Memory Device Monitoring for Targeted Row-Hammer Refresh
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Solution Overview
Problem
Volatile memory devices like DRAM experience data loss due to row hammering, where intense access to one word line affects adjacent cells, leading to voltage distribution issues and data loss in adjacent memory cells.
Innovation Solution
A memory device with a monitoring cell array that detects victim memory cell rows and performs a refresh operation based on generated bit data, including a refresh manager to execute row hammering and normal refresh operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the space between word lines is reduced to increase memory density, then manufacturing precision is improved, but row hammering susceptibility increases causing data loss
Solution Approach 1:
The patent applies preliminary action by performing a refresh operation on the victim memory cell row before data loss occurs. The monitoring cell array continuously monitors voltage levels and detects when a victim row is affected by row hammering, triggering a refresh operation in advance to prevent data loss. This is evident in the embodiment where the refresh manager performs a refresh operation on the victim memory cell row based on the victim memory address generated from monitored bit data.
2Reliability
If monitoring and refresh operations are added to prevent row hammering, then data retention is improved, but device complexity increases
Solution Approach 1:
The patent merges the monitoring function and refresh operation into a unified row hammering prevention system. The monitoring cell array, bit data decoder, and refresh manager work as an integrated system where monitoring bits are generated, decoded to identify victim rows, and trigger refresh operations automatically. This merging reduces overall system complexity compared to having separate independent monitoring and refresh systems.
Solution Approach 2:
The system applies self-service by using the memory device's own resources to detect and correct row hammering effects. The monitoring cell array uses the same memory structure to monitor itself, and the refresh operation is automatically triggered and executed by the memory device's internal refresh manager without requiring external intervention, making the system self-protecting.
3Reliability
If refresh operations are performed on all memory cell rows, then data retention is improved, but energy consumption increases
Solution Approach 1:
The patent applies local quality by performing refresh operations only on specific victim memory cell rows that are identified as being affected by row hammering, rather than refreshing all memory cell rows uniformly. The monitoring cell array monitors specific locations and the refresh manager targets only the affected rows based on decoded victim memory addresses, thereby reducing unnecessary energy consumption on rows that do not require refreshing.
Solution Approach 2:
The system performs partial action by executing refresh operations only on the necessary victim rows identified through monitoring, rather than performing excessive full-array refreshes. This selective approach refreshes only the minimum required portions of memory to prevent data loss, optimizing energy efficiency while maintaining data retention reliability.
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
Improves electrical characteristics by mitigating row hammering effects through targeted refresh operations, reducing data loss in volatile memory devices.
Implementation Method 1
the degree by which charges of a memory cell connected with one word line may be affected by a voltage distribution of an adjacent word line increases
Implementation Method 2
A volatile memory device such as a dynamic random access memory (DRAM) may determine data based on charges stored in a capacitor
Data Source
AI summary
A memory device, including a memory cell array including a plurality of memory cell rows; a monitoring cell array configured to detect a victim memory cell row of the plurality of memory cell rows, and to generate bit data; a bit data decoder configured to: receive the bit data, and based on the bit data, generate a victim memory address including address information about the victim memory cell row; and a refresh manager configured to perform a refresh operation on the victim memory cell row based on the victim memory address.