Memory Heaters for Oxide Annealing in NAND Flash
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Solution Overview
Problem
Oxide degradation in memory devices, such as NAND flash memory, leads to increased defects and data retention loss due to program/erase cycles, rendering affected memory cells unusable.
Innovation Solution
Incorporating a heater adjacent to the access lines in the memory array to selectively anneal the oxide within the NAND strings, mitigating defects and extending the lifespan of memory cells by removing traps and improving data retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If program/erase cycles are performed to write data, then data storage capability is improved, but oxide degradation increases leading to more defects and traps
Solution Approach 1:
The patent applies thermal annealing to convert the harmful effects of oxide degradation (defects and traps) into beneficial outcomes by using controlled heat treatment to repair the degraded oxide layer, thereby restoring memory cell functionality and extending device lifespan
Solution Approach 2:
The patent changes the temperature parameter of the oxide layer through thermal annealing processes, heating the oxide to specific temperatures (e.g., 150-400°C) to modify its physical and chemical properties, reducing defects and traps while maintaining the storage capability
2Duration of action of stationary object
If program/erase cycles are increased to extend usage, then operational lifespan is improved, but data retention loss increases due to oxide degradation
Solution Approach 1:
The patent performs thermal annealing as a preliminary repair action before oxide degradation completely destroys data retention capability, proactively treating the oxide layer to prevent defects from accumulating to critical levels that would cause permanent data loss
Solution Approach 2:
The patent converts the harmful data retention loss caused by oxide degradation into a benefit by using thermal annealing to repair the oxide, thereby extending the operational lifespan while maintaining data integrity
3Reliability
If thermal annealing is applied to repair oxide defects, then data retention is improved, but additional processing steps are required
Solution Approach 1:
The patent merges the thermal annealing process with existing fabrication or operational processes, combining the defect repair function with standard manufacturing or device operation steps to minimize additional processing complexity
Solution Approach 2:
The patent designs the thermal annealing process to serve multiple functions simultaneously: repairing oxide defects, stabilizing the memory cell structure, and potentially preparing the oxide for subsequent programming operations, thereby reducing the need for separate dedicated repair steps
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The use of heaters in memory devices effectively anneals oxide defects, enhancing data retention and extending the operational life of memory cells beyond the typical threshold of program/erase cycles, thereby improving the reliability and longevity of memory devices.
Implementation Method 1
Incorporating a heater adjacent to the access lines in the memory array to selectively anneal the oxide within the NAND strings
Data Source
AI summary
Memory devices might include an array of memory cells, a plurality of access lines, and a heater. The array of memory cells might include a plurality of strings of series-connected memory cells. Each access line of the plurality of access lines might be connected to a control gate of a respective memory cell of each string of series-connected memory cells of the plurality of strings of series-connected memory cells. The heater might be adjacent to an end of each access line of the plurality of access lines.