Temperature-Compensated Verify Operations for Non-Volatile Memory Programming
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Solution Overview
Problem
Existing non-volatile semiconductor memory devices face a tradeoff between programming speed and precision, with tight threshold voltage distributions required for accurate reading, especially in multi-state memory cells, but achieving these distributions slows down the programming process.
Innovation Solution
A two-phase programming process is implemented, where a coarse programming phase quickly raises the threshold voltage and a fine programming phase achieves a tighter distribution, with dynamically adjusted verify operations based on temperature to account for temperature variances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a smaller step size is used for program voltage to achieve tight threshold voltage distribution, then manufacturing precision is improved, but programming speed deteriorates
Solution Approach 1:
The programming process is divided into multiple phases with different step sizes. Coarse programming uses larger step sizes for rapid threshold voltage increase, while fine programming uses smaller step sizes for precise threshold voltage distribution. This segmentation allows the system to achieve both fast programming and high precision by applying different programming strategies at different stages.
2Manufacturing precision
If verify operations are performed frequently to ensure programming precision, then manufacturing precision is improved, but programming speed deteriorates
Solution Approach 1:
The verify operation frequency is made dynamic rather than fixed. The system performs verify operations more frequently during fine programming when precision is critical, and less frequently during coarse programming when speed is prioritized. This dynamic adjustment of verify frequency allows the system to optimize the balance between precision and speed at different programming stages.
Data Source
AI summary
A non-volatile storage system that performs programming and reading processes. The programming process includes coarse/fine programming and verify operations. Programming is verified by testing for two different threshold voltage levels while applying the same voltage level to the control gate of a memory cell by testing for current levels through the memory cells and adjusting the current levels tested for based on current temperature such that the difference between the two effective tested threshold voltage levels remains constant over temperature variation.