The most desirable device structure for high density nonvolatile memory (NVM) is the crossbar architecture composed of two electrode lines (bit-line and word-line) perpendicular to each other with memory materials sandwiched in between. This provides the highest density attainable in a 2-dimensional (2D) planar crossbar architecture (4F2 where F = minimum feature size). Furthermore, this planar structure is conducive to multi-layer integration, wherein multiple levels of 2D arrays are fabricated on top of each other forming a highly dense 3D memory array.
The Technical Explanation
Prof. Tour has demonstrated Non-Volatile Memory behavior with SiOx. SiOx is the most common and lowest cost material in the semiconductor industry. These SiOx memory elements have shown desirable performance metrics such as extremely high ON-OFF ratio, multi-bit capability, low energy consumption, and X-ray hardened property by conducting nano-filaments forming at a sub-5-nm scale. The devices have fast switching speed and good stability suitable for future memory applications.
The novelty in Weebit’s SiOx memory
The SiOx-based material is a new concept for a memory structure. The achieved performances are born from the unique SiOx characteristics which allows to produce a highly manufacturable cost effective ReRAM Technology.
Through the SiOx material, many of the critical requirements for future nonvolatile memory can be met such as reliable nano-scale memory filament formation, improved rewriting times, high memory stability, low power consumption, and multi-bit capability.
Advantages
Preliminary results have demonstrated remarkably fast switching speed in the range of 1000 times faster than the most advanced NAND Flash technology. Weebit cell shows the ability to meet the demand for the future device requirements.
As Flash technology is scaled down, it’s cycling endurance is dramatically reduced, which created severe reliability issues. To compensate for these flaws, expensive error correction and wear leveling circuitry is required.
Weebit’s memory cell will require significantly lower power during device operation. This lower power will be a great advantage increasing battery life not only in any battery operating device, but also in computing and datacenters to save energy on heat dissipation solutions.
Weebit’s ReRAM has the potential of further scaling beyond the Flash limit, thus providing smaller cells which enable to store more information (higher density) and reduce production cost.
Weebit’s memory cell is based on SiOx material which is the most common, studied and available dielectric material in the semiconductor industry, thereby avoiding extremely expensive capital industry re-tooling costs.
One of the weaknesses of the traditional Flash technology is its radiation sensitivity. High energy radiation easily causes electrons to escape from the floating gate thus creating errors, which require costly solutions and limits the density of radiation hardened devices.
Weebit’s ReRAM (unlike Flash) does not confine electrons in a floating gate therefore it is a natural radiation hardened memory cell. This capability was demonstrated in the International Space Station (ISS) as Prof. Tour memory samples showed great performance after 2 years in space.
