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Micron bets big on pseudostatic RAM, NAND flash

Posted: 16 Sep 2004 ?? ?Print Version ?Bookmark and Share

Keywords:micron? pseudostatic? ram? nand? flash?

Micron Technology Inc. is looking to boost its sales of memory chips going into fast-selling cellphones and flash memory cards.

The company has started producing 128Mb pseudostatic RAMs, which are specialized DRAMs that include an SRAM interface. Because of their denser memory array and SRAM-like features, pseudostatic RAMs have overtaken six-transistor SRAMs in cellphones in recent years, hitting a peak of 60 percent of the market for RAM used in cellular handsets, according to the company.

Micron has a lot riding on the new device. It's one of the few pseudostatic RAM chips on the market at such a density and is the company's first mobile RAM chip to use a smaller memory cell architecture that Micron has applied to DRAMs used in PCs.

The size of a conventional DRAM cell is equal to the square of the given lithography feature size multiplied by coefficient of eight (8F2). Micron, however, said it has compressed the cell enough to reduce the coefficient to six (6F2).

Shorter lines

Aside from reducing the die size by 20 percent--which translates into lower production costs--the smaller cell size shortens the memory's signal lines, lowering capacitance and boosting performance.

While other suppliers are expected to shrink their memory cells in a similar manner, Micron claims it has a four-year head start over the International Technology Roadmap for Semiconductors.

Micron intends to ship its version of pseudostatic RAM, which it calls CellularRAM, to companies producing multichip packages, as well as to makers of NOR-type flash memories that also provide MCPs. For now, Micron has no plans to make and sell its own MCPs directly to cellphone makers.

Meanwhile, Micron is preparing to start volume production of its first NAND flash device, a 2Gb chip intended for flash storage cards, starting in Q4. That will be followed next year by a 1Gb device. The NAND devices will be built using the company's most advanced 90nm process technology.

Several semiconductor makers have recently entered the market for NAND devices with the expectation that the parts will largely replace NOR devices in cellphones. Samsung Electronics Co. Ltd and Toshiba Corp. have the lion's share of the $2.6 billion market. Renesas Technology Corp. and newer entrants Infineon Technologies AG, STMicroelectronics, Hynix Semiconductor Inc. and Spansion also make NAND-type devices.

Micron said it will be one of the few companies making the larger, 2Gb chips. "We have more customers than we can serve at the moment," said Achim Hill, senior director of marketing at Micron.

Micron had attempted to make NOR-type flash memory for flash storage cards but then pulled out several years ago when it became clear that NOR couldn't match the density advantage of NAND. "There's no question where the market is going," said Paul Dlugosch, strategic market planner at Micron.

Going forward, cellphone manufacturers plan to adopt NAND and mobile DRAM simultaneously as chipset vendors attach the needed memory interface circuitry to their devices, Dlugosch said.

- Anthony Cataldo

EE Times

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