Numonyx, the memory joint venture between STMicroelectronics and Intel is now shipping samples of phase change memory (PCM) chips — durable, high density flash memory — and will start shipping PCM chips commercially later this year, CEO Brian Harrison said at a press conference on Monday.
"We expect to bring it to market this year and generate some revenue," Harrison said. "It is one to two years before it becomes widely commercially available."
Numonyx's samples and near-term commercial shipments are a big deal for PCM, the technology has been stuck in the proverbial "a few years away" phase for a long time. "It could be cheaper than flash within a couple of years," analyst Richard Doherty in said in 2001, predicting the technology might hit the market in 2003.
"We are making good progress," Stefan Lai, one of Intel's flash memory scientists, said in 2002.
The delays in PCM have stemmed from the difficulty of preparing the technology for the commercial market, and stiff competition from existing flash memory.
In PCM, a single 'dollop' of a special metal alloy of germanium, antimony and tellurium (GeSbTe) called a chalcogenide acts as a single bit. Using a laser the metal is heated between 150 and 600 degrees Celsius causing it to move between liquid and crystalline form. The crystalline form has high resistance while the liquid form has low resistance, allowing the binary to be encoded.
However, a vast improvement in traditional flash memory has kept PCM out of the market. In the last few years Intel and ST made a significant progress in controlling the material, Harrison said.
Intel and ST have figured out a way to produce PCM chips on the manufacturing lines developed for standard chips. That has eroded the barriers to bringing PCM to market. Although Philips, IBM, and others have made progress in PCM, only Samsung is close to coming out with chips commercially, Harrison said.
Why will the world want PCM? Performance, says Numonyx CTO Ed Doller. PCM chips can survive tens of millions of read-write cycles, he said — far more than flash. Reading data to PCM chips takes 70 to 100 nanoseconds, which is as fast as NOR flash. Data can be written to the chips at a rate of 1 megabyte a second, or equivalent of NAND flash. There is also no erase cycle, making it similar to DRAM.
In other words, you have the best attributes of three different types of memory— plus, PCM will potentially use far less power.
The cost is also coming down fast. By next year, Numonyx hopes to make PCM chips, using 45-nanometer processes, which can hold two bits of data per cell. If that's possible, those chips would compete in price with single-bit-per-cell NAND flash, the memory that's being put into solid-state drives today, said Doller.
But the most important thing is that scientists believe they will be able to increase the density of these chips comparatively easily. In the future, standard flash chips will need additional circuitry for error correction and other functions. Not so with PCM.
The smaller the bits become, the less heat that will be required to flip them. "The most important thing is that it is scalable," Doller said.
