Memory Cell Programming with Concurrent Redundant Storage
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Solution Overview
Problem
In semiconductor memory devices, the challenge lies in ensuring data integrity during power loss events, particularly during multi-pass programming operations, where initial pages of data can be corrupted due to overlapping threshold voltage distributions and limited storage capabilities, leading to difficulties in distinguishing between data states.
Innovation Solution
The solution involves concurrently storing backup data in separate memory cells, either as Single-Level Cell (SLC) data or by encoding Multi-Level Cell (MLC) data into SLC data, allowing for recovery of initial pages in case of power loss. This is achieved through a first, foggy program pass followed by a second, fine program pass, where SLC data is stored in backup sets, enabling accurate data retrieval even after power loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If MLC programming is used to increase storage density, then storage capacity is improved, but data reliability deteriorates due to overlapping threshold voltage distributions and corruption during power loss events
Solution Approach 1:
The patent segments the programming process into multiple passes (first pass and second pass) and segments the data storage into primary memory cells and backup memory cells. The initial pages of data are programmed in the first pass, and additional pages are programmed in the second pass. Backup copies of the initial pages are stored separately to enable recovery if power loss occurs during the second pass, thus resolving the contradiction between storage density and data integrity.
2Reliability
If backup data is stored to protect against power loss, then data reliability is improved, but device complexity increases due to additional storage requirements
Solution Approach 1:
The patent applies preliminary action by storing backup copies of the initial pages of data before performing the second programming pass. This advance preparation ensures that if power loss occurs during the second pass, the data can be recovered from the backup copies without requiring complex error correction or data reconstruction mechanisms, thus improving reliability while managing device complexity.
3Manufacturing precision
If multi-pass programming is used to improve data states, then manufacturing precision is improved, but loss of time increases due to multiple programming operations
Solution Approach 1:
The patent performs preliminary programming of the initial pages of data in the first pass, establishing a foundation that enables faster second pass programming. The backup copies are also created during the first pass, allowing the second pass to proceed efficiently without requiring time-consuming error correction or data verification operations, thus reducing overall programming time while maintaining manufacturing precision.
Data Source
AI summary
Apparatuses and techniques are described for programming data in memory cells while concurrently storing backup data. One or more initial pages of data are programmed into both a primary block and a first backup block in a first program pass. A power loss then occurs which can corrupt the data or otherwise prevent reading of the one or more initial pages of data from the primary block. The one or more initial pages of data are read from the first backup block and used to perform a second program pass in which one or more additional pages of data are programmed into the primary block. Single bit per cell data can be stored in a second backup block to decode the one or more initial pages of data as read from the first backup block.