Semiconductor Memory Device Threshold Voltage Distribution Error Correction
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Solution Overview
Problem
Flash memory devices face errors due to overlapping voltage distributions, leading to reduced distance between adjacent voltage distributions and increased likelihood of data output discrepancies, which are challenging to correct with limited error correction methods.
Innovation Solution
A semiconductor memory device that converts threshold voltage positions in overlapping voltage distributions into position information codes and performs error correction using these codes to accurately determine data states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the distance between adjacent voltage distributions is reduced to enable low power consumption operations, then power consumption is reduced, but the overlapping portion between voltage distributions increases leading to higher error rates
Solution Approach 1:
The patent divides the threshold voltage distribution into multiple segments by introducing intermediate threshold voltages (ITVs) between adjacent voltage distributions. These ITVs create distinct regions that separate overlapping voltage distributions, allowing the system to maintain low power consumption while reducing errors through improved voltage discrimination. The segmentation transforms a single overlapping distribution into multiple distinguishable segments.
Solution Approach 2:
The patent introduces intermediate threshold voltages (ITVs) as intermediary elements between adjacent voltage distributions. These ITVs act as mediators that resolve the conflict between reduced voltage distance and increased overlapping. By positioning ITVs in the overlapping regions, the system can accurately distinguish between adjacent voltage levels even when they are closely spaced, thereby maintaining data accuracy while enabling low power operation.
2Quantity of substance
If multiple determination voltages are used to distinguish multi-bit data in memory cells, then data storage capacity increases, but the complexity of voltage distribution management and error correction increases
Solution Approach 1:
The patent segments the multi-bit data storage by dividing the threshold voltage range into multiple distinct regions using intermediate threshold voltages. Each region corresponds to a specific data state, and the ITVs create clear boundaries between these regions. This segmentation simplifies the management of voltage distributions by providing well-defined separation points, making it easier to distinguish between multiple data states without increasing system complexity.
Solution Approach 2:
The patent changes the voltage parameters by introducing intermediate threshold voltages that modify the voltage distribution characteristics. These ITVs alter the voltage landscape to create distinct, separable regions for multi-bit data storage. By adjusting and introducing these intermediate voltage levels, the system can manage complex multi-bit storage while maintaining clear distinction between data states, thereby reducing the complexity of voltage distribution management.
3Reliability
If error correction codes are used to correct data errors from overlapping voltage distributions, then data accuracy improves, but the number of bits required for error correction is limited and may not suffice for highly overlapping distributions
Solution Approach 1:
The patent applies preliminary action by introducing intermediate threshold voltages before the read operation to prevent errors from occurring in the first place. Rather than relying solely on post-read error correction, the ITVs are positioned to proactively separate overlapping voltage distributions, ensuring that the sensed data is already distinguished and less prone to errors. This preventive approach reduces the burden on error correction codes and extends the effective correction capability.
Solution Approach 2:
The patent adds another dimension to error handling by introducing intermediate threshold voltages as an additional layer of discrimination beyond traditional ECC methods. This dimensional addition creates a new voltage space that separates overlapping distributions, effectively extending the error correction capability without being constrained by the limited number of correction bits. The ITVs provide an extra degree of freedom in distinguishing data states.
Data Source
AI summary
A semiconductor memory device includes an information generation unit configured to convert positions of threshold voltages of memory cells in threshold voltage distributions based on determination voltages included in an overlapping portion between the threshold voltage distributions to generate a plurality of position information codes, and an error correction unit configured to sequentially receive the plurality of position information codes and perform an error correction operation for data of the memory cells.