Semiconductor Memory Controller Intervening Program Operation
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Solution Overview
Problem
Current semiconductor memory devices face challenges in ensuring reliable operation due to variations in threshold voltage distributions during write operations, leading to inaccurate program verification and potential data corruption.
Innovation Solution
A semiconductor memory device that includes a control circuit executing a write operation with multiple program and verification phases, where the control circuit applies different voltages for program and verification operations, and includes intervening operations to stabilize electron leakage, ensuring accurate data retention and reduced threshold voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single program voltage is applied to the word line during write operation, then the operation process is simple and fast, but the threshold voltage distribution varies inaccurately leading to poor data retention
Solution Approach 1:
The write operation is segmented into multiple phases: a first program operation with a first program voltage, an intervening program operation with a second program voltage, and a second program operation with a third program voltage. This segmentation allows different voltage levels to be applied at different stages, improving threshold voltage distribution accuracy and data retention while managing complexity through structured multi-phase operation.
Solution Approach 2:
The write operation employs periodic program and verify cycles with intervening operations between them. This periodic structure includes applying program voltages, performing verify operations to check data retention, and inserting intervening program operations to stabilize electron leakage. The periodic action ensures accurate threshold voltage programming while maintaining reliable data storage.
2Measurement precision
If program verify operation is performed immediately after program operation, then the verification is timely, but electron leakage is not stabilized leading to inaccurate verification results
Solution Approach 1:
An intervening program operation is performed as a preliminary action between the main program operation and the program verify operation. This intervening operation stabilizes electron leakage before verification begins, ensuring that the subsequent verify operation measures accurate data retention. The preliminary action prepares the memory cells in a stable state for reliable verification.
Solution Approach 2:
The intervening program operation acts as an intermediary step between programming and verification. It mediates the transition by stabilizing electron leakage and threshold voltage distribution, creating optimal conditions for accurate verification. This intermediary operation ensures that verification results reflect true data retention rather than transient electron leakage effects.
3Productivity
If high program voltage is applied continuously, then programming speed is fast, but threshold voltage fluctuates excessively reducing data accuracy
Solution Approach 1:
The program voltage is made dynamic rather than static, varying through different levels (first, second, and third program voltages) across different operation phases. This dynamic voltage application allows aggressive programming when needed while providing voltage reduction and stabilization phases that control threshold voltage fluctuations. The dynamic approach maintains high programming speed while ensuring precision through voltage modulation.
Solution Approach 2:
The program voltage parameter is changed across different operation phases, transitioning from a first program voltage during initial programming to a second program voltage during intervening operations, and to a third program voltage during later programming stages. This parameter change strategy enables effective programming while controlling threshold voltage distribution accuracy, preventing excessive fluctuations that would reduce data precision.
Data Source
AI summary
A semiconductor memory device includes memory cells, a word line connected to gates of the memory cells, and a control circuit configured to execute a write operation on the memory cells. The write operation includes a first program operation during which a first program voltage is applied to the word line, a first verify operation during which a first verification voltage is applied to the word line to determine whether or not the first program operation passed, a second program operation during which a second program voltage is applied to the word line, and a second verify operation during which a second verification voltage is applied to the word line to determine whether or not the second program operation passed. The control circuit is configured to execute at least one intervening program or verify operation between the first program operation and the first verify operation.