Nonvolatile Memory Erase Control Using GIDL String Selection
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Solution Overview
Problem
Existing nonvolatile memory devices face challenges in improving threshold voltage distribution and erase efficiency, particularly in flash memory-based storage devices, which affect the reliability and performance of storage solutions like eMMC, UFS, and SSDs.
Innovation Solution
The implementation of a nonvolatile memory device with ferroelectric material-based memory cells and a method utilizing Gate Induced Drain Leakage (GIDL) for selective erase operations, allowing for improved threshold voltage distribution and erase efficiency through incremental step pulse programming and bidirectional scatter collection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional erase operations are used in nonvolatile memory devices, then erase functionality is provided, but threshold voltage distribution is degraded and erase efficiency is limited
Solution Approach 1:
The patent applies different voltage parameters to different string selection lines during erase operations. Specifically, it uses a first erase voltage on a first string selection line and a second erase voltage (different from the first) on a second string selection line. This parameter differentiation enables bidirectional threshold voltage control, improving threshold voltage distribution while maintaining high erase efficiency through selective voltage application.
Solution Approach 2:
The patent implements localized erase operations by applying specific voltages to selected string selection lines while applying different voltages to unselected string selection lines. This local quality approach allows precise control over which memory strings are erased, improving both threshold voltage distribution for selected cells and overall erase efficiency by avoiding unnecessary operations on unselected cells.
2Manufacturing precision
If selective erase operations are implemented on smaller units, then erase precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the erase operation control by providing separate string selection lines for different string groups (first string selection line for first string group, second string selection line for second string group). This segmentation enables independent control of erase operations on different strings, achieving high erase selectivity while managing complexity through modular voltage control architecture.
Solution Approach 2:
The patent implements multi-functional string selection lines that can serve both selection and erase control purposes. The same string selection lines used for normal operation are also utilized for controlling erase voltages, reducing the need for additional dedicated control lines and thereby limiting the increase in device complexity despite enhanced selectivity.
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
Enhances erase inhibition efficiency and improves threshold voltage distribution by enabling selective erase operations on smaller units such as cells, strings, or planes, thereby improving the reliability and performance of storage devices.
Implementation Method 1
applying a Gate Induced Drain Leakage (GIDL) voltage to at least one string selection line corresponding to a selected string from among the plurality of strings
Implementation Method 2
each of the plurality of memory cells having a ferroelectric material
Data Source
AI summary
A method of operating a nonvolatile memory device includes applying a ground voltage to a selected wordline among the wordlines, applying an erase pass voltage to at least one unselected wordline among the wordlines, applying an erase voltage to a selected bitline among the bitlines, applying an erase prohibition voltage to an unselected bitline among the bitlines, and applying a Gate Induced Drain Leakage (GIDL) voltage to at least one string selection line corresponding to a string selected from among the plurality of strings.