Charge Loss Measurement Cell Wear Leveling
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Solution Overview
Problem
Flash memory devices face limitations in erase endurance, leading to uneven wear across memory blocks, which can result in data errors and reduced device lifetime due to the inability to accurately measure wear levels beyond simple erase cycles.
Innovation Solution
Implementing a method that measures threshold voltage changes in charge loss measurement cells to calculate an effective erase count, allowing for controlled wear leveling by identifying and managing the wear levels of memory blocks based on actual wear characteristics, including temperature and time since last operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple erase count is used to track memory block usage, then device complexity is reduced, but measurement precision of actual wear level deteriorates
Solution Approach 1:
The patent introduces charge loss measurement cells as intermediary structures between the memory blocks and the control logic. These measurement cells physically reflect the actual wear state of memory blocks through threshold voltage changes, providing an accurate mediator for wear assessment without requiring complex monitoring of each block's operational history
Solution Approach 2:
The patent replaces the mechanical/count-based tracking system (simple erase count) with an electrical measurement system (threshold voltage measurement). By substituting the mechanical counter with an electrical property measurement, the system achieves precise wear detection while maintaining relatively simple device architecture
2Reliability
If wear leveling is performed based on actual wear measurement, then reliability of data storage is improved, but device complexity increases
Solution Approach 1:
The charge loss measurement cells automatically reflect the actual wear state of memory blocks through their threshold voltage changes during normal operation. The system leverages this self-indicating property to enable accurate wear leveling without requiring external monitoring equipment or complex control mechanisms, thus improving reliability while minimizing added complexity
3Measurement precision
If threshold voltage measurement is performed on all memory blocks, then measurement precision of wear level is improved, but productivity of data operations deteriorates
Solution Approach 1:
The patent segments the wear measurement function by introducing dedicated charge loss measurement cells that are spatially separated from the main data storage cells. This segmentation allows the measurement cells to be accessed independently and quickly, providing precise wear information without requiring time-consuming measurements of all data cells, thus maintaining high data operation productivity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the performance and extends the lifetime of nonvolatile memory devices by maintaining uniform wear levels across memory blocks, preventing premature wear and data errors.
Implementation Method 1
measuring a threshold voltage change of the at least one charge loss measurement cell
Data Source
AI summary
A nonvolatile memory device comprises a memory core and a controller for controlling the wear level of a memory block in the nonvolatile memory device. The controller determines the wear level of a memory block by obtaining data of an actual wear level from a charge measurement cell of a selected region of the memory cell, and stores the wear level of the selected region in an erase count table.