Memory Device Read Signal Voltage Adjustment for Cell Deterioration
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Solution Overview
Problem
Non-volatile memory devices face challenges in maintaining read reliability due to threshold voltage changes caused by cell deterioration, leading to errors in data storage and retrieval, especially in multi-level cell systems where small changes in threshold voltage can affect read reliability.
Innovation Solution
A memory device performs a dummy read operation to calculate the level of deterioration of memory cells by counting on-cells and off-cells using a cell counter and latches, and adjusts the read signal voltage based on the count values to correct for deterioration, thereby enhancing read operation reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dummy read operation is performed to detect cell deterioration, then read reliability is improved, but operation time is increased
Solution Approach 1:
The patent performs a dummy read operation before the actual read operation to detect cell deterioration in advance. This preliminary action allows the system to characterize the memory cell array's state and determine appropriate read voltage levels before real data is read, preventing read errors without delaying the actual data retrieval process.
Solution Approach 2:
The patent uses the results of the dummy read operation to feedback-adjust the read voltage levels for subsequent operations. By monitoring the distribution of read results from the dummy operation, the system determines optimal voltage thresholds that compensate for cell deterioration, creating a closed-loop system that adapts to aging effects.
2Reliability
If read signal voltage is adjusted based on cell deterioration, then data integrity is improved, but device complexity is increased
Solution Approach 1:
The patent dynamically adjusts the read signal voltage parameter based on the detected deterioration level of memory cells. Instead of using a fixed voltage, the system varies the voltage threshold according to the characteristic distribution obtained from dummy reads, allowing the same hardware to adapt to changing cell conditions without adding complex circuitry.
Solution Approach 2:
The memory device performs self-characterization through dummy read operations to understand its own state. The system uses its own read results to determine appropriate operating parameters, eliminating the need for external monitoring or complex control mechanisms while maintaining data integrity.
Data Source
AI summary
A memory device includes a page buffer unit including a plurality of latches latching each of a plurality of pieces of dummy data of selected memory cells according to a plurality of dummy signals provided by a word line of the selected memory cells, and a control logic comparing a count value of a first count latch among the plurality of latches with a reference count value, determining whether to count a second count latch other than the first count latch according to a result of the comparison, and correcting a level of a read signal provided by the word line of the selected memory cells in a read operation.