Multi-Level Cell Read Voltage Adjustment for Error Reduction
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Solution Overview
Problem
As multi-level cells (MLCs) in non-volatile memories store more bits of information, the margin between threshold voltages for different states decreases, leading to overlapping distributions and increased errors during read operations due to external factors like coupling and leakage.
Innovation Solution
Modifying read voltages by applying a range of preliminary voltages between upper and lower limits for adjacent states to determine a read voltage that activates the minimum number of cells, thereby reducing errors by discriminating between states effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multi-level cells store more bits of information, then storage capacity is improved, but the margin between threshold voltages for different states decreases leading to overlapping distributions and increased errors
Solution Approach 1:
The patent applies preliminary read voltages to the multi-level cells before the actual read operation to determine which read voltage will activate the minimum number of cells. This preliminary action identifies the optimal read voltage that discriminates between adjacent states, preventing erroneous activations and reducing read errors while maintaining high storage capacity
Solution Approach 2:
The patent dynamically adjusts the read voltage parameter based on the stored data states. By modifying the read voltage applied to the word line according to the specific state being read, the system optimizes discrimination between adjacent threshold voltage distributions, thereby maintaining high read accuracy despite increased storage density
2Measurement precision
If read voltage is increased to discriminate between states, then state discrimination is improved, but adjacent states may be erroneously activated
Solution Approach 1:
The system performs a preliminary read operation with multiple candidate read voltages before the actual data read. This preliminary action identifies which read voltage produces the minimum number of activated cells, ensuring optimal state discrimination without causing erroneous activations of adjacent states
Solution Approach 2:
The patent uses feedback from the preliminary read operation to determine the optimal read voltage for the subsequent actual read. By monitoring which read voltage activates the minimum number of cells and using this information to adjust the read voltage for data retrieval, the system achieves precise state discrimination while minimizing errors
Data Source
AI summary
Methods of operating a multi-level non-volatile memory device can include accessing data, stored in the device, which is associated with read voltages and modifying the read voltages applied to a plurality of multi-level non-volatile memory cells to discriminate between states stored by the cells in response to a read operation to the multi-level non-volatile memory device. Related devices and systems are also disclosed.