Nonvolatile Memory Data Migration and Reprogramming
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Solution Overview
Problem
Nonvolatile memory systems face reliability issues due to threshold voltage shifts in memory cells during the surface mount technology process, leading to data loss and instability in charge trap flash memory cells.
Innovation Solution
A nonvolatile memory system with first and second areas, where data is initially written in the first area using a single level cell programming scheme and then migrated to the second area using a multi level cell programming scheme during the first boot operation, with reprogramming of the second area to compensate for charge loss without erasing existing data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is stored in charge trap flash memory cells using conventional programming, then data can be retained, but threshold voltage shifts occur during surface mount technology process leading to data loss and instability
Solution Approach 1:
The patent performs a reprogram operation on the second area before final data storage to pre-compensate for charge loss and threshold voltage shifts that will occur during subsequent manufacturing processes. This preliminary action ensures that even after threshold voltage degradation, the data remains stable and retrievable.
Solution Approach 2:
The patent changes the programming parameters by performing a reprogram operation with adjusted voltage and time parameters on the second area. This parameter modification compensates for the threshold voltage shifts caused by the surface mount technology process, maintaining data integrity despite environmental changes.
2Adaptability or versatility
If an erasing operation is performed on the second area to reprogram data, then data can be rewritten, but the erasing process increases operation time and complexity
Solution Approach 1:
The patent extracts the erasing step from the reprogramming process. Instead of performing a complete erase cycle followed by reprogramming, the method directly reprograms the second area while preserving the erased state information, thereby eliminating the time-consuming erasure phase while maintaining the ability to rewrite data.
Solution Approach 2:
The second area is pre-prepared in an erased state before data migration, so that when reprogramming is needed, the data can be directly written without requiring a subsequent erasure operation. This preliminary preparation enables faster data rewriting operations.
3Reliability
If data is migrated from the first area to the second area during first booting, then reliability is improved through reprogramming, but the booting process becomes more complex
Solution Approach 1:
The operating system image is pre-written to the first area during manufacturing before the device is shipped. During the first booting operation, the system automatically migrates this pre-stored image to the second area and performs reprogramming, ensuring reliability without requiring user intervention or complex external processes.
Solution Approach 2:
The memory system performs the data migration and reprogramming operation autonomously during the first booting sequence without requiring external control or user input. The system self-manages the transfer from the first area to the second area and automatically executes the reprogram operation to ensure data integrity.
Data Source
AI summary
An operating method of a nonvolatile memory system including first and second areas is provided. Data stored in the first area is migrated to the second area when a first booting operation is performed. The data stored in the second area is reprogrammed. The first booting operation is a booting operation performed when the nonvolatile memory system is first powered on after mounted on a printed circuit board. The reprogramming is a program operation performed on the data stored in the second area without performing an erasing operation on the data stored in the second area.