SAN FRANCISCO Hundreds of rectangles, each the size of a grain of rice, cover a shiny platter of silicon at a research facility belonging to Micron Technology Inc..
These cells contain circuits etched at a width of 50 nanometers -- 2,000 times thinner than a human hair -- the leading edge in a shrinking process in which a single memory chip can now hold hours of music or hundreds of digital pictures.
But makers of memory chips are looking ahead to a day, not too far off, when technology based on silicon bumps up against the laws of physics and memory can't be made any smaller, with implications for gadgets like MP3 players and digital cameras.
"You get in to the 25-nanometer regime and there may need to be a new structure for nonvolatile memory," Mike Splinter, chief executive of Applied Materials Inc., the world's biggest supplier of tools for making microchips.
"I'm quite nervous about this because 25 nanometers is not that far away, and if you have to change a process in a couple generations, then that is really challenging," Splinter told Reuters in a recent interview.
That would slow the development of things like digital music players and cameras, for which current flash memory -- used to store music and images -- will not suffice beyond the next couple of years.
Until now, this shrinking of memory and processors has been governed by an industry maxim known as Moore's Law, formulated by Gordon Moore in 1965, three years before he helped found chip maker Intel Corp..
Moore stated that the number of transistors that could be housed on a given area of silicon doubles every two years. He later reduced the time period to 18 months.
The end of Moore's Law is expected to come more quickly for memory chips than processors because of the different ways in which they work. Whereas the circuits on processors act as pipes that guide streams of electrons, memory chips use pools of charged electrons to store data, and it gets harder to read the data as the number of electrons in each pool shrinks.
Such concerns aren't far from the mind of Tom Trill, a marketing director for Micron rival Samsung Electronics Co. Ltd. of South Korea, the biggest memory chip company in the world.
"It's a question we've had forever, and we've always had an answer," Trill told Reuters. "There's been a resurgence in terms of pessimism ... in the last few months."
The concerns have major memory makers pouring hundreds of millions of dollars into perfecting the next big technology.
The possible alternatives sound like science fiction: M-RAM, P-RAM, molecular memory and carbon nanotubes.
"In the next decade we're going to need some significant new technologies," Mark Durcan, Micron's chief operating officer, said at the company's Boise headquarters.
Other major chip firms working on new technologies include Intel, South Korea's Hynix Semiconductor Inc., Europe's Infineon and Japan's Toshiba Corp., Hitachi Ltd. and Fujitsu Ltd..
One of the most promising new technologies is P-RAM, or phase-change memory, in which the physical state of a germanium alloy is changed between crystalline and amorphous to store data, rather than a change in electrical charge. The same principle stores music on a CD.
In what analysts said was a major step forward for phase-change memory, International Business Machines said in December it had developed a prototype chip that performed 500 times faster than current flash memory while using less than half the power.
Importantly, IBM researchers showed the technology can be used to create circuits as small as 20 nanometers, less than half the size of current cutting-edge flash technology.
"It's like a green light to the industry to say, OK, let's invest in this technology going forward," said Spike Narayan, IBM's senior manager for nanoscale science.
Other promising new technologies include magnetic memories that use magnetic fields instead of electrical charge; polymers or custom-designed molecules whose electrons can be easily manipulated; and carbon nanotubes. The problem with most of those is being able to make them cheaply in large quantities.
Just like today's memory market, in which four different kinds of memory are all multibillion-dollar markets, future technologies will probably each find their own niche.
New technologies will likely be cross-licensed throughout the industry, which is now dominated by five companies that make more than 80 percent of total output. The next five firms account for all but 1 percent of the rest.
"There's probably only an opportunity for some of those smaller five to be melted into the larger five, but nothing that would shake up the whole industry," said Doug Freedman, an analyst with American Technology Research.
New memory technologies will all have to meet several key requirements, such as being able to store a lot of data, read and write that data quickly, and be able to retain that data when the power is switched off.
Perhaps most crucially, they have to use current manufacturing techniques or be so attractive that companies will be willing to spend heavily on all-new factories.
"Every two years someone comes up and says they have found better memory technology, but there's always some technical limitation, and this has gone on for 30 years," said analyst Jim McGregor with market research firm In-Stat.
"All these different memory technologies hold a lot of promise. The only problem is that until you get a group of semiconductor companies, or at least one big one, to throw billions of dollars to get it over that learning curve, it's not going to happen."