As an SoC process, embedded DRAM (eDRAM) has never quite lived up to its potential.
NEC Electronics Inc. is trying to change that by introducing an eDRAM structure designed to eliminate the performance and cost compromises that accompany most eDRAM processes.
Using a standard 1.2V CMOS logic process, NEC will offer up to 256Mbits of eDRAM in increments of 8Mbits, with typical speeds from 200 to 800MHz. The eDRAM is designed to replace SRAM in high-end networking, consumer, computing, and wireless applications, moving the technology beyond its current niches in graphics and peripherals.
"Previously, the biggest issue with embedded DRAM was that it was a high-end process aimed at low-end applications," said Hamid Aslam, senior technical marketing manager of embedded DRAM marketing at NEC, Santa Clara, Calif. "The features of NEC's eDRAM will open up the high end also."
The UX4D, being unveiled today for 0.15-micron designs, and the 0.13-micron UX5D, set for a December release, use a cylindrical stacked capacitor structure to increase yield and a low-temperature metal-insulated-metal capacitor process to boost performance. A 90nm version is in development, NEC said.
The process is designed to be done on one fab line without special DRAM equipment. One of the drawbacks of other eDRAM efforts was the need to physically transfer a design from a logic fab to a memory fab, then back to the logic fab, adding significant mask costs, said Hideya Horikawa, senior design engineering manager of embedded DRAM marketing at NEC.
"Our eDRAM process uses fewer than nine additional steps, compared to our competitors, which add 13 to 20 extra steps," Horikawa said.
But while NEC's approach may be technically better than competing offerings, the perennial question remains unanswered: "Why would you pay extra to embed DRAM when you can buy a standard DRAM and get change back from your dollar?" asked Jordan Selburn, an analyst at iSuppli Corp. in San Jose. "There aren't a whole lot of applications that need the added performance."
Pricing for the eDRAM was not disclosed, though NEC said there will be "some premium" on the process.