Memory Device Word Line Voltage Sequencing for Read Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The reliability of read operations in memory devices is compromised due to the improper application of voltages to word lines, leading to incorrect data retrieval and potential misinterpretation of memory cell states.
Innovation Solution
A memory device and operating method that apply sub-pass voltages to adjacent word lines before applying target pass voltages and a read voltage to the selected word line, ensuring a stable channel length and accurate data sensing by controlling the voltages applied to unselected word lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If target pass voltages are applied to all unselected word lines simultaneously, then the read operation can be completed quickly, but the channel length becomes unstable leading to incorrect data retrieval
Solution Approach 1:
The patent segments the unselected word lines into two groups: adjacent word lines (closer to the selected word line) and other unselected word lines (farther from the selected word line). Different pass voltages are applied to each group sequentially, with adjacent word lines receiving sub-pass voltages first, then target pass voltages after the selected word line is activated. This segmentation resolves the contradiction by maintaining stable channel length in adjacent regions while still completing the read operation efficiently.
Solution Approach 2:
The patent applies sub-pass voltages to adjacent unselected word lines before applying the read voltage to the selected word line. This preliminary action prepares the channel structure in advance, preventing channel length instability when the read voltage is subsequently applied. The sub-pass voltages are applied at a timing earlier than the read voltage, ensuring that the channel is properly formed before data sensing begins.
2Reliability
If pass voltages are applied to unselected word lines before the selected word line, then the channel length is stabilized, but the read operation timing becomes complex
Solution Approach 1:
The patent applies different pass voltages (sub-pass voltages vs. target pass voltages) to different groups of unselected word lines based on their proximity to the selected word line. Adjacent word lines receive sub-pass voltages first, while other unselected word lines receive target pass voltages. This local differentiation simplifies the timing control compared to a uniform approach, as each group can be controlled independently with appropriate voltage levels.
Solution Approach 2:
The patent changes the voltage parameter applied to unselected word lines based on their position relative to the selected word line. By using sub-pass voltages for adjacent word lines and target pass voltages for other unselected word lines, the patent optimizes both channel stability and timing control. The voltage levels and application timing are adjusted as parameters to resolve the contradiction between reliability and control complexity.
Data Source
AI summary
There are provided a memory device and an operating method of the memory device. The memory device includes: a plurality of pages each comprising a plurality of memory cells; a peripheral circuit for, in a read operation of a selected page among the pages, applying a read voltage to a selected word line connected to the selected page, sequentially applying sub-pass voltages and target pass voltages higher than the sub-pass voltages to adjacent word lines adjacent to the selected word line, and applying the target pass voltages to the other unselected word lines; and a control circuit for controlling the peripheral circuit. Before the read voltage is applied to the selected word line, the control circuit controls the peripheral circuit to apply the sub-pass voltages to the adjacent word lines, and apply the target pass voltages to the other unselected word lines.