Non-volatile Memory Select Gate Drift Compensation
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Solution Overview
Problem
Non-volatile memory devices using charge-trapping material face data retention issues due to structural defects and drift in select gates, leading to operational errors and potential loss of NAND strings.
Innovation Solution
The system tests select gates for abnormalities and converts non-select gate memory cells into select gates to maintain data integrity by operating them as supplemental select gates, ensuring continuous memory operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If select gates are used to control memory operations, then memory cell selection is enabled, but data retention deteriorates due to structural defects and drift in select gates
Solution Approach 1:
The patent monitors threshold voltage parameters of select gates over time and detects drift beyond predetermined ranges. When drift is detected, the system changes operational parameters by converting adjacent memory cells into supplemental select gates, thereby compensating for the degraded select gate and maintaining reliable memory operations
Solution Approach 2:
The patent proactively monitors select gate health through threshold voltage measurements and prepares compensatory measures in advance. By detecting drift before complete failure occurs and pre-converting adjacent memory cells into supplemental select gates, the system cushions against potential data loss and maintains continuous operational reliability
2Reliability
If select gates are monitored and converted memory cells are used as supplemental select gates, then data retention is improved, but device complexity increases
Solution Approach 1:
The patent implements a self-monitoring and self-healing mechanism where the memory system automatically detects select gate drift through threshold voltage measurements and autonomously converts adjacent memory cells into supplemental select gates without external intervention. This self-service approach manages the increased complexity internally while presenting a simplified interface to users
Solution Approach 2:
The patent makes adjacent memory cells multi-functional by enabling them to serve both as data storage cells and as supplemental select gates when needed. This universality allows the same physical structures to perform multiple functions, managing complexity by reusing existing components rather than adding dedicated monitoring and compensation hardware
Data Source
AI summary
A non-volatile memory system includes a plurality of groups of connected non-volatile memory cells (e.g., charge trapping memory cells), a select line, and a plurality of select gates connected to the select line. Each select gate is connected at an end (e.g. source end or drain side) of one of the groups of memory cells. The system includes one or more control circuits that are configured to determine whether the select gates are abnormal. If a select gate is determined to be abnormal, then one of the memory cells connected to the select gate is converted to operate as a select gate. The system will then perform memory operations by operating the converted memory cell as a select gate.