[HN Gopher] Infra-Red, in Situ (Iris) Inspection of Silicon
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Infra-Red, in Situ (Iris) Inspection of Silicon
Author : etiam
Score : 83 points
Date : 2023-03-08 13:17 UTC (9 hours ago)
(HTM) web link (www.bunniestudios.com)
(TXT) w3m dump (www.bunniestudios.com)
| hagmonk wrote:
| DARPA has been thinking about this:
| https://www.darpa.mil/attachments/AISS_ProposersDay_LeefSlid...
|
| (aside: fascinating example of a US military slide deck, like a
| 90s fever dream made in Harvard Graphics)
|
| Here's also a Voices from DARPA episode, which suggests they've
| been funding research since at least 2012:
| https://blubrry.com/voices_from_darpa/30975140/episode-17-gu...
|
| In terms of ensuring designs are not tampered with seems like
| watermarking is the direction they're exploring.
|
| Another fascinating concept was the "silicon odometer" to ensure
| recycled chips aren't reintroduced into the supply chain.
|
| Asianometry has a fascinating video on that issue:
| https://youtu.be/7epnv43jGV8
| 1970-01-01 wrote:
| >How Does It Work? Silicon goes from opaque to transparent in the
| range of 1000 nm to 1100 nm (shaded band in the illustration
| below). Above 1100 nm, it's as transparent as a pane of glass;
| below 1000 nm, it rapidly becomes more opaque than the darkest
| sunglasses.
|
| So expect to see more epoxy blobs on top of chips.
| shash wrote:
| There's a reason these chips are left open. Thermal performance
| for example might tank if they tried to epoxy those.
| josh2600 wrote:
| Just want to say what a gift Bunnie is to the hardware hacking
| community. Thank you for all of the work you do helping to push
| hardware forward in our world!!
| meatmanek wrote:
| IRIS in the title should be all-caps as it's an acronym;
| Lowercasing the final letters made me think this was going to use
| some weird quirk of the human iris.
| buildbot wrote:
| Really really cool! Will have to give this a try with my
| monochrome camera.
|
| I wish there was a bit more detail on possible lenses, its hard
| to find optics that work well past 1000nm.
|
| It's pretty interesting how much the fall off is between 920 to
| 1070nm - on my camera, 920nm can be exposed perfectly in daylight
| at around 1/10th of a second, 1070nm needs 4 minutes worth of
| time to match the same exposure!
| alexbock wrote:
| I enjoy monochrome infrared photography at wavelengths longer
| than 1000 nm using a Sigma sd Quattro (no Bayer filter and the
| sensor IR filter is reversibly user-removable). To reduce
| exposure times as much as possible, I've been testing an AR-
| coated near infrared achromatic doublet (AC254-050-B-ML) with a
| 3D-printed housing to attach it to the camera mount with a
| manual focusing barrel. The next step is to design a fast
| double gauss lens that can similarly be assembled from readily
| available NIR-coated stock lens elements.
| buildbot wrote:
| I've wondered about doing this a lot! How is the image
| quality with the doublet? I love the Quattro series of
| cameras but hate the software personally. I may someday pick
| up a sd Quattro H...
| formerly_proven wrote:
| Looking around, normal industrial (like Pregius) or CCTV
| (Starvis) sensors are only optimized up into the ~950nm range
| and drop to near-zero rapidly. The NIR-optimized Starvis seem
| to be a lot better than normal general purpose sensors already
| (not sure if this difference comes mainly from different Bayer
| arrays, in the QE curves these have a very, very distinct hump
| in the 850-950nm where R/G/B channels seem to have a bandpass).
| There are some sCMOS cameras (like PCO's stuff [1]) which would
| seem to be about an order of magnitude more sensitive at 1050
| nm than these.
|
| And then there's of course the famed "black silicon". [2]
|
| My money would be on InGaAs sensors [3] being the best in this
| range. I would also suspect these are subject to funny
| import/export restrictions, nevermind the price.
|
| [1] https://www.pco.de/scientific-cameras/pcopanda-42-bi/ ~10%
| QE at 1050 nm [2] https://1.bp.blogspot.com/-wrj9PudX2YM/WkSB-
| PL-9vI/AAAAAAAAQ... [3]
| https://www.princetoninstruments.com/wp-content/uploads/2020...
| buildbot wrote:
| I do wonder what silicon difference a NIR optimized starvis
| would have vs. the consumer IMX211 silicon, smaller
| monochrome sensors of the same gen seem fine past 1000NM.
| Bayer filters would make sense as the actual difference.
| [deleted]
| bunnie wrote:
| Hi! thanks, I'm the post's author.
|
| I had the same concern you have about finding "just the right
| lens", but was pleasantly surprised to find the $180
| camera/lens combo linked in the post worked just fine. In fact
| basically every piece of optics I had in my lab could pass
| light at 1050nm, and I have a bit of everything from cheap
| stuff bought over the counter in Shenzhen to brand-name
| microscopes. I tried lenses from 6 different vendors and they
| all worked about the same in terms of passing light (but of
| course the fidelity of the image scales with cost, better lens
| tolerances are just more expensive).
|
| My guess is that uncoated glass should be transparent in the
| 1050nm band, but some lenses have AR coatings that limit the
| bandwidth. A lot of my lenses _do_ have AR coating (based on
| the greenish tint I see in the reflections), but I guess the
| bandwidth of the coating used on most visible-light lenses is
| just wide enough for 1050nm to slide through.
| buildbot wrote:
| That's very good to know, thanks for the response! Love your
| work :)
| eigenform wrote:
| I'd love to try this some time. Fritzchens Fritz has some other
| great examples of IR die shots too!
|
| [^1]: https://www.flickr.com/photos/130561288@N04/52465673068/
|
| edit: Oh, bunnie also mentions this in a previous post! See
| https://www.bunniestudios.com/blog/?p=6656
| bunnie wrote:
| His images are great! Discovering his photofeed was one of the
| puzzle pieces that sent me down this path in the first place. I
| give him a shout-out in the post :)
| eigenform wrote:
| I only noticed after actually reading the article :^) Lovely
| work!
| wcerfgba wrote:
| This is really cool. What kind of wavelength would be needed to
| actually 'see' stored data inside silicon and be able to read
| that out?
| Taniwha wrote:
| It doesn't really work that way, data in silicon is largely
| stored with charge - if the photons are fat enough to bounce
| off that charge they're also likely to erase it
| LoganDark wrote:
| > if the photons are fat enough to bounce off that charge
| they're also likely to erase it
|
| Isn't this how EPROMS are erasable by UV light?
| lightedman wrote:
| I wonder if the technique used for inspecting solar silicon could
| work here. Just apply power and check its IR emissions.
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