NAND Flash Self-Verification for Data Integrity
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Solution Overview
Problem
As memory devices shrink to smaller die sizes to reduce manufacturing costs and increase storage density, 3D NAND flash memory faces reliability challenges due to aggressive scaling, leading to issues with data integrity and error correction, particularly in double programming events where memory cells may be incorrectly programmed or verified.
Innovation Solution
Implementing a redundant backup method using NAND self-verification, where first and second pages in a NAND flash memory device are programmed redundantly with multiple programming and verifying operations, and a read operation is performed by the device to self-verify the data, allowing for immediate detection of errors and reducing the time burden of external verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If memory devices are scaled to smaller die sizes to reduce manufacturing cost and increase storage density, then storage density and manufacturing cost are improved, but reliability and data integrity deteriorate due to process technology limitations and aggressive scaling
Solution Approach 1:
The patent performs preliminary verification actions during the programming process itself. The NAND flash memory device executes verification operations immediately after programming operations to detect and correct errors before data is considered fully stored, preventing error propagation and ensuring data integrity despite scaling challenges
Solution Approach 2:
The NAND flash memory device performs self-verification of programmed data using its internal resources without requiring external host intervention. The device's internal firmware executes read operations and error correction algorithms autonomously, allowing the system to maintain reliability through self-diagnosis and self-correction mechanisms
2Reliability
If redundant programming and verification operations are performed to ensure data integrity, then reliability is improved, but programming time and operational complexity increase
Solution Approach 1:
The patent merges the programming and verification operations into a single integrated process. Instead of separate programming and verification passes, the device performs verification immediately after each programming operation within the same operational sequence, reducing total time by eliminating idle transitions and overlapping operations
Solution Approach 2:
The verification operations continue seamlessly after programming without interrupting the operational flow. The device maintains continuous useful action by immediately transitioning from programming to verification mode, keeping the data path active and avoiding idle states that would increase total operation time
3Measurement precision
If external host devices perform read operations to verify programmed data, then data integrity can be confirmed, but the time required for verification increases significantly
Solution Approach 1:
The NAND flash memory device performs self-verification of programmed data using its internal read capabilities and firmware. This eliminates the need for external host devices to perform verification read operations, significantly reducing verification time while maintaining accurate error detection and correction through the device's internal error correction code (ECC) mechanisms
Data Source
AI summary
The present disclosure provides a method of data protection for a NAND memory. The method includes programming first and second pages of a NAND flash memory device according to programming data such that data stored in the first and second pages are redundant. The programming of the first and second pages includes a plurality of programming operations using a plurality of programming voltages and a plurality of verifying operations to determine whether programmed memory cells of the first page have threshold voltage levels according to the programming data. The method also includes determining a completion of the programming of the first and second pages based on each of the plurality of verification operations returning a pass result. The method also includes performing, after the determining, a read operation on the second page by the NAND flash memory device to self-verify the data stored at the second page.