Anti-Row-Hammer DRAM With Three-Phase Word Line Voltage Control
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Solution Overview
Problem
In dynamic random-access memory (DRAM) devices, the narrowing cell interval due to advancements in process technology leads to increased disturbances from adjacent cells and word lines, affecting data integrity and refresh characteristics, making it difficult to maintain reliable data access and storage.
Innovation Solution
A memory device with a three-phase word line controller that generates specific operating voltages to manage word lines, applying selected, first unselected, and second unselected voltages to different word lines to mitigate the row hammer effect and enhance data reliability, using a configuration that includes PMOS and NMOS transistors and sub-word line drivers to control voltage application based on row addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cell interval is narrowed to increase integration, then memory density is improved, but disturbance from adjacent cells and word lines increases affecting data integrity
Solution Approach 1:
The patent applies different voltage levels to different groups of word lines based on their proximity to the activated word line. Specifically, first unselected voltage is applied to first adjacent word lines, second unselected voltage is applied to second adjacent word lines, and third unselected voltage is applied to non-adjacent word lines. This localized differentiation of voltage levels protects vulnerable cells near the activated line while maintaining overall system density.
Solution Approach 2:
The patent changes the voltage parameter of unselected word lines based on their spatial relationship to the activated word line. By adjusting voltage levels (first unselected voltage, second unselected voltage, third unselected voltage) according to distance from the active line, the patent mitigates row hammer effects and maintains data integrity without sacrificing memory density.
2Reliability
If three-phase voltage control is implemented to protect against row hammer effect, then data reliability is improved, but device complexity increases
Solution Approach 1:
The patent segments the word lines into multiple groups based on their proximity to the activated word line: first adjacent word lines, second adjacent word lines, and non-adjacent word lines. Each segment receives a different voltage level, allowing targeted protection against row hammer effects while simplifying the control logic compared to individual control of each word line.
Solution Approach 2:
The patent dynamically adjusts the voltage levels of unselected word lines based on the activated word line's position and the spatial relationship between word lines. The three-phase word line controller dynamically assigns first, second, or third unselected voltages to different word line groups during each access operation, providing adaptive protection without requiring complex static control structures.
Data Source
AI summary
A memory device is provided that comprises: a memory cell array having a plurality of memory cells connected between a plurality of word lines and a plurality of column lines; a three-phase word line controller configured to generate a selected operating voltage, a first unselected operating voltage, and a second unselected operating voltage having a lower level than the first unselected operating voltage; and a row decoder connected to the plurality of word lines, configured to apply the selected operating voltage to an activated word line on the basis of a row address, and to apply the first unselected operating voltage or the second unselected operating voltage to a deactivated word line.