FeRAM enables 1.6 GB/s R/W
17 February 2009
Highest-bandwidth, highest density non-volatile RAM unveiled
Toshiba announced the prototype of a new FeRAM chip (Ferroelectric Random Access Memory). The new chip realises storage of 128-megabits and read and write speeds of 1.6-gigabytes a second. Full details of the new FeRAM will be presented at the International Solid-State Circuits Conference 2009 in San Francisco, USA.
The new FeRAM modifies Toshiba's original chainFeRAM architecture, which significantly contributes to chip scaling, with a new architecture that prevents cell signal degradation, the usual tradeoff from chip scaling.
Chip scaling causes signal degradation as the stored polarisation of memory cell gets smaller. By shortening the data-line pitch and using chain architecture to decrease the number of memory cells connecting to sense amplifiers, Toshiba maintained the same cell signal level without any chip area penalty. Furthermore, improvement of the sensing technique reduced the parasitic capacitance and realised a reading signal of 200 mV, sufficient for practical application.
ChainFeRAM in the earlier generation of 64-megabit FeRAM employed a data-line design in which neighbouring data-lines operated in sequence: one is off when the other is on. This allowed off lines to provide a noise barrier between on lines, contributing to chip scaling and fine performance. Previous chain architecture collected four data-lines but Toshiba has increased the number of data-lines to eight, which led to a decrease in the total chip area. The combination realises an upscaled FeRAM with a density of 128-megabit.
Furthermore, a new circuit that predicts and controls the fluctuations of power supply supports high-speed data transfers. This new circuit rapidly realises the voltage required for read and write, allowing the new FeRAM to add a DDR2 interface and maximises data transfers at a high throughput at low power consumption, realising read and write speeds of 1.6-gigabytes a second. In developing the new FeRAM, Toshiba broke its own record of 32-megabit density and 200-megabites-a-second data transfers, pushing performance to eight times faster than the transfer rate of the previous records and the fastest speed of any non-volatile RAM.
FeRAM combines the fast operating characteristics of DRAM with flash memory's ability to retain data while powered off. Toshiba will continue R&D in FeRAM, aiming for further capacity increases and eventual use in a wide range of applications, including the main memory of mobile phones, mobile consumer products, and cache memory applications in products such as mobile PCs and SSDs.
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