Sacrificial Memory Strings for Low-Latency Read Disturb Detection
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Solution Overview
Problem
Existing memory devices suffer from read disturb issues, leading to increased error rates and reduced performance due to the corruption of data on adjacent wordlines during frequent read operations, which conventional error detection methods struggle to address efficiently.
Innovation Solution
Incorporation of sacrificial strings within memory blocks, comprising sacrificial memory cells that do not store data, which are used to detect read disturb by shifting states when affected, allowing for a low-latency string sensing operation to identify and correct the issue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If frequent read operations are performed on memory devices, then data access speed is improved, but read disturb occurs causing data corruption on adjacent wordlines
Solution Approach 1:
The patent applies preliminary action by performing read disturb detection using sacrificial strings before data corruption occurs. The sacrificial strings are monitored during or between normal read operations to detect voltage shifts caused by read disturb, allowing the system to take corrective action (such as refreshing affected data) before actual data loss occurs, thus maintaining both high read speed and data integrity
2Device complexity
If conventional error detection methods are used, then device complexity is minimized, but detection latency increases reducing performance
Solution Approach 1:
The patent uses sacrificial strings as intermediary elements that specifically absorb and indicate read disturb effects. These sacrificial strings act as mediators between the read operation and the detection mechanism, providing early warning signals through voltage threshold shifts before actual data corruption occurs, enabling faster detection without requiring complex monitoring of all data bits
Solution Approach 2:
The sacrificial strings perform preliminary detection of read disturb conditions before they propagate to actual data storage locations. By monitoring these dedicated detection strings, the system can identify potential errors early and initiate corrective actions before they affect operational data, reducing overall detection latency
3Measurement precision
If sacrificial strings are added to detect read disturb, then detection capability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by separating the memory structure into functional data storage regions and dedicated detection regions (sacrificial strings). This segmentation allows the detection function to be implemented in isolated, standardized units that can be manufactured using existing processes, reducing overall manufacturing complexity while improving detection precision
Solution Approach 2:
The sacrificial strings serve multiple functions: they act as both structural elements of the memory array and as dedicated detection sensors for read disturb. This multi-functionality reduces the need for separate detection circuits and manufacturing steps, thereby improving detection capability without proportionally increasing manufacturing complexity
Data Source
AI summary
Control logic in a memory device determines to initiate a string read operation on a first memory string of a plurality of memory strings in a block of a memory array, the block comprising a plurality of wordlines, wherein the first memory string is designated as a sacrificial string. The control logic further causes a read voltage to be applied to each of the plurality of wordlines concurrently and senses a level of current flowing through the sacrificial string while the read voltage is applied. In addition, the control logic identifies, based on the level of current flowing through the sacrificial string, whether a threshold level of read disturb has occurred on the block.