Memory Controller Recovery Read for Defective Word Line Failures
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Solution Overview
Problem
Existing semiconductor memory devices face challenges in recovering data when a word line defect occurs during a program operation, leading to incomplete programming and data loss due to short paths between word lines.
Innovation Solution
A method involving a controller that transmits an erase command to partially erase affected pages, followed by a recovery read command to read data from adjacent pages, and applies read voltage to both affected word lines to ensure data recovery, with error correction and reprogramming to another memory block if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a program operation is performed on a memory page, then data is programmed to the memory device, but if a word line defect occurs during programming, data loss occurs and the programmed data cannot be recovered
Solution Approach 1:
The controller performs a read operation immediately after a program operation to verify data integrity before deleting the data from the buffer memory. This preliminary verification action prevents data loss by detecting programming failures early, allowing the system to recover data from the memory device before the buffer memory is cleared.
Solution Approach 2:
The system implements a feedback mechanism where the read operation results are used to determine whether to retain or delete the data in buffer memory. When a read operation fails to retrieve the programmed data, the feedback triggers data recovery operations, including re-reading from the memory device and re-programming to a different memory block.
2Productivity
If data is deleted from buffer memory after successful program operation, then buffer memory space is freed, but if a word line defect is detected later, data recovery becomes difficult
Solution Approach 1:
The controller performs a read verification operation before deleting data from buffer memory, ensuring data integrity is confirmed while the data is still accessible. This preliminary check allows the system to maintain buffer memory utilization while preventing irreversible data loss by detecting issues before data deletion.
Solution Approach 2:
The read operation provides feedback on data integrity status, which controls the decision to delete or retain data in buffer memory. This feedback mechanism optimizes buffer memory utilization by retaining data only when verification succeeds, while enabling recovery procedures when verification fails.
3Reliability
If an erase operation is performed on a defective memory block, then further data loss is prevented, but the memory block becomes unusable
Solution Approach 1:
The system extracts or isolates the defective memory block from the usable memory space by performing an erase operation on it. This separation prevents the defective block from causing further data loss while removing it from the pool of usable memory, effectively protecting data integrity at the cost of reducing available memory capacity.
Solution Approach 2:
The erase operation on the defective memory block, while reducing usable capacity, converts the harmful defective block into a protective measure. By erasing the defective block, the system prevents potential data corruption from spreading to other memory areas, transforming a liability into a data protection mechanism.
Data Source
AI summary
A method of operating a controller includes transmitting a program command to a memory device, receiving a message indicating that a program operation corresponding to the program command is failed from the memory device, and transmitting an erase command for performing an erase operation on a page corresponding to the program command to the memory device in response to the message.