Patterning aluminum with the photoresist "lift-off" method----make money online

hey everyone I thought of giving anupdate on my thin film transistorprogress so whenever we want to makesomething like a TFT or displaytechnology or anything like that we haveto have a way to pattern all these thinfilms on a substrate and so I'm going toshow you one possible method calledphotoresist liftoff so the processstarts by loading a microscope slideinto this which is called a spin coaterand I built this just from a relativelycheap DC brushed motor and an acrylictube and this thing spins a few thousandrpm once it gets going it takes a good 5or 10 seconds to spin up and once it'sat speed I drip a little bit ofisopropyl alcohol on the slide and toclean it off and the alcohol flies offthe side and then I apply a little ofthis which is a photoresist that Ibought on eBay and the seller wasselling this for doing home PCBs butunfortunately I don't know exactly whatchemical it is it's green that's that'sabout all I know and it's positive it'sa positive photoresist so the spincoater will fling off most of the resistand I'll let it spin for another 30seconds or so to make sure that thelayer thicknesses as consistent aspossible and I'm guessing that the layeris somewhere around 1 micron maybe a fewmicron or something in that range but Iunfortunately I have no easy way oftesting it next I put the microscopeslide on the hot plate at about ahundred degrees C for one minute andthis will drive off all of the solventsin the photoresist to make sure thatthere's just that base polymer left nextI expose the photoresist to ultravioletlight through a pattern and in this caseI'm just using sort of a reallyprimitive resolution test that I made onmy vinyl cutter and so it has line pairsof descending thickness the ultravioletlamp is an electrophoresis illuminationsystem so if you're going to be doingDNA analysis some of the dyes that areused are UV or phosphorescent basicallyin UV so you would put the gel on top ofthis thing and it would light it up withUV lightthe device has 615 watt UV lamps inthere and they peak at 312 nanometer Icalculated this to have somewhere about20 millivolts per square cm of UV at thesurface and that should be enough toexpose the slide in about maybe 30seconds or even less than that probablymore like 10 seconds but I leave it onfor about 30 seconds to a minute just tobe sure so we're kind of at this stephere on the paper and after the exposureprocess is done you can actually see thecolor change so the resist changes fromsort of a lime green to a light bluecolor in the areas that it's beenexposed to the ultraviolet light nextwhat we want to do is get rid of theresist that we exposed to UV so wedevelop it and the same seller that isselling this on eBay also is selling anunlabeled developer these mysterycrystals here which I'm pretty sure aresodium hydroxide and these are not thebest things to use I'm trying to getsome sodium metal silicate which is amuch more forgiving developer theproblem with sodium hydroxide is that itgoes from underdeveloped to over developvery quickly and Mike's electric stuffhelpfully pointed out that sodium metalsilicate pentahydrate is is a muchbetter choice so I've got some of thaton order so after the developing processwe've got the pattern photoresist andthe developer has removed it where wherethe photoresist was exposed to UV lightso after letting the slide dry note thatit can only be rinsed in water at thispoint if he tried to rinse it withalcohol or acetone the photoresist wouldcompletely degrade so we're sticking toaqueous stuff at this point after dryingI loaded the slide into my vacuumchamber and did some thermal depositionof aluminum so this process will workwith sputtering - of course that mysputter gun needs just a few more tweaksto be reliable enough to use so I'mgoing to go back to thermal evapoand the trick here is that theevaporation of the aluminium will comeinat fairly close to a right angle to thesurface so that all the depositionhappens on horizontal surfaces andyou'll see in a minute here that Ididn't quite get this to work because mycoating thickness was so high buttypically the photoresist would be likea micron thick and the stuff that you'reactually laying down would be far lessthick than that probably more like ahundred nanometers so there would beplenty of room here where the therewould be no vertical wall made becausethe photoresist is so much higherhowever this is actually one case wherehaving a negative photoresist is betterbecause the the angle of this cliff hereis a little bit more inclined with anegative photoresist so that when youdeposit from the top these walls willstay very clean with a positivephotoresist the wall angle kind of looksmore like this so that you end up withmore of a wall to coat and this willleave some some unwanted material aswe'll see later so after the depositionis done the entire slide is coated withaluminum and then we put it in a solventlike acetone a very aggressive one andthe acetone will seep under here anddissolve the photoresist now in thiscase the aluminum layer was so thickthat there was actually a connectorgoing between the layer that I depositedon top of the photoresist and the layerthat went right down to the slide so Ihad like basically little streamers orflags hanging off but luckily I blewthose off with a pipette and the endresult was actually not too bad sohere's a picture of it under themicroscope and the markings on the onthe ruler there are 1 millimeters facingso this line is you know probably acouple hundred micron the neat thingabout this technique is that we don'thave to use an etchant so we can keepputting layers down without worryingabout incompatibility at the etchantwith the layer beneath it so for exampleif we wanted to deposit silicon dioxideon glass we could do that and not haveto worry about her harming the glasslayer underneath with the same agentthat would attack both okay see you nexttime byeTop Search Keyword : online earning, , make money online, earn money online, online earning, online earning sites, make money online free, online money income, earn money online free, money online, best way to earn money online, online income site, money earning websites, best online earning sites, easiest way to earn money online, earn money payment bkash, online money income site 

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