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<B0101>
+q45
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<glowplug`>
Good afternoon all.
<Sync_>
hello
<Sync_>
glowplug`: thought about the direct litho for a bit
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<Sync_>
I still think an interferometer is the cheapest and best way to do the position measurement
<Sync_>
the resolution/cost factor is very good
<glowplug`>
I'm working on the interferometer. Came to that conclusion as well.
<glowplug`>
Will be constructing a simple michealson and a bunch of micrometers to position the sample. What was your conclusion with the direct litho?
<Sync_>
there are 100nm resolution glass scales, which would be cool
<Sync_>
yeah a michelson is easy to do
<glowplug`>
It would be, but I can probably get 250nm accuracy with the cheap interferometer for pennies.
<Sync_>
I should head to the scrapyard and see what machines they currently rip apart
<glowplug`>
What are your opinions with the direct litho vs mask
<Sync_>
well
<Sync_>
direct litho is probably fine for experimental work
<glowplug`>
At most universities from what I understand they use masks and spinning each layer with resist.
<Sync_>
yup
<Sync_>
it's cheaper if you have the equipment
<glowplug`>
I think that will be fairly easily to accomplish.
<Sync_>
and for most experiments you only use a single mask set
<Sync_>
hmm actually, reading the paper again, I almost have everything I'd need
<Sync_>
I'd only have to get some mirrors for the interferometers
<Sync_>
and somehow build an xy stage
<glowplug`>
If you give me a month I can send you an interferometer.
<glowplug`>
I know thats quite awhile.
<glowplug`>
Have a lot of personal crap going on right now thats keeping me from making progress.
<glowplug`>
Do you have micrometers? Spinny doohickie? (technical term).
<Sync_>
well I have a few for measuring stuff
<Sync_>
I have a few laser xy stages
<glowplug`>
We need a table with x y tilt and pan adjustments with micrometers.
<glowplug`>
I can build one.. but I need time.
<Sync_>
I'd just need to order stuff from edmund or thorlabs
<glowplug`>
That will cost you a leg + arm.
<Sync_>
well mirrors are cheap
<glowplug`>
I can build the table and the interferometer for ~$50 total. Depending on how much strugle I have putting together the tiny gearboxes.
<glowplug`>
I can use my CNC to cut 50/50 glass for 30 cents per 10mm square. Its a pain in the ass to cut glass but I can do it.
<glowplug`>
Add cute little acrylic stands and a dollor store diode you have the worlds cheapest interferometer. Haha
<glowplug`>
There are a few more things I haven't worked out
<Sync_>
let me just look what thorlabs has for me
<glowplug`>
Alignment markers. Is a cheap 100x microscope and a point and shoot camera sufficient?
<Sync_>
oh, that's an interesting problem
<Sync_>
but yeah probably
<glowplug`>
The "actual" 100x microscopes that are ~$25 are probably unsuitable.
<glowplug`>
We need to find the actual optics. Seperately.
<glowplug`>
Then rig the point and shoot to the optics. This is pretty common stuff for telescope builder types. Do you know anyone that does that stuf?
<Sync_>
well the actual optics sould be a microscope lens
<glowplug`>
Right. I've never purchased anything like that.
<Sync_>
one could just make a setup that you put on the lens to aling
<Sync_>
and then take off
<glowplug`>
But if I know its dimensions I should be able to get a ghetto mount for it that we could slap the point and shoot on.
<glowplug`>
Then we have a cute little screen to align our markers.
<glowplug`>
So the next. It's basically unaffordable to build a cartesian machine with 1um repeatable accuracy. It just wont happen.
<Sync_>
hm, thorlabs has vis beamsplitter cubes at 135€
<glowplug`>
I can build a beamsplitter for 30 cents.
<glowplug`>
Thorlabs can jump off a cliff. Haha
<Sync_>
or budget plates for 25
<Sync_>
well I'm used to order from them
<glowplug`>
Like I said if you can wait a month I can send you the stuff for free.
<glowplug`>
Also there are beamsplitters in cdrom drives which is a low cost option that doesnt require waiting for me to setup my CNC for glass.
<glowplug`>
You can probably find a pile of cdroms for free or <$5
<glowplug`>
So the CNC thing. I'm not confident I can do it. So I've been trying to find an alternative.
<soul-d>
indeed telescope work bit diferent but you might get some intresting tools
<glowplug`>
I started thinking about laser projectors. Galvos aren't really suitable for exposing resist. They are super fast and not accurate enough.
<soul-d>
google for ATM in full Amature telescope making
<soul-d>
i assume theory behind the light stuff is same just have to do different calculations
<glowplug`>
For the galvos?
<glowplug`>
By the way did you just change names? Haha
<Sync_>
yeah beamsplitters are not too bad commercially
<soul-d>
no just another someone :P
<glowplug`>
At any rate. Imagine a laser projector configuration. Two motors and two mirrors. The motors are microstepping servos with a 500/1 gearbox reduction.
<glowplug`>
Oh I see. Haha
<glowplug`>
So basically its the worlds worste laser projector that can draw a blue dot on a wall very very slowly and not make pictures at all.
<glowplug`>
But it can expose photoresist with 1 micron repeat accuracy. =)
<glowplug`>
I'm sorry. Microstepping steppers.
<azonenberg>
glowplug`: i considered that
<azonenberg>
I think cartesian mounting is a better option
<azonenberg>
even 10um accuracy is good enough
<azonenberg>
Bear in mind you only need 1cm or so of travel
<azonenberg>
don't even think about that kind of accuracy across a large field
<Sync_>
it's not that hard over a large area
<glowplug`>
This thing might have a large field but it wouldn't be an extra cost if it did.
<glowplug`>
Cartesian adds all sorts of costs that the projector configuration avoids.
<glowplug`>
With no rotational to linear motion 90% of the cost is removed.
<glowplug`>
No ball screws, ball nuts, no linear encoder ect.
<azonenberg>
Maskless litho is great for making masks, but difficult to align to an existing pattern
<azonenberg>
I still think your best bet is to use direct write for making masks, then a contact aligner
<glowplug`>
That is the plan for sure. Masks make everything very easy.
<azonenberg>
With a contact aligner you just have a little track above the mask assembly
<azonenberg>
microscope slides in, tweak the micrometer knobs until the mask is lined up with the wafer
<glowplug`>
At any rate. Let me attempt the projector configuration with 10um as an accuracy target. If it works I will make and send out masks. If I fail then I waste a bunch of time. Haha
<azonenberg>
then slide it out and bring the UV lamp in
<glowplug`>
Except we are going to have an awesome color LCD for alignment because thats what badasses do.
<Sync_>
hmm, the new blue lasers sure made stuff easier
<Sync_>
no need to drag the ALC909 out
<glowplug`>
Yeah I'm just going to grab a blu-ray diode and call it.
<glowplug`>
I even get a free beamsplitter from the drive.
<Sync_>
I like my tankless water heater with operation light
<glowplug`>
So does anyone have a plan for the spinny thingy?
<Sync_>
yes
<Sync_>
after I finish my exams I'll try to come up with something
<glowplug`>
Alright we are counting on you. No pressure. =P
<Sync_>
other option is just to buy a spincoater
<Sync_>
they are not too terribly expensive
<glowplug`>
Oh and if I fail with the projector configuration then I will be building a SCARA robot to try and replace it. If that fails then I don't know. Trust me it wont fail. =)
<glowplug`>
The way I determine if I DIY something is if the manufacturer of that thing doesn't have prices on their main page.
<glowplug`>
=P
<glowplug`>
I think spincoater meets that requirement. Haha
<glowplug`>
It looks like the "bio" people do spincoaters.
<azonenberg>
Building a spin coater isnt that har
<azonenberg>
hard*
<azonenberg>
i've homebrewed one already but it's too bulky
<azonenberg>
i'm going to try and shrink it using a BLDC from an RC airplane
<azonenberg>
will post plans once i finish
<glowplug`>
What RPM does the coater run at and what accuracy +/- do you need?
<azonenberg>
My current coater is a flat plate on the end of an electric drill :p
<glowplug`>
Interesting. Thats more than I can spend though. Haha
<Sync_>
well it's clearly not worth that
<glowplug`>
There is an open source BLDC controller now. That will give you the option to use an optical encoder and get extremely precise RPM control.
<Sync_>
it's just a bldc
<glowplug`>
If you need ~1% then an ESC won't work.
<Sync_>
there are enough opensource bldc controllers since a few years
<azonenberg>
Yeah
<glowplug`>
They are all piece of shit dead ends though.
<glowplug`>
The only one thats worth a damn, with decent code. Actually let me get the link onesec.
<glowplug`>
It is a scanner. Sort of. It slowly scans a beam in the x,y.
<azonenberg>
For spam reasons i'm limiting editors to confirmed accounts
<glowplug`>
You did it! Awesome!
<glowplug`>
Account glowplug. =)
<glowplug`>
for email you can use raincloudcomputers@lavabit.com
<glowplug`>
The principle is that although it scans slowly compared to a laser projector. It will fully develop the resist along its path. And the path is any position on the x,y plane.
<glowplug`>
Honestly if it fails it's only because I designed or built it poorly. In principle it will work.
<Sync_>
azonenberg: that does not resolve for me
<glowplug`>
I'm on the page. =)
<azonenberg>
Sync_: i just made the subdomain like 15 minuts ago
<azonenberg>
dns might not have propagated yet
<Sync_>
yeah probably
<glowplug`>
I have to go for a bit. See if you guys can hunt down and stalk a telescope maker type. I will try also.
<soul-d>
even my super duper fiber con can't find it yet
<glowplug`>
I'm so lucky. Haha
<glowplug`>
Back in a bit.
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<soul-d>
if i had the money i would have made a 1meter scope already
<soul-d>
or few small ones for that matter
<soul-d>
still need guider for my 10"
<Sync_>
meh
<soul-d>
well plus im lazy to gather all the stuff i think it had to do with ability to damp up the aluminum layer
<soul-d>
or mess about with silver stuff but you need to redo that like every few years
<Sync_>
if you do not protect the al it will also go dull
<Sync_>
you can just send the mirror away to a coater and get it coated
<Sync_>
or if you want get a wideband dielectric coating
<soul-d>
knowing netherlands /europe i better can buy the mirror if there is even company able to do it i know there was a
<soul-d>
place but still size limited
<Sync_>
a lot of companies do that in europe
<soul-d>
havent looked at it since like 8 years it's that glowplugh mentioned it
<Sync_>
you could also do it yourself
<Sync_>
sputtering Al is quite easy
<azonenberg>
Easy?
<azonenberg>
i've heard Al in particular needs very high output powers
<azonenberg>
due to the need to break through the oxide
<azonenberg>
compared to other materials that have less tough oxides
<Sync_>
yeah you need assloads of power but when you are evaporating it is not that special
<azonenberg>
Evaporating vs sputtering is a big difference :p
<Sync_>
true, but even sputtering is ok
<Sync_>
I did not have an issue in my jar
<azonenberg>
i want to build myself a DC sputtering rig
<azonenberg>
How hard do you think that'd be?
<azonenberg>
I have a mechanical roughing pump
<Sync_>
not very hard
<azonenberg>
but no other vacuum hardware atm
<Sync_>
I did it in a jam jar
<azonenberg>
Lol
<Sync_>
that's enough if it can get low enough
<azonenberg>
i think i'd get something a little nicer than that
<Sync_>
no shit, but lazyness :D
<Sync_>
now that I have the machines I'll build something more adequate
<glowplug>
He is using galvos though which is why it's so wobbly.
<Sync_>
I wonder if that will lead to issues due to the angular beam direction
* Sync_
browses his stash of vacuum flanges
<glowplug>
I thought about that. There exists optics that will take the beam from any angle and deflect downwards.
<glowplug>
It also might not be an issue with a very small work area. Lets say 50x50mm.
<glowplug>
Is 50mw sufficient to expose the resist?
<Sync_>
laser with a maximum power of 3 W at 514 nm and 300 mW at 457 nm. This high power
<Sync_>
output can be used for a second harmonic generation, while typical beam power required for
<Sync_>
the exposure of color-center masks [1] is of the order 100 mW. An electro-optical modulator
<glowplug>
Looks like I might as well use blu-ray then which is way over those power levels. But theres no cost difference.
<glowplug>
I'm fine with that. =)
<Sync_>
I'd still like to use my tankless water heater
<glowplug>
For which process?
<glowplug>
Under Metalization does "sputter coater" refer to the HIPIMS device?
<Sync_>
haha no you do not get the joke
<Sync_>
I have a huge argon laser
<Sync_>
which basically just is a water heater...
<glowplug>
OH Haha
<Sync_>
well at least it tells you when it is on
<glowplug>
Speaking of tube lasers. I need to figure out how to frequency stabalize shitty lasers so I don't need one. Think I'm going to attempt it with an FPGA.
<Sync_>
what do you want to do?
<glowplug>
For the interferometer.
<Sync_>
use henes
<Sync_>
they are cheap enough on ebay
<Sync_>
an fpga is not needed, you just need to control the temperature and the current precisely
<glowplug>
A frequency stabalized dollar store laser is 10% the cost though. =)
<glowplug>
You need many discrete configurations though correct? Such as amplifiers, comparaters ect.
<glowplug>
That could all be integrated into a ~$10 coolrunner type CLPD
<azonenberg>
glowplug: if you can focus it sufficiently a bluray diode is going to be much cheaper
<azonenberg>
Just use short pulses
<azonenberg>
what you want to avoid is using so much power that you ablate the resist :p
<glowplug>
Wait what am I thinking. We don't need the interferometer now correct?
<glowplug>
Assuming I can keep the sample still during exposer.
<Sync_>
you need a precision current source with a few passives and a pid temperature controller
<Sync_>
which is just any micro with a high resolution temperature senor
<Sync_>
if you do a projector you do not need any interferometers
<Sync_>
they still are for a moving xy stage
<azonenberg>
I think you will still have to do a fixed laser and moving x-y
<azonenberg>
its much easier to move the sample by microns
<azonenberg>
than to try to steer a beam by millionths of a degree
<Sync_>
yeah
<glowplug>
I can totally steer a beam by millionths of a degree.
<azonenberg>
accurately? :p
<azonenberg>
and repeatably?
<azonenberg>
there's a reason nobody does this
<glowplug>
One person did it. On Youtube. Hahaha
<azonenberg>
With what kind of resolution?
<glowplug>
Horrible. Because he used Galvos.
<azonenberg>
And what do you plan to do
<glowplug>
But steppers with a 200/1 gear reduction should give enough resolution.
<azonenberg>
Lol
<azonenberg>
Do the trig
<Sync_>
enjoy your backlash
<azonenberg>
If you want 1um shift
<Sync_>
and yeah do the trig
<azonenberg>
at say a 10cm distance
<azonenberg>
any idea what fraction of a degree that is? :P
<glowplug>
Backlash in the gearbox? I did do the trig but for 10mm above the sample.
<azonenberg>
10mm?
<azonenberg>
you realize you need room for the optics
<glowplug>
In 1/4 of a second of movement at 200 pulses per second you get 1/4 full rotation. 200 reduction gives you .001 degrees change in that period.
<azonenberg>
Ok
<azonenberg>
0.001 degrees
<azonenberg>
do you know how huge that is?
<glowplug>
Let me find my notes onesecond.
<glowplug>
I got .048mm travel with 1 second of motor rotation at 10mm from the sample.
<azonenberg>
48 microns
<azonenberg>
thats huge
<glowplug>
Nope I have 1000/1 reduction here not 200. Thats why.
<glowplug>
Thats for a full second of motor rotation.
<Sync_>
uhh
<Sync_>
1000 times reduction with gears
<azonenberg>
LOL
<Sync_>
do you know how large that is
<Sync_>
what the hell are you smoking
<glowplug>
How large 48 microns is?
<glowplug>
That is with a full second of rotation or 200 pulses.
<azonenberg>
1000:1 reduction...
<azonenberg>
how much backlash is that gonna be at the low end?
<glowplug>
Right. That is with a 4 stage planetary. Laser cut out of acrylic.
<azonenberg>
five or ten revolutions maybe?
<glowplug>
I mean there is going to be backlash no matter what. Whether its in the gearbox or the ball screw.
<glowplug>
At least this way the machine costs $100 total instead of $2,000 to get results.
<azonenberg>
Completely useless results
<Sync_>
you need to move 5.7µ°
<glowplug>
The only reason it wouldn't have 10 micron repeat accuracy is if the gearbox's were absolutely horrible.
<glowplug>
5.7u degrees sounds scary. But we have to make adjustments of that accuracy everywhere. Even down to aligning the sample.
<glowplug>
Having a stepper do it isn't that crazy.
<Sync_>
o.0
<Sync_>
I want to see that
<azonenberg>
having a stepper do 175,000 steps per revolution?
<azonenberg>
oh, and that assumes you can fit your optics in 1cm from the sample
<azonenberg>
Which is rather unrealistic especially for a homebrew setup
<azonenberg>
i'd expect more like 10cm
<Sync_>
I mean shit, it is easier to build an xy table that does that
<Sync_>
and then you can scan a *very* small area
<glowplug>
No stepper has 175,00 steps per revolution. Thats what the reduction is for.
<Sync_>
because your focus will deteriorate
<azonenberg>
That was the other reason i wanted to go x-y
<azonenberg>
you dont need to mess with the focus
<Sync_>
yes but your quad planetary has an assload of play
<Sync_>
you cannot avoid it
<Sync_>
that's why there are hypocycloid drives and harmonic drives
<glowplug>
I cannot avoid gear reductions anyways. On a SCARA, Cartesian, doesn't matter.
<glowplug>
Hypocycloid drives are unsuitable due to wobble no?
<azonenberg>
yes, but it's better to move the sample a large distance
<azonenberg>
than a mirror a tiny distance
<Sync_>
the reduction you need is just unrealistically small
<Sync_>
or rather large
<glowplug>
If a Hypocycloid drive is suitable I will use that.
<glowplug>
I assumed the offcenter mass would make it useless.
<Sync_>
you need a good one
<azonenberg>
i still think a Cartesian micrometer screw with a geared stepper is probably the best option
<glowplug>
Ok then I will concede that the 4 stage planetary probably has too much backlash for mirror positioning of that accuracy.
<azonenberg>
and interferometers for positional feedback
<glowplug>
If I can get a hypocycloid drive laser cut and get my 1000/1 with only 2 stages then I think it is work trying.
<azonenberg>
I want to build a Michelson interferometer some time soon just to play with
<azonenberg>
And do the math for how many teeth you'd need on the gears
<glowplug>
That would eliminate any backlash in the system.
<azonenberg>
how big are these gears gonna be?
<glowplug>
I did. With 4 stages that reduction is possible with gears that fit on a NEMA-23 sized stepper.
<azonenberg>
How many teeth
<glowplug>
But I agree that would likely have too much play.
<azonenberg>
And yeah
<azonenberg>
You will want positive feedback
<azonenberg>
and you cant get that with beam steering
<glowplug>
And the hypocycloid drive (if stable) would work.
<azonenberg>
moving the sample, though, allows you to move with the beam blanked
<Sync_>
are you really expecting lasercut pieces to be accurate enough for that
<glowplug>
For a hypocycloid drive?
<Sync_>
yes
<Sync_>
I mean it'll spin
<Sync_>
but will it really be backlash free?
<Sync_>
the one I have is wire EDM'd
<glowplug>
All hypocycloid drives are backlash free.
<glowplug>
Just not wobble free.
<glowplug>
And that is something I don't have the answer for. I don't know how much it will wobble.
<glowplug>
The cost difference between my proposed system and the "traditional" is a factor of 50.
<Sync_>
there are just too many engineering problems with your idea
<glowplug>
I think it is worth persuing even for a short time if the design could enable people to contribute to the project who can't afford a $3000+ setup.
<glowplug>
There are problems. Thats why I brought it up. And my backup plans.
<glowplug>
But I think the hypocycloid gearbox could work if it was designed well enough to not wobble.
<azonenberg>
if i want to fool with interferometry
<azonenberg>
specs claim that 400nm movement accuracy is possible and so if i sample at a few KHz i should easily be able to pick up sub-wavelength shifts
<glowplug>
4 available.
<glowplug>
Those are extremely nice.
<azonenberg>
Well don't buy them before i get some :p
* azonenberg
adds 2 to cart
<glowplug>
Haha
<azonenberg>
Ordered
<azonenberg>
Seller has good feedback and they're only $35 each
<azonenberg>
even if they arent good enough for fab i have a lot of other uses in mind
<Sync_>
they are a little small
<azonenberg>
Sync_: bear in mind we're talking about putting a single die on it
<azonenberg>
I actually wanted to use them for microscopy
<Sync_>
get me the other two azonenberg
<azonenberg>
Sync_: You buy them :P
<Sync_>
oh he ships world wide
<Sync_>
that's nice
<azonenberg>
I feel like it should be possible to hook a stepper up to them
<azonenberg>
I want to make an x-y CNC stage for my microscope
<azonenberg>
to do automatic scanning of large areas
<glowplug>
You can send individual pulses to a stepper. The resolution of the machine I described earlier (assuming it could be built) would be 200/48 microns or 240nm.
<glowplug>
So my backup plan. Lets see if I can get it shot down too.
<glowplug>
The SCARA robot.
<Sync_>
azonenberg: he has a nice xy stage too
<azonenberg>
Sync_: i wanted linear ones for the interferometer experiments
<azonenberg>
i'll look at his other stuff after payday :p
<glowplug>
Actually it suffers from all of the same basic problems as the projector configuration. Plus some others.
<Sync_>
XY axis RMS repeatability < 0.7 μm
<Sync_>
nice.
<glowplug>
Alright let me put it this way. I'm going to attempt the configuration I described in the off chance it does something useful we would have significantly cheaper litho. If I fail (~97%) then I'm only out a few bucks.
<azonenberg>
for my cnc microscope i dont even need that good
<azonenberg>
i just need to find an area of the sample
<azonenberg>
oh and i need to get my camera working in linux
<glowplug>
In the meantime I will also plan an x/y stage with interferometer feedback ect. ect.
<glowplug>
What type of camera do you have?
<Sync_>
aah I want that xy stage
<Sync_>
that would solve all issues :D
<azonenberg>
Sync_: go buy it?
<Sync_>
yeah I'll do
<azonenberg>
if you dont, in a couple of days i might :p
<azonenberg>
Do you think a cheap pointer-level laser diode from digikey is stable enough to use for some quick fooling around with inteferometry?
<Sync_>
not so sure
<glowplug>
Yeah there was a video on YouTube I watched last night with a dollor store laser and he got a pretty good pattern.
<azonenberg>
i mean i wouldnt use it for precise measurements
<azonenberg>
but just to fiddle with the technique
<Sync_>
I read a paper that said it depends on the diode
<Sync_>
but I'd get a hene
<azonenberg>
For a production system i might
<glowplug>
You probably have to ditch the optics but the cheap diodes should work for experimentation.
<glowplug>
If you have a really good quality current source it will work for sure.
<azonenberg>
This laser has an integrated supply
<azonenberg>
i have no idea how stable it is :p
<glowplug>
I would pull its supply and the optics.
<azonenberg>
its a pointer-style sealed unit
<glowplug>
Yeah
<soul-d>
they did that feynman expiriment thought experiment now btw
<glowplug>
Just hack it up then use your own lense and current source.
<glowplug>
And it will work awesome for a michealson setup.
<glowplug>
The diodes are generally fine with everything else being junk.
<Sync_>
azonenberg: a hene on ebay should be under 20$
<azonenberg>
One thing at a time lol, i dont have enough time to build the whole thing now
<soul-d>
not the first
<soul-d>
old news :P
<Sync_>
just saying :D
<glowplug>
The cheapest tubes I could find was a pair of two for $50.
<glowplug>
But who knows what shape they are in.
<glowplug>
The newish looking tubes are ~$75+
<Sync_>
just wait and bid
<Sync_>
I have a few and none was more than 25$
<azonenberg>
Sync_: are diode lasers just not stable enough for interferometry?
<glowplug>
They are!
<glowplug>
But hene lasers are extremely stable by nature.
<glowplug>
And a frequency stabalized hene laser is near perfect.
<glowplug>
Diode lasers are good for experiment ect.
<glowplug>
One of the best youtube videos from MIT. They make a simple michealson with a diode laser and calculate its wavelength. Very accurate.
<Sync_>
azonenberg: the beam quality is a lot better
<azonenberg>
Sync_: well i guess one nice thing about HeNe is a known output wavelength
<Sync_>
that too
<azonenberg>
So you can have numbers measured in nm rather than in wavefronts :p
<Sync_>
yeah
<glowplug>
The MIT experiment used a 650nm diode and 1/4 transitions were clearly visible. So that is fairly accurate.
<glowplug>
Of course even if the laser was affordable they have top dollar optical equipment. =P
<glowplug>
Yeah what you need to do for the diode laser interferometer is have really good optics and be able to adjust mirror very accurately.
<Sync_>
one could just measure the wavelength
<glowplug>
Absolutely. It would be a pain compared to hene but fun nonetheless.
<glowplug>
Of course you need to already have a good laser to do that. O.o
<Sync_>
it would be connecting the fiber to the wavelength meter
<glowplug>
Do you guys really have every cool toy? Haha
<glowplug>
Just so I understand fully. The current prevailing / preferred design of the direct litho.
<glowplug>
It is a moving x,y stage driven by steppers?/servos? with a gear reduction. A mirror on all sides that are monitored by a series of interferometers for position encoding.
<glowplug>
Flip down microscope with a point and shoot cam on the top. Micrometers for manaul adjustment.
<glowplug>
That was with manual alignment and no optical table. Pretty good in my opinion.
<glowplug>
There is actually a PDF "laser scanner for direct writing lithography". Their design is quite a bit different than mine but with 1 micron accuracy and claiming that .5 is possible in principle.
<glowplug>
Beam positioning is by modulation not mechanical actuation. Interesting.
<glowplug>
Alright so a single HeNe laser gives feedback for both the X and Y. That is interesting.
<Sync_>
yes
<glowplug>
Did you see the cost estimations for the device? LOL
<Sync_>
not too bad
<Sync_>
this is 95
<Sync_>
keep that in mind
<glowplug>
We want manual digital control of the stage for positioning correct?
<glowplug>
Analog joystick sort of thing.
<Sync_>
not really, some kind of pc interface would be nice, linuxcnc would do just fine
<glowplug>
Could just do a custom interface in linuxcnc.
<glowplug>
With the camera output right in the software.
<Sync_>
you don't even need a custom interface
<Sync_>
the camera does nothing after you alinged everything
<glowplug>
It would make automatic alignment possible. Thats just a toy though.
<glowplug>
The PDF says servos. I wonder what the gear reduction is.
<glowplug>
So you intend on using hypocycloid gearboxes and servos?
<Sync_>
no
<glowplug>
What kind of motor configuration?
<Sync_>
some kind of dc servo with a high resolution encoder
<glowplug>
Won't you need a gearbox?
<Sync_>
probably, but 10fold would do
<Sync_>
because the real positioning is done by the interferometer
<glowplug>
I've been working a little on the encoder problem.
<glowplug>
CD's have .5 micron resolution. You could build a very accurate encoder with cdrom guts and a ring with alternating 1-0 pattern written by the burner.
<glowplug>
Could theoretically be millions of steps per rotation.
<glowplug>
The pattern could be written by rigging the burner to be stationary and spinning the ring under it at a set rpm.
<Sync_>
I'll just buy one
<glowplug>
What resolution do you need?
<glowplug>
How many steps I should say.
<Sync_>
that depends on the gearing
<glowplug>
Well for example a decent servo driven articulated robot has about 200,000 steps per revolution.
<glowplug>
I'm sure we need more than that.
<Sync_>
not really, I suspect the guys that make the stage I posted use something around 2800 step/rev wheels
<glowplug>
Then there must be a massive reduction in the x,y stage?
<Sync_>
~20-30 I suppose
<glowplug>
So thats 200-300 between the rotational and linear motion.
<glowplug>
Thats 840,000 steps per linear travel.
<glowplug>
Unfortunately I don't know very much about the design of those x,y stages. Does it make any sense to DIY the table itself?
<Sync_>
no
<glowplug>
I thought you would say that.
<glowplug>
Well at least everybody else appears to be well funded. Haha
<azonenberg>
well funded, lol
<azonenberg>
i'm a grad student
<azonenberg>
after rent and food i have a few $k a year to spend on fun stuff at most
<glowplug>
So it's just Sync_ thats well funded? xD
<Sync_>
probably
<glowplug>
Hahaha
<glowplug>
Well my encoder discs will be CD's. I'll put the designs on the wiki then hopefully other under-funded people can experiment. =)
<glowplug>
I have fully conceded on the projection configuration. They exist (since 1989 apparently) but the design is not straitforward and there are too many variables that make it too error prone.
<Sync_>
it's not really that I actually have a lot of money, but when I do I spend it
<Sync_>
ah nice
<Sync_>
avago makes 20000imp/r encoders
<Sync_>
that makes for 80000 counts after quadrature decoding
<glowplug>
How much?
<Sync_>
good question
<glowplug>
Uh oh. Prices arent on the website. Warning!
<azonenberg>
glowplug: doing it on CDs is nontrivial
<azonenberg>
they include error correcting codes and framing
<azonenberg>
you cant just burn a timecode using regular burner firmware
<Sync_>
unfortunately they are not avalible anymore
<Sync_>
but I bet they are around 200$
<Sync_>
maybe less
<Sync_>
BUT they have nice new encoders
<Sync_>
I'm just trying to figure out what they used in the stage
<glowplug>
Yes I'm still working on that. It would be necessary to digitally modulate the laser diode directly and to read the photodiode output directly bypassing the drives uC.
<glowplug>
In the PDF they say "DC Servo Motors". =(
<Sync_>
yeah I guess they have a +-4-30 reduction
<Sync_>
5 is realistic with encoders avalible at that time
<Sync_>
glowplug: actually they are not that bad
<glowplug>
We need three of them though. =)
<Sync_>
two
<glowplug>
Oh right. Then the piezo for the Z which I have no experience with. =(
<glowplug>
How much for disc + encoder?
<Sync_>
I suppose one could live without autofocus for a while
<glowplug>
Yeah I think autofocus will need to be added later.
<Sync_>
around 100$ per set
<glowplug>
Hey thats actually not that bad. Digikey must have very bad prices.
<Sync_>
for a 17bit absolute encoder
<Sync_>
that's pretty badass
<glowplug>
I'll still take a crack at my CD rom encoders for free each. =)
<glowplug>
We haven't talked about control much.
<glowplug>
If we pipe everything into an FPGA, interferometer output, encoder output, and also use the FPGA for motor control we will have very good latency with very low cost.
<Sync_>
I'd just rig linuxcnc to it
<glowplug>
LinuxCNC can't be used for encoder feedback loops its too slow.
<glowplug>
There is FPGA motion control IP that will do up to 8 servos with encoder feedback. Just integrate the interferometer output into the control logic.
<glowplug>
It is open loop. But there is very little load on the steppers.
<glowplug>
For submicron though I would think that encoded servos are more reliable.
<azonenberg>
Submicron is a whole other animal
<glowplug>
Haha
<azonenberg>
At that point i might think about switching from laser to e-beam
<azonenberg>
or alternatively using nearfield optics
<azonenberg>
Neither is easy
<azonenberg>
But ~1um with lasers should be very doable
<glowplug>
A lot of these costs can be even further reduced.
<glowplug>
Still need ~$100 for the blu-ray laser + lens.
<glowplug>
But you can save $50 on the controller, $300 on the stage + micrometers, Digital microscope can be made for ~$30 thats another $120 savings.
<glowplug>
Based on these numbers it can probably be done for ~$400 total.
<azonenberg>
microscope for $30?
<azonenberg>
lol
<azonenberg>
i dont think so
<azonenberg>
you cant even get a good objective for that much
<Sync_>
yeah I'm not a huge fan of that design
<glowplug>
The webcam design?
<Sync_>
it sure does work but it's openloop
<azonenberg>
Sync_: I like their design but i feel like it can be improved quite a bit
<azonenberg>
i'd want to clone it first
<glowplug>
Oh the entire stage.
<Sync_>
yeah the idea is great
<azonenberg>
then add closed-loop feedback
<glowplug>
I agree with closed-loop. Thats pretty much a no brainer.
<glowplug>
Do you have a link to the sort of microscope optics that would be suitable?
B0101 has joined #homecmos
<Sync_>
meh do I really have to fire up the vpn for access
<azonenberg>
I'd use an Olympus objective from ebay
<azonenberg>
machine a custom tube
<glowplug>
You keep getting kicked? =(
<azonenberg>
then use a nicer camera, maybe a HD webcam
<Sync_>
oh
<glowplug>
I suppose the worlds view of our progress will be through that microscope.
<Sync_>
reminds me
<Sync_>
microscope
<glowplug>
So that is probably a good idea.
<azonenberg>
Well
<azonenberg>
you want to use a nicer one for inspection
<azonenberg>
this would be just for alignment
<azonenberg>
Actually, screw that
<azonenberg>
you might not even need the uscope
<azonenberg>
if you're doing direct write
<azonenberg>
to make masks
<Sync_>
yeah
<azonenberg>
you can forget about alignment since once etched the mask wil then be used in a contact aligner
<Sync_>
no need to align anything
<glowplug>
The scope is for calibrating the machine.
<glowplug>
It wont work correctly the first go.
<glowplug>
And also uploading images / video to the wiki.
<azonenberg>
You will want another scope for inspection of work
<azonenberg>
the one on there won't be a nice one you can actually use for general imaging
<glowplug>
How much will the "actual" scope cost?
<azonenberg>
I got mine on ebay for $250 + $250 + $50
<azonenberg>
body, head, and illuminator respectively
<glowplug>
O.U.C.H.
<Sync_>
that's not a lot
<azonenberg>
that's a lot?
<azonenberg>
lol
<Sync_>
to put that in perspective
<azonenberg>
New, it was probably five or ten grand
<azonenberg>
$500ish is dirt cheap
<Sync_>
shit I have spent over 4k on my mill
<Sync_>
so what.
<glowplug>
One thing you guys have to realize.
<glowplug>
The cheaper this stuff is the more people can contribute.
<glowplug>
There is a cascading effect of money and support to a project.
<azonenberg>
It's never going to get to the point of being home-PCB-etching availability
<azonenberg>
I'm shooting for "affordable by a hackerspace"
<azonenberg>
Or by a sufficiently insane hobbyist
<glowplug>
But it can get down to "enthousiest garage fab shop with a modest income".
<glowplug>
Right. That seems a good target.
<glowplug>
But equipment under $2000 total (for everything) is probably realistic for that goal. Not $20,000 total.
<Sync_>
wat
<azonenberg>
$2000? Lol
<azonenberg>
$10K is more what i was hoping to, after lots of tuning
<azonenberg>
the prototype stuff will probably cost me more like 50k
<Sync_>
30k is a good starting point imho
<Sync_>
which is affordable for a hackersapce
<Sync_>
~space even
<glowplug>
The spincoater can be made for ~$100. These guys have litho 1um litho with ~$500 in parts.
<azonenberg>
well, once i get out of school
<azonenberg>
high on my list of major purchases is a secondhand FESEM
<glowplug>
$500 for a good microscope.
<Sync_>
oh yes azonenberg
<glowplug>
We are at $1,100. What other major components are absolutley necessary?
<Sync_>
they can be had quite cheaply
<azonenberg>
glowplug: Consumables
<Sync_>
yeah comsumables
<Sync_>
vacuum parts
<azonenberg>
Dopants from emulsitone are $500 each for P and N type
<azonenberg>
or is it $250?
<azonenberg>
that much again for undoped spin-on-glass
<azonenberg>
$300ish for a bottle of photoresist
<Sync_>
photoresist
<azonenberg>
HMDS can be had cheap in small volume
<azonenberg>
trace metal grade TMAH
<Sync_>
a wafer is 10-30$
<azonenberg>
not sure what the going rate on that is
<Sync_>
I guess tmah can be cheap
<Sync_>
but in small units hmm
<Sync_>
dunno
<Sync_>
I'd say 5k minimum for a basic setup
<Sync_>
access to a machine shop is neccessary tho
<azonenberg>
Yeah
<glowplug>
For consumables we can order in volume then do pre-packaged kits for the community.
<glowplug>
You get the economy of scale plus the cost to each hobbyist is very low.
<glowplug>
The vacuum is for which process? How strong of a vacuum?
<Sync_>
seriously, this is not the kind of thing you can pull off with a tutorial
<Sync_>
vacuum for any kind of metal deposition or plasma etching
<azonenberg>
And for evaporation you need 1E-6 torr range
<glowplug>
No I don't think tutorial. I think there are enough hobbyists out there with general knowledge of this stuff but thinking that its completely out of reach without school / work equipment.
<azonenberg>
so diffusion pump range at best
<glowplug>
They just need to be proven wrong.
<Sync_>
plasma etching wants 10^-2mbar and evap 10^-4 or better preferrably
<azonenberg>
Sputtering can be done as high as 30mtorr but that's after you have a good argon purge
<azonenberg>
So you need to get the chamber down quite a bit lower first
<glowplug>
What is the plasma etching for? This is the part of the process that I now nothing about.
<glowplug>
*know
<azonenberg>
I was initially hoping to get 10um features working with just wet etches
<azonenberg>
that might be wishful thinking
<azonenberg>
i've done 20 with wet etches experimentally and they worked fine, though i had some adhesion problems here and there
<glowplug>
I'm not sure that these FET's are switching 10kw however.
<Sync_>
they could
<Sync_>
they are not but they could
<glowplug>
This is an interesting design.
<glowplug>
The FET's are switching AC?
<Sync_>
they receive dc
<Sync_>
and make ac out of it
<glowplug>
Ahh ok I thought it was a solid state AC voltage regulator.
<glowplug>
So we are positive that a furnace with gas purging and 1200C max temp is available for $1000?
<Sync_>
about that
<glowplug>
The DIY option is probably in the $300 range + ~100 hours labor.
<glowplug>
Maybe less. Hard to say.
<glowplug>
Plus misc and consumables thats hovering at $4500-$5000
<glowplug>
For an absolute basic setup
<glowplug>
Those numbers are with the retail furnace.
<Sync_>
yeah what I said basically
<glowplug>
I wonder if it is realistic to complete a device in a distributed way. I do the litho, mail out to doping, mails out to oven, ect. ect.
<glowplug>
It would be slow but maybe possible.
<Sync_>
some processes cannot have a lot of time between them
<Sync_>
because of oxidation and contamination
<glowplug>
Ahhh yeah.
<glowplug>
Plus USPS likes to drop kick packages.
<glowplug>
Litho can be outsourced but everything else is probably best kept in a single lab.
<Sync_>
well mask making can be outsourced
<Sync_>
otherwise it takes ages
<glowplug>
By outsourced I mean one hobbyist makes a set of masks then mails those out to another hobbyist with the lab.
<Sync_>
yeah but you could also get commercial masks
<glowplug>
Absolutely.
<Sync_>
it's the same thing basically
<glowplug>
Agreed. Just the price difference. And quality. Haha
<glowplug>
What is your opinion about the PDF litho setup with the steppers? Asside from obviously switching to closed loop servos. What about the lack of interferometer feedback?
<glowplug>
Maybe thats something we can add later?
<Sync_>
yeah
<glowplug>
Thinking the same thing.
<glowplug>
I have a way way way better picture of whats going on now.
<glowplug>
Is the furnace considered FEOL?
<glowplug>
Is it its own category?
<azonenberg>
Furnace is probably FEOL since its not used once you put down metal
<glowplug>
Alright I'll add to the wiki. =)
<glowplug>
What else is FEOL?
<azonenberg>
Everything that happens before you put down the first metal layer
<glowplug>
That would include Litho then.
<azonenberg>
I'd file litho separately
<azonenberg>
since its done everywhere
<glowplug>
Good point.
<glowplug>
So for a basic setup there isn't much FEOL then.
<azonenberg>
Not too much, since we arent doing ion implantation etc
<azonenberg>
The acronyms stnad for "front end of line" and "back end of line" respectively btw
<azonenberg>
in reference to the order wafers normally go through the tools during fab
<glowplug>
Yup. =)
<glowplug>
Just burned through the wikis.
<glowplug>
These are the parts I knew *zero* about. Haha
<glowplug>
So the contact mask aligner and sample alignment optics are part of the same apparatus correct?
<azonenberg>
Yes
<azonenberg>
Initially we'll do manual alignment
<glowplug>
At this stage we are aligning the sample to be exposed in UV through the resist.
<glowplug>
*mask
<azonenberg>
Mask is to be clamped in place firmly
<azonenberg>
so we just need an x-y-theta stage
<azonenberg>
(manual)
<azonenberg>
with a relatively imprecise Z axis
<azonenberg>
Move the wafer up to just below the mask
<azonenberg>
line it up
<azonenberg>
bring it up into contact
<glowplug>
Right it needs pan and tilt also. :/
<azonenberg>
slide the microscope off and load the exposure lamp
<azonenberg>
Nop[e
<azonenberg>
nope*
<azonenberg>
Just rotation
<glowplug>
Ohh I see. Derp.
<azonenberg>
As long as you machine things such that the stage and the mask are sufficiently parallel
<azonenberg>
you just need to line up two in-plane images
<glowplug>
This apparatus also needs a small vacuum correct?
<Sync_>
pfft no fancy thing as 3d capacitors like we have on dram now? ;D
<glowplug>
OR are we just bolting the sucker down?
<azonenberg>
Light vacuum for the chuck to hold the wafer down is helpful
<azonenberg>
but that's nothing
<azonenberg>
any pump can do that
<glowplug>
Right.
<azonenberg>
Same with the spin coater
<azonenberg>
You could potentially even just use double-stick tape
<azonenberg>
but vacuum is less likely to damage stuff
<glowplug>
Agreed. And the tape is probably more expensive.
<glowplug>
So the microscope for this apparatus.
<glowplug>
Expensive unit or cheap unit?
<Sync_>
I guess getting the wafer off is quite tricky
<azonenberg>
relatively nice
<azonenberg>
But you only need one objective
<azonenberg>
not a full set
<glowplug>
~$200 optics?
<Sync_>
I guess you could use a single optic microscope
<azonenberg>
One objective, custom-made tube
<azonenberg>
then a camera on the top
<azonenberg>
You need two of them
<Sync_>
they are not too expensive even new
<azonenberg>
to see two sets of alignment marks at once
<azonenberg>
otherwise you wont get the theta right
<glowplug>
Right. One comes into focus you take a snapshot then bring the other into focus.
<azonenberg>
One on each side of the wafer
<azonenberg>
you align it approximately by naked eye
<azonenberg>
to get it into the FOV of the microscope
<azonenberg>
then tweak the stage to line it up exactly
<glowplug>
Two cameras you mean? And one scope?
<azonenberg>
you'd use a split-field view on the computer
<azonenberg>
No
<azonenberg>
Two objectives, two cameras
<azonenberg>
an inch or so apart
<glowplug>
I've seen a single scope/camera configuration.
<azonenberg>
That is... not nearly as good
<glowplug>
You focus onto one marker then snapshot it.