Systems and methods for improving radiation tolerance of memory
Inventors
Ray, Biswajit • Milenkovic, Aleksandar
Assignees
University of Alabama in Huntsville
Publication Number
US-12237032-B1
Publication Date
2025-02-25
Expiration Date
2041-08-04
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Abstract
A system for improving radiation tolerance of memory senses an amount of radiation exposure and, based on the sensed amount of radiation exposure, determines whether to perform one or more techniques for mitigating the effects of the radiation exposure. As an example, the system may perform a data refresh operation by re-writing data that has been corrupted by radiation, or the system may adjust the reference voltage used to read memory cells. In another example, the system may perform a fault repair operation by re-programming cells that have erroneously transitioned from a program state to an erase state. The system may selectively perform different radiation-mitigation techniques in a tiered approach based on the sensed amount of radiation in order to limit the adverse effects of the more invasive techniques.
Core Innovation
The invention discloses systems and methods for improving the radiation tolerance of memory, specifically flash memory. The system senses the amount of radiation exposure to the memory and determines, based on the sensed amount, whether to apply one or more techniques to mitigate the effects of radiation-induced charge leakage. The memory controller may use various operations such as adjusting the reference voltage (read voltage) used to read memory cells, performing data refresh operations by re-writing corrupted data, or executing fault repair operations by re-programming cells that have erroneously transitioned states due to radiation.
The problem addressed is the vulnerability of flash memory to ionizing radiation, which induces errors in stored data by causing charge leakage from the memory cells. This limits the use of flash memory in high-radiation environments like space vehicles and satellites, as shielding is not always feasible or cost-effective. Prior art relies heavily on physical shielding or uniform error correction approaches, which may not be optimal or efficient.
To overcome these limitations, the system selectively and adaptively applies different radiation-mitigation techniques in a tiered manner according to the amount of radiation sensed. For example, less invasive techniques like adjusting read voltage may be performed for low radiation exposure, while more invasive methods like data refresh are reserved for higher exposure levels. Additionally, for 3D memory structures, the system can vary ECC strength and data placement based on the region's susceptibility to radiation, further improving the efficiency and resiliency of the memory system.
Claims Coverage
The patent claims cover several inventive features centered around radiation-aware memory management techniques. There are multiple independent claims, most notably Claim 1, Claim 5, Claim 8, Claim 9, and Claim 13.
Radiation-based adaptive adjustment of read voltage
A memory controller determines a value indicative of an amount of radiation that the electronic device receives and, based on this value, adjusts the read voltage applied to at least one memory cell. If the detected value is within a first range, the controller adjusts the read voltage to compensate for charge leakage. This adjustment is applied as a mitigation operation to counteract radiation-induced errors.
Tiered response with data refresh operation based on radiation range
The memory controller performs a data refresh operation for charge leakage if the sensed radiation value is in a second range greater than the first range. The system uses a tiered approach, where different operations are selectively performed depending on whether radiation exposure is low or high, allowing more aggressive mitigation only when necessary.
Data refresh with targeted charge re-injection to erroneous cells
The memory controller, during a data refresh operation, forces charge into cells associated with data errors so that the affected cells are transitioned from an erase state to a program state. The operation specifically targets cells in error, restoring their correct state to compensate for radiation effects.
Partial programming with program and stop commands
The memory controller forces charge into erroneous cells with a program command and interrupts the forcing action with a stop command after a certain period. This enables precise control over the restoration of cell states in response to data errors caused by radiation.
Radiation-based method for compensating for charge leakage
A method for determining a value indicative of the radiation exposure, comparing it to thresholds, and performing at least one compensatory operation on flash memory. The selected operation depends on whether the value is in a first or second range, with read voltage adjustment in the lower range and data refresh in the higher range, thereby adaptively mitigating charge leakage.
Targeted re-writing of erroneous data based on radiation exposure
A method involving determining radiation exposure, comparing to a threshold, and, based on that, re-writing data in flash memory, particularly by forcing charge into cells with data errors to transition them from an erase state to a program state.
The inventive features focus on adaptively and selectively mitigating radiation-induced charge leakage in flash memory through operations such as read voltage adjustment, data refresh, targeted charge injection, partial programming, and tiered operational strategies responding to sensed radiation values.
Stated Advantages
Limits adverse effects of invasive radiation-mitigation techniques by using less invasive operations when possible, thus extending memory life.
Efficiency is improved by allocating stronger error correction resources only to the regions or data most susceptible to radiation.
Reduces frequency of data refresh operations, thereby mitigating memory degradation and increasing overall memory system longevity.
Allows continued operation and reliability of flash memory in high radiation environments without significantly increasing cost.
Enables prioritized protection for high-priority data by placing it in memory regions less affected by radiation.
Documented Applications
Use in electronic devices such as smartphones, mobile devices, tablets, personal digital assistants, personal computers, game consoles, game cartridges, memory cards, USB flash drives, and solid-state drives.
Deployment in vehicles or satellites that travel in outer space or other high-radiation environments.
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