From Newsgroup: comp.arch
On 4/21/2024 5:02 PM, MitchAlsup1 wrote:
BGB wrote:
On 4/20/2024 11:28 PM, John Savard wrote:
On Thu, 18 Apr 2024 22:41:01 +0000, mitchalsup@aol.com (MitchAlsup1)
wrote:
In the early 1980s someone (Amdahl?) was working on wafer scale
lithography, apparently we have now arrived.....
Actually, several companies were. The one mentioned, Trilogy, was the
one that spun off of Amdahl. There was also the company that was going
to make the solid state storage wafer for the Sinclair, the name of
which was Anamartic. Texas Instruments and ITT also researched its
possibilities.
On the other side of things, I am wondering what sorts of densities
and clock speeds are possible with printed electronics on a plastic
substrate (such as PET).
Information on the subject is fairly sparse, but inks seem to be
available (albeit expensive), albeit with some variation as to printer
technology. Seems to be be either organic or inorganic inks, with
inkjet, offset, and screen printing, as the main variations in printer
technology (with different inks for the different methods).
To determine wire delay per unit length, one would need the LRC values
of the conductor and insulators. Copper on Epoxy allows for transmission speeds of ½ that of light, and I think you would be resistance limited.
So, we need:: 1) Ohms per square, 2) inductance per unit length, and 3) capacitance per unit area.
Dunno there...
It looks like a lot of the metallic inks are silver or copper based.
Not entirely sure how it works. Apparently one needs to bake the sheet
for the components in the ink to turn into their final forms, but around 80-120C is well below the melting points of silver or copper (but, they apparently somehow sinter at these temperatures).
Would need to have an oven that does accurate temperature control, since
if part doesn't get hot enough, the ink wont set correctly, and if too
hot, the PET substrate might warp or melt, ...
Though, I will assume that by inkjet, they don't mean just using a
repurposed consumer-grade printer (possibly with the ROM's hacked to
allow them to use refilled ink cartridges, with the non-standard inks).
Then again, with these things, they have created a situation where
there are a lot of old inkjet printers around, mostly because it is
often cheaper to buy a whole new printer than to buy the ink refill
cartridges for said printer (vs, say, laser printers where the printer
is more expensive, but the toner refills are more reasonable).
Looking around, it seems some people are instead using the more
"office style" inkjet printers for this (which apparently allow for
refilling the ink cartridges).
Also seems the N and P doped inks are rarer and more expensive than
the conductive metallic and insulator inks.
No information on what sorts of densities are possible; crude guess is
it is roughly a ~ 133333um process, based on the assumption of a 300
dpi printer (possibly more or less).
300 DPI is 1995 technology, I would be surprised if you could not find
4800 DPI printers. This, alone, changes the lambda by 160×.
The stuff I was aware of, printer resolution was usually assumed to be
between 72 to 300 DPI.
Apparently (looks up stuff), inkjet typically ranges from 300 to 720 DPI
(with 600 to 1200 for laser printers, and 1000 to 2400 for photo printers).
Not sure of the DPI of a generic office-style inkjet printer (assuming
one gets one of the ones that allows for refillable ink cartridges).
If one assumes, say, 6-dots width for a transistor, this would be ~
50x50 transistors per square inch, or possibly ~ 200k transistors per
page...
Generally, the planar technologies had 6 lambda (min) source and drains
with 4 Lambda gates and one would need 9 lambda to drop a contact on
a source or drain. So, a minimum contacted transistor would be 9+4+9
= 22 lambda wide. Generally one wanted 4 lambda between different active regions, to the pitch of this minimum contacted transistor would
be 9+4 = 13 lambda.
OK.
So, I guess similar would hold if one had a 1200 DPI printer...
But, only 50k for 600 DPI.
Seems like this could handle a lot of 8/16 era CPUs on a sheet.
Though, saw a video talking about it, and they had a printed Cortex-M0
on a smaller piece of plastic (around 4in^2 IIRC), but the video didn't
say what sort of printer or inks they were using, so...
I guess, if one could get it to run at MHz speeds, this could be
enough for a CPU.
Though, would likely need multiple passes through the printer to print
something like this, say:
Print transistor layers;
Bake the sheet;
Print insulator and metal trace layers;
Bake;
Print more insulator and metal trace layers;
Bake;
...
Your typical 2 layer metal CMOS process in 1.5µ had 200 steps in it.
1) spin on resist
2) bake resist 3) expose resist (mask 1: P-wells and N-well contacts)
4) develop resist
5) etch resist
6) clean wafer
7) ion-implant exposed wafer
8) clean wafer
8 similar steps for N-wells
17) deposit polysilicon
18) bake polysilicon
19) spin on resist
20) bake resist
21) expose resist
22) develop resist
23) etch resist
24) clean wafer
25) spin on resist
26) bake resist
27) expose resist (P-Channel)
28) develop resist
29) etch resist
30) clean wafer
31) P-channel implants (arsenic)
32) spin on resist
33) bake resist
34) expose resist (N-Channel)
35) develop resist
36) etch resist
37) clean wafer
38) N-channel implants (phosphorous)
Then, for each contact layer one has 8 steps, and for each metal layer
one would have 10 steps. Then a thick passivation, then cutting of the bonding pads, and finally, a back lap of the wafer to clean contaminates
and a 3 atom thick gold sputter so one can solder the Si die to the
package.
So, the problem becomes one of how does one get the pads attached to
the "other" components in the system ??
I am guessing the process for inkjet on a plastic substrate is somewhat different from that used for optical lithography on silicon.
But, the information I had seen implies it is mostly printing onto the
sheet, and then baking the sheet so that all the components sinter
together, then more printing, and more baking, for each layer.
Well, unless it is print/dry/print/dry, with baking as a final step
(where dry is done at a lower temperature than bake).
Also not obvious which of the various types of ink one would use, etc...
Possibly, a person could also print vias and then do multiple layers
of transistors per page, possibly up to some set limit.
Not entirely sure how one would go about mapping digital logic onto
printable layers though. This may well be the hard part.
Straightforward place and route.
There is a pretty big gap between Verilog and the actual transistors.
But, yeah, in concept, probably some way to compile Verilog to a
netlist, and then to convert the netlist to the various component layers.
I will make a guess that there are probably no Verilog to
semiconductive-ink-PNG compilers.
Though, probably actually TIFF, as one needs a format that can hopefully specify things in terms of the CMYK system, so that hopefully it prints
stuff with the correct inks, rather than blending them all together...
....
John Savard
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