ReRAM NVM shines, even in High-Rad applications – Embedded Computing Design

June 22, 2023

To say that non-volatile memory (NVM) is ubiquitous is an understatement. From our consumer devices to industrial and medical/healthcare applications, even in our cars, NVM is ubiquitous. It is used to store operating system, program files, our images, videos and other data. In environments with high levels of radiation, such as aerospace and medical devices, choosing the right NVM can be a key consideration as radiation can affect the operation of many technologies.

However, flash memory has its limitations in terms of speed, power, cost and endurance, meaning there are both economic and technical challenges designers face when incorporating flash memory into SoCs. Therefore, designers continue to look for NVM alternatives, especially for SoCs in high radiation applications, where the embedding of flash memory requires more complexity and redundancy.

Flash memory is highly sensitive to radiation due to its dependence on the buildup of electrical charge. Radiation can affect flash memory through cumulative exposure, displacement damage, or the effects of a single event. The damage caused can range from reversal of state to permanent alteration of atomic structure. This problem gets worse with smaller process geometries.

To complicate matters further, the use of flash memory in high radiation environments complicates the design process, as designers must incorporate error correcting code (ECC) and redundancy to ensure continuous operation, leading to size, higher costs and latency.

New memory technologies, such as ReRAM, are helping overcome some of these challenges, including radiation sensitivity. ReRAM, which stands for Resistive Random Access Memory, is unaffected by ionizing radiation, because there is no direct interaction between the radiation and the storage mechanism. ReRAM is just starting to become a mainstream technology, offering radiation resistant alternatives to conventional flash memory.

Shown is the Weebit Nano ReRAM module integrated into a RISC-V based SoC.

Weebit Nano, a developer of advanced semiconductor memory technologies, and the Nino Research Group (NRG) of the University of Florida Department of Materials Science and Engineering are studying the effects of radiation on Weebit Nano ReRAM technology under various conditions . The results confirm that ReRAM arrays are tolerant of high levels of radiation and can maintain data integrity and memory functionality after being subjected to high doses of gamma irradiation.

Without going into painstaking details here, the results of the study conclusively show that all distribution properties in both the high-strength state (HRS) and low-strength state (LRS) were preserved. Therefore, the researchers confirmed that after high-dose irradiation, Weebit Nano ReRAM technology was able to preserve information and can be completely reprogrammed.

Only 16 kbit arrays were characterized for this study. In the next phase, researchers will extend the irradiation experiments to include the type of radiation sources that cover the full spectrum of radiation environments that can be encountered in typical medical and aerospace applications.

These initial studies are only the starting point for investigations into the radiation tolerance of Weebit Nano’s ReRAM. Weebit Nano ReRAM modules will also be included in future irradiation experiments, enabling broad characterization of the company’s technology for rad-hard applications. Subsequently, an in situ test facility will be constructed at the University of Florida Training Reactor Facility (UFTR). The goal of this last phase is to gain a deeper understanding of memory behavior when operating in real-time radiation environments.

*Note that the full study is detailed in the Design Considerations for Embedded NVM in High Radiation Applications white paper.

Richard Nass’ key responsibilities include setting direction for all aspects of OSM’s ECD portfolio, including digital, print and live events. Previously, Nass was Brand Director for Design News. Previously, he led the content team for UBM’s Medical Devices Group and all custom properties and events. Nass has been in the OEM engineering business for over 30 years. Previously, he led the Content Team at EE Times, Embedded.com and TechOnLine. Nass holds a BSEE degree from NJIT.

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