Memory Device Row Hammer Mitigation via Adjacent Word Line Refresh
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Solution Overview
Problem
As manufacturing processes for memory devices are scaled down, the interval between adjacent word lines narrows, leading to adverse effects on charges in memory cells connected to adjacent word lines due to repeated voltage distributions, resulting in data damage known as the row hammer phenomenon.
Innovation Solution
A memory device with a refresh manager that initializes a count for a row of the memory cell array, transmits a refresh command, writes first data during normal refresh operations, and writes second data into an adjacent word line when row hammering occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If manufacturing processes are scaled down to increase storage density, then the interval between adjacent word lines narrows, but repeated voltage distributions cause charges in adjacent word line memory cells to be adversely affected (row hammer phenomenon)
Solution Approach 1:
The refresh manager performs preliminary actions by detecting row hammer conditions and proactively refreshing adjacent word lines before data corruption occurs. The system monitors access patterns and preemptively executes refresh operations on vulnerable word lines to prevent charge leakage and maintain data integrity.
Solution Approach 2:
The refresh manager acts as an intermediary between normal refresh operations and row hammer protection. It detects when row hammer conditions occur and inserts specialized refresh operations into the refresh sequence, targeting adjacent word lines for additional protection without disrupting normal memory operations.
2Reliability
If normal refresh operations are performed repeatedly on the same word line, then data is maintained, but row hammer phenomenon occurs causing data loss in adjacent word lines
Solution Approach 1:
Instead of only refreshing the currently accessed word line, the system inverts the approach by also refreshing adjacent word lines. The refresh manager identifies adjacent word lines to the currently accessed word line and performs refresh operations on those as well, thereby preventing the row hammer effect from spreading to neighboring memory cells.
Solution Approach 2:
The refresh operation is segmented into different types: normal refresh operations for currently accessed word lines and protective refresh operations for adjacent word lines. The refresh manager divides the refresh task into these segments and executes them in sequence, ensuring both data maintenance and protection against row hammer effects.
Data Source
AI summary
A memory device includes a memory cell array having a plurality of word lines and a plurality of common source lines therein, which constitute a row. A refresh manager is provided, which is configured to perform a refresh operation for the memory cell array. The refresh manager is further configured to: (i) initialize a count for the row of the memory cell array, (ii) transmit a refresh command to the memory cell array, (iii) write first data into the row when the refresh operation for the memory cell array is a normal refresh operation, and (iv) write second data into a row associated with a word line adjacent to a word line in which row hammering has occurred, when the refresh operation for the memory cell array is not a normal refresh operation.