Multi-Level Flash Memory Controller Backup Repair Mechanism
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Solution Overview
Problem
In nonvolatile semiconductor memory systems, programming errors or malfunctions can result in permanent loss of data in multi-level cells, particularly affecting the least significant bit (LSB) when the most significant bit (MSB) programming fails, which compromises the performance and data integrity as integration density increases.
Innovation Solution
A nonvolatile memory system with a memory controller that includes a buffer memory, a repair memory, a fail position detector, and a repair unit to store and compare data, determining and repairing bit errors, and using backup mechanisms to recover data in case of programming failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-level nonvolatile memory cells are used to increase data storage capacity, then the amount of stored data per unit memory chip area increases, but programming errors can cause permanent data loss particularly affecting the least significant bit
Solution Approach 1:
The patent applies preliminary action by backing up the least significant bit (LSB) data to a separate backup location before programming the most significant bit (MSB). This advance preparation ensures that if MSB programming fails or causes data corruption, the original LSB data can be recovered from the backup location, preventing permanent data loss while maintaining high storage capacity.
Solution Approach 2:
The patent introduces an intermediary backup storage location that mediates between the multi-level memory cells and the data integrity requirement. This backup location acts as a protective intermediary, storing critical LSB data separately so that programming operations on MSB do not directly threaten the integrity of existing data, thus resolving the contradiction between high capacity and data reliability.
2Productivity
If integration density is increased to improve performance, then more data can be stored per chip, but programming errors and malfunctions become more frequent
Solution Approach 1:
The patent implements beforehand cushioning by creating a backup copy of LSB data before high-density programming operations. This cushioning mechanism absorbs the impact of programming errors that become more frequent at high integration densities, allowing the system to maintain high productivity while protecting against data loss from increased error rates.
Solution Approach 2:
The patent applies discarding and recovering by temporarily setting aside (discarding) the LSB data to a backup location during MSB programming operations. If programming errors occur, the original data can be recovered from the backup, enabling the system to handle higher programming error rates associated with increased integration density without permanent data loss.
3Productivity
If multi-bit data is programmed in memory cells, then storage efficiency improves, but bit errors in previously programmed data can occur due to programming failures
Solution Approach 1:
The patent applies preliminary action by backing up LSB data before attempting to program multi-bit data. This advance preparation ensures that if programming failures occur and cause bit errors in previously programmed data, the original information can be recovered from the backup, maintaining storage efficiency while preventing information loss.
Solution Approach 2:
The patent implements feedback by checking whether programming operations were successful and whether bit errors occurred in previously programmed data. Based on this feedback, the system can retrieve and restore original data from backup locations, thereby maintaining high storage efficiency while correcting programming-induced bit errors.
Data Source
AI summary
A nonvolatile memory system includes a host system, a memory controller, and a flash memory chip including multi-level flash memory cells. The memory controller includes a backup memory adapted to store a backup copy of previously programmed data from the multi-level flash memory cells when further programming of the multi-level flash memory cells fails. The backup copy of the previously programmed data is used to detect and correct any errors in the previously programmed data before reprogramming the previously programmed data to different multi-level memory cells in the nonvolatile memory system.