
How Reliable Are FinFETs? - Lind5
https://semiengineering.com/how-reliable-are-finfets/
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phkahler
I'm still amused at how the west coast is starting to pay attention to "those
guys in the rust belt". ;-) I'm reminded of when I interviewed at TI and they
were just coming across some foreign concepts. Some people have a practice of
refreshing peripheral registers (like port direction and such) on a regular
basis. What happens if the bit flips, and now that button on your door doesn't
work? But then for some reason you disconnect the battery and everything is
fine? Why would the bit flip? Transients, latch-up? And you're going to be
connected to a battery for 6-10 years right? This stuff has all been seen, and
it's not always just a reboot to fix it.

~~~
danjayh
At the company I work for, we've been struggling with the fact that nobody has
made a new-design CPU or SOC that's suitable for our safety-critical, "high
integrity at the source" application with modest radiation exposure (avionics)
for over ten years. We finally just gave up waiting and designed our own.
We're told by our senior folks that they've received calls from their
counterparts at several west coast companies (apple, qualcomm, etc.)
expressing interest & best wishes for what we are doing.

~~~
londons_explore
I don't understand why you would radiation harden a chip...?

Why not just have three exactly identical chips, run the exact same code on
them, and compare results? If results ever differ, you power cycle the bad
one, self test it, and you're good to go again.

Sure you have to not use on-chip random number generators, and make sure you
don't have any non-deterministic things in your silicon (eg. things that
depend on PLL locking time), but that sounds pretty trivial.

~~~
planteen
Because there are two distinct types of radiation effects in space: ionizing
and upsets. Multiple computers voting solves the upset problem, but not the
ionizing one. Ionizing is a measure in krad of how much radiation a part can
be exposed to in its life and keep working. Ionizing radiation changes
semiconductors in fun ways (e.g., gate voltage thresholds shift). They are
fabbed in exotic ways like silicon on sapphire. When you want a satellite to
last 20 years at geostationary orbit, you account for this! For example, I
believe the Juno probe to Jupiter's life will be limited by ionizing
radiation.

~~~
pavanky
On a related note, would multiple computers voting also require a higher power
draw compared to a radiation hardened chip?

~~~
jacquesm
Yes.

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trevyn
Yep, "solid state" components are not actually solid state!

~~~
mrob
They're really solid state, ie. they're transistors not vacuum tubes. But
"digital" components are not always digital ("digital" is a leaky
abstraction).

~~~
trevyn
The metal atoms actually move over time simply as a result of electrical
current flow! Parts will fail because of this, depending on how they're
designed.
[https://en.m.wikipedia.org/wiki/Electromigration](https://en.m.wikipedia.org/wiki/Electromigration)

~~~
kogepathic
It's not just structures within silicon you need to worry about. Lead-free
solder is susceptible to growing tin whiskers [0], which can cause short
circuits. Often you can't even see the growth of these whiskers as they're
under a BGA or on a microscopic level.

IIRC, NASA still requires all space hardware to be manufactured with leaded
solder to avoid having a multi-million/billion dollar mission ruined by some
tin whiskers.

[0]
[https://en.wikipedia.org/wiki/Whisker_(metallurgy)](https://en.wikipedia.org/wiki/Whisker_\(metallurgy\))

~~~
Posibyte
The same is required for many projects that sit in exceedingly cold
environments. In these situations, leaded solder is required to ensure that
the solder joints don't decay (or crumble away completely) from tin pest [0]
in the low temperatures.

[0]
[https://en.wikipedia.org/wiki/Tin_pest](https://en.wikipedia.org/wiki/Tin_pest)

