DRAM-sized SRAM cell cuts power

DRAM-sized SRAM cell cuts power
Steve Bush A new style of silicon SRAM memory cell promises to offer DRAM-like densities while cutting power consumption by 90 per cent. “Power consumption should be between 20 and 100 times less than DRAM because leakage is low and there is no need to continually refresh it,” said co-developer Alan Seabaugh of Raytheon’s research labs. Power consumption of DRAM is currently 1?W/Mbit and SRAM is 0.1?W/MHz, according to Seabaugh. Raytheon’s SRAM cells, based on prototype samples, are expected to consume 0.01?W/MHz. The cell uses tunnel diodes. It has been available in compound semiconductors like InP and GaAs for some time but fabricating it in silicon has been problematic. “The difficulty is making a suitable tunnel diode in silicon. The original silicon types are not compatible with the standard CMOS process, nor are the resonant tunnelling diodes used in compound semiconductors.” Coming to the rescue is a device called the silicon resonant interband tunnel diode. This particular one has been jointly developed by Raytheon, the University of Delaware and the US Naval research labs and is compatible with CMOS processing. At this time only a few of the diodes have been demonstrated. It uses a SiGe heterostructure, but other information is scarce. More details are expected to be revealed at the US VLSI symposium in June. See Technology.


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