Andrew "bunnie" Huang's IRIS Robot Peers Behind Silicon Chips to Uncover Their Secrets in Minutes

Automating the process of taking IRIS scans of back-side silicon chips, this robot aims to provide easier physical verification.

Gareth Halfacree
1 month agoHW101 / Security

Andrew "bunnie" Huang is continuing to develop the Infrared In-Situ (IRIS) chip inspection system, developing a robot for automated imaging, dramatically reducing the time it takes to peer inside a compatible semiconductor chip.

"At the time when I released the initial [IRIS] paper," Huang explains, "every picture was manually composed and focused; every sharp image was cherry-picked from dozens of fuzzy images. It was difficult to reproduce images, and unsuitable for automatically tiling multiple images together. The technique was good enough for a demo, but shaky as a foundation for full-chip verification.

"Over the past year, I’ve refined the technique and implemented a fully automated system that can robustly and [repeatably] image whole chips at micron-scale resolution in a matter of minutes."

This IRIS robot aims to make silicon-chip verification more accessible — albeit only for back-side silicon packaged parts. (📹: Andrew "bunnie" Huang)

Huang unveiled IRIS back in March last year, taking advantage of a chip packaging technique that exposes the back side of the bare silicon and the material's infrared transmissibility. Using a lightly-modified off-the-shelf inspection camera and strong infrared emitters, IRIS is able to peer through the silicon layer to the components beneath — revealing the chip's layout non-destructively, and allowing it to be verified against the submitted design.

As Huang notes, though, the process was extremely time-consuming: getting a blurry low-resolution shot of a chip was easy, but capturing with enough detail to be of use at a semi-modern feature size was much more challenging. That's where the new IRIS robot comes in: taking away the drudgery to deliver high-quality IRIS scans in minutes.

"Basically, it's an IR camera attached to a microscope, a nanometer-resolution focusing mechanism, and a pair of 1,050nm light sources that have continuously adjustable azimuth and zenith," Huang explains. "An explicit goal of this project is to open source all of IRIS, so that anyone can replicate the imaging system. Democratizing chip verification is important because a credible threat of being caught reduces the incentive of adversaries to deploy expensive Trojan-implantation capabilities."

"The idea is not for everyone to have one of these robots in their home (but how cool would that be!)," Huang notes, "rather, the idea is that most users could utilize an inexpensive but somewhat fiddly setup and compare their results against reference images generated by the few users like me who have fully automated systems."

Huang's full write-up is available on his blog, along with links to the source files under the CERN Open Hardware License 2 Strongly Reciprocal and GNU General Public License 3 or GNU Affero General Public License 3 for the hardware and software respectively; detailed documentation on building your own IRIS system is to follow in due course.

Main article image courtesy of Andrew "bunnie" Huang.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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