Semiconductor Memory Self-Refresh with Idle-State Row-Hammer Care
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Solution Overview
Problem
Semiconductor memory devices like DRAM suffer from row-hammer attacks that compromise data retention due to charge leakage, necessitating care refresh operations which reduce self-refresh performance efficiency.
Innovation Solution
A semiconductor memory device and method that performs a care refresh operation upon receiving a self-refresh exit command, determining the refresh operation status, and executing the care refresh only when in an idle state, ensuring it does not interfere with the self-refresh cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a care refresh operation is performed to defend against row-hammer attacks, then data retention reliability is improved, but self-refresh performance efficiency deteriorates
Solution Approach 1:
The patent applies preliminary action by performing the care refresh operation in advance during the self-refresh exit period, before the self-refresh cycle would normally proceed. By proactively refreshing victim cells during this idle window, the system prevents charge leakage issues before they affect data retention, while avoiding interference with the main self-refresh performance
2Reliability
If a separate care refresh sequence is executed, then row-hammer defense capability is improved, but refresh operation speed deteriorates
Solution Approach 1:
The patent merges the care refresh operation with the self-refresh exit sequence by integrating the care refresh control logic into the existing self-refresh control circuitry. This combination allows the care refresh to be executed as part of the normal self-refresh operation flow, eliminating the need for separate refresh sequences and maintaining high refresh operation speed while providing row-hammer defense
3Reliability
If care refresh is performed during self-refresh cycle, then victim cell charge restoration is improved, but self-refresh efficiency deteriorates
Solution Approach 1:
The patent extracts the care refresh operation from the main self-refresh cycle by executing it specifically during the self-refresh exit period when the refresh controller would otherwise be idle. This extraction ensures that victim cell charge restoration is achieved without consuming additional energy or time from the active self-refresh cycles, thereby maintaining self-refresh efficiency
Data Source
AI summary
A self-refresh method of a semiconductor memory device including: receiving a self-refresh entry command; performing a self-refresh cycle based on the self-refresh entry command; receiving a self-refresh exit command; based on receiving the self-refresh exit command, determining a refresh operation status; and based on determining that the refresh operation status indicating an idle state, executing a care refresh operation corresponding to row-hammer care.