Semiconductor Memory Word Line Disturbance Mitigation
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Solution Overview
Problem
As the integration of memory increases, the reduced space between word lines in semiconductor memory devices leads to increased coupling effects, causing data degradation in memory cells adjacent to frequently activated word lines, known as word line disturbance, which degrades data within expected retention time and requires separate addresses for refresh operations.
Innovation Solution
A semiconductor memory device with a row control unit that sequentially activates and precharges word lines with a high activation frequency, along with adjacent word lines, and a mode exit control unit that determines when to exit the target activation mode based on the number of activation operations, allowing for refresh without separate addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the space between word lines is reduced to increase integration, then the degree of integration increases, but the coupling effect between adjacent word lines increases causing data degradation
Solution Approach 1:
The patent applies preliminary action by performing refresh operations on adjacent word lines before data degradation becomes critical. The system identifies frequently activated word lines and proactively refreshes their adjacent neighbors, preventing coupling-induced data loss before it occurs during normal operation.
Solution Approach 2:
The patent implements local quality by applying different refresh strategies to different regions of the memory array. Specifically, memory cells adjacent to frequently activated word lines receive enhanced refresh operations, while other cells follow standard refresh protocols. This localized approach addresses coupling effects only where they occur most frequently.
2Reliability
If refresh operations are performed on adjacent word lines, then data degradation due to word line disturbance is prevented, but separate addresses are required increasing operation complexity
Solution Approach 1:
The patent implements self-service by enabling the memory device to automatically identify frequently activated word lines and determine which adjacent word lines require refresh operations. The system uses internal counters and detection logic to autonomously make refresh decisions without external controller intervention, eliminating the need for separate refresh addresses.
Solution Approach 2:
The patent applies universality by designing the row control unit to perform multiple functions: normal word line activation, identification of frequently activated word lines, determination of adjacent word lines needing refresh, and execution of refresh operations. This multi-functional approach consolidates what would otherwise require separate addressing mechanisms into a single integrated process.
3Productivity
If frequent activation of a word line occurs, then operational efficiency increases, but adjacent memory cells experience data degradation due to coupling effect
Solution Approach 1:
The patent implements feedback by using counters to monitor the activation frequency of each word line. When a word line exceeds a predetermined activation threshold, the system automatically triggers refresh operations on adjacent word lines. This closed-loop feedback mechanism dynamically adjusts refresh operations based on actual usage patterns, maintaining data integrity without sacrificing operational efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively prevents data degradation due to word line disturbance by refreshing memory cells connected to frequently activated word lines, reducing the time required to maintain data integrity and eliminating the need for separate addresses during the refresh process.
Implementation Method 1
the data of a memory cell may be degraded within an expected retention time of the memory cell to be refreshed
Data Source
AI summary
A semiconductor memory device includes a plurality of word lines each of which are connected to a plurality of memory cells, a row control unit suitable for sequentially activating and precharging a word line corresponding to a target address and a predetermined (N) number of adjacent word lines during a target activation mode, and a mode exit control unit suitable for counting the number of activation operations by the row control unit during the target activation mode to determine whether or not to exit from the target activation mode.