
X-rays could be used to cut down on problems bringing a new CPU to market - poiuz
https://arstechnica.com/science/2017/03/bright-x-rays-reveal-3d-structure-of-processors-and-defects-lurking-within/
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gliese1337
The article doesn't make this clear, but this is an excellent example of an
area where "pure research" and practical technology overlap. Free electron
lasers are essentially particle accelerators (of the same sort used in, e.g.,
the LHC) with special configurations of magnets stuck on the end. They are
large, expensive to build, and expensive to operate for essentially all the
same reasons that research accelerators are. So advances in physics which lead
to advances in accelerator technology, which allow further advances in pure
physics, also directly impact the practicality of using FEL X-ray sources for
imaging microchips (among other things).

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aylons
They aren't "essentially" particle accelerators, they are full-blown
accelerators, linear accelerators, specifically.

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kurthr
Most of the problems with binging new digital ASICs to market have to do with
the failure of -XRay-Lithography- EUV (now called Extreme UV) to provide fast
enough exposures despite decades of development and billions in research
investment. This is a hard problem, but quadruple patterning is also nasty and
expensive at 7nm. Even if you can identify the error... if you can't make
almost every one of a couple billion transistors correctly, you can't make a
modern CPU.

I'd recommend reading a few recent articles on the topic:

The problem with lithography
[http://spectrum.ieee.org/semiconductors/devices/leading-
chip...](http://spectrum.ieee.org/semiconductors/devices/leading-chipmakers-
eye-euv-lithography-to-save-moores-law)

A depressing conclusion [https://www.hpcwire.com/2016/07/28/transistors-wont-
shrink-b...](https://www.hpcwire.com/2016/07/28/transistors-wont-shrink-
beyond-2021-says-final-itrs-report/)

An optimistic expert [https://www.semiwiki.com/forum/content/6590-scott-jones-
iss-...](https://www.semiwiki.com/forum/content/6590-scott-jones-iss-talk-
moores-law-lives.html)

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teddyh
This could be useful to reverse-engineers who may want to do security
verification (are there a hidden backdoors in this chip outside its
specifications?) or to simply clone a chip outright.

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astrodust
I'm surprised lithography hasn't been replaced with something more nanoscale
in origin like some kind of atomic deposition process where individual atoms
are precisely bombarded onto the substrate to build up the features atom by
atom.

It would take longer to manufacture each chip, but if the machines to do the
deposition were relatively cheap and simple to construct, they're not that far
off of electron beams, the result could be a massively parallel manufacturing
process.

~~~
deepnotderp
"Longer" if you're talking atom by atom is an understatement, you're going to
almost never finish. Electron beams might be something relevant, but they're
already being investigated.

E-beam lithography is a thing, and as with all next-gen litho techniques, it
too has its fair share of problems. For example, shot noise is a major problem
which means that every time you halve your node, you're going to halve your
throughput. This is devastating for semiconductor manufacturing, TSMC is
already working double shifts trying to match demand.

Also, the important thing to realize about semiconductors is that
demonstrating something in the lab is a relatively easy ordeal, but making it
mass manufacturable in a timely fashion with good yields is a herculean task.
You can actually use X-ray litho for something more "nanoscale in origin" but
it's really, REALLY difficult to make it in production.

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jpmattia
> _You can actually use X-ray litho_

Wouldn't that result in a threshold shift? (X-rays are well beyond Si02
bandgap, so you'd get electron-hole pairs in the oxide. The electrons are
fairly mobile, but the holes get trapped iirc.)

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libeclipse
> Essentially, it takes a very long time to obtain each pattern, and you need
> a lot of patterns. By the time you've finished imaging, management has
> brought you your golden watch.

What does this last part about the golden watch mean? Is it a reference to
retirement?

~~~
doubleplusgood
Some companies gave out wristwatches commemorating significant tenures.
There's even a Domino's Rolex.

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deegles
Pardon my ignorance, but would it be possible to use X-rays to read the
contents of memory? Say, in a TPM or Secure Enclave? I feel like if you had an
accurate enough beam you could detect if a memory cell is "charged" or not.

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anfractuosity
I'm not sure about whether you can do that with x-rays, however you might find
this paper interesting - 'Reverse engineering Flash EEPROM memories using
Scanning Electron Microscopy' \-
[http://www.cl.cam.ac.uk/~sps32/cardis2016_sem.pdf](http://www.cl.cam.ac.uk/~sps32/cardis2016_sem.pdf)

~~~
ComputerGuru
Thank you for that relevant article and interesting read. I don't know why
you're being downvoted, but I did my part to restore the balance.

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ajross
It's an article about a paper published in Nature about X-Ray tomography to
image nm-scale features in modern ICs.

And the only image presented in the whole article is a completely unrelated
Chipworks die shot at about 10um per pixel.

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oakwhiz
Wouldn't this method also erase any EEPROMs on the die?

