<berndj> azonenberg, auto-darkening helmets ftw indeed!
<berndj> azonenberg, some pics of "alligator skin" reminiscent of your fluoride-permeable PR layers http://cool.conservation-us.org/jaic/articles/jaic39-03-005.html
<azonenberg> lol
<azonenberg> Looks messy
<azonenberg> will check it out more in the morning, bedtime for me
<azonenberg> i have a date with a SEM tomorrow morning :)
<berndj> bring flowers
<azonenberg> berndj: flowers? I'm bringing etched wafers :P
<azonenberg> you have to know how to treat these things
<azonenberg_work> berndj: remember, flowers are not high-vac compatible unless dried first :P
<B0101> hi azonenberg
<azonenberg_work> hi
<B0101> a lot research is undergoing now that my lab is finally finished
<B0101> how your lithography test process?
<B0101> *hows
<azonenberg_work> B0101. i hope you are keeping nnotes for us to see?
<azonenberg_work> and i'm imaging dies on the sem now
<azonenberg_work> pics coming soon
<bart416> azonenberg, couldn't you theoretically do lithography with the SEM? :P
<azonenberg_work> They dont have a litho system installed on this one
<azonenberg_work> uploading pics, h/o
<mrdata> what magnification is that?
<azonenberg_work> scale bar at bottom
<bart416> mrdata, 1000x :P
<mrdata> oh yes
<azonenberg_work> That's copper on silicon
<azonenberg_work> here's another die with resist still on it http://colossus.cs.rpi.edu/~azonenberg/images/homecmos/2011-09-20/die_i7_005.jpg
<mrdata> good job
<azonenberg_work> which means ican definitely use less PR and potentially get better resolution etc
<azonenberg_work> and use shorter exposures
<azonenberg_work> I also have to do more work in etching silicon
<azonenberg_work> metal patterning and litho at 20um scales is clearly a solved problem at this point
<azonenberg_work> But before i can get a working device i need to be able to etch the Si
<azonenberg_work> One thing to explore is etching of SiO2
<mrdata> yes
<mrdata> HF is your friend
<mrdata> but oh boy does it burn
<azonenberg_work> oh, its more complicated than that
<azonenberg_work> HF penetrates my photoresist :P
<azonenberg_work> At least, it does when i etch Ta2O5
<azonenberg_work> SiO2 is easier to etch
<mrdata> that would be a problem
<azonenberg_work> i also have no way of generating SiO2
<azonenberg_work> So i might buy an oxide-coated wafer to test on
<mrdata> try etching glass?
<azonenberg_work> Borosilicate? Soda-lime?
<mrdata> how does the chip fab industry do this?
<azonenberg_work> Neither has the same characteristics of fused quartz
<azonenberg_work> They normally use HF-resistant PR
<azonenberg_work> or a plasma etch
<azonenberg_work> Anyway so i'm thinking of picking up one of these http://www.mtixtl.com/thermaloxidewafer300nmsio2layeronsi1002diax050mmtptype1s2wksdelivery-1-1.aspx
<azonenberg_work> This is <100> so i can't get vertical etches (V-trenches only)
<azonenberg_work> Which means its useless for comb drive work
<azonenberg_work> But i could test etching of SiO2
<azonenberg_work> The other option is to try and bum a few hours of furnace time off a lab on campus
<bart416> how precise does your temperature have to be?
<azonenberg_work> bart416: Not very, not at all
<azonenberg_work> But you want to be relatively uniform to avoid heat-stress cracking
<bart416> throw it in a pyrex beaker and put it on the barbecue or your kitchen oven :P
<azonenberg_work> Its not that simple
<azonenberg_work> I need to hit 1200C
<azonenberg_work> lol
<bart416> ah, 1200C
<bart416> build a clay furnace
<azonenberg_work> Could be +/- 200
<mrdata> Sale Price: USD$79.95 ??!? omg that's expensive
<bart416> If you blow into it with a hairdryer you can reach those temperatures
<azonenberg_work> mrdata: thats a 4-inch wafer with a whopping 1000nm of oxide
<azonenberg_work> = THICK
<azonenberg_work> Anyway so thats one idea
<azonenberg_work> Basically, its all boiling down to one basic problem
<azonenberg_work> I have no idea how to take a pattern in photoresist and put it into something KOH-resistant
<azonenberg_work> swkhan: Do you by any chance have a high-temp furnace at your lab?
<azonenberg_work> And if i mailed you a wafer could you grow oxide on it and mail it back? :P
<azonenberg_work> mrdata: I tried Ta2O5 patterned by liftoff, that failed because it dissolved into my resist
<mrdata> read the patent literature?
<bart416> btw azonenberg you were asking about how to cast that plastic
<bart416> the guys at instructables there used something called smoothcast 300, and I looked it up
<azonenberg_work> I tried Ta2O5 etched by HF through photoresist, that didnt wok beccause HF penetrated my resist
<bart416> And it's pretty much what you need to cast those turret parts
<azonenberg_work> Ta2O5 etches slower than SiO2 by far
<azonenberg_work> so if i use a thick photoresist layer it should survive exposureto the brief HF dose it'll take to eat a micron of thermal oxide
<azonenberg_work> But SiO2 is etched by KOH slowly
<azonenberg_work> It will work as a mask for shallow etches but not deep (thorugh wafer) ones
<azonenberg_work> mrdata: Almost nobody does a full-wet etch process for bulk micromachining
<mrdata> what do they do?
<azonenberg_work> The de facto standard is to use LPCVD Si3N4 over a thin thermal oxide layer
<azonenberg_work> Nitride can be etched by HF easily, even throuhg a photoresist mask
<azonenberg_work> But i have no way of getting a wafer with nitride on it
<mrdata> let's his imagination wander to nitrides;
<azonenberg_work> This whole mess with tantalumfilm was caused by me not being able to generate Si3N4
<mrdata> dont they use harsh things like HCN and NH3 to make nitrides?
<azonenberg_work> No
<azonenberg_work> Among other things reactive sputtering of a silicon target
<azonenberg_work> in an Ar + N2 atmosphere
<azonenberg_work> will deposit nitride
<mrdata> oh
<azonenberg_work> add a little O2 or sputter SiO2 (i forget which) and you get an oxynitride
<azonenberg_work> But like i said, i dont have access to anything like that
<azonenberg_work> The last idea i had was to try patterning Ta2O5
<azonenberg_work> by HF etch through a metal hardmask
<azonenberg_work> I'm going to try that toniht
<azonenberg_work> photoresist over Cu+Cr over Ta2O5
<azonenberg_work> expose, develop
<azonenberg_work> etch metal in SC2
<azonenberg_work> then etch Ta2O5 through metal with HF
<mrdata> but, the goal is to deposit lines and dots of doped semiconductor onto a substrate
<azonenberg_work> No
<azonenberg_work> The goal in this case is to etch a vertical pattern into a wafer
<azonenberg_work> for MEMS
<azonenberg_work> Doping is a much easier problem if i have a furnace
<mrdata> use CO2 laser?
<azonenberg_work> Spin coat doped SiO2 (Phosphosilicafilm + Borosilicafilm) onto a wafer
<azonenberg_work> pattern with HF
<azonenberg_work> backfill with undoped
<azonenberg_work> and heat in a furnace to diffuse
<azonenberg_work> I can evaporate aluminum which i'd use instead of copper since its MOS compatible
<azonenberg_work> And i'd need to use an alternate developer (TMAH based, or possibly ammonia based) since NaOH / KOH kill PN junctions
<azonenberg_work> Basically, if i had $2K to spare i could probably make transistors with what i have now
<azonenberg_work> $1.2k for furnace, the rest for dopants
<mrdata> should a furnace really cost that much?
<azonenberg_work> mrdata: a nice one? Yes
<mrdata> if you made some transistors, i would like to have some
<azonenberg_work> metal ion free developer
<mrdata> would a CO2 cutting laser help?
<azonenberg_work> mrdata: NOt that i can think of
<azonenberg_work> trace metal grade tmah woot
<azonenberg_work> So i'd need that, $250 each for P and N type dopants
<azonenberg_work> $250 for Silicafilm
<azonenberg_work> Thats the min order (4 fl oz), if anyone wants to buy some subset of it off me feel free :P
<mrdata> 4 fl oz for $250?
<azonenberg_work> Yes
<mrdata> seems really expensive
<azonenberg_work> thats what i was quoted before
<azonenberg_work> And trace metal grade chems are rarely cheap
<azonenberg_work> But you dont need nearly that much
<azonenberg_work> bear in mind the 4 ounces of Tantalumfilm i got, well...
<azonenberg_work> i've used maybe 2 ml of 250 :p
<azonenberg_work> actually no
<azonenberg_work> sub 1
<azonenberg_work> So lets see - i already have PR
<azonenberg_work> i can get TMAH and dopants
<azonenberg_work> i'd need a furnace
<azonenberg_work> i can evaporate aluminum
<azonenberg_work> i can etch aluminum with HCl:H2O2
<azonenberg_work> FEOL process needs something to align dopants to, so i'd probably put a sacrificial aluminum layer down and etch alignment crosshairs into it
<azonenberg_work> Then spin coat N type dopant
<azonenberg_work> Spin coat PR, HF etch to pattern the N diffusion
<azonenberg_work> Backfill with Silicafilm, bake to diffuse dopant
<azonenberg_work> Optionally repeat the process if I'm doing P+ diffusion anywhere (assuming P type wafers)
<azonenberg_work> HF to strip oxide
<azonenberg_work> coat gate oxide
<azonenberg_work> evaporate metal gates
<azonenberg_work> spin coat PR, pattern gates
<mrdata> it's a lot of steps
<azonenberg_work> spin coat main dielectric layer
<azonenberg_work> spin coat PR, pattern gate contacts
<azonenberg_work> evaporate metal 1
<azonenberg_work> *gate and source/drain contacts
<azonenberg_work> at that point i should have workin gMOS transistors
<azonenberg_work> gotta go, i'm halfway across campus from my office hours that start in 5 mins
<azonenberg_work> back in a few
<mrdata> that's odd. the logs seem to be missing after 1940 h UTC
<mrdata> past 20 minutes is unrecorded?
<azonenberg_work> back
<azonenberg_work> And the logs are flushed to disk every ~30 mins iirc
<azonenberg_work> ask wolfspraul
<azonenberg_work> he set it up
<mrdata> ok, there we go
<mrdata> logs agree
<azonenberg_work> nice overview of the dies i was working on
<azonenberg_work> Gotta love that insane depth of field
<azonenberg_work> and here's a long shot of one of my patterns http://colossus.cs.rpi.edu/~azonenberg/images/homecmos/2011-09-20/die_i7_002.jpg
<berndj> mrdata, a CO2 laser is at 10.6µm, so the smallest spot you could make would be of about the same order, if you had a very fast lens.  i think that's getting a bit coarse for what azonenberg_work wants to be able to do
<azonenberg_work> berndj: Yeah
<azonenberg_work> If i was going to do laser direct write litho i'd use UV
<azonenberg_work> 385nm or so
<azonenberg_work> with a ~1um spot
<azonenberg_work> Thats actually on the list of methods to research
<mrdata> ok
<berndj> lol, got a spare excimer laser lying around?
<azonenberg_work> berndj: if i had one i'd be using it already
<mrdata> checks his pockets
<azonenberg_work> I'm thinking bluray actually
<mrdata> sorry
<azonenberg_work> diode laser
<berndj> google "sam's laser faq" if MTI's prices are too steep
<azonenberg_work> berndj: i'm aware of the site
<mrdata> yeah, you can make a N2 laser ithink, from aluminum flashing and air
<berndj> azonenberg_work, do you really need 1200C to grow oxide, or do you need that only if you want it to grow quickly enough that you don't do it overnight
<azonenberg_work> but i doubt they can help me with my problem with MTI's prices
<azonenberg_work> berndj: it's quadratic with temperature i think, up to a point
<azonenberg_work> let me look up the equation
<berndj> dunno... for someone as disciplined as you, you could probably pull off a DIY Ar/Kr laser
<berndj> excimer would be a bit harder though :(
<azonenberg_work> berndj: i dont need a lot of power
<azonenberg_work> 100 mJ/cm^2 or so
<azonenberg_work> is the complete exposure dose
<berndj> how much coherence do you need?
<azonenberg_work> bearing in mind that my die is well under that
<azonenberg_work> Zero
<azonenberg_work> I need a focused spot that i can aim
<berndj> oh :(
<azonenberg_work> that is relatively monochromatic
<berndj> otherwise i was about to suggest the N2 laser
<azonenberg_work> This is basically going to be a raster scan
<azonenberg_work> when i say zero, i mean i dont need coherence at all
<berndj> if you're willing to sacrifice some power, maybe
<azonenberg_work> But it has t obe narrow
<azonenberg_work> The plan is basically to raster scan the laser across the die
<azonenberg_work> a ~1mm field at ~5um resolution is 200x200 pixels
<azonenberg_work> blankign as necessary
<azonenberg_work> just like those cheap laser projectors people mak
<azonenberg_work> except the die is a lot closer
<azonenberg_work> and the theta tolerance is smaller
<berndj> wait, are we talking ablation or PR exposure?
<azonenberg_work> berndj: PR exposure
<azonenberg_work> ablation needs waaaay ore
<azonenberg_work> more*
<berndj> ah, hence you need <400nm lines
<azonenberg_work> energy
<azonenberg_work> Yes
<azonenberg_work> But the spot size can be large as i am making what might be a projection mask rather than a contact one
<azonenberg_work> I'm not projecting onto the di
<azonenberg_work> its a mask (metalized microscope slide)
<berndj> OT: i cut a section through weld beads i ran yesterday, and i'd like to etch them somehow so i can see the various zones.  suggestions?  I have HCl and H2O2, could that work?
<berndj> (it's a crappy weld, but i want pics for my blog)
<azonenberg_work> What is the material
<berndj> mild steel
<azonenberg_work> and whats the goal, show grain boundaries?
<azonenberg_work> First step is to polish it
<berndj> not necessarily even that, just to show the differences where crystals are smaller vs where they are larger
<azonenberg_work> Re oxide growth rate...
<berndj> polish - to what degree?  i suppose having filed it flat isn't enough :)
<azonenberg_work> berndj: optical polish is ideal :p
<berndj> well, i *do* have SiC and rouge for my telescope making
<berndj> lol @ your SEM micrograph showing a 5000µm scale (aka 5mm)
<berndj> thinks look so alien under an SEM!
<azonenberg_work> berndj: yeah
<azonenberg_work> gotta love that depth of field
<azonenberg_work> extreme sharpness
<berndj> what did you put those chip on?  it looks like... salami?
<azonenberg_work> standard ted pella carbon tape lol
<azonenberg_work> its pitch black under visible light
<azonenberg_work> These are all <110> orientation as you can see by the edges
<azonenberg_work> which are angled rather than perpendicular (i.e. parallelogram as seen from top down)
<azonenberg_work> Somebody said http://colossus.cs.rpi.edu/~azonenberg/images/homecmos/2011-09-20/die_i7_002.jpg looked like a sewer grating lol
<berndj> http://www.cleanroom.byu.edu/OxideTimeCalc.phtml another calculator that actually works (for me - the other one barfed when i tried it)
<berndj> lol, they do look a bit like sewer gratings
<berndj> ouch, a 1000nm oxide will take 9200 hours to grow at 700C
<berndj> dry.  wet seems faster?  #todayilearned
<azonenberg_work> berndj: wet is a lot faster
<azonenberg_work> and yeah lol
<azonenberg_work> So at room temp?
<azonenberg_work> Or hot but not THAT hot?
<azonenberg_work> Isnt gonna happen
<berndj> yeah :(  even self-cleaning ovens don't reach 700C
<berndj> i think up to about 500C, but unless you leave your wafer there for a month, not very practical
<azonenberg_work> lol yeah
<azonenberg_work> Let me put it this way
<azonenberg_work> at 1200C the wall of your oven is glowing yellow
<bart416> You'd have to build your own clay blast furnace azonenberg
<azonenberg_work> bart416: or buy one
<bart416> Depends on how big your budget is
<bart416> A blast furnace isn't that hard to build
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