#homecmos IRC log for Tuesday, 2011-11-01

--- Tue Nov 1 201100:00
azonenbergYay, my Ni arrives tomorrow22:09
azonenbergnow i can finally try KOH etching with a proper hardmask :)22:09
bart416azonenberg, I did something far more useful!22:23
soul-dnice , here ill need to use shed so probably won't do much during winter    did find some vacuum stuff but those are called "vacuum excicator"   there is a cheap 5 eur -> http://www.labstuff.nl/contents/media/1g.jpg  wich is supposed to be  a stolp kind of thing just looks like bottle to width is 3,1")22:38
soul-dthe problem is not that the 5 euro might hurt but donno about actualy putting a vacume on it22:38
soul-dyou have any ranges   you typacily want to work at ? like specs of pump   ?22:39
soul-dnot to mention shipping it trough mail :)22:40
azonenbergMy guess is that a dessicator will not go below, maybe, 1/10 atmosphere22:46
azonenbergbut you need to hit the 1E-6 torr range to get good evaporation22:47
azonenbergSo, let's see - my next wafer will be a 50mm <110>22:48
azonenbergOne 8x8 block in the middle, thats 64 3x3mm dies22:48
azonenbergplus 12 more around it on each side22:48
azonenbergthats another 4822:48
azonenberg112 dies out of one wafer? That should work nicely22:49
soul-dk have any links of correct products22:49
azonenbergNo, unfortunately22:49
azonenbergvacuum is on the list of things to explore22:49
azonenbergbut i havent done much with it yet22:49
soul-ddoes it have to be glassware then ? or like like somthing with a porthole view type of construction although glass has it's advantage with it being inert to most stuff22:55
azonenbergGlass bell jar is what i plan to use22:56
soul-dneed to build a good safe haven first anyhow for stuff like that  but just wondering  would all metals be vapable ? like alu and silver  just all the same ? since always wanted to make own telescope  but  never wanted to do the silver stuff with chemicals maybe lookup how they vapped up their mirrors  (and maybe a area for you to look at ) ATM amature telescope making23:04
azonenbergAll metals can be evaporated, given enough heat23:05
azonenbergi qualify that23:05
azonenbergFor example, tungsten would be a little bit tricky ;)23:05
azonenbergIt's used in fab often though, but deposited by sputtering23:05
azonenbergYou can definitely evaporate aluminum23:06
soul-donly read the word in the books but process wasn;t explained23:06
azonenbergit's actually easier than sputtering it, you need a lot of power to sputter it because you need to break the native oxide off the target23:06
azonenbergand you dont know what sputtering is?23:06
azonenbergIt's an alternative deposition process that runs at higher pressures than evaporation23:06
azonenbergWhen you evaporate, you usually run at the `1E-6 torr range23:06
azonenbergevaporation is much higher, more like 5E-2 torr23:07
azonenbergyou fill the chamber with an inert gas, typically argon23:07
azonenbergand run high voltage through it23:07
azonenbergthe resulting plasma ionizes the gas and causes the gas atoms to strike your target (the material being deposited) and knock atoms off by kinetic energy23:07
soul-doh yeah i did read on it23:08
azonenbergnote that you are mechanically knocking metal atoms off, so the bulk material is well below the boiling or even melting point23:08
soul-dsomthing with dark regions of plasma ?23:08
azonenbergin fact, the target is usually cooled for long depositions specifically to keep it from heating too much23:08
azonenbergSince the pressure is so much higher, the deposition is usually pretty conformal23:08
azonenbergas opposed to evaporation which won't coat vertical structures (edges pointing straight toward the deposition source) well23:08
azonenbergSometimes this is good and sometimes it's bad, but its a factor to consider23:09
soul-dprobably hard to setup at home :P23:10
azonenbergNot really23:11
azonenbergi'm in contact with a prof at a SUNY school that is building one on the cheap as a demonstration23:11
azonenbergIN terms of homebrewing, sputtering needs a more complex apparatus and a means of feeding tiny amounts of inert gas into the chamber23:12
azonenbergevaporation needs much harder vacuum23:12
azonenbergyou need a second stage pump23:12
azonenbergbut sputtering level vacuum is within the reach of a mechanical pump23:12
azonenbergAnd the lack of deep vacuum is a nontrivial problem as turbopumps are expensive and diffusion pumps are slow23:14
azonenbergSo sputtering is actually higher on my feasibility list23:14
azonenbergall i'd need is an argon canister from a welding supplier and a needle valve23:15
soul-dyou do need to have nice buget for it all though23:17
azonenbergYeah, its not a cheap hobby23:19
azonenbergbut a few grand vs a few million? Huge improvement23:19
--- Wed Nov 2 201100:00

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