Standards for 3D memory chips set

Founding members of the Alliance, Tezzaron Semiconductor Corp. and Ziptronix Inc., are already fabricating memory chips using the IMIS port, the first versions of which will be available by the end of 2008.

"Today's high-speed processor cores need 3D interconnect with very high-sustained bandwidth that is beyond any existing or planned DDR memory technology," said Robert Patti, CEO, Tezzaron.

Owing to the low capacitance of the "intimate" connection achieved by stacking a memory die atop a processor die, power consumption is about 24?W/pin compared to 30mW to 40mW per pin for DDR. That low power in IMIS's 1,000-pin parallel connection between processor and memory limits power consumption to less that 3W, compared to over 30W for conventional interconnects.

"We believe that IMIS solves the processor makers' bandwidth problems to achieve multigigabit memories—typical access times to our DRAMs is 7ns," said Patti. "We are getting DRAM densities at near SRAM speeds and better than DRAM costs," he added.

The IMIS port measures 450? by 2,000? and contains a pin grid that is 19 cells high by 80 cells wide, each cell measuring 25?². Processor manufacturers modifying their dies to include an IMIS port will be able to add compatible memory chips from any member of the 3D-IC Alliance, which includes about half dozen members.

- R. Colin Johnson
EE Times