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<Sync>
azonenberg: my prof told me to try regular photoresist for pcbs
<Sync>
it should work pretty good
<azonenberg>
regular resist?
<azonenberg>
define regular
<Sync>
as in the stuff you buy in the electronics store to coat your pcbs
<azonenberg>
as opposed to cmos grade?
<azonenberg>
it'd be cheaper for sure
<Sync>
yeah, he said for our structure sizes and general conditions it is not neccessary to get professional resist
<azonenberg>
what are yo utrying to do ?
<azonenberg>
i've done 5 micron features with pcb resist :p
<Sync>
nothing special, just had a chat with him after the lecture
<azonenberg>
basically, pcb resist isnt trace metal grade
<azonenberg>
but for anything non-cmos it should be fine
<Sync>
trying to do cmos will require some serious effort
<Sync>
the worst enemies are Ni and Au
<azonenberg>
How about K and Na :P
<Sync>
Ni diffuses through Si at room temp
<Sync>
that caused some headaches here
<azonenberg>
or, heaven forbid, Li
<azonenberg>
Si(Li) EDS detectors cant even be turned on at above cryogenic temps :P
<Sync>
yeah but you don't have those on your tweezers :P
<azonenberg>
oh
<azonenberg>
wait, you were using Ni-plated tweezers to handle chips
<azonenberg>
and that caused problems? o_O
<Sync>
yes
<Sync>
it ruined the wafer
<azonenberg>
Did you do any high-temp processing on it?
<Sync>
we were wondering why our HEMTs were so slow
<Sync>
no
<Sync>
they were just sitting around
<azonenberg>
wow
<azonenberg>
i was going to say, it would make sense if you had heated it
<azonenberg>
but at room temp, wow
<Sync>
just from the edge handling
<azonenberg>
The entire wafer?
<azonenberg>
or just dies near it
<Sync>
it was distributed through the whole wafer
<azonenberg>
Wow
<azonenberg>
over how long
<Sync>
not equally but still
<azonenberg>
diffuison over that much of a distance must take a while at room temp through solids, right?
<Sync>
I suspect a few weeks
<azonenberg>
And how did you trace it to Ni contamination?
<azonenberg>
its a heavy metal, i wouldnt expect it to diffuse that fast
<Sync>
we looked at every process step
<azonenberg>
Na or K i could understand
<Sync>
because it just did not make sense that the devices were so slow
<Sync>
so it HAD to be metal contamination
<Sync>
but we could not see why
<azonenberg>
So more to the point, when you changed tweezers
<Sync>
and then we did one wafer being anal no metal came in contact with
<azonenberg>
did the problem go away?
<Sync>
and it worked
<Sync>
yes
<azonenberg>
wow
<azonenberg>
And you're sure it was Ni
<azonenberg>
rather than, say, K contamination on that particular pair of tweezers?
<Sync>
those were Ni plated stainless tweezers only used to handle wafers
<Sync>
in our flowbench
<azonenberg>
Did you do any testing on those tweezers, i mean
<azonenberg>
to confirm
<Sync>
we put them in the ultrasonic cleaner and tried again
<Sync>
and it still failed
<azonenberg>
Hmm, interesting
<azonenberg>
because i'd believe it was metal contamination
<Sync>
so we are pretty confident that it is ni
<azonenberg>
but i'm skeptical that it's the actual tweezer metal
<azonenberg>
as opposed to a contaminant
<azonenberg>
Is Ni known to diffuse at room temp?
<azonenberg>
it just seems counterintuitive that something so heavy would diffuse from momentary contact at room temperature with no high-temp processing
<azonenberg>
if you had a metal chip on the wafer and put it in a furnace i could understand
<azonenberg>
through a whole wafer no less ,rather than just the dies near where it was handled
<Sync>
it was strange
<Sync>
we did not really investigate after we found the issue
<Sync>
it seems the selfdiffusion rate is around 10^-8m²/s
<Sync>
it was a really strange problem
<azonenberg>
i mean for B and P i'm used to hearing of tens of minutes to hour diffusions at 1200C
<azonenberg>
and thats for a few microns
<azonenberg>
i wouldnt expect horizontal diffusion through several cm of Si to take place at room temp at any appreciable rate
<azonenberg>
as opposed to if you were diffuisng in through the surface from contamination in a bath etc
<Sync>
plz wait, I have to start my process
<azonenberg>
Does your lab have a rule about only CMOS-grade resist on the coaters?
<azonenberg>
the cleanroom here does
<Sync>
I don't think so
<Sync>
I suspect that there was some thermal process after that.
<azonenberg>
after you handled them?
<Sync>
just reading some protocols again
<azonenberg>
And was there an RCA clean first? :P
<azonenberg>
if not, there's your problem :P
<Sync>
we always hf dip, priahna, ozone and hf dip wafers before every process
<azonenberg>
is piranha good at trace metals?
<azonenberg>
i'm used to using RCA-2 for that
<Sync>
we ususally have no trace metal on the surfaces
<azonenberg>
well you did this time
<azonenberg>
which is why i'm asking
<Sync>
we used wafers from the same carrier
<Sync>
and the same prep
<Sync>
and after we changed the tweezers it was fine
<Sync>
aha.
<Sync>
the wafers had some heating done to them in the 400-600°C range but not all of them where we made lifetime measurements
<azonenberg>
and were they cleaned before that?
<azonenberg>
if not, there's your problem
<Sync>
and in those that were kept at room temperature it was less pronounced
<Sync>
yes they have gone through our regular process
<azonenberg>
RT diffusion i would expect little to none, 600C is significant
<azonenberg>
no, i mean during the lifetime measurements
<azonenberg>
were they cleaned before going in the oven?
<Sync>
yes
<azonenberg>
Your clean sucks :P
<Sync>
so how does that explain the bad lifetime on the wafers that were just stored for further processing?
<Sync>
:P
<Sync>
something strange was going on obv.
<soul-d>
so no NERD_N_130F in mail yet :( would expected this revision in stock since it was used as example
<azonenberg>
soul-d: Lol
<soul-d>
no complaint information either
<soul-d>
can't even complain
<azonenberg>
Yeah, the resellers have a habit of taking a long time
<azonenberg>
and if you go to the vendor you have to wait for the 9-month factory lead time plus many years of firmware updates
<azonenberg>
why cant they just ship with full firmware images from the factor???
<azonenberg>
factory*
<soul-d>
you might want to include an age code :P
<soul-d>
_xxJ would be comon on chips to
<azonenberg>
soul-d: standard JEDEC date code will be included in the packaging information section
* azonenberg
is date code 9033 :P
<soul-d>
anhow http://imgur.com/jnpEC would expected beter then 30 mA but i should probably focus on measureing the resitance maybe put in a coil of few can's and get rid of paint of it first
<azonenberg>
what is this apparatus?
<soul-d>
target is generating oxigen
<azonenberg>
i see a red bull can and a hose, that can't be good
<soul-d>
outer can is -
<Sync>
wat. pressure just went through the roof in thermal cleaning
<soul-d>
adn the can is the sacrificial one
<soul-d>
should gerate oxigen if im correct :P
<soul-d>
outer can should generate hydrogen and be protected a bit but did read metal can have hydrogen somthign failure and become brittle
<Sync>
hydrogen embrittlement
<Sync>
but that is not going to be a problem there
<Sync>
mostly pronounced when welding
<soul-d>
and i want to oxdize copper :P to cuprous oxide or somthing so don't realy expect much since i doubt reaction happens quick but formula din't mention heat or something
<soul-d>
now i only have to figure out how to increase current to reasonably test it
<Sync>
how about just heating copper?
<soul-d>
no thats the black oxide
<soul-d>
i want the red one cuprous (i) oxide
<soul-d>
one is CuO other is Cu2O
<Sync>
ah yes true
<soul-d>
im doing it to learn an do some chemistry ofcourse i could probable buy most stuff cheaply
<Sync>
bah
<Sync>
goddamn machine
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