Semiconductor Memory Flag Cell LSB MSB Programming Sequence
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Solution Overview
Problem
Semiconductor memory devices face challenges in ensuring reliable operation, particularly during sudden power-offs, where distinguishing between Least Significant Bit (LSB) and Most Significant Bit (MSB) data is critical for maintaining data integrity and correcting errors.
Innovation Solution
A method and semiconductor memory device design that includes a peripheral circuit and control logic to perform program operations on LSB and MSB data, utilizing flag cells and threshold voltage classifications to verify program states, ensuring accurate data programming and error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flag cell programming is performed simultaneously with LSB and MSB data, then programming speed is improved, but data integrity and error correction capability deteriorate due to inability to distinguish programming stages during power-off
Solution Approach 1:
The patent applies preliminary action by first programming the LSB data and verifying it before initiating MSB data programming. The flag cell is programmed only after LSB verification is complete, ensuring that the programming stage can be correctly identified even if power is lost during MSB programming. This sequential approach prioritizes data integrity over programming speed.
Solution Approach 2:
The flag cell serves as an intermediary indicator that records the programming stage. By using this dedicated flag cell to mark whether LSB or MSB programming has been performed, the system can distinguish between programming stages during power-off recovery, enabling proper error correction while maintaining the ability to handle multi-stage programming.
2Productivity
If flag cell is programmed before LSB verification, then programming throughput is improved, but measurement precision of program state verification deteriorates
Solution Approach 1:
The patent ensures that LSB data programming and verification are completed before the flag cell is programmed. This preliminary verification step guarantees that the program state can be accurately measured and confirmed before transitioning to MSB programming, maintaining verification precision while still achieving improved throughput through efficient sequential processing.
3Reliability
If separate programming loops for LSB and MSB are implemented with verification steps, then data reliability is improved, but device complexity increases
Solution Approach 1:
The patent segments the programming process into distinct LSB and MSB programming loops, each with its own verification step. The flag cell is used to mark the completion of LSB programming, enabling the system to track the programming stage. This segmentation improves data reliability by ensuring proper verification at each stage while organizing the complexity into manageable, structured components.
Solution Approach 2:
The flag cell acts as an intermediary that simplifies the control logic by providing a clear binary indicator of the programming stage. Instead of complex state tracking, the flag cell's programmed or unprogrammed state directly indicates whether LSB or MSB programming should proceed, reducing the overall system complexity while maintaining reliable multi-stage programming.
Data Source
AI summary
Provided herein may be a semiconductor memory device and a method of operating the same. The method of operating a semiconductor memory device may include performing a program operation on a Least Significant Bit (LSB) of a page, and performing a program operation on a flag cell and a Most Significant Bit (MSB) of the page based on an operation of verifying at least one of a plurality of program states. The data stored in the flag cell may be data indicating whether data programmed according to the program operation is LSB data or MSB data.