Image: Fujio Masuoka
NAND Flash Memory
Category: Memory and Storage
The saga that is the invention of flash memory began when a Toshiba factory manager named Fujio Masuoka decided he’d reinvent semiconductor memory. We’ll get to that in a minute. First, a bit of history is in order.
Before flash memory came along, the only way to store what passed for large amounts of data at the time was to use magnetic tapes, floppy disks, or hard disks. Many companies were trying to create solid-state alternatives, but the choices, such as EPROM (or erasable programmable read-only memory, which required ultraviolet light to erase the data) and EEPROM (the extra E stands for “electrically,” doing away with the UV) couldn’t store much data economically.
Enter Masuoka at Toshiba. In 1980, he recruited four engineers to a semisecret project aimed at designing a memory chip that could store lots of data and would be affordable. Their strategy was simple. “We knew the cost of the chip would keep going down as long as transistors shrank in size,” says Masuoka, now CTO of Unisantis Electronics, in Tokyo.
Masuoka’s team came up with a variation of EEPROM that featured a memory cell consisting of a single transistor. At the time, conventional EEPROM needed two transistors per cell. It was a seemingly small difference that had a huge impact on cost.
In search of a catchy name, they settled on “flash” because of the chip’s ultrafast erasing capability. Now, if you’re thinking Toshiba rushed the invention into production and watched as the money poured in, you don’t know much about how huge corporations typically exploit internal innovations. As it turned out, Masuoka’s bosses at Toshiba told him to, well, erase the idea.
He didn’t, of course. In 1984 he presented a paper on his memory design at the IEEE International Electron Devices Meeting, in San Francisco. That prompted Intel to begin development of a type of flash memory based on NOR logic gates. In 1988, the company introduced a 256-kilobit chip that found use in vehicles, computers, and other mass-market items, creating a nice new business for Intel.
That finally pushed Toshiba to greenlight Masuoka’s invention. His flash chip was based on NAND technology, which offered greater storage densities but proved trickier to manufacture. Success came in 1989, when Toshiba’s first NAND flash hit the market. And just as Masuoka had predicted, prices kept falling.
Digital photography gave flash a big boost in the late 1990s, and Toshiba became one of the biggest players in a multibillion-dollar market. At the same time, though, Masuoka’s relationship with other executives soured, and he quit Toshiba. (He later sued for a share of the vast profits and won a cash payment.)
Today, NAND flash is a key piece of gadgets and space probes alike—and is beginning to replace even hard disks as the storage medium of choice in laptop and desktop computers.