Storage Device Pass Voltage Adjustment for Read Reliability
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Solution Overview
Problem
As the integration degree of storage devices increases, their electrical characteristics degrade, leading to reliability issues during read operations due to increased internal resistance differences between source and drain areas in memory cell strings.
Innovation Solution
The storage device adjusts pass voltages applied to unselected word lines based on the position of the selected word line, applying a higher pass voltage to unselected word lines in the source area to compensate for internal resistance differences and prevent read disturbance, thereby improving the reliability of the read operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the integration degree of the storage device is increased, then the storage capacity is improved, but the electrical characteristics are degraded and reliability is deteriorated
Solution Approach 1:
The patent applies different pass voltages to different regions (source area vs. drain area) of the memory cell string based on the position of the selected word line. This local differentiation of voltage conditions compensates for the integration-induced electrical characteristic degradation by optimizing the read operation parameters for each specific region, thereby maintaining reliability while preserving high storage capacity.
2Device complexity
If a single pass voltage is applied to all unselected word lines, then the device complexity is reduced, but read disturbance occurs due to internal resistance differences
Solution Approach 1:
The patent implements local quality by applying different pass voltages (first pass voltage for drain area, second pass voltage for source area) to unselected word lines based on their position relative to the selected word line. This resolves the read disturbance caused by internal resistance differences while maintaining manageable device complexity through systematic voltage selection based on word line position.
Solution Approach 2:
The patent dynamically adjusts the pass voltage applied to unselected word lines based on the position of the selected word line. The control logic selectively applies either the first or second pass voltage depending on whether the selected word line is in the drain area or source area, making the voltage application adaptive and position-dependent to prevent read disturbance.
Data Source
AI summary
There are provided a storage device and an operating method thereof. A storage device includes a string including a plurality of memory cells, peripheral circuits for, in a read operation of a selected memory cell, applying a read voltage to a selected word line electrically coupled to the selected memory cell, and selectively applying a first pass voltage and a second pass voltage higher than the first pass voltage to unselected word lines electrically coupled to the other unselected memory cells according to a position of the selected word line, and a controller for controlling the peripheral circuits.