Semiconductor Memory Word Line Refresh Control
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Solution Overview
Problem
As memory device integration increases, word line disturbance causes data loss in semiconductor memory cells due to coupling effects between neighboring word lines, leading to potential data damage or loss before memory cell refreshment.
Innovation Solution
A semiconductor memory device with a detection block to identify word lines with high activation frequencies and a control block to sequentially refresh normal and redundancy word lines, including target and adjacent word lines, to prevent data loss from word line disturbance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the integration degree of memory device is increased, then the space between word lines becomes narrower and more memory cells can be packed, but the coupling effect between neighboring word lines increases causing data loss
Solution Approach 1:
The patent applies preliminary action by performing a refresh operation on the target word line and its adjacent word lines before data loss occurs. The detection block identifies word lines with high activation frequencies in advance, and the refresh operation is executed proactively to prevent coupling effects from causing data damage, thus resolving the contradiction between high density and data reliability.
2Productivity
If word line activation frequency is increased to improve data access speed, then productivity increases, but word line disturbance increases causing data damage
Solution Approach 1:
The patent implements feedback by using the detection block to continuously monitor the activation frequency of word lines. When a word line exceeds a predetermined activation threshold, the system provides feedback through the refresh operation to mitigate the harmful effects. This closed-loop approach allows high productivity through frequent activations while maintaining data integrity through automated refresh based on detected activation patterns.
3Reliability
If refresh operation is performed on all word lines continuously, then data integrity is maintained, but energy consumption and time loss increase
Solution Approach 1:
The patent applies local quality by performing refresh operations selectively only on word lines that meet specific criteria (detected by the detection block as having high activation frequencies) rather than uniformly refreshing all word lines. This localized approach maintains data integrity where needed while minimizing unnecessary energy consumption and time loss on word lines that do not require refresh, thus resolving the contradiction between reliability and energy 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
The solution effectively prevents data damage in memory cells by refreshing word lines with high activation frequencies and their neighbors, ensuring data integrity and minimizing losses due to word line disturbance.
Implementation Method 1
As the coupling effect between neighboring word lines increases, data may be affected in memory cells coupled to word lines that are adjacent to a frequently activated word line
Implementation Method 2
changes in the amount of charge stored in the cell capacitors CAPL−1 and CAPL+1 included in the memory cells CL−1 and CL+1 may increase, and data of the memory cells CL−1 and CL+1 may be damaged or even lost
Implementation Method 3
data may be damaged or lost as electromagnetic waves are generated by neighboring circuits that are toggling between active and non-active states. These electromagnetic waves may induce an increase or decrease in the charge of capacitors in neighboring memory cells
Data Source
AI summary
A semiconductor memory device includes a plurality of normal word lines and a plurality of redundancy word lines which are disposed adjacent to the normal word lines, a detection block suitable for detecting a first word line whose active history satisfies a predetermined condition and a second word line adjacent to the first word line as a target word line and a target neighboring word line, among the normal word lines and the redundancy word lines, and a control block suitable for sequentially refreshing the normal word lines and the redundancy word lines whenever a refresh command is applied, and additionally refreshing the target word line, the target neighboring word line and a normal word line adjacent to the redundancy word lines among the normal word lines.