A Circuit That Sees Radiation Strikes Could Keep Errors at Bay

Engineers are working on a circuit that will help chip designers avoid vulnerabilities to common radiation-induced errors

2 min read
A white box with an open side displaying many green circuit boards stacked edge on.
Back sampling chain circuits preparing to be bombarded with neutrons.
Photo: Chris Kim/University of Minnesota

For a short time, it looked like the worlds electronics would be safe (well, safer) from radiation. With the switch from planar transistors to FinFETs, ICs suddenly became naturally resistant (literally) to having their bits flipped by a neutron splashing into them and blasting lose a small cloud of charge. But two things are now making them vulnerable again: One is the move to operating at voltages so low, that it’s easier for a pulse of radiation-induced charge to flip a transistor on or off. The other is how the unprecedented density of those transistors is giving radiation more targets than ever.

Engineers at the University of Minnesota are nearing a solution that could help bring down the rate of so-called logic soft errors—signals temporarily flipped by a radiation strike. It’s a circuit called a back-sampling chain that has, for the first time, allowed them to reconstruct the strike pulse—called a single event transient—resulting from the radiation strike. In research to be presented in June at the IEEE VLSI Symposia in Kyoto, Kim’s team shows that the back-sampling chain (BSC) circuit—a kind of cross-connected chain of inverters—can detect orders of magnitude higher number of strikes compared to previous approaches.

A blue circuit board with many microchips and other electronic componentsAn array of back sampling chain circuits were tested in a spray of neutrons.Photo: Chris Kim/University of Minnesota

“There hasn’t been a way to visualize these strike pulses,” says Chris H. Kim, the electrical engineering professor at the University of Minnesota who led the research. “The back-sampling chain circuit can measure the response of the circuit to the radiation event. We can also back calculate the strike current induced by each particle.”

Kim’s group is using the neutron strike data collected from the BSC circuit to develop a design tool that will help engineers avoid low-voltage designs that would be too sensitive to soft errors. There are no tools right now “that combine radiation data with circuit analysis and system design,” says Kim.

The BSC could also be integrated into chips destined for complex systems in spacecraft and other things that operate in harsh environments. The goal here is to collect data on the system in operation. “Once you have that data, you can map it to system level failure and use it to fine tune the supply voltage or clock frequency,” says Kim.

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The Transistor of 2047: Expert Predictions

What will the device be like on its 100th anniversary?

4 min read
Six men and a woman smiling.

The luminaries who dared predict the future of the transistor for IEEE Spectrum include: [clockwise from left] Gabriel Loh, Sri Samavedam, Sayeef Salahuddin, Richard Schultz, Suman Datta, Tsu-Jae King Liu, and H.-S. Philip Wong.

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The 100th anniversary of the invention of the transistor will happen in 2047. What will transistors be like then? Will they even be the critical computing element they are today? IEEE Spectrum asked experts from around the world for their predictions.

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