Nonvolatile Memory Read Retry Voltage Adjustment
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Solution Overview
Problem
Nonvolatile memory devices experience read errors due to changes in threshold voltage distributions caused by factors like program or erase operations, defects in insulating layers, and environmental stress, leading to decreased read margins and reliability.
Innovation Solution
A method and device for reading nonvolatile memory devices that includes performing read retry operations by adjusting either the selection read voltage applied to the selected memory cell or the non-selection read voltage applied to non-selected memory cells, until the read operation is successful, to mitigate read errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed selection read voltage and non-selection read voltage are applied to memory cells, then the reading operation is simple and fast, but read errors occur due to threshold voltage distribution changes
Solution Approach 1:
The patent applies dynamics by transitioning from fixed voltage levels to dynamic voltage adjustment. The control logic dynamically modifies the selection read voltage and/or non-selection read voltage based on detected read errors and retry operation requirements, allowing the voltage parameters to adapt to changing threshold voltage distributions in memory cells
Solution Approach 2:
The patent implements parameter changes by varying the voltage parameters (selection read voltage and non-selection read voltage) during read operations. When read errors are detected, the control logic changes these voltage parameters to different levels to attempt successful reading, thereby addressing threshold voltage distribution variations
2Reliability
If read retry operations are performed by changing voltage levels, then read error prevention is improved, but reading time and operation complexity increase
Solution Approach 1:
The patent applies feedback by implementing a read retry mechanism where the control logic detects read errors and uses this feedback information to determine whether voltage adjustment is necessary. The system feeds back the read operation result and adjusts voltage parameters accordingly, creating a closed-loop system that only incurs time penalty when errors occur
Solution Approach 2:
The patent implements preliminary action by preparing multiple voltage levels for selection read voltage and non-selection read voltage in advance. When a read error is detected, the system can immediately retry with pre-prepared voltage combinations without needing to recalculate or wait for voltage generation, reducing the time penalty of retry operations
Data Source
AI summary
In a method of reading a nonvolatile memory device, the method comprising, a reading operation of reading data of a selected memory cell; and a read retry operation of performing one or more read operations by changing a non-selection read voltage applied to non-selected memory cells until the read operation succeeds, when it is detected that an error has occurred in the operation of reading data.