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From: BGB <cr88192@gmail.com>
Newsgroups: comp.arch
Subject: Re: 208 B transistors !!
Date: Sun, 21 Apr 2024 19:02:55 -0500
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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.

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