RRAM Takes on Flash

Several vendors are trying to create the next flash memory breakthrough, but one company thinks it has the inside track. By James E. Gaskin

NAND Flash, the nonvolatile memory used in smartphones, SSDs (solid-state drives), and many other devices, keeps dropping in price. But the physics of silicon lithography indicates we can’t keep shrinking its size. “These warnings have been out a long time,” says Jim Handy, analyst at market research firm Objective Analysis. “Intel warned they couldn’t make flash below 60 nm [nanometers], but now they’re shipping chips made at 16 nm.” Companies are searching for new ways to make nonvolatile memory, and Santa Clara, Calif.-based start-up Crossbar Inc. believes it has the best option with its RRAM (resistive RAM).

“RRAM is higher density, has more endurance and longevity, and is 20 times faster than NAND flash while using a fraction of the electricity,” says Hagop Nazarian, vice president of engineering at Crossbar. “RRAM works in 3D, so you can stack chips to increase memory from 16GB to 32GB with another layer, and 64GB with another two.” Crossbar has silicon wafers in testing now, and expects to ship product in two to three years.

Crossbar’s RRAM uses a pair of electrodes separated by their proprietary amorphous silicon switching media that moves silver ions into a filament that dramatically lowers resistance. Reversing the current moves the silver ions in the other direction, breaking the filament and raising resistance.

Handy counts numerous Crossbar competitors also trying to create the next flash memory breakthrough. “HP said they’d have their memristor [technology] shipping by now, but it’s not. RRAM, MRAM [magnetoresistive RAM], ReRAM, and PCRAM [phase-change memory] are all significantly more expensive than NAND flash, and cost is just about everything in memory.”

Nazarian believes Crossbar’s RRAM has the inside track. “We have filed over 100 patents and 30 have been issued. Our technology is CMOS compatible with multiple layers, using techniques chip foundries already use, so we will be able to add embedded memory onto microcontrollers. We’ll serve all markets for memory, from the smallest device in the Internet of Things to the largest servers.”

“NAND flash will be around for another decade,” says Handy. “There will be a couple more generations of current technology, then three generations or more of 3D NAND flash. But someday NAND flash prices will level out because of the technology difficulties, and these other memory options will drop enough to match their price.”

When the switch does come, resellers will have few changes to operations to integrate the new memory, says Handy. Controller makers may be able to scale back complexity of the controller chips. “You may update your 2103 iPhone with 1TB of NAND flash to a 4TB model with a new memory type.”