Semiconductor Memory Tracking Read Voltage Determination
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Solution Overview
Problem
Semiconductor memory devices face challenges in maintaining accurate data retrieval due to shifting threshold voltage distributions caused by read disturbance and data retention issues, which affect processing capability and reliability.
Innovation Solution
The implementation of a semiconductor memory device with a control circuit that performs tracking read and shift read operations by applying multiple voltages to determine optimal read voltages for memory cells, reducing the need for extensive tracking reads and minimizing read disturbance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If tracking read operations are performed to determine optimal read voltages, then measurement precision is improved, but loss of time increases due to multiple read operations
Solution Approach 1:
The patent performs tracking read operations to determine optimal read voltages in advance before actual data read operations. By pre-determining the read voltages that correspond to threshold voltage distribution boundaries, the system avoids performing multiple tracking reads during subsequent read operations, thus reducing time loss while maintaining measurement precision.
Solution Approach 2:
The patent creates a voltage mapping table that stores the correspondence between read voltages and threshold voltage distributions. This copied information is then reused for multiple read operations, eliminating the need to repeatedly perform tracking reads and reducing time consumption while maintaining accurate voltage determination.
2Measurement precision
If multiple read voltages are applied to memory cells, then measurement precision is improved, but object-affected harmful factors increase due to read disturbance
Solution Approach 1:
The patent performs the necessary tracking read operations to determine optimal read voltages immediately after program operations and before actual data read operations. By completing voltage determination in advance, the system minimizes the number of additional tracking reads needed during subsequent operations, thereby reducing read disturbance to stored data.
Solution Approach 2:
The patent uses the results of tracking read operations to feedback and determine the optimal read voltages that correspond to threshold voltage distribution boundaries. This feedback mechanism ensures that subsequent read operations use precisely calibrated voltages, improving measurement precision while minimizing the need for repeated tracking reads that would cause read disturbance.
Data Source
AI summary
A semiconductor memory device includes a memory cell array including a plurality of memory cells, a word line connected in common to gates of the memory cells, and a control circuit configured to execute a read operation on the memory cells by applying a first read voltage to the word line to determine for each of the memory cells whether or not the memory cell has a threshold voltage that is below the first read voltage and a second read voltage to the word line to determine for each of the memory cells whether or not the memory cell has a threshold voltage that is below the second read voltage. The control circuit determines the first read voltage by applying at least first to third voltages to the word line, and determines the second read voltage based on the first read voltage.