Systems and methods for hardening flash memory to radiation
Inventors
Ray, Biswajit • Kumari, Preeti
Assignees
University of Alabama in Huntsville
Publication Number
US-11164642-B1
Publication Date
2021-11-02
Expiration Date
2039-02-11
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Abstract
A method for radiation hardening flash memory performs accelerated aging on the flash memory by program-erase (PE) cycling the flash memory. Such accelerated aging induces trap states in the tunnel oxide layer of the flash memory, which results in improved ionizing radiation tolerance. The number of cycles used to harden a given memory cell is optimally determined in order to limit effects of the radiation hardening on the reliability of the cell.
Core Innovation
The invention provides systems and methods for hardening flash memory against radiation by inducing accelerated aging through program-erase (PE) cycling. During this process, memory operations such as programming and erasing are repeatedly performed on flash memory cells for a predetermined number of cycles. This action intentionally creates trap states within the tunnel oxide layer of the flash memory cells.
By creating these trap states via controlled PE cycling, the flash memory cells exhibit improved tolerance to ionizing radiation. Experimental results show that this technique can increase radiation tolerance of the memory by more than 25%, compared to fresh, non-cycled memory. The methods optimize the number of cycles to ensure the memory cells gain desired radiation hardness without significantly degrading overall reliability.
The invention addresses significant limitations of commercial NAND flash memory for space applications, where ionizing radiation can cause rapid charge loss from the floating gate and data corruption. Prior techniques, such as software or hardware redundancy, compromise memory density. The proposed solution enables improving radiation tolerance without reducing storage capacity, providing an efficient and scalable technique for enhancing the reliability of flash memory in radiation-prone environments.
Claims Coverage
The patent contains one independent claim, which defines the primary inventive feature of the invention.
Radiation hardening flash memory using optimally selected program-erase cycles
A method that includes: - Selecting a specific number of program-erase (PE) cycles to achieve a desired amount of radiation hardening for flash memory. - Performing a radiation hardening process on a flash memory cell, wherein the process involves: - Successively executing program-erase (PE) cycles on the memory cell using a controller, performing for each cycle both a program operation and an erase operation. The method covers optimizing the number of PE cycles to balance hardening against wear on the cell.
The above inventive feature establishes a process for radiation hardening flash memory by applying a selected number of program-erase cycles, managed by a controller, to optimize the memory's resistance to ionizing radiation while considering cell reliability.
Stated Advantages
Improves radiation tolerance of flash memory by more than 25% compared to fresh memory.
Enables commercial multi-level cell (MLC) NAND flash chips to be made radiation hard by controlled aging.
Optimizes hardening to maintain memory reliability by limiting wear through empirically determined PE cycles.
Documented Applications
Hardening flash memory for use in space electronic systems where radiation tolerance is critical.
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