Non-Volatile Memory Voltage Control for Back Pattern Dependency
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Solution Overview
Problem
The back pattern dependency (BPD) effect in non-volatile memory devices reduces the read margin by changing the channel resistance of non-selected cells during the transition from program verification to read operation, making it difficult to discriminate between on-cells and off-cells, leading to potential read errors.
Innovation Solution
A method and device that apply different voltages during program verification and read operations, where a verification voltage is provided to the selected memory cell and a first pass voltage to non-selected memory cells during program verification, and a read voltage with a higher second pass voltage is applied to non-selected memory cells during the read operation, reducing the difference in channel resistance and improving the BPD effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high pass voltage is applied to non-selected memory cells during program verification, then the verification operation can be performed, but the channel resistance of non-selected cells changes during transition to read operation, reducing the read margin
Solution Approach 1:
The patent applies different pass voltages to non-selected memory cells depending on the operation mode: a first pass voltage during program verification and a second pass voltage during read operation. This parameter change compensates for the threshold voltage shift caused by back pattern dependency, maintaining consistent channel resistance and read margin across different operation transitions.
2Productivity
If the threshold voltage of non-selected cells changes due to data pattern transitions, then the program verification can proceed, but the channel resistance difference between program verification and read operation increases, making it difficult to discriminate on-cells from off-cells
Solution Approach 1:
The patent dynamically adjusts the pass voltage applied to non-selected cells based on the operation mode. By changing the voltage parameter from a first pass voltage during program verification to a second pass voltage during read operation, the patent compensates for threshold voltage shifts and maintains stable channel resistance, ensuring accurate cell discrimination throughout the operation sequence.
Data Source
AI summary
A non volatile memory device and method of operating including providing a verification voltage to a gate of a selected memory cell within multiple memory cells and providing a first pass voltage to a gate of a non-selected memory cell within the memory cells during a program verification operation; and providing a read voltage to the gate of the selected memory cell and providing a second pass voltage to the gate of the non-selected memory cell during a read operation. The second pass voltage is greater than the first pass voltage.