<azonenberg>
I think i might try immersion litho later tonight
<azonenberg>
See if i can get even a small portion of my field to expose nicely at 2um feature size
<azonenberg>
and, if i'm feeling bold, fool with double patterning to hit 1um
<azonenberg>
Though perhaps "bold" isnt the best word to use to describe making lines *thinner* :P
<berndj>
immersion and double patterning still seem like magic to me
<azonenberg>
Double patterning isnt that bad
<azonenberg>
in this case the goal would be to create 1/2 sized lines at 1/2 the spacing
<azonenberg>
Start out by exposing a normal line/space mask
<azonenberg>
But do so for half the usual time
<azonenberg>
Develop just enough that you can see the marks
<azonenberg>
then re-expose with the pattern 90 degrees out of phase
<azonenberg>
Develop again
<azonenberg>
The only spots that will get removed when you develop are those that were hit by both exposure steps
<azonenberg>
since each on its own is too weak to fully dissolve the resist
<azonenberg>
Now you have 1/2 sized lines at the usual spacing
<azonenberg>
Etch
<azonenberg>
Strip resist and re-coat
<azonenberg>
Repeat the entire process 180 degrees out of phase
<azonenberg>
now you have two patterns of half-width lines at normal spacing
<azonenberg>
each shifted by 180 degrees
<azonenberg>
the end result is half-width lines at half spacing
<azonenberg>
I might try doing this at the 20um process (which is relatively well established) and immersion litho (for 2um) separately
<azonenberg>
get each working decently well
<azonenberg>
and only then attempt combining the two to hit 1um
<azonenberg>
then if i can get better mask fab capabilities, 500nm on at least a Poc level might be possible
<swkhan>
azonenberg: still working on copper electroplating of silicon and am reading more before i try anything stupid =p
<swkhan>
i can't figure out why chromium is so good at adhesion but i ran into one paper that i really liked that i'd like to share
<swkhan>
i also need a bit of advice =)
<azonenberg>
sure
<swkhan>
i really really really like this paper: www.ims-chips.de/content/pdfpublicationorig/471orig.pdf (copper electroplating for integrated rf-devices). there's only one term i don't quite get. the iv. conclusions section on page 6 says "A paddle cell has been successfully used for the electrochemical deposition of smooth, bright Cu blanket films onto 4" Si wafers. The uniformity of the film thickness can be kept within tight limits by activation of a copla
<azonenberg>
and re adhesion, h/o *finds paper*
<berndj>
oh, does double patterning just mean you can more finely control the *phase* of your spacial distribution but you still can't cheat and achieve a higher spatial *frequency*?
<azonenberg>
berndj: No
<azonenberg>
Let me make a graphic, h/o
<azonenberg>
You can double frequency
<berndj>
see, that seems like magic to me!
<azonenberg>
It relies on you having better alignment precision than exposure precision
<azonenberg>
for example, in my case i am limited by resolution of mask printing
<azonenberg>
but can do micron or evne submicron alignment
<berndj>
oooh i think i get it - at least in your case (not diffraction limited)
<azonenberg>
Correct
<berndj>
oooh i think i get it even in diffraction limited cases
<berndj>
you pattern every *2nd* "line" in each step, thereby staying within the diffraction-limited possibility?
<azonenberg>
Effectively, yes
<azonenberg>
Re double patterning
<azonenberg>
Let's say the smallest feature you can do on a mask is 5 um
<azonenberg>
but you can align down to 1 um
<swkhan>
azonenberg: did you get a chance to see the paper btw?
<azonenberg>
first you expose the blue mask halfway
<azonenberg>
then shift by 2.5um and expose the green
<azonenberg>
the red area is the only area that's fully exposed
<azonenberg>
This gives you 2.5um lines on 5um centers
<azonenberg>
etch these, strip resist, re-coat
<azonenberg>
repeat the process to put another set of 2.5um lines on 5um centers phase-shifted 180 degrees from the existing one
<azonenberg>
the end result is 2.5um lines on 2.5um centers with four exposures
<azonenberg>
I'm hoping to use a similar technique on my hypothetical 2um process (assuming i get immersion litho working) to shrink from 2 down to 1
<azonenberg>
immersion would let me use the highest objective on my microscope to achieve 100x reduction, taking a 200um sized mask and making 2um features
<azonenberg>
swkhan: looking now
<azonenberg>
They say copper is resistant to KOH but i had some issues with that
<azonenberg>
i need to try again now that i have a Cr adhesion layer on
<azonenberg>
Ok, here we go
<azonenberg>
They used a sputtered Ti + TiN adhesion layer
<azonenberg>
then a thin Cu layer to start the plating off of
<azonenberg>
and electroplated 6um of Cu on top of that
<azonenberg>
swkhan: Ok, very interesting paper but it doesnt eliminate the need for sputtering
<azonenberg>
it just means you can do thicker layers faster
<azonenberg>
your question?
<swkhan>
sorry i was helping a labmate
<swkhan>
i see that they have a sputtered layer too and i'm hoping i don't really need it somehow.. =\
<swkhan>
i was more interested in the section on blanket deposition on the wafer for right now
<azonenberg>
The Ti/TiN is both adhesion and a barrier to prevent the Cu from diffusing into the Si
<azonenberg>
Ti is adhesion and TiN is barrier
<azonenberg>
if you dont care about copper contaminating your silicon then you can skip the barrier layer
<swkhan>
the conclusion and a few other sections say something about the activation of a coplanar auxiliary cathode
<swkhan>
well i just need a metal contact layer. what happens if silicon is contaminated by copper?
<azonenberg>
So the wafer is the cathode and the plating source is a flat anode
<azonenberg>
but it looks like they throw an extra cathode in there somewhere else to modify the shape of the field
<swkhan>
i plan to run IV measurements with the bottom contact. later i want to try patterning
<azonenberg>
reference 4 should talk more about it
<azonenberg>
And what are you using your silicon for?
<azonenberg>
a mechanical substrate or actually as a semiconductor?
<azonenberg>
I dont know the exact effects but afaik transition metals ions in general will reduce charge carrier lifetime
<azonenberg>
Which is generally bad for any kind of CMOS etc
<azonenberg>
And as long as your feature size isnt too small and you have photoresist and some common lab chemicals available, patterning is the easy part
<swkhan>
i don't think i'm really using the silicon as anything over than as a mechanical layer to hold everything up
<swkhan>
i don't have photoresist, but i'm willing to learn. i think it was this paper that got me really interested in it though. you can remove some photoresist with just acetone? =D
<swkhan>
you know so much it's incredible
<azonenberg>
I use Shipley SP24 positive photoresist
<azonenberg>
i'm now using the second of the two methods described there
<swkhan>
oh right rpi guy =D
<azonenberg>
?
<azonenberg>
yeah, i'm at rpi
<swkhan>
we talked about how cool rpi is
<azonenberg>
we?
<swkhan>
and i have a friend who just moved there
<swkhan>
you and me
<azonenberg>
your friend a grad student?
<swkhan>
he will be a transfer student (undergrad)
<swkhan>
but he's 23
<azonenberg>
ah
<swkhan>
he's super motivated and interested in physics
<azonenberg>
is 21 and a phd student in comp sci
<swkhan>
oh wow. 22 and to-be PhD student this fall
<swkhan>
in comp sci?
<swkhan>
wow
<azonenberg>
Yes, i did my undergraduate work in CS (also at RPI)
<swkhan>
EE here, but this is so far removed from what i learned
<azonenberg>
and am now studying cs at the grad level
<swkhan>
what do you study / research?
<azonenberg>
i started out doing lithography with the electronics club for PCB fab
<azonenberg>
got into nanotech when i landed a consulting gig summer after freshman year that later led to an ongoing relationship with the company
<azonenberg>
i was just doing numerical modeling of their device at first lol
<azonenberg>
next thing i knew i was helping with process development, failure analysis, and wafer test
<swkhan>
wow
<azonenberg>
and then it became a hobby lol
<azonenberg>
But its unrelated to my academic work
<swkhan>
that's so cool
<swkhan>
i love people like that =D
<azonenberg>
my thesis research is on embedded systems security with a focus on smart grid
<swkhan>
i'm still trying to work around the adhesion layer issue
<azonenberg>
i suggest you not try to work around having an adhesion layer
<azonenberg>
and instead work around sputtering as the means of getting it there
<swkhan>
hmm
<swkhan>
see this is quickly getting complicated
<azonenberg>
if you want your film to stick *at all* you need one
<swkhan>
i'm doing this primarily because our sputterer is broken
<azonenberg>
and lol, of course its complicated
<swkhan>
it may be fixed now
<azonenberg>
there is a good reason most hobbyists etc dont even consider doing microfab
<azonenberg>
only the crazy ones like me :0
<azonenberg>
;) *
<swkhan>
the secondary reason is to learn how to come up with a process of my own
<swkhan>
we appreciate the crazy ones =)
<azonenberg>
Lol
<azonenberg>
And re process development, if you are only doing this to get around the sputter coater being down, unless it's down permanently, thats the wrong reason
<azonenberg>
by the time you get the process working it will almost certainly be fixed
<azonenberg>
However, you may want to consider electroplating *anyway* if you need a thick layer
<azonenberg>
since it's much faster than sputtering
<swkhan>
well i never get a chance to learn new things like this and just experiment
<azonenberg>
You have one now
<azonenberg>
I'm just saying
<azonenberg>
if you want to do it for educational value, go ahead
<swkhan>
the grad student in my lab who supervises me (sort of) always encourages us to use the simplest route possible
<azonenberg>
but unless your sputtering system is totally borked and will be for >1 month
<swkhan>
it's fine in terms of productivity, but i feel like in 4 years i won't graduate with a meaningful PhD
<azonenberg>
dont do it with the hope it'll be faster
<swkhan>
it's been down for 1 week. i was hoping i could learn enough to get to the point where i could do this on my own by the end of the week
<swkhan>
lol!
<swkhan>
am i that predictable? =\
<azonenberg>
I got the idea already
<azonenberg>
Anyway so if you do want to put the time into developing the process, go for it
<azonenberg>
Just make sure its for the right reasons
<azonenberg>
If the sputtering system is going to be repaired soon you may want to try implementing the exact process those guys did, or very similar
<azonenberg>
Or if you have access to an evaporator
<swkhan>
azonenberg: that's what i wanted to do: implement their process as much as possible. i was going to immediately shoot down any part of their process that i couldn't do (sputter) and consider the things i can't do right now but maybe could do with a little effort (photolithography)
<swkhan>
i don't have access to an evaporator either
<azonenberg>
Litho is definitely within the reach of a dedicated individual with minimal resources
<azonenberg>
spin coating is the first step which should not be too difficult
<swkhan>
by the way, i'd like to clarify something... i was told that an evaporator can damage silicon
<swkhan>
something about radiation damage
<azonenberg>
swkhan: um
<azonenberg>
Are you talking e-beam or filament evaporation?
<swkhan>
maybe i should have read the nuclear chemistry chapter =\
<swkhan>
e-beam definitely damages stuff
<swkhan>
i don't think filament evaporation should i guess
<azonenberg>
filament evaporation will not damage your sample for use as a mechanical substrate
<azonenberg>
as long as it doesnt mind a little heating
<azonenberg>
Also, very interesting
<azonenberg>
i think i figured out why my etch wasnt working
<azonenberg>
CrO2
<swkhan>
ah i think it was e-beam evaporation that i read about that makes sense
<azonenberg>
swkhan: If you can get access to a filament evaporator that will work nicely
<swkhan>
it used to be i couldn't learn from anything but really good lectures. but video lectures are time consuming and i have to really scrub through to find something good. textbooks are my current obsession
<swkhan>
i learn a lot from them and i'm getting better at reading through them
<swkhan>
i'm simultaneously reading a few papers
<swkhan>
but papers really vary in quality
<azonenberg>
Agreed
<swkhan>
and going from one paper to the reference can mean going from a paper that totally resonates with me to a paper that doesn't at all
<swkhan>
my basics are not so good either
<swkhan>
so i'm strangely strongest in chemistry right now
<swkhan>
i'm reading about solid state physics (ashcroft and mermin)
<azonenberg>
chem is one of my big weak points lol
<swkhan>
but i'm reading a paper right now that claims it does not need a seed layer and they get some level (haven't read it yet) of improved adhesion between copper and silicon
<azonenberg>
my theoretical EE knowledge is mostly in digital stuff (given my comp sci background) and much of what i know about microfab etc is applied
<azonenberg>
link?
<swkhan>
maybe i'm lying. maybe i'm really better with EE stuff right now digital, analog stuff
<swkhan>
but i feel like the only thing i've totally taught myself is chemistry
<azonenberg>
and analog stuff is naother hole in my skills :P
<swkhan>
analog guides my intuition about what a device "looks like"
<azonenberg>
come on, show me the paper :P
<swkhan>
sorry sorry =p
<swkhan>
link.aip.org/link/?ESLEF6/4/C5/1
<swkhan>
phew good thing i run screen. accidentally killed xterm
<azonenberg>
copper compound, vitamin c, ammonium fluoride, and something else? And no adhesion layer required?
<azonenberg>
vvery interesting
<swkhan>
=D
<swkhan>
ammonium fluoride... i'll have to check how expensive that is
<swkhan>
i wish you were in my lab =)
<azonenberg>
swkhan: i'm pretty sure it can be synthesized from HF and ammonia *confirms*
<swkhan>
wow it's expensive
<azonenberg>
in trace metal grade? Probably
<swkhan>
well i should read the paper first
<swkhan>
i'm easily not the smartest girl in the EE department, but i'm saddened that i am probably the most knowledgeable in my lab of the next batch of grad students. i don't know very much and i can't learn much from my peers =\
<swkhan>
so if you were in my lab... =)
<azonenberg>
for some stuff intelligence matters less than the level of applied knowledge
<azonenberg>
let's se...  ammonium fluoride, copper sulfate, ascorbic acid, sodium potassium tartrate, and methanol
<azonenberg>
and ascobic or fumaric acid is key to adhesion? hmm
<azonenberg>
this process is selective to silicon
<azonenberg>
that could be problematic if you want to deposit over oxide
<swkhan>
mm, in fact i'm sure that will be problematic
<swkhan>
i guess i should be looking at copper deposition on glass. but we have so many wafers and not much glass
<swkhan>
i get too caught up with the mindset the grad student has: make do with what you got
<swkhan>
sometimes "what you got" could be expanded by making a trip to ace or home depot
<swkhan>
for pretty cheap
<azonenberg>
Yeah
<azonenberg>
Figure out what you want to do first
<azonenberg>
then look at how other people have done it
<azonenberg>
then see how you can do something of the sort
<swkhan>
that makes sense
<swkhan>
now i'm curious about metal silicide layers
<swkhan>
why do they form? what does that even mean?
<swkhan>
i know silicon is weird. it has different behavior than carbon (for example carbon likes to bond with itself but silicon likes to bond with oxygen)
<swkhan>
it has to do with the 3p orbitals and the size of overlap but i am not sure why.
<swkhan>
but i get sidetracked easily
<swkhan>
goal: get copper on silicon
<swkhan>
this might work
<swkhan>
btw, NH4F is dangerous when heated
<azonenberg>
copper on silicon, or copper on dielectric over silicon?
<swkhan>
so luckily they did this at room temperature
<azonenberg>
And fluoride compounds in general are dangerous
<swkhan>
ah, yes, i want it to be copper on dielectric
<azonenberg>
it decomposes to ammonia + HF, right?
<swkhan>
yes
<azonenberg>
HF can definitely get nasty :P
<azonenberg>
Though in the 3% concentration i use it's not that bad
<azonenberg>
Of course when you say "not that bad" compared to 49% HF you arent saying much :P
<swkhan>
can i make copper sulfate from my copper conductive tape and H2SO4?
<azonenberg>
swkhan: copper conductive tape is copper + adhesive
<swkhan>
here's my plan so far. i have some copper conductive tape and i think i have some sulfuric acid.
<azonenberg>
you dont want adhesive
<swkhan>
right
<azonenberg>
pure copper is easy to get hold of
<swkhan>
i want to clean the adhesive with methanol and acetone
<azonenberg>
buy wire from radioshack :P
<swkhan>
i also have wire
<azonenberg>
Use wire
<swkhan>
but we have a lot more conductive tape than wire
<swkhan>
and i heard the wire is expensive
<azonenberg>
Um, lol
<azonenberg>
how much wire do you want?
<azonenberg>
a mile?
<swkhan>
well i want to use this process from now on to make my bottom electrode at least
<swkhan>
i should check that this works on glass first
<azonenberg>
i am nearly certain that the process in the paper you just linked does not
<azonenberg>
$43.25 for 1/2" copper double sided tape
<azonenberg>
you could buy two pounds of pure copper or one pound of CuSO4 for that price
<swkhan>
wow
<swkhan>
point made and conceded =)
<azonenberg>
So while using copper tape might be justifiable if you needed it RIGHT NOW
<azonenberg>
if you can afford to wait a little bit, go buy the stuff :P
<azonenberg>
in fact, copper sulfate is a common enough material some other lab on your campus will probably have some
<swkhan>
it's nearly 10 pm. i want to try something before the end of tonight. i am desperate enough to use the vitamin supplements my labmate left on her desk =p
<swkhan>
maybe
<swkhan>
we're in a weird building
<swkhan>
everyone does astrobiology
<swkhan>
we're one of a few labs that does cvd stuff
<azonenberg>
lol
<swkhan>
for an EE lab
<swkhan>
we're treated like second class citizens at nasa... for now
<swkhan>
i'll get my real nasa badge soon enough. in the mean time i have my lowly "special building for kiddos" badge -_-
<azonenberg>
lol
<swkhan>
random person on the internet says: "Silicon dioxide is a molecule (neutral), not an ion. You can only electroplate electrically charged ions but not molecules which do not have an electrical charge."
<swkhan>
that makes sense
<azonenberg>
That's depositiong, though
<azonenberg>
you can only deposit ions
<azonenberg>
You can deposit on a molecule by electroplating
<azonenberg>
with the caveat that said molecule mus be conductive
<azonenberg>
for example you can deposit onto a doped silicon surface or a metal
<azonenberg>
but not onto an insulator
<azonenberg>
If you are depositing onto an insulator i can almost guarantee you will need some sort of PVD
<swkhan>
hmm
<swkhan>
can i somehow ionize SiO2?
<azonenberg>
Are you trying to deposit SiO2 onto something?
<swkhan>
no
<azonenberg>
Or deposit something on SiO2
<swkhan>
yes
<azonenberg>
In the second case, ionizing wont help you
<azonenberg>
basically what would happen if you tried is that as soon as a few ions hit the surface the SiO2 would charge up
<azonenberg>
and become neutral
<azonenberg>
the bond is covalent and not ionic so you wont be able to do anything of the sort
<swkhan>
oh yeah it is covalent =\
<azonenberg>
electroless chemical plating is possible but i know little about it
<swkhan>
hmm
<azonenberg>
Do you have access to high vacuum anywhere?
<azonenberg>
1E-6 torr range
<swkhan>
no i don't
<swkhan>
i have access to ~5E-1 torr range
<azonenberg>
Not low enough for evaporation but enough for sputtering
<swkhan>
ah it's the cvd reactor though
<azonenberg>
thing is, sputteirring makes up for that by being more complex to set up :P
<swkhan>
so i can't really change it much
<swkhan>
and i've heard about metals can cause deep level traps
<azonenberg>
lol i see
<azonenberg>
Yeah
<azonenberg>
sorry to say i think you're pretty much out of luck at this point
<swkhan>
noooooo!
<azonenberg>
if you're willing to wait for some common materials to arrive there are options
<azonenberg>
for example, if you had access to a sputter coater of some sort, even a tiny one for SEM sample prep
<swkhan>
nope =\
<azonenberg>
you could deposit enough of a conductive layer on your sample to electroplate over that
<swkhan>
hmm so i'm trying to consider the advantages of each
<swkhan>
pure sputtering: very fast, no chemicals, costs me about $15/hour maybe $7.50/hour at night
<swkhan>
sputter seed layer, electroplate: very cheap with materials i have (effectively $0 cost), i get to learn something new
<swkhan>
pure electroplating: free, i get to learn a lot of new things
<swkhan>
disadvantages
<swkhan>
oops cost shouldn't have been there. i'm getting sleepier and sloppier =\
<swkhan>
pure sputtering: minor disadvantage of cost and currently down so can't really do it
<azonenberg>
pure electroplating, disadvantagee: can't deposit on nonconductive materials :P
<swkhan>
yes =(
<swkhan>
well as far as i know now there may be a method around it somehow...
<azonenberg>
electroless copper plating is possible
<swkhan>
i really want to try the berkeley paper's recommendations without as many additives. i don't have rochelle's salt or ascorbic acid
<azonenberg>
but i suspect that it wont be doable with materials you have in house
<swkhan>
but i do have methanol
<azonenberg>
The ascobic acid (or fumaric acid) was crticial for adhesion
<azonenberg>
methanol was almost unnecessary
<swkhan>
oh right that's right i got that backwards
<swkhan>
i thought fumaric was not necessary
<swkhan>
awwww
<azonenberg>
If you had more time and budget i know of an electroless gold plating solution
<azonenberg>
that could be followed by electroplating of copper
<azonenberg>
you spin coat the stuff, then bake in air to decompose the precursors and form a few tens of nm of metallic gold
<swkhan>
time is not too big of an issue. budget is
<swkhan>
ooh
<swkhan>
shiny =D
<azonenberg>
$500 for 4 ounces of the solution :P
<swkhan>
o_o
<azonenberg>
emulsitone goldfilm
<swkhan>
oh ya that stuff
<swkhan>
maybe i can look around for stuff like ascorbic acid
<azonenberg>
*checks if the MSDS has any info on composition* nope
<azonenberg>
and i dont think that will help
<swkhan>
i want to figure out whatever "hydrogen scavenger" is
<azonenberg>
the point is, it wont help because your surface isnt silicon
<azonenberg>
the process was selective for deposition on silicon only
<azonenberg>
and electroplating requires a conductive surface
<azonenberg>
You need to figure out how to deposit a conductive layer of some sort over the dielectric
<azonenberg>
either by itself, thick enough to use as-is
<azonenberg>
or as a seed layer for electroplating
<azonenberg>
i dont see any alternatives
<azonenberg>
electroless nickel is an option that works on nonconductive materials
<azonenberg>
you could then follow it with plating of copper
<azonenberg>
or just use the nickel as-is
<swkhan>
can i use nickels (like the coins) as nickel sources?
<azonenberg>
United states nickels do not contain any Ni
<azonenberg>
since about the 1950s
<swkhan>
oh lol
<azonenberg>
canadian ones do still afaik
<azonenberg>
USA are all ZnCu alloy
<swkhan>
or even pennies... they are electroplated copper on zinc right?
<azonenberg>
I dont know how the copper is deposited, but yes
<azonenberg>
they're Cu plating over Zn
<swkhan>
hmm, do you think that's a cheap form of copper?
<swkhan>
or do i run the risk of getting too much zinc off of it?
<swkhan>
i seem to remember zinc really likes to be sacrificed
<swkhan>
it has a higher electrochemical potential so it's easy to get it to reduce
<azonenberg>
You will get a ton of zinc in the solution and the plating is very thin
<azonenberg>
you want cheap copper?
<azonenberg>
Find broken electronics
<azonenberg>
or scrap AC power cords
<swkhan>
electricity is free here
<swkhan>
my time is somewhat free
<swkhan>
our research group's budget is next to nothing =(
<swkhan>
or at least that's how we're told to perceive it
<swkhan>
then magically i am told every once in a while to "find a way to spend $6000 by friday" on a thursday evening
<azonenberg>
:P
<azonenberg>
I've done filament evaporaion of copper on Si by getting the copper out of a power cord
<swkhan>
you're awesome =D
<azonenberg>
from a broken inkjet printer someone left on the loading dock and marked "trash"
<swkhan>
lol!
<azonenberg>
you'd be amazed at the resources that can be obtained by dumpster diving
<swkhan>
i once made a pulse chopper using spare components from a power supply that was chucked in the e-waste bin by the economics department
<azonenberg>
You have dedicated e-waste bins there?
<azonenberg>
There's your copper source
<swkhan>
well that was at ucsc
<swkhan>
at nasa we have nothing about bureacracy bins
<azonenberg>
lol
<swkhan>
so point being if i need to refine something using electricity, time, and especially if it doesn't need me to be watching it... that's perfect
<azonenberg>
Copper from power cords is easily pure enough to plate with
<swkhan>
if i want to get this done at least on silicon tonight, i'm going to probably end up using the copper wire
<azonenberg>
Silicon, sure
<swkhan>
but ascorbic acid =\
<azonenberg>
But it wont be insulated
<swkhan>
that's okay for now
<azonenberg>
And what would you do then?
<azonenberg>
dont you need to pattern it?
<swkhan>
i might be able to get away with this...
<swkhan>
bottom contact on the whole sample
<azonenberg>
you never did mention what you are trying to build in the end
<swkhan>
(not necessarily a full wafer but whatever)
<swkhan>
then deposit a metal oxide and then probe it with a IV curve tracer
<swkhan>
the probe could serve as the second contact
<swkhan>
so i don't even need to pattern just yet. i want to get the proof of concept that the metal oxide does something useful
<swkhan>
a postdoc in our group was saying that he worries that when you have the probe make contact two things happen
<swkhan>
1. you scratch the surface [unless you use contact mode AFM (STM really)]
<swkhan>
2. the pressure of the probe affects the IV relationship
<swkhan>
what are your thoughts on 2. especially?
<azonenberg>
Do you have access to a wirebonder?
<swkhan>
nope
<azonenberg>
Figures
<azonenberg>
You can get around both potentially
<azonenberg>
but the methods for doing so introduce unique problems of their own
<azonenberg>
Explain the structure a bit more?
<swkhan>
the structure?
<azonenberg>
of what you're trying to build
<swkhan>
silicon (maybe with a thin native oxide) with copper on it (bottom contact) then metal oxide on top of the bottom contact then i can use the tungsten probe of my IV curve tracer to serve as the top contact
<azonenberg>
And what is the desired device?
<swkhan>
how thick is the SiO2 layer on top of Si (100) if i haven't done anything special for it
<azonenberg>
Very thin
<azonenberg>
Not enough to be an effective insulator
<swkhan>
whatever i can get. capacitor, variable resistor
<azonenberg>
i think its on the order of 10A
<swkhan>
okay so when people say they "thermally grew" silicon dioxide... how do they do it? what's going on when they have it in some sort of chamber?
<azonenberg>
Dry or wet?
<swkhan>
with lots of heat i mean
<azonenberg>
The basic process is the same
<swkhan>
10A wow
<azonenberg>
Stick wafer in oven
<azonenberg>
heat to 1200C or thereabouts
<azonenberg>
hold for an hour or so and cool slowly
<bart416>
And due to that booze and cigars for everybody!
<azonenberg>
lol
<bart416>
Though you might not want to smoke the cigars
<bart416>
They're cuban so you'll probably get arrested for having them in the US
<azonenberg>
lol
<bart416>
And not joking, I do actually have a box of Cohiba Siglo IV 's :P
<bart416>
But those are for special occasions
<bart416>
Like after beating the crap out of a hard exam
<bart416>
Or winning an insane contest
<azonenberg>
is not a fan of tobacco
<bart416>
neither
<bart416>
I actually hate smoking
<bart416>
But cigars it's the idea that counts :P
<azonenberg>
And i try not to smoke pot too much either...
<azonenberg>
the smell of burning carbon composition is kinda irritating
<azonenberg>
to say nothing of the fact that you're destroying a perfectly fine variable resistor from overcurrent
<bart416>
lol
<bart416>
Cuban cigars are quite different from cigarettes though
<bart416>
Also one of the only reasons I'm not on the floor dropping dead >_>
<bart416>
(I'm allergic to regular cigarettes)
<azonenberg>
why are they so different? i mean i know they smell a lot different
<azonenberg>
but its the same stuff burning, right?
<bart416>
Don't think it is
<bart416>
Cigars don't have all the chemical crap added to them
<azonenberg>
they add stuff to cigarettes?
<bart416>
Yes
<azonenberg>
shows how little i know about such things lol
<bart416>
Tobacco in cigarettes is chemically altered
<azonenberg>
o_O
<bart416>
They add chemicals to make them more addictive, at least they used to
<bart416>
Now it's "flavour"
<bart416>
In other words, the same thing, lol
<azonenberg>
to make them more addictive? o_o
<lekernel>
bart416, why is supersymmetry crap?
<bart416>
I failed a course on the subject when I was doing physics :P
<lekernel>
I'm not saying it isn't, I actually do not understand it
<lekernel>
just wondering about your thoughts
<bart416>
Well, the issue with supersymmetry in my opinion is that it's "too nice"
<bart416>
It's more of a construct than an actual theory if you ask me
<azonenberg>
doesnt know enough about physics to be able to say much about it
<bart416>
I'm not going to try to explain it over the internet
<bart416>
And I woiuldn't try reading wikipedia about it either if their reputation on physics keeps up
<bart416>
lol
<azonenberg>
lol
<azonenberg>
has never tried reading wp on any physics more advanced than newtonian mechanics
<azonenberg>
i can say their info on semiconductor fab is usually spot on
<bart416>
The text is usually too retarded to read on theoretical physics models
<bart416>
And if you try to correct them they link to some flawed internet page written by a 14 year old who got his hands on a book and tried to post a summary online
<azonenberg>
lol
<berndj>
that reminds me, britneyspears.ac actually has some pretty real semiconductor physics
<berndj>
despite apropos-nothing pics
<azonenberg>
?? lol
<berndj>
tbh i haven't seen too many wikipedia articles that were clearly written by bombastic know-nothings
<azonenberg>
i usually stick to the highly technical pages on rather non-controversial topics
<azonenberg>
and just use them for summaries and rely on journal articles for details
<berndj>
and keeping 1e6+ articles right is a battle against entropy
<berndj>
took me a while to figure out, for example, why they had silicon's boiling point at 2500K or so
<berndj>
celsius/fahrenheit confusion in that case
<azonenberg>
They had a crew going through all of hte phsyical data and fixing it afaik
<bart416>
That's another thing, theoretical physics is SI or CGS unit systems
<bart416>
Not their damned imperial system
<azonenberg>
Boiling point 3538 K,3265 °C,5909 °F
<lekernel>
i'm reading "the road to reality" by Penrose atm, but I still have not reached supersymmetry
<azonenberg>
that looks reasonable
<bart416>
lekernel, well skip that part
<bart416>
The LHC delivered a final headshot to it :D
<bart416>
Lets see what my periodic table lists as boiling point of silicon
<azonenberg>
doesnt have CRC tables on hand
<bart416>
2953K
<bart416>
at 1 bar of pressure
<azonenberg>
Hmm
<bart416>
Melting point is 1412°C
<azonenberg>
I see two major values being mentioned online - 2355 and 3265C
<azonenberg>
Trying to find a reliable source for either
<berndj>
some previous editor made it 2355, so there's a link there
<bart416>
btw azonenberg, looked on another MSDS
<bart416>
e) Melting/freezing point Melting point/range: 1.410 °C - lit.
<bart416>
f) Initial boiling point and
<bart416>
boiling range
<bart416>
2.355 °C - lit
<azonenberg>
Very interesting
<azonenberg>
well, as i dont plan to boil silicon any time soon, i'll live with the situation :p
<bart416>
boiling silicium, what could possibly go wrong :')
<berndj>
if i knew where my periodic table was that predated wikipedia, i'd look it up there
<berndj>
but then what about wikipedia's table of vapour pressures?  those seem consistent with the higher boiling point
<azonenberg>
Yeah, after a bit more reading the higher value looks right
<bart416>
Just buy a good periodic table
<bart416>
I think sigma aldrich sells their own ones azonenberg
<bart416>
Maybe piggy back it on another order azonenberg?
<azonenberg>
maybe
<bart416>
Well yeah, I have two; one from taminco that has a nice list with a redox scale that's pretty complete
<bart416>
and acid constants
<bart416>
And then another one from where I worked for a while that lists pretty much every single isotope known to mankind that's stable enough to be worth mentioning :D
<azonenberg>
lol nice
<bart416>
I'm going to guess azonenberg lost power
<bart416>
wb azonenberg
<azonenberg>
ISim decided to drive my machine into swap lol
<azonenberg>
So hard that wpa_supplicant's latency increased beyond the allowable limit
<azonenberg>
and the wifi dropped :P
<azonenberg>
i dont know why it decided it needed >3GB of ram
<azonenberg>
but it was using 70%+ of my memory lol
<azonenberg>
i now have a killall command on an SSH session in another machine
<azonenberg>
ready to go at a moment's notice if things go bad
<bart416>
lol
<azonenberg>
Oh, and the worst part is that it should have aborted
<azonenberg>
there was a syntax error in one of the verilog files
<azonenberg>
somehow it synthesized *something*
<azonenberg>
that, well, blew up :p
<azonenberg>
Lol, found the bug
<azonenberg>
an initial block was turned into an always
<azonenberg>
simulator went into an infinite loop collecting more and more waveform data without advancing the timer at all
<berndj>
you implemented ECRAY!
<azonenberg>
lol
<azonenberg>
woo my ted pella order gets here on thursday
<azonenberg>
copper pellets for evaporation, a selection of tungsten filaments, some more general lab gloves, and diamond polishing compound for cross section prep
<azonenberg>
i needed somethign midway between 60nm colloidal silica and 1500 grit sandpaper :p
<swkhan>
yay azonenberg =)
<azonenberg>
hopefully by middle of next month i'll have some nice cross section pics to show
<swkhan>
azonenberg: i'm trying to learn solid state physics but i'm getting stuck on a section about the drude model for metals
<swkhan>
"Given that the momentum per electron is p(t) at time t, let us calculate the momentum per electron p(t + dt) an infinitesimal time dt later. An electron taken at random at time t will have a collision before time t + dt, with probability dt/tau, and will therefore survive to time t + dt without suffering a collision with probability 1 - dt/tau."
<swkhan>
"If it experiences no collision, however, it simply evolves under the influence of the force f(t) (due to the spatially uniform electric and/or magnetic fields) and will therefore acquire an additional momentum f(t) dt - O(dt)^2."
<swkhan>
where does O(dt)^2 come from? they say it is big O notation
<berndj>
s = ut + at^2/2 by analogy
<berndj>
no, wrong degree
<berndj>
swkhan, in physics you often just add terms of higher degree to make things more accurate - then figure out the coefficients later
<swkhan>
trying to add additional terms of higher degree makes sense
<swkhan>
but in this situation, i'm not sure where that's coming from
<azonenberg>
swkhan: Are you doing some kind of DSMC?
<swkhan>
don't know what that is =\ i don't know anything
<swkhan>
but, no, i'm not. i'll check it out at some point though
<berndj>
inside the metal the force is unlikely to be perfectly isotropic; i imagine that O(dt^2) term captures that
<swkhan>
it's weird that they bring that up
<swkhan>
because they try to explain drude's model of metals
<swkhan>
which is basically an application of kinetic molecular theory to electrons
<azonenberg>
When i first read that section it sounded very much like it
<swkhan>
so electrons are treated as a gas where each of the constituent particles don't interact with each other except for when they mechanically collide into one another
<azonenberg>
Yeah, i've seen similar models
<azonenberg>
Not as easy to model as a Fermi gas but not too bad either
<swkhan>
i guess for the sake of pushing on i'll concede what berndj said and come bother you all if i find anything interesting
<swkhan>
oh btw azonenberg that berkeley paper on electroplating copper on silicon had a followup paper that was interesting as well
<azonenberg>
ooh?
<swkhan>
they explained why they use HF and follow it up with a methanol dip
<azonenberg>
HF is probably to strip native oxide and make it more conductive
<azonenberg>
methanol, not sure off the top of my head
<swkhan>
it gets terminated with hydrogens apparently and so the surface is really hydrophobic
<azonenberg>
Oh, yeah
<swkhan>
making it really difficult to electroplate
<azonenberg>
The methanol fixes that?
<swkhan>
they don't know why though
<azonenberg>
Thats actually a common sign of when your oxide strip is complete
<azonenberg>
if you pull it out of the HF and water beads up
<azonenberg>
if you're doing a single die in a tray of HF it'll actualyl float to the surface
<azonenberg>
sometimes
<swkhan>
whoa
<azonenberg>
because it picks up bubbles from reaction products
<azonenberg>
the hf pulls back and doesnt want to touch it
<swkhan>
another thing i don't understand is why people use 1% concentrations of HF
<azonenberg>
and eventually it floats
<azonenberg>
i normally use 3%
<swkhan>
can you etch / clean with any old acid?
<azonenberg>
i can buy it over the counter at my local grocery store
<azonenberg>
and it doesnt fume like 49% etc
<swkhan>
ah!
<swkhan>
i have sulfuric and phosphoric and base wise i have sodium hydroxide
<swkhan>
silicon is such a weird and interesting element
<swkhan>
if carbon makes life exist, silicon makes it worth living =)
<azonenberg>
lol
<berndj>
part of that is probably because it's one of the most studied elements
<berndj>
rivalled only by iron or uranium
<berndj>
azonenberg, is your rust remover pretty much only HF and hydroxylic acid, or is there other stuff in it?