Memory Controller Recovery of Failed Select Transistors
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Solution Overview
Problem
Existing storage devices often fail to maintain the reliability of select transistors, leading to unreliable access to storage areas due to threshold voltage failures in select transistors such as source and ground select transistors.
Innovation Solution
A memory controller and storage device system that identifies and programs select transistors in a fail state based on test read information, adjusting the number of recovery operations to restore them to a pass state, thereby improving reliability and minimizing delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If select transistors are not monitored and recovered, then device complexity is reduced, but reliability deteriorates due to threshold voltage failures
Solution Approach 1:
The memory controller performs test read operations to identify select transistors in fail state before they cause access failures. By detecting and recovering failed transistors in advance through preliminary testing and programming operations, the system prevents reliability degradation without requiring complex real-time monitoring mechanisms during normal operation
Solution Approach 2:
The memory controller autonomously identifies failed select transistors through test read operations and automatically recovers them by programming the identified transistors. This self-diagnosis and self-recovery mechanism improves reliability without requiring external intervention or complex additional hardware components
2Reliability
If all failed select transistors are recovered, then reliability is improved, but loss of time increases due to recovery operations
Solution Approach 1:
The memory controller identifies the specific number of select transistors in fail state and performs programming operations only on the identified transistors rather than all transistors. This partial action approach recovers reliability by addressing only the necessary failed components, minimizing unnecessary recovery operations and time loss
Solution Approach 2:
The system applies different treatment to different select transistors based on their individual threshold voltage states. By identifying and recovering only those transistors in fail state while leaving already-functional transistors unchanged, the system optimizes recovery time while maintaining reliability
Data Source
AI summary
An operation method of a storage device comprising a memory device that includes a memory block having a plurality of strings and a memory controller configured to control the memory device, the operation method includes identifying a number of select transistors in the fail state in the memory block, based on test read information indicating that a threshold voltage state of each of a plurality of select transistors included in each of the plurality of strings is the fail state, and programming the identified select transistors according to the number of select transistors in the fail state.