<azonenberg>
Would allow some interesting MEMS processing with no need to do film deposition (except for metal evaporation but that's a bit easier to homebrew than PECVD)
<azonenberg>
only downside for my application is that it's (100) orientation and not (110)
<azonenberg>
but it might be able to live with that
<azonenberg>
i think using laserlab masks and that, i could make a comb drive with my current lab setup plus the evaporator on campus
<azonenberg>
a full wafer of them, no less
<azonenberg>
I'd just need some hot phosphoric acid to go through the nitride... let's see
<azonenberg>
Thermal oxide in KOH is 7.7nm/min, or 23nm/min in room temp 10:1 HF
<azonenberg>
Phosphoric barely touches it
<azonenberg>
0.18nm/min
<azonenberg>
Nitride in HF is slow (<1 nm/min) but phosphoric is 2.7nm/min
<Sync_>
oh dual side polished
<azonenberg>
actually that's for Si-rich, stoichiometric is 4.5nm/min and high-RI is 20nm/min
<azonenberg>
Yes, and coated on both sides
<azonenberg>
So let's assume stoichiometric for now
<azonenberg>
50nm means just over ten minutes in the wet etch
<azonenberg>
Negligible undercut for MEMS-sized features
<azonenberg>
ten minutes in hot phosphoric
<azonenberg>
Then switch to HF to go through the thermal oxide, using the nitride as a mask
<Sync_>
quite expensive tho
<azonenberg>
assuming we use my very weak (~2%) HF but slightly heated it should be about the same, 23nm/min
<azonenberg>
so 300nm will be around 15 minutes
<azonenberg>
Which will also eat about 5nm of the nitride, but not enough to matter
<azonenberg>
Now we have bare Si exposed and can do a KOH etch
<azonenberg>
And yes, but it means i can do MEMS work with my current lab
<azonenberg>
no need for a furnace or CVD etc
<azonenberg>
not even spin-on glass
<azonenberg>
as long as i can live with that particular oxide-nitride stackup
<azonenberg>
now to make sure 10 minutes in hot phosphoric won't kill my photoresist...
<Sync_>
I should ask if I can use the other cleanroom when nobody is processing there
B0101 has joined #homecmos
<azonenberg>
Looks like some resists peel in hot phos
<Sync_>
I could make you some wafers for a lot less :D
<azonenberg>
etch rates of between 50 and 100nm/min
<azonenberg>
so ten minuts would be 0.5 to 1 micron
<azonenberg>
significant, but not enoguh to have breakthrough
<azonenberg>
this might actually work
<Sync_>
yeah
<azonenberg>
i might want to get myself HMDS to prime it, and i still need a better spin coater
<azonenberg>
But if i could design myself a comb drive that would work with <100> wafers using a KOH etch
<Sync_>
we had to vent the MBE yesterday :/
<azonenberg>
why?
<Sync_>
wiggle stick got stuck
<azonenberg>
And lol, it would be nice if you could make me some wafers but i think thats unlikely
<Sync_>
the threaded rod that actuates the wafer handler
<Sync_>
got unscrewed
<Sync_>
(that happens regularily)
<azonenberg>
lol
<Sync_>
but is not an issue because you can screw it back in
<azonenberg>
once you vent it
<Sync_>
but we found out if the wafer is in the clamp you cannot screw it back in
<Sync_>
no it is on the air side
<azonenberg>
oh, hmm
<Sync_>
but when the wafer is in the clamp the hole is offset at an angle
<Sync_>
so you have to vent
<azonenberg>
oh, i see
<Sync_>
I should be able to
<Sync_>
we have a company inhouse that does research on furnances
<Sync_>
so we have shitload of unused ones
<azonenberg>
of unused wafers? lol
<azonenberg>
with known films on them?
<azonenberg>
My current thinking is
<azonenberg>
contact litho using LaserLab mask
<B0101>
hi, does anyone know how to polish wafers?
<Sync_>
we have some shitty wafers we don't want to use for experiments
<azonenberg>
i can get by with pretty loose alignment
<Sync_>
I can use them for free
<azonenberg>
front to back
<Sync_>
and oxidizing is not too bad
<azonenberg>
then front to metal will be pretty loose tolerances too
<Sync_>
B0101: on a lapping machine
<azonenberg>
Well, i need oxide + nitride
<azonenberg>
KOH eats Si for breakfast and likes SiO2 for dessert
<azonenberg>
but nitride is too crunchy
<Sync_>
I'll ask around
<Sync_>
but I think it'd be possible
<azonenberg>
Anyway, no immediate need
<azonenberg>
i want to try with the MTI wafer since thats something i can readily source
<azonenberg>
and that's contingent on me getting a better spin coater
<Sync_>
and haha, the ebeam evap control got a bit out of hand on the other MBE
<Sync_>
and melted a bit of the crucible
<azonenberg>
I know a guy wh odid that here
<Sync_>
it was quite annoying to pound that Si block out of there
<azonenberg>
got in some trouble for it :p
<B0101>
hmm, I am not sure about getting wafers off ebay
<B0101>
Darn: I don't get why certain students actually tried consuming CuSO4, darn, report coming up...
<azonenberg>
consuming?
<azonenberg>
like, ingesting?
<azonenberg>
that can't be healthy
<B0101>
ingesting? yes, though according to the other lab tech, the student only consumed a little bit
<azonenberg>
o_O
<azonenberg>
these are... college students?
<azonenberg>
they should know better...
<Sync_>
no
<Sync_>
they don'T
<Sync_>
also, why not taste it?
<azonenberg>
Darwin award?
<Sync_>
#yolo *hides*
<Sync_>
but being a college student doesn't mean that you know anything tbh
<azonenberg>
lol
<Sync_>
hm CuSO4 was used as an emetic agent
<Sync_>
can't be that bad.
<B0101>
I don't think CuSO4 taste sweet, does it? o_O
<Sync_>
no
<Sync_>
it tastes bitter
<azonenberg>
makes sense given the sulfate
<azonenberg>
still, you have to wonder what said person was thinking
<soul-d>
i read copper is verry toxic when i was researching it a bit
<Sync_>
it works because it irritates the stomach walls like most cytotoxins
<azonenberg>
soul-d: copper ions are not exactly healthy
<B0101>
according to the original incident report, the student claims that CuSO4 tasted sweet
<azonenberg>
B0101: ...
<Sync_>
then it was not coppersulfate
<Sync_>
or he has a very strange taste
<Sync_>
heavy metal ions in your body are generally not too good
<azonenberg>
Te lab accidents i normally hear about are things like "poured chemical into wrong beaker, blew up"
<azonenberg>
the*
<azonenberg>
not "decided to randomly drink some chemical" lol
<Sync_>
I'm annoyed to some degree by a lot of that safety craze
<Sync_>
especially when it gets in the way of working safely
<B0101>
here, I am shocked: the students don't even get latex gloves when working with chemicals, especially corrosive ones
<B0101>
Imagine handling HCl, or even HNO3 w/o gloves
<B0101>
I have written letters to the safety department, but no responses even after the 3rd letter
<Sync_>
huh
<Sync_>
hcl is not bad
<Sync_>
I have some scars on my hands where NaOH tried to soap up my hands
<B0101>
ah, NaOH... some students even teacher's think that basic chemicals can be treated like innocous chemicals
<Sync_>
it could be worse
<Sync_>
if the solution is not too awfully concentrated you just wash it off your hands
<Sync_>
I can see where the "hurr wear gloves for everything" comes from, but there usually is no real need for them
<B0101>
wow... just to do hydrogen test: 'Placed zinc metal into test-tube, poured conc. HCl into test-tube, student stoppered off test-tube. Started heating up test-tube from bottom,causing test-tube to explode"
<B0101>
2 incidents in 1 day, same lab session...
<Sync_>
that is quite an achievent to stopper it off so hard that it explodes
<B0101>
I don't know how a student managed to do that, as all the time we tried that, the stopper pops off the test-tube
<Sync_>
it is possible, probably overheated the tube
<B0101>
no matter what the cause, the lab techs are going to be in trouble once science dept asks
<B0101>
speaking about safety: I believe that labs should be safe, except when people do stupid things
<Sync_>
well, most safety aspects are about training, there are not that many constructive safety measures you can take in an R&D lab
<Sync_>
you can provide proper workspaces, appropiate for the job, like fume hoods and such but apart from that
<B0101>
but then here, the war on terror is getting so absurd that people have difficulty setting home labs here
<B0101>
in fact, if they suspect you being a terrorist, they arrest you and under my country's law, the can detain anyone without trial for 2 years and that may be extended depending on the government
<B0101>
just as long as 1 officer suspects, even without evidence, that still applies
<B0101>
so actually, the so-called safety rules here just hinder the school lab from operating with audits and checks from the government
<B0101>
they think as if some student or lab tech is going to make explosives or something
<Sync_>
but that's what they do :D
<Sync_>
we made all kinds of explosives in chemistry class in school
<B0101>
heck, If I try to do that here, I'm doomed
<Sync_>
way more fun than regular high school chemistry
<B0101>
heh, too bad I have no chance to experience that here
<Sync_>
you just have to have cool teacher
<B0101>
here, law doesn't allow it
<Sync_>
here too
<Sync_>
but who cares
<berndj>
i thought the royal navy gave their sailors CuSO4 to prevent them from catching gayitis
<berndj>
our high school science teacher regularly drpped slices of sodium into a tube of bromine
<berndj>
made a nice bang
<berndj>
i can't find a reference for CuSO4 in the royal navy; quite possibly a crappy HS textbook / bogus storytelling from the teacher
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<B0101>
hmm, I am not sure how they deposit copper onto boards to make copper boards for PCB making, anyone has any idea?
<Sync_>
electroplating
<Sync_>
a thin foil is glued on in the first place and then the rest is deposited
<B0101>
hmm, I not sure if we can create different layers of CuO and Cu2O to make devices
<Sync_>
wut
<B0101>
I was thinking that since both CuO and Cu2O are semiconductors, if we can create different layers of the 2 on one board, we may be able to make simple things like transistors
<Sync_>
probably not
<B0101>
ok then, and can we melt bits and pieces of silicon to make ingots?
<Sync_>
probably but what would a Si ingot do?
<B0101>
well, I am looking for ways to obtain Si and other semiconductor materials as the supplier I usually go to has increased the price
<Sync_>
manufacturing your own wafers is quite impossible or rather very unlikely due to the cleanliness issues
<B0101>
I want to try to make a simple NMOS transistor
<Sync_>
then just get wafers from ebay
<Sync_>
but do not expect anything from the transistor
<Sync_>
the problem more or less with wafers from unknown sources is that you really do not know what specs they have or how good they are qualitywise
<Sync_>
which are things you want to eliminate in semiconductor manufacturing
<B0101>
darn, now I have to risk buying potentially impure wafers or buy a pack of 25 for $5000
<Sync_>
for a very very basic transistor grade of the wafer is not the prime concern
<berndj>
would a FET of either polarity be easier to make than a BJT?
<Sync_>
yes
<Sync_>
two contacts, oxide, gate
<Sync_>
much easier
<berndj>
B0101, i think i read in a book somewhere that they do some electroless nickel (or even paladium? but maybe that's just for plated vias) on a board and then plate the rest of the thickness with copper
<Sync_>
yep
<berndj>
Sync_: metal gate, i'm guessing?
<Sync_>
most fabs use a palladium process
<Sync_>
it doesn't really matter
<Sync_>
use anything conductive
<berndj>
it matters if you want to DIY :)
<Sync_>
but yes a metal gate is probably what you want to use
<Sync_>
no
<Sync_>
:D
<Sync_>
I guess you could use conductive epoxy
<berndj>
paper + fibreglass epoxy + copper foil :)
<berndj>
then you can use cheap HSS drills too
<berndj>
yeah, jeri ellsworth used conductive epoxy for her FETs
<Sync_>
I'd just evap some copper
<berndj>
(btw azonenberg you need to get her into this channel!)
<berndj>
evap? sputter? i thought the pcb material might not be so high vacuum compatible
<Sync_>
wat, I was talking about the fets
<Sync_>
pcb material is just so cheap to buy
<berndj>
oooh sorry, got confused there
<Sync_>
there is no need to diy
<berndj>
for fun!
* berndj
points Sync_ at the first 4 letters of the channel name
<Sync_>
yes, but there really is no point besides fun
<Sync_>
I do plated vias at home but that's as far as I'd go
<B0101>
wow, even optics shops carry silicon wafers??? O_o
<Sync_>
Si is IR transparent
<berndj>
i might still make DIY PCB just because it makes drilling easier, because then i can use paper, for example. HSS-friendly. HSS drills seem to come smaller than TC drills (while still fitting my budget)
<berndj>
you plate vias with that palladium process?
<Sync_>
yes
<berndj>
cool!
<Sync_>
you can just get phenolic pcbs
<berndj>
didn't think you could still get those (but i'm a n00b)
<Sync_>
and carbide tooling is not too expensive
<berndj>
well, i can buy 0.3mm drills for pocket change at a local shop; i wouldn't even know where to get the same size in carbide
<berndj>
never mind what it'll cost me
<Sync_>
a very high quality one will run you 14€
<Sync_>
but it'll last a long time
<Sync_>
you could also resharpen the drills
<berndj>
14 euro??? where!?
<Sync_>
hoffmann
<berndj>
last quote i had from a local supplier was R700 (just under $100 i guessconvert) for a 0.5mm carbide drill
<Sync_>
R?
<berndj>
south african rand
<Sync_>
58€
<Sync_>
that is quite a ripoff
<berndj>
it's possible it's optimized for different uses, namely metal fabrication, not making holes in PCBs
<Sync_>
a .3mm HSS drill should run you around 6€ in a good quality
<Sync_>
the only thing that can be changed is the cutting geometry
<berndj>
yeah, something close to that, not 5x more
<Sync_>
and that does not matter too much when drilling pcbs
<berndj>
and the length of the spirally bit, forget its name
<berndj>
the flutes
<Sync_>
yeah the flute angle is something to be considered but for hobby production it does not matter at all
<berndj>
guy i spoke to said they can go up to 70:1 l:D ratio (which is wholly unneeded for PCB)
<Sync_>
yeah it is possible but only with specialized geometry
<berndj>
i mean the *length* of the flutes
<berndj>
which at 0.3mm would be a 21mm hole
<Sync_>
yeah with very small bits it tends to be a problem but with regular pcbs every drill should cut it
<berndj>
do the PCB shops drill one board at a time or do they drill a whole stack at a time?
<Sync_>
haha
<Sync_>
they do one at a time
<Sync_>
drilling a stack will break your drill
<berndj>
and they run their drills at an unholy rpm, right?
<Sync_>
yeah
<Sync_>
sometimes over 100000rpm
<Sync_>
but that's nothing too special
<berndj>
no? lol, so what is?
<Sync_>
well you can buy spindles made for that on every corner
<berndj>
i still need to build a PCB drill. biggest obstacle is figuring out how to chuck it
<berndj>
probably a collet is easiest
<Sync_>
just get a dremel or proxxon tool
<berndj>
lol, you must live in a first-world country
<berndj>
i thought those tools have rather suboptimal runout?
<Sync_>
they work fine for diy pcbs
<Sync_>
I just call kavo or gmn and they are happy to sell me a spindle that can do it
<berndj>
the joys of being in a first-world country :-/
<Sync_>
(I actually do not want to pay their prices but it'd be possible)
<Sync_>
I'd think they'd be happy to ship to south africa
<berndj>
i'm sure. i just don't feel like running the credit card gauntlet. (i don't have one (yet?) and don't really want one - rarely miss having one)
<Sync_>
but really a dremel tool or such will do it for you
<berndj>
i guess that's my fallback. those are easy to get here
<Sync_>
we use a mb140 and the proper drill for it at our hackerspace and it is very good
<berndj>
in what city are you btw?
<Sync_>
hannover
<berndj>
i'm also german
<Sync_>
I suspected that
<Sync_>
:D
<berndj>
my family's from ex-germany though (bautzen and further east even)
<Sync_>
cool
<Sync_>
that's close to my home town
<berndj>
just don't say uhyst?
<Sync_>
not that far east but colditz
<berndj>
i recognize that name
<Sync_>
close to grimma
<Sync_>
how did you end up in SA?
<berndj>
my mother's family had a schloss in pannewitz 100+ years ago, but i guess we gambled the estate away or something
<berndj>
we ended up in the SA because of the 7 day war! suez canal was closed so the tug my dad worked on had to go via cape town
<berndj>
fell in love with the place and decided to move here
<berndj>
anyway, i'm jealous of you first world people with your proper hackerspaces :)
<Sync_>
move back to the civilized world :P
<berndj>
we have one here, but it only just got started and it's mostly just software people. i guess we don't have the density of engineers that you have in europe / north america
<Sync_>
most of the people in hackerspaces do not have an academic engineering background
<berndj>
i mean "engineer" more broadly - maker types