'd be buying them, $80ish for a 10x16 inch sheet is a great price
<nmz787>
hmm, so you'd need a CNC
<azonenberg>
considering you can cut that up and get a full mask set
<azonenberg>
you can fit 10+ 2-inch wafer masks on that sheet
<azonenberg>
with enough margin to hold in an aligner
<nmz787>
would you build or buy an XY table?
<azonenberg>
For mask making, neither - like i said i'm going to just buy professional masks
<nmz787>
from where?
<azonenberg>
laserlab.com
<nmz787>
you wouldn't happen to be in NYC area?
<azonenberg>
Upstate, actually - near albany
<nmz787>
hmm, I was up in Rochester for a while, but been in NYC for ~2months
<azonenberg>
Ah, nice
<nmz787>
I have friends in Albany though
<azonenberg>
i see
<azonenberg>
i'm right across the river (RPI)
<nmz787>
so are you effectively buying the film from laserlab.com?
<nmz787>
or credits from them?
<nmz787>
i don't see BYO-film
<azonenberg>
Yeah, you buy the film
<azonenberg>
from them
<azonenberg>
You email the GDS and pay, a day or so later the mask shows up at your front door
<azonenberg>
i havent ordered from them for this project but a group i consulted for used them for a low-res MEMS mask
<nmz787>
seems pretty reasonable
<nmz787>
could effectively cut out the laser CNC in my setup, if I can figure out lithography
<nmz787>
i've made some transistors in a lab i audited once
<nmz787>
but that used a stepper
<azonenberg>
lol
<azonenberg>
Yeah, i intend to start with contact litho and then make an H-line stepper in the future
<nmz787>
what's H line?
<azonenberg>
that will be a much bigger project and most likely wait until i have a full time job
<azonenberg>
mercury vapor H line
<azonenberg>
the wavelength
<azonenberg>
405nm
<nmz787>
using it for mono light for interferometric positioning?
<azonenberg>
alternatively I-line, 365nm
<azonenberg>
No, the exposure wavelength
<nmz787>
ah
<azonenberg>
Either of those is a pissibility
<nmz787>
where would you get the gear?
<nmz787>
the stepper?
<azonenberg>
Make it from scratch
<azonenberg>
i mean i'd buy leadscrews and piezos etc
<azonenberg>
probably use encoders for rough positioning and interferometers for fine
<nmz787>
hmm, and still order the masks?
<nmz787>
oh, is that how they'd do it
<azonenberg>
That's a long-term project
<azonenberg>
first step is to do contact litho
<nmz787>
see i got confused after the interferometer and thinking of how much vibration the whole system would have
<nmz787>
and then needing an optical vibe dampened table
<azonenberg>
i would definitely use a vibration dampening table if i went that far
<azonenberg>
at 1um features its not that bad
<nmz787>
but I'm only aiming for <10 micron sized features now
<azonenberg>
Even that is a bit tricky
<nmz787>
hmm
<nmz787>
cool
<azonenberg>
smallest i've done reliably with my homebrew setup was 20, i hit 5 experimentally
<nmz787>
so maybe I can try this laserlab.com and contact lith
<azonenberg>
but most of that was my cheap objective i was using
<nmz787>
that was you making your own masks though, right?
<azonenberg>
i was using inkjet or laser pinted 200um masks
<azonenberg>
then reducing with a horribly hacked setup
<azonenberg>
contact litho with professional masks should give good results
<nmz787>
sure, so contact should be fine with the professional film masks
<nmz787>
cool
<azonenberg>
thats the plan
<nmz787>
so is it actually in contact, or separated slightly?
<nmz787>
i imagine the photoresin is liquid or tacky
<azonenberg>
No
<azonenberg>
you bake off the solvent first
<azonenberg>
its quite solid
<azonenberg>
Normally you bring the wafer into contact, back off a micron or so, then align
<azonenberg>
then bring into full contact for exposure
<nmz787>
are there any chemistries that are suited to home/home-business?
<azonenberg>
for photoresist?
<nmz787>
i'd just be doing soft-lithography
<azonenberg>
i dont know as much about fluidic stuff
<azonenberg>
DNQ-novolac can be obtained for PCBs from injectorall.com
<azonenberg>
the solvent is a little nasty so you probably want exhaust in the area you're actually coating
<nmz787>
where you expose the resist, develop and clean off, then pour silicon on top, cure, peel off
<azonenberg>
once dried its pretty harmless
<nmz787>
silicone*
<azonenberg>
the developer is dilute NaOH / KOH / TMAH or, hypothetically but not tested, dilute ammonia
<nmz787>
hmm
<azonenberg>
and i dont know anything about microfluidic patterning of silicone or polymers in general
<azonenberg>
i've always coated it over a metal layer, then etched