Startup pioneers carbon-based FPGAs

PORTLAND, Ore. — Carbon-based memory architectures promise to revolutionize FPGA design, according to the founder of a chip startup.

Startup NuPGA was founded by Zvi Or-Bach, a winner of the EE Times Innovator of the Year Award. He previously founded eASIC and Chip Express. Or-Bach has applied for a patent, along with Rice University, for its carbon-based memory process developed by professor James Tour. The approach uses graphite as the reprogrammable memory element inside vias on otherwise conventional FPGAs.

"Using graphite in the vias as fuse is a very interesting concept," said Dean Freeman, senior analyst at Gartner Inc. "We are going to see a lot of very innovative, creative thinking along these lines in the next five years."

Rice University researchers developed a bulk chemical process that converted nanotubes into nanoribbons, providing the raw material needed to perfect a technique based on using voltage pulses to make or break connections--essentially turning the carbon ribbons into reprogrammable switches. NuPGA plans to harness these reprogrammable switches in FPGAs by inserting graphite into vias between chip layers, allowing them to be reconfigured on-the-fly.

"Graphene can become interesting when it is shaved down to below 10-nanometer widths into ribbon structures, making it much easier to modulate at low voltages," said Tour. "Graphene won't be ready to go head-to-head with Intel until 2015, when lithography dips below that 10-nanometer size. By that time, much of the market could already be using thin films of carbon materials for bulk electronics in places where silicon can't be used today."

By making thin films from his slurries of carbon nanotubes--what he calls "graphene nanoribbons"--Tour perfected the memory architecture to be used in reprogrammable switches in NuPGA's chips. The process allows a voltage pulse to reprogram FPGAs by making or breaking the connection pathway through graphite-filled vias.

A 3.5-volt pulse breaks the connection while a 3-volt signal repairs the break, allowing the device to be switched on and off any number of times. A 1-volt signal allows circuitry to interrogate the memory cell to determine its memory state.

Or-Bach said he plans to created vertical arrays of graphite embedded in the vias that connect the different FPGA layers, allowing voltage pulses to alternately split and repair connections--essentially the same process as "antifuse" FPGAs but with the ability to reprogram the connection.

Or-Bach said NuPGA's graphite-based FPGAs would begin with the graphite elements split, allowing users to heal the antifuse to reconfigure the chip.

The 10-nm-wide ribbons can be densely packed, according to Tour, and can be reprogrammed an indefinite number of times. That could make graphene memories a viable architecture that is insensitive to temperature changes and radiation, Tour added.

"We are also licensing our process for the making of thin-film sheet conductors for ink-jet printing of RFID tags and for other flexible electronic applications," said Tour.