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<B0101>
Hi, I was looking at the logs and there was this thing about interferometry. I would like to know, what is it all about?
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<Sync_>
B0101: the interferometers are for direct laser litography position feedback
<B0101>
so you guys are experimenting writing to the photoresist directly?
<Sync_>
yes
<glowplug>
Did you read through the wiki page I'm working on for the litho?
<B0101>
yup
<glowplug>
I'm going to work on the interferometer section today hopefully.
<glowplug>
It might be awhile before there are any pictures. Maybe I will toss up some drawings soon.
<glowplug>
B0101 what is your area of expertise?
<B0101>
I am no expert at anything related to semiconductors. I only do experiments and research for the learning and the understanding of the science
<glowplug>
Which parts are you most interested in? If you want we need a lot of help with the wiki. I think Andrew is working on the spincoater. We have nothing for the magnetron, the furnace, or the developer station.
<glowplug>
Also lists of supplies and suppliers with prices ect.
<B0101>
idk, is extreme DIY on your list?
<B0101>
I could also do the list of suppliers
<glowplug>
I plan on making a microscope with PVC pipe and an x,y stage out of acrylic and homemade leadscrews. Infact I think everything on the direct write litho page is ghetto. Haha
<glowplug>
As long as there is a decent chance the extreme DIY option can meet some basic requirements then its best to use those. In many countries people dont have access to retail machinery at all. And many times not enough funds.
<glowplug>
In an ideal world everything would be custom made from common materials.
<B0101>
some people have the cash, but denied access even to the basic of lab stuff
<glowplug>
Exactly. And ideally anyone would be able to contribute.
<glowplug>
Even if they are 2,000 miles from a university.
<glowplug>
Or large equipment manufacturers wont ship there.
<glowplug>
That goal may not be met immediately. Kits might be possible to help with that in the future.
<B0101>
thats why I have no choice but to DIY a lot of stuff, and even obtain some of the basic things like chemicals from the black market
<glowplug>
Even if we DIY many things there will still be some things that are hard without some access to the outside world.
<glowplug>
Where you do you live? (if you dont mind me asking)
<glowplug>
It needs a lot of work still. Are you interested in the litho or some other steps?
<glowplug>
Actually the litho is a very small part of the whole picture. Although important.
<glowplug>
It's just the part that I know the most about.
<glowplug>
Which still isn't much. O.o
<B0101>
I work with things not commonly done in the semiconductor industry
<B0101>
maybe only used for special applications
<glowplug>
Software?
<B0101>
I do software, but I research on things like transmutation of atoms using neutrons and such
<glowplug>
I see. Well we actually need quite a lot of software surprisingly. 8)
<glowplug>
I'm learning Python and Verilog right now but I's a very slow process.
<B0101>
well, for software, I work with hardware and operating systems
<glowplug>
Assembly? C?
<B0101>
I use both of them
<glowplug>
In automation and motion control Verilog and C are king. =)
<B0101>
i see
<glowplug>
We need software to control half a dozen machines give or take. Some of it could be done manually but it would be an extremely bad idea to do so.
<glowplug>
Those are more or less the basic tools.
<glowplug>
Each one needs some kind of software. The spincoater is just a BLDC motor and a timer that one is easy. The litho is LinuxCNC but we will need custom HAL scripts and GUI elements (they are Python).
<glowplug>
The sample alignment optics will need to be totally custom software. Nothing off the shelf exists for that.
<B0101>
ahhh, i see
<glowplug>
Have you done some reading on how the process works more or less?
<B0101>
for mask alignment? not really :P
<glowplug>
I mean for the entire process. =)
<glowplug>
Starting with a mask all the way to a semiconductor.
<B0101>
oh, I know most of the basics for the entire fab process
<glowplug>
Awesome! You are probably ahead of me then. Haha
<glowplug>
The mask alignment is four crosshair patterns. Two patterned on the sample (silicon wafer) and two patterned on the mask. You have two high power microscopes above each set of crosshairs. Basically you need to align the sample to the mask perfectly. Then you develop the resist using UV.
<B0101>
i see, i see. so how much of an error margin is acceptable in alignment?
<glowplug>
None. Haha
<glowplug>
The goal is to make devices with 10um detail as a starting point. Even though that is very large for semiconductors you still dont have any margin for error in alignment. Each additional layer needs to align perfectly with the previous or the devices just wont work.
<glowplug>
This is why having software assistance would be nice. =)
<B0101>
hmmm, I was thinking of using red colored lasers to aid in alignment
<glowplug>
The patterned crosshairs do a good job in terms of visualizing where the device needs to be moved.
<glowplug>
The stage that moves around under the mask will be exactly the same as the litho stage actually.
<glowplug>
Two dials, one for X and one for Y. Each turn moves the sample a very small distance (~.1mm).
<glowplug>
That comes out to about 200nm per degree. But we wont have that much accuracy anyways.
<glowplug>
Sync_ has a great PDF explaining the process I don't have the link though. =(
<B0101>
i see
<glowplug>
Be right back.
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<B0101>
sigh, I wonder what's up with all these random router resets...
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<glowplug>
Get one of these and put openwrt on it. =)
<Sync_>
that is very close to the design you linked
<glowplug>
It is actually. Haha
<glowplug>
Lets just copy his exactly. Seems good enough to me.
<Sync_>
I wont :D
<Sync_>
it is just very flimsy
<glowplug>
The center "carriage" is just a block with four guiderods and two leadscrews.
<glowplug>
I doubt that its flimsy. But even if it was its only due to travel.
<Sync_>
get a 1/10000" dti and play around a bit, you'll get a feel for what is strong and what is not
<glowplug>
We only need to move ~100mm in each direction.
<glowplug>
His moves like 2000mm in each direction.
<Sync_>
then download roarks stress and strain
<Sync_>
and play a bit with the formulas
<glowplug>
He designed this based on stress analysis ect. ect.
<glowplug>
"A reference design was created and 3D modeled using SolidWorks, along with a corresponding set of engineering calculations predicting properties such table stiffness based on component sizing. These equations were then inverted to calculate the smallest components necessary to achieve stiffness goals based on the desired lengths of travel."
<Sync_>
his isn't so large as you may think
<Sync_>
overall length is 14"
<glowplug>
I was exxagerating. =)
<Sync_>
yes he may have done that
<glowplug>
The point is that I dont think the design requires modification. Just shrinking.
<Sync_>
build one, put the dti on it, scratch head, repeat
<glowplug>
I mean this is what commercial units look like more or less.
<glowplug>
I can't imagine that the design is bad.
<glowplug>
Also the rate of movement of our stage is very very slow.
<Sync_>
well, for a cnc mill it is, if you actually want to achieve something
<Sync_>
and more stability is always better
<Sync_>
especially because one stage has to carry the other one
<glowplug>
In all x,y stages one is ontop of the other.
<Sync_>
commercial stages often use dovetail ways
<Sync_>
which is something I'd prefer but you cannot do that without a machine shop
<glowplug>
Right.
<glowplug>
And at these extremely slow speeds I just dont think theres any advantage.
<glowplug>
But I suppose thats what open standards are for.
<glowplug>
If we each build a stage our own way we can compare or even merge the designs.
<Sync_>
the problem with the second stage is the momentum, when it moves the CG will wander and twist the rods
<glowplug>
At a movement rate of 10um per second?
<glowplug>
I'm not sure there will be any twisting. O.O
<Sync_>
speed is not the important thing
<glowplug>
Twisting by forces applied by momentum over time.
<glowplug>
Speed matters for sure.
<Sync_>
time is not important.
<Sync_>
we do not fast enough for dynamics
<glowplug>
Certainly twisting is a time dependant event. =)
<Sync_>
this is a completely static system from an engineering point
<Sync_>
yes
<Sync_>
but only the maximum deflection is interesting
<glowplug>
So backlash?
<Sync_>
because that is the number you engineer for
<Sync_>
no
<glowplug>
Deflection where?
<Sync_>
imagine his XY table
<Sync_>
lets say the X is the top one
<glowplug>
All x,y stages have a top but I'm with you. Haha
<Sync_>
so the Y moves back and forth and the X right to left
<glowplug>
Right.
<Sync_>
imagine the Y is in the middle of it's travel
<glowplug>
K
<Sync_>
and now the X is at the position where the stepper is the furthest away from the Y
<Sync_>
in his pictures to the rightmost
<glowplug>
The carriage?
<Sync_>
yes
<glowplug>
Ok so what causes the deflection?
<Sync_>
now we can think of our X stage as a long rod
<Sync_>
with a function of weight
<Sync_>
that has a center of gravity somewhere
<glowplug>
Agreed. Which in my design is .5 ounches including the sample.
<glowplug>
*ounces
<glowplug>
Because the stepper has to move a nearly weightless sample and an acrylic carriage.
<Sync_>
well your stepper has a certain weight
<Sync_>
and when the CG is out of the second Y rail it'll try to bend the right one down and the other one up
<glowplug>
It does. But it would likely be bolted to the table.
<Sync_>
then you lock everything up
<glowplug>
So the part of the design that you dislike is that the stepper is elevated?
<Sync_>
you cannot have both steppers fixed to the table
<Sync_>
no, that's not the problem but just the issue why this thing needs to be stronger
<glowplug>
Right. So how do you mitigate the problem at all?
<Sync_>
making the rods stiffer by making them larger
<Sync_>
or limiting travel (or both)
<glowplug>
Agreed.
<Sync_>
(and making everything lighter)
<glowplug>
But we reduced travel by an order of magnitude and kept the same size rods.
<glowplug>
Seems legit to me. Haha
<Sync_>
I'll have to run the calculations but chances are that it'll be fine
<Sync_>
the order of magnitude is quite the overstatement
<Sync_>
we have something between a third or half his travel
<Sync_>
+-
<Sync_>
but yes I'll need to do some simulations
<glowplug>
We will be working on 7" diameter wafers?
<Sync_>
attention: 14" span does not mean 14" travel
<glowplug>
I thought you said he had 14" travel.
<Sync_>
I said overall length
<glowplug>
If the travel difference is not that great. Then I agree we should probably make a few changes. =)
<glowplug>
For starters we can use NEMA-14 steppers that are extremely thin, and tighten up that coupling joint.
<Sync_>
the other problem is that the bushings will have a clearance fit
<Sync_>
I guess nema 8 or 11 would do
<glowplug>
I couldn't find ones with 400 steps per rev that were smaller than 14.
<Sync_>
hmm true
<Sync_>
the smallest nema 14 that's in a useful format is 90g in a quick search
<Sync_>
hm those seem to be the same as the ones in old FDDs
<glowplug>
The manufacturer is schrittmotor.
<glowplug>
Really???
<glowplug>
No way those are 400s/r....
<glowplug>
I don't think the FDD steppers are that good. We might have to order directly from schrittmotor.
<Sync_>
they are pretty fine
<Sync_>
1.8° at least I do suppose they are .9
<glowplug>
The FDD steppers?
<glowplug>
If they are .9 degrees I would be amazed.
<soul-d>
:(
<glowplug>
In a good way.
<glowplug>
They are the round type also that you dislike.
<Sync_>
not in all drives
<Sync_>
I have a fes that are like the nema14 one that is square
<Sync_>
they probably are 1.8° from what I feel
<Sync_>
but you can just do halfsteps
<glowplug>
Oh you are talking about 5.25" floppy drives...
<Sync_>
soul-d?
<soul-d>
browsing tea section online supermarket for plain mint tea
<soul-d>
im at page 6 now
<Sync_>
I just get fresh mint out of the garden
<Sync_>
it's win
<soul-d>
yeah i think thats better ieda
<soul-d>
seeds are like 1 meter away
<Sync_>
you should be able to grow it insides
* soul-d
whistles
<soul-d>
know nothing about growing indoor honestly
<glowplug>
Those are unipolar. I haven't figured out its pole density.
<Sync_>
I also have some melissa and sage
<glowplug>
Where would we reliably find 5.25" floppy drives?
<soul-d>
growing buth jolokia atm
<Sync_>
the local scrapyard?
<soul-d>
anyhow quite sad all those flavored tea's page afther page
<soul-d>
ofcourse all face aroma's on black tea
<Sync_>
heh
<Sync_>
yeah
<Sync_>
I import some out of india
<Sync_>
because all the stuff you can get here is meh if you had some that was the real deal
<soul-d>
wonder if i would reacorgnise true tea
<soul-d>
same with appel juices
<soul-d>
all fruit juices
<Sync_>
heh
<Sync_>
we bring our apples to the juice place
<soul-d>
waiting till my tiney tree will bear first fruits
<Sync_>
they now even have a service where you actually get your own juice and not a mix
<soul-d>
2 years in garden now
<soul-d>
oh well super does have some funky machiene but still then the fruits come from some weird country
<soul-d>
probably pest sprayed
<Sync_>
did you buy one from a tree school?
<soul-d>
bought it in belgium from some tree thingy got send trough mail even :P
<soul-d>
had to see the face of the delivery guy
<Sync_>
hmm no local tree school?
<Sync_>
it takes quite a while for them to bear fruits
<Sync_>
we actually have pear that produced TWO damn pears in 30 years
<soul-d>
it is alive and standing so thats fine maybe this year well see
<Sync_>
I'm so close to cut it down
<soul-d>
ll dont have that much patience i think
<Sync_>
we have some apples we planted 10 years ago and they took 3-4 years to be useful
<soul-d>
lol
<Sync_>
the cherry we planted kind of dies every year
<soul-d>
"sleepy time green lemon / jasmine "
<soul-d>
i think im gonna give up on that mint tea
<soul-d>
cherrt tree we had in old garden did well as long you where quicker then birds
<Sync_>
just buy some mint and grow it
<Sync_>
it is so much better
<soul-d>
grabbed the seeds better start planting them : field mint , spear mint , agastashe rugosa to sweeten it stevia/sugarleaf
<soul-d>
and seemds indianp paintbrush/nettle leaves might be used to but since ive bought also lots of dye plants so better double check it next to what bag say's