And this gets extended without much obvious change as we move on to the next generation of technology.
This is a cross-section of a modern technology. You see there are many, many layers there. The thing that impresses me is how flat and neat each of those layers is because of a new technology adopted a few years ago that let's us planarize the surface after each thin film operation, a process that to me is completely counter intuitive. We actually go in there, take the top of the wafer and polish the thing, put it on a big wheel and spin it with some chemicals and abrasives, call it chemical mechanical polish. And this has to be uniform to a small fraction of a micron over the entire wafer surface. We 're talking optical quality polishing here. And we go through that operation many, many times as we polish the insulators, the metals, the tungsten plugs which are those more brightly colored structures.
This is a five-layer metal technology. Actually these are quarter micron technology. But maybe you get a better picture of this if we look at it more closely. So I have a couple of our engineers at our Santa Clara facility sitting next to their focus ion beam microscope, and with a little bit of luck we'll be able to look at something like this in real time. So let me move over here and see if I can scare up Tom and Kelly in Santa Clara.
Hi. How are you guys doing?
DR. GORDON MOORE: Hi. How are things going?
TOM: Hi. Just fine.
DR. GORDON MOORE: OK. This is a ProShare video conferencing system hookup we have here. Why don't you tell us what you're going to show us.
TOM: OK. I'm holding a 233 MHz Pentium processor wafer in my hand, and today we're going to demonstrate how we actually do a cross-section into a device on one of these Pentium processors.
DR. GORDON MOORE: How did they ever let you get a whole wafer out of the fab?
TOM: You have to have the right connections.
DR. GORDON MOORE: OK. You've got one under the microscope there?
TOM: Yeah. What we're going to do now is we have previously lowered one of these wafers into the microscope chamber, and we are going to switch to an optical microscope which is actually showing the wafer inside the chamber.
DR. GORDON MOORE: Oh, yeah, I can see it. This is the thing holding the wafer, and I can see some of the dies on here. It's a little hard to interpret, but I've got a pretty good idea what I'm looking at. Zoom in there a bit. I think I can see the serial number on the wafer, even. Yeah, there it is.
TOM: Yeah, that's right. That's the lot number for the wafer, and you can see the borders of the Pentium processor.
DR. GORDON MOORE: Yeah, I see the scribe lines there between the various processor chips.
TOM: OK. Now we are going to go from this notch or lot number orientation at the edge of the wafer over to a die corner, and this wafer, once again, has 265 Pentium processors on it.
DR. GORDON MOORE: That's a lot of computing power.
TOM: It is.
DR. GORDON MOORE: OK. I see we're at the intersection of four die here now showing up on the light microscope.
TOM: OK. I'll zoom up on that a little bit. Now what we are going to do is switch from this optical image over to the fixed image.
DR. GORDON MOORE: It's hard to see with the optical image.
TOM: This is it.
TOM: The FIB image allows us to go to resolutions which are actually below the wavelength of light.
DR. GORDON MOORE: Good. I see some hieroglyphics here in the middle of the cross what are those.
TOM: These are letters B, E, C, and D which are used to define the edge of the reticle field. These are used for alignment in photography.
DR. GORDON MOORE: Fine. And these are the scribe lines that make the cross, I guess.
TOM: They are. And the scribe line is about 120 microns line and the saws that actually end up dicing the wafer goes through these scribe lines.
DR. GORDON MOORE: So 120 microns is a fat hair, typical hair is about 100 microns. Those of you with coarse hair, your hair is about the size of that line there.
TOM: From here we are going to navigate over to a bond pad.
DR. GORDON MOORE: OK. I see the bond pads coming up on two different die here with the scribe line with some bright spots in the middle of it.
TOM: Yeah, these bond pads actually are about 80 microns wide and they are used to interface the die to the package.
DR. GORDON MOORE: OK. Those are a thin hair, then.
TOM: That's right. From here, we are going to go to a specific transistor. This Pentium processor has over five million transistors on it, and it's actually quite a major accomplishment for us to be able to get to the specific transistor. We typically use pad navigation. For this demonstration, we have accelerated a few of these methodologies, and we're just going to go right to the transistor now, Kelly.
DR. GORDON MOORE: OK. Now I see a bunch of horizontal lines with a spot in the middle. What am I looking at?
TOM: We're actually in the cache region of the chip, and this happens to be the data cache and these lines on the surface are for the cache and VCC power supply.
DR. GORDON MOORE: These are aluminum stripes, then, that conduct the current there. And what's the spot I'm looking at.
TOM: The spot is actually the box that we have previously built, and the transistor of interest is in the spot.
DR. GORDON MOORE: What do you mean by milled?
TOM: In the FIB, which stands for focus ion beam, we have a high energy beam that actually sputters atoms from the surface of the sample. The beam is also rastered so thus you get the box shape. So, you mill down into the sample to run a cross-section.
DR. GORDON MOORE: OK. Can we look closer at this?
TOM: Yes. Kelly can tilt the sample first. Actually, now the entire wafer is being tilted. This will allow us to look end-on into the box.
Now Kelly is going to slowly zoom up so we can look inside the box, going right inside.
DR. GORDON MOORE: How big is this box?
TOM: This box is about 10 by 10 microns.
DR. GORDON MOORE: OK. Oh, boy. This is a little one, less than a half a thousandth of an inch. Yeah, I can see the hole now, the bottom lip, and I guess that's the back wall up there.
DR. GORDON MOORE: All right. I'm starting to see some structure. I guess I can see metal 5, 4, 3, keep coming, 2 and 1. I can see all five layers of metal now on the back wafer there. This is a quarter micron technology. Those things are pretty close together. I can see the tungsten plugs also between the layers of aluminum.
TOM: We're going to do a slow scan to get a slightly higher quality image.
DR. GORDON MOORE: OK.
TOM: The contrast in the metal five and metal four are actually different aluminum grains.
DR. GORDON MOORE: OK. That's showing up quite clearly this time. OK, now I can see the bottom three layers of metal developing nicely with the tungsten plugs. Oh, there's the silicon, and you can see the trench isolation. Do you know which transistor you're looking at here in particular in this one?
TOM: We do have addresses, actually, for all of these transistors. These are actually a column address going down into the transistor.
DR. GORDON MOORE: OK. You get in here, dig down under five layers of metal and at least an equivalent number of insulator layers, find a particular transistor and try to evaluate what's wrong with it, I guess. That's pretty spectacular.
DR. GORDON MOORE: OK. Thank you.