<azonenberg> Oh, the interesting things you can find when facebook crawls all of wikipedia looking for fanpages...
<azonenberg_lab> So I'm prepping samples for an experiment to be done on thursday
<azonenberg_lab> Any ideas as to how to store microscope coverslips or slides (to be used as substrates for deposition) in a clean environment for a day or two? Preferably padded so i can carry them around
<azonenberg_lab> Looks like i need more gel boxes o_O running out
<azonenberg_lab> but i have one left
<azonenberg_lab> So now i have 17 samples which are going to be coated in 100nm ish of Cu on thursday
<azonenberg_lab> Four of <100> Si and the rest of glass
<azonenberg_lab> Next step is to expose some of these guys with simple test patterns so i can do lift-off
<azonenberg_lab> Trying half-strength photoresist (watered down with acetone) now
<azonenberg_lab> I'm expecting better resolution and shorter exposues
<azonenberg_lab> exposures*
<azonenberg_lab> At the cost of increased permeability
<CIA-67> homecmos r102 | trunk/lithography-tests/labnotes/azonenberg_labnotes.txt | Today's lab notes
<azonenberg> This is getting annoying
<azonenberg> All of my processes seem to be working decently well (so far) except the KOH isnt playing well
<azonenberg> Because i cant get hardmask to work
<azonenberg> I'm starting to wonder if maybe i should just try CMOS
<Laurenceb> why is hardmask needed?
<azonenberg> Laurenceb: Because photoresist is attacked by KOH
<azonenberg> As well as related etchants like NaOH and TMAH
<Laurenceb> silicon entchants?
<azonenberg> Laurenceb: Correct
<Laurenceb> do silicon dioxode etchants eat photoresist?
<azonenberg> Not exactly
<azonenberg> But F- ions have a tendency to diffuse through photoresist
<Laurenceb> how is it done commercially?
<azonenberg> They dont actually damage it but they appear on the other side
<Laurenceb> - dioxide etching
<azonenberg> They normally use fluoride-proof resists
<azonenberg> Also, the usual mask for silicon etching is silicon nitride
<azonenberg> Which is deposited by reactive sputtering or LPCVD
<Laurenceb> i see
<Laurenceb> i dont understand how spin coating leaves an eavent coat
<Laurenceb> *even
<azonenberg> I dont know all of the physics either, you'd think it'd be thinner in the middle and thicker around the rim
<Laurenceb> yeah
<azonenberg> I mean, there is frequently a ring around the *very* edge
<azonenberg> But that due to edge effects (surface tension etc)
<azonenberg> the thickness in the remaining area is normally extremely even
<Laurenceb> oh with my aerosol precipitator, we found you could get even a repoducable coats
<azonenberg> Interesting
<Laurenceb> as the precipitate was nonconductive and blocked the field
<Laurenceb> - allowed a static buildup that blocked the field
<azonenberg> And I think my problem is that my hardmask is soluble in alcohol
<azonenberg> But so is my photoresist
<Laurenceb> unfortunately it ended up quite thick
<azonenberg> So the two are interacting somehow
<Laurenceb> interesting
<azonenberg> The resist dissolves slowly, it doesnt disintegrate like it would with say acetone
<azonenberg> But i think its contaminating the film somehow
<Laurenceb> i saw some papers on using electrostatic dust precipitation to coat nonconductive surfaces uniformly
<azonenberg> well i just came up with a very interesting idea
<azonenberg> Gonna have to prepare some samples tonight to test
<azonenberg> One is to try using an evaporated metal hardmask to pattern tantalum chloride by a wet etch in alcohol
<azonenberg> Another one is to use evaporated metal directly as a hardmask for KOH etch (but only certain metals are compatible)
<azonenberg> And another is to use evaporated metal as a hardmask for etching tantalum oxide
<azonenberg> And still another is to try something i should have done a long time ago
<azonenberg> Now that i have ammonia i can synthesize ammonium fluoride and, by extension, buffered oxide etch
<azonenberg> Which i'm told diffuses through photoresist much less than pure HF
<azonenberg> gaah, going to be fun going to work today while thinking about this :P
<Laurenceb> heh
<azonenberg> My last attempt at buffering HF used NaOH
<azonenberg> Didnt end well
<azonenberg> Took the photoresist right off
<nathan7> \o/
<azonenberg> What, you didnt know the channel existed? Been working here for like two months lol
<nathan7> Nope
<nathan7> cool.
<Laurenceb> before copper was used on commercial fab, was CPM necessary?
<Laurenceb> i dont see that being practical to do cheaply
<SolidRaven> What CPM?
<SolidRaven> Stop the acronyms
<SolidRaven> They can mean loads of things
<Laurenceb> surface polishing
<SolidRaven> The thing about polishing is, you could get an old industrial machine fairly cheaply
<SolidRaven> You know, for watch making and so on
<SolidRaven> Those are usually rather precise
<SolidRaven> So with minor modifications you should be able to get them to the level required to polish a wafer
<Laurenceb> i was interested in tabletop fab
<SolidRaven> You somehow see this as a huge machine
<SolidRaven> It generally isn't
<SolidRaven> I'm talking about watch making equipment :P
<SolidRaven> Goes in the same category as those small lathes
<SolidRaven> That's actually another thing you could use to polish them
<SolidRaven> Assuming you find a good enough tool
<SolidRaven> You know Laurenceb a good average lathe will let you go down to 10µm or even smaller
<SolidRaven> And some of the better CNC lathes can go sub micrometer...
<SolidRaven> So really, look into it
<SolidRaven> But don't use the automatic feed of a small lathe if you want precision, too much shocks :(
<SolidRaven> Actually, now that I think of it
<SolidRaven> cooling, you'll need that if you use a lathe
<SolidRaven> Blast it with a jet of nitrogen
<SolidRaven> So go and get your jewelry lathe that's precise enough
<SolidRaven> :P
<Laurenceb> interesting
<SolidRaven> The reason lathes are generally not used at such precision is the lack of measurement instruments and the lack of need to do so
<SolidRaven> It's cheaper to work at a precision of 0.1mm than at 0.01 or 0.001mm
<SolidRaven> But mechanically they're capable of going down to that precision
<azonenberg_work> Laurenceb: I think you meant CMP
<azonenberg_work> Not CPM
<Laurenceb> oops
<azonenberg_work> And it was still used before copper damascene processing to some extent
<azonenberg_work> Most submicron aluminum processes use it
<Laurenceb> interesting
<azonenberg_work> The reason is that the depth of field of your litho process is less than the thickness of a metal layer
<azonenberg_work> So you need to have a flat surface for exposing the mask onto
<azonenberg_work> I was actually expecting to planarize during some of my processing so i bought a quart of 50nm colloidal silica slurry from ted pella
<azonenberg_work> Havent had a chance to actually try any real processing with it
<Laurenceb> thats small
<azonenberg_work> Thats the particle size, it can actually polish to below that
<azonenberg_work> Probably 10-25nm surface roughness as a guess
<azonenberg_work> In any case its far better than i need for depositiong 50-100nm (or thicker) films with 5-20um horizontal feature sizes
<azonenberg_work> Lol so just for the heck of it i was reading up on metal etchants and found a section on platinum
<azonenberg_work> The two etches they suggest are aqua regia and molten sulfur :P
<SolidRaven> Not really a shocker
<SolidRaven> You just listed two of the few things capable of harming platinum
<azonenberg_work> I'm surprised they didnt just say "effectively indestructible"
<azonenberg_work> as i dont think either of those etches is very selective :P
<azonenberg_work> They'll eat almost anything you can try to mask it with
<SolidRaven> well, aqua regia doesn't harm polymers all that much
<azonenberg_work> Hmm
<azonenberg_work> gets terrible idea
<SolidRaven> + you could use titanium oxides to protect the wafer...
<azonenberg_work> Does aqua regia eat silicon?
<SolidRaven> Those are resistant to aqua regia
<SolidRaven> Not sure
<SolidRaven> But I doubt it'll be healthy for the other wafer
<azonenberg_work> I was going to suggest using a platinum or gold hardmask (which i can sputter or even deposit by sol-gel)
<azonenberg_work> then use aqua regia to etch it through photoresist
<azonenberg_work> Half jokingly, i dont want to have the stuff around right now (no fume hood)
<SolidRaven> That'd probably work
<SolidRaven> I wonder if it harms silicium
<azonenberg_work> In the meantime what i want to try is making some BOE
<SolidRaven> Get a silicium crystal and dump it in some aqua regia
<SolidRaven> The chemistry department should have some spare aqua regia anyway
<SolidRaven> It's ideal for cleaning things
<azonenberg_work> If i can get my photoresist to survive a BOE etch then i'm in good shape
<azonenberg_work> spin coat tantalum oxide and pattern by straightforward wet etch
<SolidRaven> azonenberg, seriously if you use titanium you could use aqua regia to etch!
<azonenberg_work> I have no way to deposit titanium
<azonenberg_work> At least not yet
<azonenberg_work> I'd need to sputter or evaporate and i dont have the equipment for either atm
<SolidRaven> You could also use the aqua regia to deposit gold on a surface now that I think about it
<SolidRaven> But that'd require a (large) current :(
<azonenberg_work> Lol
<azonenberg_work> Electroplating gold from aqua regia? Yeah
<azonenberg_work> Though...
<azonenberg_work> I could synthesize copper chloride easily enough and electroplate it potentially
<azonenberg_work> I just dont know if it would give good results
<azonenberg_work> I also dont think copper would work well as a hardmask