Flash Memory Program Sequencing to Reduce Word Line Interference
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Solution Overview
Problem
As storage density increases in data storage devices like flash memory, cells become more susceptible to disturbances, leading to errors due to cell damage, charge leakage, and temperature effects, which existing technologies fail to adequately address.
Innovation Solution
A program sequencing method where memory cells on word lines are programmed in a monotonically increasing sequence, with cells on subsequent word lines being programmed to states above a threshold before those on previous word lines are programmed to states below the threshold, reducing word line interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If storage density is increased, then storage capacity is improved, but cell susceptibility to disturbances increases leading to higher error rates
Solution Approach 1:
The patent applies preliminary action by programming word lines in a specific sequence before reading operations. The controller programs word lines in an order that ensures lower-order word lines are programmed after higher-order word lines, preventing charge leakage-induced errors before they can occur during read operations.
2Ease of operation
If conventional programming sequences are used, then programming simplicity is maintained, but word line interference causes programming errors
Solution Approach 1:
The controller performs preliminary sequencing of word line programming operations. By establishing the correct programming sequence in advance (higher-order word lines before lower-order word lines), the system prevents word line interference without requiring complex real-time adjustments during programming.
3Device complexity
If charge leakage is allowed to occur naturally, then programming operations are simpler, but data integrity deteriorates due to cell state changes
Solution Approach 1:
The patent implements preliminary action by pre-determining and executing a specific programming sequence that prevents charge leakage from causing incorrect state changes. The controller ensures that word lines are programmed in reverse order (highest to lowest address) so that any charge leakage during the process cannot flip bits incorrectly, thereby preserving data integrity without adding complex error correction mechanisms.
Data Source
AI summary
Apparatuses, systems, methods, and computer program products are disclosed for program sequencing. An apparatus includes a block of non-volatile storage cells having a plurality of word lines. The word lines are organized into a monotonically increasing sequence. The apparatus includes a controller for the block. The controller is configured to program a set of storage cells of a word line to one or more storage states above a predetermined threshold and to program a set of storage cells of a previous word line adjacent to and before the word line in the sequence, to one or more storage states below the predetermined threshold after programming the set or storage cells of the word line to the one or more storage states above the predetermined threshold.