Shaping Codes for Memory Retention via Digit Pattern Encoding
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Solution Overview
Problem
Memory cells in non-volatile memory devices, such as NAND flash, experience degradation due to repeated program and erase cycles, leading to decreased data retention and reduced device lifespan.
Innovation Solution
A shaping code system that encodes received digit patterns into shaping digit patterns, adhering to a constraint limiting consecutive digit values, skewing programmed data states towards lower threshold voltage levels to enhance data retention and extend device lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If memory cells are subjected to repeated program and erase cycles, then memory device capacity and usage flexibility are improved, but memory cell performance degrades and data retention decreases
Solution Approach 1:
The patent applies preliminary action by encoding data before programming to prevent degradation issues before they occur. The encoder modifies the data pattern to reduce the likelihood of adjacent cells being programmed to extreme threshold voltage levels, thereby preemptively mitigating the wear and data retention problems that would result from repeated program/erase cycles.
2Quantity of substance
If adjacent memory cells are programmed to extreme threshold voltage levels, then data storage capacity is maximized, but lateral charge spreading increases and causes errors
Solution Approach 1:
The patent applies preliminary anti-action by using an encoder to prevent harmful data patterns before they are programmed to memory. The encoder identifies and modifies patterns that would cause adjacent cells to be programmed to extreme threshold voltage levels (000 or 111), thereby preemptively counteracting the lateral charge spreading effect that would otherwise occur during programming.
3Speed
If data is programmed without encoding constraints, then programming speed is maintained, but threshold voltage distribution becomes uneven and increases retention noise
Solution Approach 1:
The patent applies preliminary action by performing data encoding before the programming operation. This preliminary step shapes the data pattern to achieve a more uniform threshold voltage distribution across memory cells, reducing retention noise and improving data reliability without significantly impacting overall programming speed.
Data Source
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AI summary
Apparatuses and methods associated with shaping codes for memory are provided. One example apparatus comprises an array of memory cells and a shaping component coupled to the array and configured to encode each of a number of received digit patterns according to a mapping of received digit patterns to shaping digit patterns. The mapping of received digit patterns to shaping digit patterns obeys a shaping constraint that limits, to an uppermost amount, an amount of consecutive digits of the shaping digit patterns allowed to have a particular digit value.