Flash Memory Data Compensation via Inter-Cell Interference Probability
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Solution Overview
Problem
As flash memory cells degrade over time, their threshold voltages shift, leading to increased misjudgment probability and data error rates during read cycles, especially after repeated erasures, as the cells' characteristics deviate from pre-defined slicing voltages.
Innovation Solution
A data compensating method that utilizes inter-cell interference (ICI) patterns to adjust the storing states of central cells by calculating and comparing the occurrence probabilities of ICI patterns within a defined statistic voltage range, thereby reducing data error rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If flash memory cells are used for repeated erasures and storage operations, then the storage capacity and durability are improved, but the threshold voltage shifts and misjudgment probability increases
Solution Approach 1:
The patent performs preliminary characterization of inter-cell interference patterns during manufacturing or initial operation. By pre-calculating and storing ICI patterns and their occurrence probabilities for different cell states, the system prepares compensation data in advance that can be quickly applied during read operations to correct threshold voltage shifts caused by degradation.
Solution Approach 2:
The patent implements a feedback mechanism where the actual read results and error patterns are used to refine the ICI pattern database. By continuously monitoring misjudgment occurrences and updating the occurrence probabilities of different ICI patterns, the system adapts to degradation over time and improves compensation accuracy for future read operations.
2Speed
If traditional reading methods are used without compensation, then the read operation is simple and fast, but the data error rate increases due to threshold voltage shifts
Solution Approach 1:
The patent pre-calculates ICI patterns and their occurrence probabilities during manufacturing or initial operation, storing this compensation data in lookup tables. During actual read operations, the system simply retrieves and applies the pre-computed compensation values based on the observed ICI pattern, avoiding complex real-time calculations while maintaining high read speed and low error rates.
Solution Approach 2:
The patent introduces an intermediary compensation mechanism that sits between the raw read signal and the final data interpretation. By using ICI pattern databases as an intermediary layer, the system translates degraded threshold voltage readings into corrected data values without requiring fundamental changes to the read operation itself, thus maintaining speed while improving reliability.
3Reliability
If ICI pattern compensation is applied to all cells, then the data error rate is reduced, but the computational complexity and processing time increase
Solution Approach 1:
The patent applies ICI pattern compensation selectively based on the specific cell state and observed interference patterns. Rather than uniformly processing all cells with the same compensation algorithm, the system identifies the relevant ICI pattern type for each cell and applies only the necessary correction from the corresponding database entry, reducing overall computational complexity while maintaining error correction effectiveness.
Solution Approach 2:
The patent implements a tiered compensation approach where full ICI pattern analysis is applied only when necessary (e.g., when error correction is actually needed), while routine reads use simpler verification. The system performs partial compensation for common cases and reserves full compensation processing for borderline or error-prone situations, optimizing the balance between reliability improvement and computational overhead.
Data Source
AI summary
A data compensating method for a flash memory is provided. Firstly, a first threshold voltage distribution curve of the cells of the flash memory with a first storing state is acquired. Then, a second threshold voltage distribution curve of the cells of the flash memory with a second storing state is acquired. Then, a first occurrence probability of a first type ICI pattern of the first storing state is calculated according to a statistic voltage range and the first threshold voltage distribution curve. A second occurrence probability of the first type ICI pattern of the second storing state is acquired according to the statistic voltage range and the second threshold voltage distribution curve. During a read cycle, storing states of central cells corresponding to the first type ICI pattern are compensated according to the first occurrence probability and the second occurrence probability.