Nonvolatile Memory Block Erasure Detection and Bad Block Isolation
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Solution Overview
Problem
Repetitive erasure and program operations in nonvolatile memory devices degrade physical characteristics and reduce memory cell reliability, leading to decreased performance over time.
Innovation Solution
Implementing erasure detection units within nonvolatile memory devices to count and track the number of erasure operations on each memory block, designating blocks with excessive operations as 'bad' to prevent further use and maintain device reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If repetitive erasure and program operations are performed on memory blocks, then the memory device can be used extensively, but the physical characteristics of memory cells are degraded and reliability decreases
Solution Approach 1:
The patent applies preliminary action by detecting and counting erasure operations before the memory block becomes completely unreliable. The erasure detection unit monitors each erasure operation and increments a counter, allowing the system to proactively identify blocks approaching their reliability threshold before actual failures occur.
Solution Approach 2:
The patent implements feedback through the control unit that receives detection signals from erasure detection units, counts the number of erasure operations, and compares the count against a reference value. This feedback mechanism allows the system to dynamically adjust block status based on accumulated wear, ensuring reliable operation by preventing further use of degraded blocks.
2Reliability
If erasure detection units are added to each memory block to track erasure operations, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the monitoring function into discrete erasure detection units, with each unit assigned to a specific memory block. This modular approach allows independent tracking of each block's erasure count, enabling granular reliability management without requiring complete system redesign.
Solution Approach 2:
The erasure detection units are integrated directly into the memory block structure, allowing each block to self-monitor its own erasure operations. The detection units automatically generate detection signals when erasure voltages are applied, eliminating the need for external monitoring circuitry and reducing overall system complexity.
Data Source
AI summary
A nonvolatile memory device includes a plurality of memory blocks, a plurality of erasure detection units provided at the plurality of memory blocks, respectively, and configured to each detect erasure of the respective memory blocks, and a control unit configured to determine that a memory block is a bad memory block when a number of erasure operations performed on the memory block as detected by the respective erasure detection unit is greater than a reference value.