Nonvolatile Memory Controller Selection Transistor Recovery
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Solution Overview
Problem
As semiconductor manufacturing advances, storage devices face challenges in maintaining reliability due to reductions in scale and changes in structure, leading to potential degradations in nonvolatile memory devices.
Innovation Solution
A storage device with a nonvolatile memory device and a controller that monitors and manages selection transistors, performing read operations and program operations to recover degraded transistors, ensuring reliable operation by adjusting critical values and performing recovery operations based on threshold voltage monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If semiconductor manufacturing technologies advance to increase integration and memory capacity, then storage device capacity increases, but reliability of storage devices degrades
Solution Approach 1:
The controller performs read operations on selection transistors before they fully degrade, and executes program operations to adjust their threshold voltages proactively. This preliminary maintenance approach prevents reliability degradation before it affects storage operations, addressing the contradiction by maintaining reliability while supporting high capacity through advanced manufacturing
Solution Approach 2:
The system continuously monitors the threshold voltages of selection transistors through read operations and uses this feedback to determine when program operations are needed. This closed-loop feedback mechanism ensures that selection transistor characteristics remain within acceptable ranges, maintaining reliability despite increased integration density
2Reliability
If selection transistors are monitored and program operations are performed frequently to maintain reliability, then storage device reliability improves, but device complexity increases
Solution Approach 1:
The controller monitors threshold voltage parameters of selection transistors and performs program operations when these parameters drift outside acceptable ranges. By focusing on specific electrical parameters rather than comprehensive transistor characterization, the system maintains reliability while limiting the increase in controller complexity to manageable levels
Data Source
AI summary
A storage device includes a nonvolatile memory device including memory blocks and a controller configured to control the nonvolatile memory device. Each of the memory blocks includes a plurality of cell strings each including at least one selection transistor and a plurality of memory cells stacked on a substrate in a direction perpendicular to the substrate. The controller controls the nonvolatile memory device to perform a read operation on some of selection transistors of a selected one of the memory blocks and to perform a program operation on the selection transistors of the selected memory block according to a result of the read operation.