Memory Refresh Control for Word Line Disturbance
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Solution Overview
Problem
As memory integration increases, the reduced interval between word lines leads to increased coupling effects, causing word line disturbance that damages data in memory cells connected to frequently activated word lines, resulting in data degradation before memory cells are refreshed.
Innovation Solution
A memory system with an address detection unit and control unit that identifies and refreshes word lines with high activation frequencies, activating adjacent word lines without separate commands or addresses to prevent data degradation and reduce the time required for refresh operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the interval between word lines is reduced to increase memory integration, then memory density is improved, but coupling effect between adjacent word lines increases causing word line disturbance
Solution Approach 1:
The patent applies preliminary action by detecting the activation history of word lines in advance and proactively refreshing adjacent memory cells before data degradation occurs. The memory controller monitors how many times each word line has been activated and preemptively refreshes neighboring cells that are at risk, preventing word line disturbance before it damages the data.
Solution Approach 2:
The patent implements feedback by continuously monitoring the activation history of word lines and using this information to control the refresh operation. The memory controller counts activations of each word line and adjusts the refresh strategy based on this feedback, refreshing adjacent cells selectively when a word line exceeds a predetermined activation threshold.
2Reliability
If frequent refresh operations are performed on all memory cells to prevent data degradation, then data reliability is improved, but the time required for refresh operations increases
Solution Approach 1:
The patent applies local quality by selectively refreshing only those memory cells that are adjacent to frequently activated word lines, rather than refreshing all memory cells uniformly. This targeted approach focuses refresh resources on the specific locations where word line disturbance is most likely to occur, improving data reliability where needed while minimizing unnecessary refresh operations elsewhere.
Solution Approach 2:
The patent uses partial action by performing refresh operations on only a subset of memory cells - specifically those adjacent to word lines with high activation counts. This partial refresh strategy is sufficient to prevent data degradation in the vulnerable regions without the time penalty of refreshing the entire memory array.
3Productivity
If selective refresh of adjacent word lines is implemented without commands or addresses, then refresh operation speed is improved, but control complexity increases
Solution Approach 1:
The patent applies self-service by enabling the memory controller to automatically manage the refresh process without external intervention. The controller autonomously monitors word line activation counts, identifies adjacent cells requiring refresh, and executes refresh operations independently, freeing the system from the need for external commands or addresses and improving refresh speed.
Solution Approach 2:
The patent implements universality by designing the memory controller to perform multiple functions: it manages normal read/write operations, monitors word line activation history, determines which cells need refreshing, and executes refresh operations. This multi-functional approach consolidates control logic within the memory controller, avoiding the need for separate control mechanisms and reducing overall system complexity.
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
Prevents word line disturbance by refreshing memory cells connected to frequently activated word lines, minimizing the time needed for refresh operations and enhancing memory system performance.
Implementation Method 1
As the interval between the word lines is reduced, a coupling effect between adjacent word lines increases
Implementation Method 2
data of a memory cell connected with a word line adjacent to a frequently activated word line is damaged. This is known as word line disturbance
Implementation Method 3
the amounts of charges of the cell capacitors CAPL-1 and CAPL+1 are changed, so that the data of the memory cells CL-1 and the CL+1 may be degraded
Data Source
AI summary
A memory includes a plurality of word lines each of which are connected to one or more memory cells, an address detection unit suitable for detecting a target address of a target word line among the plurality of word lines, wherein the target word line has an activation history satisfying a predetermined condition, and a control unit suitable for activating one or more word line among the plurality of word lines each time a refresh command is applied, and activating one or more adjacent word lines in response to a refresh command after detection of the target address, wherein the adjacent word line is adjacent to the target word line and identified by the target address.