Non-volatile Memory Erase Verification Segmentation
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Solution Overview
Problem
Existing non-volatile memory devices face challenges in efficiently performing erase operations and verifying erase success across multiple string selection lines, leading to potential data loss and operational inefficiencies.
Innovation Solution
A method is introduced for operating non-volatile memory devices with vertically stacked memory cells, involving erase operations, erase verification, and fail column information storage to identify and address failed strings, ensuring thorough erase verification and preventing data loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If erase verification is performed on all strings across multiple string selection lines, then erase operation reliability is improved, but operation time increases
Solution Approach 1:
The erase verification process is segmented into multiple passes, each handling a subset of string selection lines. In each pass, only unverified strings are verified, allowing the operation to be divided into manageable chunks that can be processed systematically without requiring verification of all strings in a single time-consuming operation.
Solution Approach 2:
The method performs preliminary verification on subsets of strings in each pass, identifying and recording failed strings before proceeding to subsequent passes. This preliminary action on specific string selection lines allows the system to progressively verify all strings across multiple passes while tracking verification status to avoid redundant operations.
2Reliability
If failed strings are identified and stored for re-erasing, then data loss prevention is improved, but device complexity increases
Solution Approach 1:
A fail column information storage mechanism acts as an intermediary between the erase verification process and the re-erase operation. This intermediary component records which strings failed verification and guides subsequent re-erase operations, preventing data loss by ensuring that only failed strings are re-erased while avoiding unnecessary operations on already successful strings.
3Reliability
If multiple passes are used to verify different string selection lines, then erase completeness is improved, but processing time increases
Solution Approach 1:
The multiple-pass verification process maintains continuity of useful action by systematically progressing through different string selection lines in each pass. Each pass continues the verification work on unverified strings without interruption, ensuring that the entire set of strings is eventually verified while maintaining efficient use of processing resources across passes.
Data Source
AI summary
Provided is a method of operating a non-volatile memory device including a plurality of strings, each string including a plurality of memory cells vertically stacked on a substrate. The method includes performing an erase operation on memory cells corresponding to a plurality of string selection lines, performing an erase verification operation on first strings connected to a first string selection line from among the plurality of string selection lines, storing fail column information corresponding to a first fail string, which is erase-failed, from among the first strings, and performing an erase verification operation on second strings connected to a second string selection line from among the plurality of string selection lines, when the first strings are erase-passed.