CPU, DRAM ride organic substrates at ISSCC

SAN FRANCISCO – Papers at the International Solid State Circuits Conference described the first simple microprocessor and DRAM structures built on organic substrates as well a process for printing both n- and p-type transistors on a plastic substrate.

The rudimentary nature of the devices made it clear that it's still early days for low cost, low power organic electronics. "We will see if in 20 years time half the designers here will be working on silicon and half on plastic," Jo De Boeck, a senior vice president at Belgium's Imec research institute said at an ISSCC keynote.

Imec researcher Kris Myny described a simple 8-bit processor that handled up to six instructions per second in an averaging routine. It implemented arithmetic, logic and bit-shift functions and had three programmable registers.

The 3,381-transistor device had the equivalent of 30 pin outs and consumed 92 microwatts at 10V. It was built in an organic process developed by Polymer Vision (Eindhoven, Netherlands), a flexible display maker.

The Imec device actually had more transistors than the Intel 4004, an early silicon processor. Like the Intel chip it used only P-type transistors.

Operating the device was a challenge. Imec developed an instruction generator block on a separate foil substrate with hard-coded instructions inserted into the processor via a traditional development board.

"Ideally you want an embedded microprocessor with non-volatile memory and 8-bit input and output, but the organic technology is not mature enough for this," Myny said.

Engineers need to drive organic processors up to kilohertz frequencies by optimizing critical paths and using high mobility semiconductor materials, he said. He also called for more complex circuit capabilities including n-type transistors, something demonstrated in a separate ISSCC paper.

Myny said the fledgling field also needs a process technology roadmap. The four papers in the ISSCC session all used significantly different organic thin-film transistor processes.

Imec's Kris MyNy holds an 8-bit processor etched on foil.

2. Flexible DRAM, printable CMOS