Re: 6561 Die Shot Reversing Explorations
Posted: Sat Jan 06, 2018 11:56 am
Looks very cool so far. Optical would definitely show more since like you said, there is some transparency.
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Would certainly be worth trying optical. In the 6561 image, the detail can still be seen under the metal, but its much less clear.Kakemoms wrote:The 6561 pictures had been taken with an optical microscope, while these are imaged with an electron microscope. I could try to take some optical pictures to get "through" the insulation/passivation that covers most of the chip. Its usually just glass on old ICs, so its possible to see through it (but not the metal lines).
Probably not strictly required, but would certainly be nice. In most cases I can make out what is under the metal in the 6561 images, but not having the metal there in a set of images would make life a lot easier.Kakemoms wrote:If I need to remove metal to make a composite picture, then that can be done with chemicals.
If you look at http://visual6502.org/wiki/index.php?ti ... _MOS_6502D it sounds like I have to strip the metal and polysilicon(or oxide maybe) to get the diffusion layer showing. In that case, optical won't show it very well, so electron microscopy is actually better. Given that I can imagine the whole chip with 12 pictures (compared to 200 optical), its also slightly faster. I will take a couple of optical pictures and upload to demonstrate the difference.lance.ewing wrote:Would certainly be worth trying optical. In the 6561 image, the detail can still be seen under the metal, but its much less clear
Probably not strictly required, but would certainly be nice. In most cases I can make out what is under the metal in the 6561 images, but not having the metal there in a set of images would make life a lot easier.
I've been thinking more about this and suspect that before it can be useful to someone else, I'll have to go back through the SVG that I've been slowly putting together in Inkscape over the past couple of years and convert those bits of diffusion underneath the polysilicon to something else. At the very least introduce the gap in the diffusion, but perhaps also a polygon of another colour to represent the thin gate oxide. I'm not sure whether to simply have it so that when diffusion is immediately beside polysilicon on either side that the thin gate oxide is implied under the polysilicon, or whether it should show this thin oxide visually. The design rules state that there needs to be at least 1 λ between a parallel diffusion and polysilicon edge (when those edges are unrelated, i.e. not used in a transistor or connected together with a buried contact), so it seems that we could leave it out and let it be implied. Any thoughts?Kakemoms wrote:Ok. I think what is confusing me is that you draw the diffusion areas as contineous green areas even beneath the polysilicon.
Well, as I said its mostly personal preference and as you said, its easy to spot the transistors and know were the diffusion is absent. I am not so shure about the pullup-resistor though: Will there be a diffusion layer beneath it or is the polysilicon depletion what gives a long channel (of higher resistivity)? I would think its only the polysilicon that defines a larger resistivity value (by being longer), but I don't really know. One should be able to see that from the 6502 reconstruction on visual6502.lance.ewing wrote:I've been thinking more about this and suspect that before it can be useful to someone else, I'll have to go back through the SVG that I've been slowly putting together in Inkscape over the past couple of years and convert those bits of diffusion underneath the polysilicon to something else. At the very least introduce the gap in the diffusion, but perhaps also a polygon of another colour to represent the thin gate oxide. I'm not sure whether to simply have it so that when diffusion is immediately beside polysilicon on either side that the thin gate oxide is implied under the polysilicon, or whether it should show this thin oxide visually. The design rules state that there needs to be at least 1 λ between a parallel diffusion and polysilicon edge (when those edges are unrelated, i.e. not used in a transistor or connected together with a buried contact), so it seems that we could leave it out and let it be implied. Any thoughts?Kakemoms wrote:Ok. I think what is confusing me is that you draw the diffusion areas as contineous green areas even beneath the polysilicon.
Well, not much would happend until you melt Aluminium at 660C. Since the buried doped layers are not visible until one strips away the top metal and oxide, you wouldn't see the change in carrier concentration either. Anyway, it would be barely visible in an electron microscope, so not much action there either..pixel wrote:Just to sport the infrared idea I'm wondering what kind of movie you'd get if you'd heat the chip up very slowly.
Yeah, this is great! I started by rotating it 90 degrees to the right so that it matches what I am familiar with from staring at the 6561 image for so long. It is clear that the 6560 and 6561 designs are predominantly the same. The interesting bits will be trying to spot the differences. So who is good at that game? How many differences can we spot?Kakemoms wrote:Anyway, here is the full 6560R0 chip from my electron microscopy session. Its not perfect with polymer or dust in several areas, but you can at least trace all metal lines (and most polysilicon lines).
It seems to me Kakemoms took images using an electron microscope for the 6560.lance.ewing wrote:... I can recognise a lot of the same structures from the 6561, but it is virtually impossible to recognise the transistors. I wonder what they did to get the surface looking so clear with the 6561E die shot? I don't know much about the process they go through.
I think he said he will try optical next. One thing I like about the electron microscope is that it seems to show a 3-d effect.eslapion wrote: It seems to me Kakemoms took images using an electron microscope for the 6560.
The die shots of the 6561 are from an optical system.
Yeah, I love that as well. The surface actually is 3D like this, so I assume the 3D effect we are seeing is how it really is. I think if someone were to try to reverse the logic from this diagram, then determining what side the light and dark edges are on would reveal whether it is diffusion or polysilicon. One goes down and the other goes up, which seems to give a different shade on the equivalent edge. When there is a lot of polysilicon and diffusion edges close to each other, it becomes quite difficult though. That is where the optical colours would be very useful.norm8332 wrote:One thing I like about the electron microscope is that it seems to show a 3-d effect.
Makes perfect sense. The electron microscope acts like a super accurate sonar revealing only the surface. The optical microscope works by reflection and transparency but you can't tell what's in front and what's behind. Silicon being the main ingredient of glass, the layers are semi-transparent.norm8332 wrote:I think he said he will try optical next. One thing I like about the electron microscope is that it seems to show a 3-d effect.eslapion wrote: It seems to me Kakemoms took images using an electron microscope for the 6560.
The die shots of the 6561 are from an optical system.