What Plasmas Have to Do with Computer Chips

you oh this is such an amazing device can you imagine I've got more power in this little device this computer the cell phone then giant rooms full of computers when they first started and with this device I'm connected to the world there's many cell phones in the world as people or coming up to it pretty close this is only possible because of the advent of modern computer technology the ability to take transistors and turn them smaller and smaller and smaller and what I want to tell you about in this clip is how that's done let's look at the first integrated circuit this was made by dr. Kirby in the late 1950s it's the first integrated circuit and it is pretty big not a foot but you know maybe maybe ten centimeters a few inches that was the 1950s this is today the scale lengths you have to look through microscope or even electron microscope to see them and things have gone from 10 centimeters to 10 nanometers we've gone from 10 centimeters right that's point one meters 2 point 1 2 3 4 5 6 7 8 9 meters 10 to the minus 1/2 10 to the minus 9 8 orders of magnitude nothing else has ever increased that quickly every two years the number of transistors on a given chip a given size doubles does your automobile get twice as good and twice as fast twice as much gas mileage for the same price every two years do your clothes suddenly become out of some fantastic fabric that's twice as good every two years the construction materials get better generally but every two years double and functionality no way only this revolution has taken place and it is not by accident you see Gordon Moore one of the founders of Intel made a prediction and it became known as Moore's law and it said the number of transistors in a chip will double every two years did he have some prophetic sense no he could just see back here in the 70s how things were going but because it worked economically because people bought the products and then the same people bought the new products and two years later the same people bought the new products this is a goldmine for consumers not only does it give us much better functionality we've led to these handheld brains that are like Star Trek right I can't quite beam us up they certainly can allow us to talk to anyone anywhere in the world anytime we want for pennies this economic revolution of increasing these chips happened because they saw a pattern and they made a road map and they said aha to get from here here this has to get better this has to go better this part has to get better and therefore people and resources were put into fearing out how to do that and if it all arrived on time your chip got better and better and better and today we're down to this 11 nanometer node in 2015 the computers you're going to buy or will buy shortly by the end of this year or into 2016 will be made at that spatial scale continue the next note after 11:00 each of these are about the square root of two right if we put the same number of transistors on a chip the size of one individual feature has to go down by the square root of two 1.4 the next one after 11 is probably 7 and then 5 and then 3 and you might say how far can this go well an individual layer of atoms is about 3/10 of one nanometer these devices are called solid state which means they work on collective properties not individual properties of an atom and how many atoms do you mean to get a solid state affect how many layers I don't know let's say if it were 10 layers well then 3 nanometer node would be about it if it turns out to be 7 layers well you could go one more node after that this is gonna get us another 10 years on this progression we'll then micro electronics be at some stopping point I doubt it there are things where you can use individual atoms things like quantum computing there's also the case where perhaps the individual size won't get any smaller but we can start stacking more and more things that's already happening today vertically the functionality and the volume will double every 2 years not just the functionality across an area and of course it's not just that the sizes gets smaller their power increases this is talking about the number of computations you can do per second sort of the total brain power of a chip and the line you see up here this is the brain of a mouse and we're there folks this lines the human brain a few orders of magnitude to go but we may in the in the next 10 years get to that point just an absolutely amazing progression of modern technology how is it done in the end and you see something like this and you see different material on top of another material those are going to be the basis of a transistor NPN Junction or the other way around and if I connected the wires in the right way I might have three different transistors here how do I get to a pattern like this well first I start out with single crystal silicon it could be germanium arsenide some other type of semiconductor and we're gonna deposit a layer this is gonna be our active layer part of our transistors in the end the blue stuff and then we have to put something called a resist across the top so we got to spread it out then we come to the very first real key step and that's called making a pattern lithography light is shown through a mask it comes down over this and part of this material it's orange material in the picture here turns green really turn green but it changes its property only where it's exposed so I can take a pattern and I can go to expose this chip all at once remember this isn't just making chips smaller every couple of years it's making them smaller economically it's making them smaller for the same price the beauties of these processes is it doesn't just happen in one little location the entire wafer today that's 300 millimeters across 30 centimeters across the entire wafer gets acted at once and it turns into hundreds and hundreds of computer chips so we make a pattern now we do something that's called develop you take away the part of the pattern that was either exposed or not exposed next step is called echar we have to make some kind of process that is going to eat away at the blue stuff without hurting the orange stuff and that's now made a pattern out of this blue material we then have to do some other edging process to take off the orange and we're left with this but you know there's gonna be one more process after that because we're gonna repeat this whole thing and we also have to deposit this is just one layer we're gonna have to now put down another layer of silicon or another layer of silicon dioxide or layers of metal wires that are going to connect to these and we're gonna have to do it over and over and over and over on a particular computer chip pattern edge and deposit in the end if I took away all the insulator the wires that would connect to the different transistors together will look something like this looks like some modern architecture here but remember if I put a billion transistors on a chip it's only gonna do something smart like my cell phone if they're connected the right way and most of the work in making a chip is actually making these connections is actually connecting the right transistors together to the right other elements and getting it all to feed in some logical sensible pattern and to make those wires to connect this transistor here to one of them that's over here sometimes the wires are going to have to go up you're gonna have to go across you're gonna have to come back down over and down again without letting any of those wires touch each other I look at an actual scanning electron microscope picture of the metal layers in a chip you can see they look something like this and if we make a cross-section you see it perhaps even better here are the transistors the three junctions of any transistor you can see a wire comes up here this wire comes up here goes across and connects Dec to this one right but it's probably going to go several other ways and when you see a large chunk like this that's because it's coming towards you or away from you across the pattern then it would connect over to someplace else and so on and so on there are at least eight approaching ten layers of this interconnect technology that connects the transistors in the proper pattern most of the work in making the chip is not making the first layer although obviously that's critical but it's making all of these other ones let's look at each of these three things in turn first patterning back in the 1980s in the 70s even the 90s there were lasers or light sources that were still smaller than the feature and that's great because you can shine a light through something it makes a shadow the shadow falls down on top of the pattern and you simply transfer it by a shadow very simple direct straightforward lithography problem was that Moore's law here is continuing down in size and the wavelength of the light used did not continue to decrease you might say well why didn't they just keep making lasers at smaller wavelengths well you can't that's tough 193 actually is a one forty eight one but chips were already so small it didn't make much sense this became very very difficult yeah of course we have succeeded we are making eleven nanometer chips you'll notice there's this area down here at EUV thirteen nanometer light thirteen and a half actually do research in that area and it has been something people have been trying to do and knowing that we had to do way back in here it's really difficult because it's not a laser anymore it's actually a plasma hot ionized gas you take ten of all things ionize it up to about plus ten the plus twelve and a tiny bit a few percent of the energy you put into it goes into the light the 13 nanometer light you want and that light goes in all directions so you have to collect it with a mirror not just any mirror 13 nanometer light is almost 100 electron volt photons it's not really x-rays yet but it's on its way to them and they don't bounce off of normal stuff like a shiny piece of metal you actually have to make some very particular structures bilayer structures in a mirror to be able to get them to reflect in the first place at all this technology has been difficult an actual device that makes the 30 nanometer light looks like this all of this is a huge laser which hits that tiny 30 micron wide tin droplet at 50 thousand times a second 50,000 different droplets every second bursting it into this plasma where you collect this little bit of light this technology does work and soon in the next year or two the chips that are being made or that will be made soon after that will utilize it it's been a difficult time so how have they continued the Moore's Law progression even though the wavelength of the light has been so large well they've had a lot of clever intelligent things at one point they actually put it underwater not the whole tool on the drop of water right at the end because the wavelengths go down by the index of refraction so you effectively get a 30% game they've also used things by not just printing with shadows but printing with interference patterns just like you might have these to the lights come out and in places where they they constructively interfere and destructively interfere you place your pattern where you have that interference difficult but it worked and finally what they've resorted to is double or even quadruple patterning explained that remember my lithography step can only print something this wide I can't put it through a narrower slit the wavelength of light is so much longer it just says I don't know I don't even see that right you can't see smaller than the wavelength so we make this big pattern okay we etch it out but we want something half this size so we deposit we put the resist on we make another pattern this next pattern is offset a little bit right here because it's offset a little bit I now edge through that and I end up with things that are half as small I've had to do two different lithography steps and two different etch steps where is I had a smaller wavelength of light I could have done it in one another even cleverer way that involves some of the deposition so I start up here and this is as close as I can make my features because of lithography and then I coat them with something remember our third thing H and deposit I then etch this back so that I sort of uniformly edged off the top and the bottom and I've left these thick spacers I use a different type of plasma etching different chemical compounds different plasma and that edges away the blue stuff now I have this what's here as a beige color and that's my mask to now etched down through the green layer which is the thing that I wanted to turn into a double pattern in the first place yet another type of etching that can get rid of this and not get rid of green and we end up with doubling the pattern we started with a lot of work because I can't print at that wavelength do this all again you have quadruple patterning do it yet again you have octuple patterning that's where many steps and chip manufacturing are going so you've got the general scheme let's now look into edging just a little bit more just as the lithography steps of today the UV uses a plasma etching uses a plasma as well this is a fairly simple inductive type of plasma it's what's used to clear off the resist after you have patterned it and in the end after you've exposed it as well if I want to do the etching for large areas a whole chip at a time and I'm doing the very detailed stuff where I need a different recipe often a thing with two parallel plates is used with the plasma in between so this is the whole semiconductor wafer by changing which gases I put in which type of plasma I create I can be sensitive to etch one type of material instead of another type of material these things are done in large factories fabrication laboratories called fabs FA B people are very very careful about cleanliness in them not because they're going to get dirty or hurt but because the chip will when I'm down to those types of scales think about what one piece of dust does ruins of the whole day that chip will have to be thrown away so these clean rooms places where the air is filtered over and over and people are covered so none of their skin cells or hair or other things can possibly create dust and fall into stuff is where this work is done in the future in fact the future is now instead of taking some general plasma that's going to eat away at something there are new steps that do atomic layer edging you do a series of steps with the plasma and you can take off one atomic layer at a time in the past you'd have to have drilled so far deep because the features were huge that this was impractical today now that we are dealing with things that are only 10 nanometers wide you can actually afford to take things off a layer at a time every time I get in pattern I also have to deposit putting on the resist is fairly easy you just sort of brush it on but filling in the metal lines filling in new silicon or silicon dioxide layers those also require plasmas one of the things that's done to make the metals is something called magnetron sputtering physical vapour deposition you take a particular type of target whatever metal it is or compound it is you want to end up coating your substrate by creating a magnetic field behind it you can trap the plasma and the plasma will make ions you put an electric field on it and it knocks things out atom by atom which then deposit onto your substrate onto your semiconductor chip there's been advances in this we work in this here's a picture of my laboratory one of our various PVD sputtering devices that were working on the newer ways to be able to get that metal coating into even smaller and smaller features here's a picture magnetrons at work two different materials being sputtered here at two different rates and you can see the place where the plasma is acting on the material this one's actually gold and this one's aluminum in the end you make a modern micro electronic chip the heart and brains of every cell phone of every computer and probably every other gizmo that is filling up space throughout your house office living space car airplane you name it micro electronics are there and will continue to be because we continue to find ways using plasmas to make them smaller and smaller and smaller at the same price that's what you need to know about how computer chips are made you [Music] you

Channel: Illinois EnergyProf

Views: 52,580

Rating: 4.9392166 out of 5

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Id: JhQaeskfoto

Length: 23min 24sec (1404 seconds)

Published: Tue May 14 2019

Reddit Comments

[u/bob12388121312]

All of the videos on this channel are fantastic.

[u/freddyt55555]

Very informative. The part about wiring the layers is mind blowing.

[u/joshcow]

Sir this is a Macdonald