<azonenberg>
But the yellow is copper and the background is silicon
<azonenberg>
I wonder if 60 sec in SC2 is too much
<azonenberg>
The film is very thin, after all
<azonenberg>
Maybe i want to water it down...
<azonenberg>
Yeah, its waaay too much
<azonenberg>
Etch Rates for Micromachining Processing - Part II, IEEE MEMS journal
<azonenberg>
gives etch rate for a similar FeCl3 based etchant as 3900nm/min
<azonenberg>
I'm using HCl : H2O2 but in PCBs they etched at about the same rate
<azonenberg>
Which means my film (rough guesstimate 200nm) would be etched throuhg in 5 sec
<azonenberg>
And then 12x overetched :P
<nathan7>
azonenberg: :o
<Laurenceb>
HF is acid
<Laurenceb>
it should etch copper
<lekernel>
Laurenceb, not all acids etch copper, e.g. hydrochloric acid does not
<lekernel>
HF, I don't know
<lekernel>
Laurenceb, also, you have passivation phenomena with some strong acids... for example pure sulfuric acid does not etch copper, but diluted sulfuric acid does (iirc)
<lekernel>
"In  the  manufacture  and  storage  of  hydrogen  fluoride  and  its aqueous  solution,  i.e.,  hydrofluoric  acid,  equipment  made  of  copper and  its  alloys  is  used"
<lekernel>
so it most probably does not ;)
<bart416>
For HF storage, just use teflon
<lekernel>
that's a 1962 document
<lekernel>
and the question isn't how to store HF but whether it can be used to etch copper
<nathan7>
lekernel: In the presence of Cu(2+) it does
<nathan7>
ahem, Cu²z
<lekernel>
HF or HCl?
<lekernel>
and I guess that's a chain reaction?
<azonenberg>
Well thats good because it means i can use evaporated copper as a hardmask for HF etching
<azonenberg>
I just might need a little bit more than i used for this deposition run
<azonenberg>
This might finally solve my patterning problems
<azonenberg>
Spin coat TaCl5, bake to oxidize
<azonenberg>
Evaporate Cu
<azonenberg>
Spin coat photoresist, develop, wet etch Cu hardmask in dilute SC2
<azonenberg>
Etch Ta2O5 through Cu with hot HF
<azonenberg>
Strip Cu in SC2
<azonenberg>
Etch Si through Ta2O5 with KOH
<azonenberg>
So i'd have *three* levels of masking
<azonenberg>
But in theory it should work
<azonenberg>
My last run seems to have had adhesion issues with the Cu, thats my only concern
<azonenberg>
Wondering if it wasnt pure enough / I didnt clean the surface adequately
<azonenberg>
but when i tried HF etching a glass substrate with Cu over it, the Cu floated off
<azonenberg>
Not damaged, but it was undercut
<bart416>
Well, HF tends to do that azonenberg
<azonenberg>
bart416: Yeah, i was hoping the Cu would actually mask it
<azonenberg>
Need to figure out if i just etched too long or what
<azonenberg>
I only need to go down around 100nm
<bart416>
For etching glass I'd just use regular photoresist to be honnest
<azonenberg>
bart416: Doesnt work
<azonenberg>
My resist allows F- to diffuse through it
<bart416>
auch :(
<azonenberg>
you get etching of the substrate with intact photoresist over it
<azonenberg>
At least, thats my working hypothesis
<azonenberg>
all i know for sure is what actually happens
<azonenberg>
not how
<azonenberg>
So my newly modified process calls for ten different operations to pattern one bulk-etch mask level into a piece of silicon lol
<azonenberg>
Spin coat TaCl5, bake
<azonenberg>
Evaporate Cu
<azonenberg>
Spin coat photoresist, soft bake
<azonenberg>
Expose, develop, hard bake
<azonenberg>
Wet etch Cu in dilute SC2
<azonenberg>
Strip PR in acetone
<azonenberg>
Wet etch Ta2O5 through Cu with HF
<azonenberg>
Strip Cu in SC2
<azonenberg>
Wet etch Si in KOH
<azonenberg>
Strip Ta2O5 in HF
<nathan7>
SC2?
<azonenberg>
Standard Clean 2, the second of two cleaning solutions in the RCA clean
<azonenberg>
1 part HCl : 1 part 30% H2O2 : 6 parts water
<azonenberg>
I use a slightly different mixture due to lack of 30% peroxide, i use 1 part conc HCl to 6 parts 3% H2O2
<azonenberg>
A little less of an oxidizer but its pretty close, just slightly slower etch rate on some materials
<nathan7>
mhm
<nathan7>
azonenberg: ebay has 30% H2O2
<azonenberg>
nathan7: Not saying it cant be obtained
<azonenberg>
But i dont have it
<azonenberg>
It also decomposes fast enough i dont want to order it
<nathan7>
Not terribly fast
<nathan7>
Just keep it in the dark and don't keep it with metal
<azonenberg>
In any case, cant do too much moe work until sunset in the USA
<azonenberg>
more*
<azonenberg>
silly photoresist and my lack of a darkroom...
<nathan7>
lol
<bart416>
H202 lasts quite a while if you keep it in the right bottles
<bart416>
As long as you don't expose it to much light and avoid heating it it'll last years
<azonenberg>
bart416: 3% or 30%?
<bart416>
Both
<azonenberg>
And i'd use an opaque plastic or brown glass bottle under a shelf
<azonenberg>
at 75F
<nathan7>
Put it in the lab freezer!
<bart416>
^that
<azonenberg>
nathan7: Dont have one (working at least)
<bart416>
put it in a fridge
<bart416>
I mean, it's not like it's really all that toxic
<bart416>
Unless if you intend to drink it
<azonenberg>
On general principle i keep lab stuff well separated from food / living spaces
<nathan7>
H2O2 is nontoxic
<nathan7>
just oxidising
<bart416>
Just keep it in a labeled teflon bottle
<bart416>
And put it somewhere in a cool cupboard
<bart416>
that's my storage procedure for 10% H202 and up
<bart416>
As long as you stay under 50% that should be safe
<azonenberg>
50%? Lol
<azonenberg>
I'm not working with rocket fule here
<azonenberg>
fuel*
<bart416>
It's only qualified as rocket fuel starting from 65% or something like that
<bart416>
lol
<azonenberg>
Lol, 50 is still quite possibly explosive
<bart416>
Nah, 50% is still safe if you don't heat it
<nathan7>
or stir it with silver spoons
<nathan7>
or silver powder
<nathan7>
really high-surface area silver powder
<nathan7>
that still gets a nice fizz out of 3%
<azonenberg>
lol :P
<azonenberg>
how about 50nm nanopowder? :p
<azonenberg>
boom
<bart416>
nathan7, don't try to feed it iron either :p
<bart416>
And never ever try to feed it alkali metals
<nathan7>
;D
<azonenberg>
Alkali metals...
<bart416>
you know, if you throw a block of potasium in water it reacts violently eh...
<azonenberg>
Rubidium plus 50% H2O2
<nathan7>
azonenberg: I dissolved 97/3 Sn/Ag solder in HCl(aq)
<bart416>
Now try throwing it in high concentration hydrogen peroxide
<bart416>
I'll stand back a bit :P
<nathan7>
;D
<bart416>
Violent is an understatement
<bart416>
Its a damned depth charge >_>
<azonenberg>
lol
<nathan7>
bart416: better, put a tube to the bottom
<nathan7>
make sure it's dry inside
<nathan7>
and drop the K in
<nathan7>
then quickly remove the tube
<nathan7>
the K will be at the bottom
<azonenberg>
lol
<bart416>
nathan7, heh we had another method
<bart416>
we put the potasium in a one of those large plastic canisters you can buy chemicals in
<azonenberg>
And puncture the lid?
<bart416>
attach a brick to it
<bart416>
attach fireworks with fuses that work under water to the lid
<nathan7>
:>
<azonenberg>
...
<bart416>
and throw it in the river
<azonenberg>
So you use a small charge to blow the lid off