Non-volatile Memory Read Voltage Offset Adjustment
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Solution Overview
Problem
Non-volatile memory devices face challenges in maintaining data integrity due to complex threshold voltage distributions, leading to read errors, as the distribution becomes more elaborate with increased data bits, causing degradation and requiring improved methods for reliable data read operations.
Innovation Solution
A method involving dummy read operations with adjustable offset voltages is implemented to assess and compensate for threshold voltage distribution degradation, ensuring accurate data read by adjusting the dummy read voltage levels based on determined degradation, thereby enhancing the reliability of read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of data bits stored in one memory cell is increased, then the storage capacity is improved, but the threshold voltage distribution becomes more complex and read errors increase
Solution Approach 1:
The patent performs a dummy read operation before the actual read operation to detect threshold voltage distribution degradation in advance. By conducting this preliminary assessment, the system can identify shifts in threshold voltage distributions caused by complex multi-bit storage, and adjust read voltages accordingly before performing the actual data read, thereby maintaining read accuracy despite increased storage capacity
Solution Approach 2:
The patent dynamically adjusts read voltages based on detected threshold voltage distribution characteristics. By changing the read voltage parameters in response to observed distribution shifts, the system compensates for the increased complexity introduced by multi-bit storage, ensuring reliable data retrieval while maintaining high storage capacity
2Reliability
If a dummy read operation is performed to detect threshold voltage degradation, then read reliability is improved, but additional time is consumed
Solution Approach 1:
The patent performs a dummy read operation on a sample or subset of memory cells rather than all cells, or uses a simplified read process for the dummy operation. This partial action approach provides sufficient information to detect threshold voltage distribution shifts and adjust read voltages, while consuming less time than a complete read operation would require, thus balancing reliability improvement with time efficiency
Data Source
AI summary
A memory device includes multiple word lines. A method of operating the memory device includes: performing a first dummy read operation, with respect to first memory cells connected to a first word line among the word lines, by applying a dummy read voltage, having an offset level of a first level, to the first word line; determining, based on a result of the performing of the first dummy read operation, degradation of a threshold voltage distribution of the first memory cells; adjusting an offset level of the dummy read voltage as a second level, based on a result of the determining of the threshold voltage distribution; and performing a second dummy read operation with respect to second memory cells connected to a second word line among the word lines, by applying a dummy read voltage, having the offset level adjusted as the second level, to the second word line among the word lines.