It's been a long haul for phase change memory, but the goal is in sight.
Numonyx, the memory joint venture between STMicroelectronics and Intel, is already shipping samples of phase change memory (PCM) chips to customers and will start shipping PCM chips commercially later this year, CEO Brian Harrison said at a press conference 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."
Hearing a CEO talk about existing samples and near-term commercial shipments is 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.
Gordon Moore, co-founder of Intel and the man for whom Moore's Law was named, had an article in the September 28, 1970 issue of Electronics predicting that Ovonics Unified Memory, another name for the same type of memory, could hit the market by the end of that decade. (The same issue of Electronics also included this article: "The Big Gamble in Home Video Recorders.")
The delays have largely stemmed from two sources. First, it's not an easy technology to master. In phase change memory chips, a microscopic bit on a substrate gets heated up to between 150 degrees and 600 degrees Celsius. The substrate is made of the same stuff as CD disks. The heat melts the bit, which when cooled solidifies into one of two crystalline structures, depending on how fast the cooling takes place. The two different crystalline structures exhibit different levels of resistance to electrical current, and those levels of resistance in turn are then as ones or zeros by a computer. Data is born.
Both Intel and ST made a significant amount of progress in controlling the material in the past few years, Harrison said.
Size matters
Second, the makers of flash memory have continued to improve their technology. Back in 2001, some believed that flash would hit a wall at the 65-nanometer level of chip design. Then that got moved to 45 nanometers. Today, manufacturers mass-produce flash at 65 nanometers and have samples at 45 nanometers. Numonyx has samples of traditional NOR flash at 32 nanometers. Why switch when the existing technology continues to work?
Again, in the past few years, Intel and ST have made progress and figured out a way to produce PCM chips on the manufacturing lines developed for standard chips. That has eroded the barriers to bringing PCM out.
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, or far more than flash. Reading data to PCM chips takes 70 to 100 nanoseconds, or 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 premium is also coming down fast. By next year, Numonyx hopes to make PCM chips, using 45-nanometer processes, that 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 get, the less heat that will be required to flip them, Doller added.
"The most important thing is that it is scalable," Doller said.
Solid-state drives are still going to be somewhat hard to find and expensive in 2008, but mass production, cheaper flash, and tech advances will start to change that in 2009 and 2010.
Micron Technology, the Boise, Idaho-based maker of DRAM and flash memory, this week unveiled plans to come out with solid-state drives. The drives function like regular hard drives. But instead of storing data on spinning disks, solid-state drives store it on NAND memory chips--the kind found in cameras and MP3 players.
Micron will start mass-producing solid-state drives in the first quarter of 2008. The first drives will hold either 32GB or 64GB of memory. While that's less than half the capacity of the average notebook drive today, it's actually more storage than most business users need, said Dean Klein, vice president of memory system development at Micron. Plus, solid-state notebooks can come out of deep sleep or launch applications far more rapidly.
"60GB to 80GB is the sweet spot for the notebook market," he said.
Micron didn't talk pricing, but the drives will likely cost a few hundred dollars, a stumbling block. For example, swapping out a 160GB standard hard drive for a 64GB solid-state drive (from Samsung) on a Dell XPS 1330 notebook costs an additional $950. Considering that the notebook with the 160GB drive already costs $1,599, the solid-state drives aren't exactly economical.
Nonetheless, the magic of Moore's Law and the ability of memory makers to take it on the chin are going to make these drives more affordable. The first thing that will happen is that toward the end of 2008, solid-state drive makers will start to incorporate multilevel cell flash chips in the drives, Klein said. Manufacturers currently use single-level cell flash.
Multilevel cell chips hold two (and soon four) bits of data per cell. The chips aren't as reliable as single-level cell memory, but the error rates are small enough to make these types of drives more than adequate for the notebook market, he added.
In addition, multilevel cell chips will enable drive makers to increase the capacity of their drives, driving down the price. At equal capacities, multilevel cell chips could cut the price of making a drive by roughly 40 percent, estimated Frankie Roohparvar, vice president of NAND development at Micron.
Meanwhile, the world is swimming in NAND flash, leading to drastic price declines. NAND prices are set to drop 57 percent this year and 52 percent next year, said Joseph Unsworth, an analyst at Gartner.
Put those two factors together, and it could be possible to come out with a 64GB solid-state drive for close to $300 toward the end of 2008, Unsworth speculated. That's still high. He estimates that only 8 million solid-state drives will get shipped in all of '08.
But after that, the industry should begin to be able to show the benefits of these kinds of drives, the Micron executives predict. Think about it. Even if price declines begin to slow, 64GB drives will likely move toward the $200 range by late 2009 and then drop to sub-$100 about 18 months after that. Hard-drive makers will continue to increase the density of their products at the same time, of course, but competition between the two technologies will become tighter.
It happened in MP3 players, after all. Most upscale players came with 1.8-inch drives. The industry, however, at one point abruptly switched to flash.
Unsworth said the flash makers are going to have to tout the supposed benefits of having a flash drive with less capacity than a spinning disk (better battery life, can withstand a drop from a table better, you may not need all that storage, etc.).
He added that notebook makers will have to cooperate by making smaller laptops that showcase the features of flash. Flash takes up less space and, because it doesn't radiate as much heat, you can eliminate a fan. Currently, the notebooks that contain flash are basically the same size as the hard-drive models.
"With MP3 players, it was easy. You just turn it sideways and quote the battery life," Unsworth said.
SANTA CLARA, Calif.--Flash memory will take over the world, if the laws of physics don't get it first, according to one of the technology's biggest backers.
On one hand, NAND flash--the kind of flash found inside digital cameras and MP3 players--is crushing the competition, Eli Harari, CEO of SanDisk, said on Wednesday at the Flash Memory Summit here.
Eli Harari, CEO, SanDisk
(Credit: SanDisk)NAND has made 1-inch hard drives obsolete. Then it's on to 1.8-inch hard drives and possibly larger 2.5-inch notebook hard drives, Harari said.
"The next big market will be video. You should expect next year to see video cameras and video camera phones that use more flash," he said. More flash notebooks will start appearing next year too.
NAND will also start replacing DRAM, the main memory used in PCs, over the next five to seven years. Because of rapid improvements, NAND has gone from being more expensive--in cost per memory bit--than DRAM in 2001 to being significantly cheaper than DRAM in 2007.
IBM and others are already working on solid-state servers that rely on NAND.
Now the bad news: it's going to become much harder to continue to improve NAND chips.
"NAND is definitely going to slow down. There are some fundamental practical limits and some fundamental physics limits," Harari said. "We have three or four generations, five at most. Beyond that, we may need a different technology."
The problem is that the different subcomponents inside these chips can't be shrunk much further. One layer, called a tunnel oxide, can probably be shrunk to about 80 angstroms. In other types of chips, this layer can be shrunk to 12 angstroms.
Data corruption is another problem. Flash memory records data by storing electrons in cells. "At 32 nanometers, you can't afford to lose more than 30 electrons" before data corruption becomes an elevated risk, he said. "Thirty electrons sounds like a lot, but it is very small." The debut of 32-nanometer chips will be sometime toward the turn of the decade.
The turning point may come with the 20-nanometer generation of chips, which will start coming out a few years later. At that point, NAND chips will be capable of holding 256 gigabits of data, and the cost per bit will be about a tenth what it is today, but it will be extremely difficult with current manufacturing technologies and materials to go further.
What are some of the alternatives? SanDisk will try to stack transistors in 3D arrays. "When land is expensive, you go up in skyscrapers," he said. The company bought Matrix Semiconductor, which invented a 3D memory chip, a few years ago. Matrix's chips, however, are not rewritable--you can't erase old data and put new stuff on it. Solving that problem will be a focus of the company's research.
Manufacturers will also put more bits in each cell. Right now, the densest chips have two memory bits in each cell. Chips with three bits per cell will probably come out in the next two to three years, and four bits after that. To date, most manufacturers haven't talked much, if at all, about three bits of memory per cell.
Other companies are also working on things like phase change memory, or mechanical actuators.
Cost will become another major issue. Fabs cost about $5 billion, and nearly 50 percent of the world's NAND factory capacity will have to be replaced in the next two years, Harari said. NAND makers thus will have to put a lot of money into construction.
The new fabs will let the most efficient manufacturers cut prices by 30 percent to 45 percent a year, he said. Unfortunately, prices have declined by 60 percent annually in the last two years.
"If the best you can do is 40 percent cost reduction, you can't have 60 percent reductions in price," he said. Consolidation may become inevitable.
Memory makers, of course, have overcome or at least postponed these problems before. Back in 2003, flash executives said the industry would start running out of tricks with 45-nanometer chips--which will start coming out in the relatively near future.
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