In RRAM, the top metal layer creates a conductive electrode, the middle is an amorphous silicon switching medium, and the lower layer is nonmetallic. When the programming voltage is applied between the two electrodes, the nanoparticles of the top electrode diffuse in the switching material and create a filament; the memory cell is conductive when the filament contacts the bottom electrode. When the reverse voltage is applied between the two electrodes, the filament is pushed back and disappears. The memory cell is non-conductive.
Crossbar refers to the electron leakage between cells as "sneak path current," which is inherent in RRAM memory.
To overcome the data error problem with its RRAM, Crossbar invented a way to hide adjacent cells from those being programmed to store data, thereby insulating them from unintentional changes. It did that by setting a specific voltage range for cells. Cells programmed between -1 volt and +1 volt are ignored, and anything outside that range can be programmed to hold new data.
The technology is called a Field-Assisted Superlinear Threshold (FAST) selector device, and it suppressed the sneak path current — marking another significant milestone needed to commercialize RRAM memory for high-density data applications.
"When we unveiled Crossbar RRAM eighteen months ago, we laid out aggressive plans to deliver a new generation of memory capable of scaling to 1 terabyte on a chip the size of a postage stamp," said Crossbar CEO George Minassian. "With this latest achievement, we are one step closer to commercialization, enabling the implementation of RRAM technology in commercial products; a ground breaking achievement that will redefine what is possible with enterprise storage and high-capacity non-volatile [systems-on-a-chip] memories."
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