Rad-hard chips protect Mars Perseverance

Perseverance has its first chance to rove around on the Martian surface recently. Integrated circuits used in navigation and other functions must be fully radiation-hardened. (NASA/JPL-Caltech)

Radiation in outer space is a major concern for astronauts who will travel one day to Mars. Radiation could also potentially cause problems for integrated circuits like those aboard the Perseverance rover already on the Jezero Crater on the surface.

The solution to shield against radiation for humans traveling for months to Mars is still being evaluated by scientists but is already well understood by chipmakers.  Science fiction describes surrounding spaceships carrying humans with water walls, since water is a good insulator.

But water insulation is not practical because of its weight, for humans or for chips.  Without some form of insulation, astronauts on long missions could suffer radiation burns on internal cells that could lead to cancer, long term illness or even death. Radiation can also knock out a chip unless it is rad-hard (radiation-hardened).

“There’s obviously a major difference between electronics and humans, but the biggest concern for radiation on electronics is from solar flares off the sun or heavy ions coming from outside the solar system,” said Josh Broline, director of marketing and applications for the high reliability and space business at Renesas.   “Those are very challenging. You can’t put a massive lead box out there; it’s just not practical. Water does a good job, but it’s heavy.”

Radiation effects on integrated circuits can cause latchups, burnouts or gate rushers and possible self-destruction.  For power management products, a radiation strike on an FPGA or CPU can cause a major disturbance in its output voltage. That may not damage the chip itself but could cause a downstream effect on the functionality of another system, potentially rendering it useless.

At Renesas, a three-pronged approach is used to protect chips against radiation honed over decades of working in various aerospace programs, Broline said. The protections are built in design, schematic device layouts and then the fab process itself. Total dose testing of ICs helps ensure predictable performance as well, Renesas said on its website.

Different materials such as silicon germanium and thinner gate oxides also help.  A thinner gate means less trappage of an ion charge, rendering it less susceptible to damage.

Ceramic materials are not necessarily helpful for radiation protection, Broline said, but are helpful to protect against extreme cold temperatures or shock and vibration. (It got down to minus-98 degrees F on Mars on St. Patrick’s Day, March 17.)

Renesas has more than 20 radiation hardened Intersil ICs aboard the rover and its seven instruments. They support mission-critical power management and distribution, inertial measurement, precision data handling and navigation. There are also Intersil voltage regulators, MOSFET drivers, switches and transmitters and receivers.

Recently, the rover had its first chance to rove 213 feet across the Martian landscape since its first landing on Feb. 18, one of many milestones it must pass before taking longer trips to gather Martian soil samples and to test out the Mars Helicopter, Ingenuity.  Cameras also got an image of the rover wheel wiggle back and forth:

The Renesas Intersil brand spans six decades with the founding of Radiation Inc. in 1950. The company claims virtually every satellite, shuttle launch and deep-space exploration mission includes Intersil products.

The company’s rad-hard chips were aboard the Hayabusa2 spacecraft that returned asteroid samples to Earth inside an armored re-entry capsule on December 6, 2020. The mission lasted six years after launching December 2014 from the Tanegashima Space Center.

Renesas is based in Tokyo while Renesas Intersil chips are designed and manufactured in a facility in Palm Bay, Florida.

Rad-hard chips used in aerospace cost in the range of hundreds of dollars but aren’t necessary custom-built.  In fact, Broline said it is more typical for the aerospace chips to borrow design ideas from commercial chips, instead of vice-versa.   “We marry up with trends and general-purpose products,” he said. “The commercial side is more bleeding edge.”

Many electronics companies use space missions to hone research and will often cite their space work to other customers even though the research is sometimes a costly investment. For Renesas, the aerospace sector is “a good-sized business with our ability to get in and get traction as opposed to a company that’s a new entry,” Broline said.

By:  Matt Hamblen

From:  https://www.fierceelectronics.com/electronics/rad-hard-chips-protect-mars-perseverance-rover-from-solar-flares-heavy-ions