Nonvolatile Memory Word Line Voltage Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Nonvolatile memory devices experience data loss due to 'erase disturbing' during the erase operation, where unselected memory cells are inadvertently erased due to inadequate voltage boosting of floating word lines, leading to reduced reliability and potential malfunctions.
Innovation Solution
A nonvolatile memory device and method that includes a high voltage application unit to apply a high voltage to unselected word lines and float them during the erase operation, ensuring that unselected memory blocks are not erased by maintaining a sufficient voltage difference between the word lines and the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ground voltage is applied to word lines of a selected memory block during erase operation, then the erase operation can be performed on the selected block, but the voltage of floating word lines in unselected memory blocks is not adequately boosted, causing data loss in unselected blocks
Solution Approach 1:
The patent applies a preliminary positive voltage to the word lines of unselected memory blocks before the erase operation begins. This preliminary voltage boost prevents the word line voltages from dropping to levels that would cause unintended erasure, thereby counteracting the harmful effect before it occurs. The positive voltage is applied in advance to ensure that when the erase voltage is applied to the substrate, the floating word lines in unselected blocks maintain sufficient voltage to prevent data loss.
Solution Approach 2:
The patent changes the voltage parameter of the word lines in unselected memory blocks from a floating state (which results in inadequate voltage boosting) to a positively biased state. By actively controlling the word line voltage to be positive during the erase operation, the patent ensures that the voltage difference between the word lines and substrate is sufficient to prevent erasure in unselected blocks, thereby resolving the data loss issue.
2Device complexity
If word lines of unselected memory blocks are left in floating state during erase operation, then the structure is simple, but the voltage boosting is insufficient causing erase disturbing
Solution Approach 1:
The patent segments the control of word lines by memory block selection. Different voltage control strategies are applied to selected and unselected memory blocks: selected blocks receive ground voltage on word lines for erasure, while unselected blocks receive positive voltage on word lines to prevent erasure. This segmentation allows the system to achieve reliable erase operation without requiring complex global control mechanisms.
Solution Approach 2:
The patent enables the word lines of unselected memory blocks to self-regulate their voltage through the application of positive voltage, eliminating the need for complex external control circuits to actively manage the floating state. The positive voltage application unit provides the necessary voltage boost automatically, reducing the complexity of the control system while maintaining reliability.
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 effectively prevents data loss in unselected memory blocks during the erase operation, enhancing the reliability and integrity of the nonvolatile memory device by ensuring accurate data retention and operation.
Implementation Method 1
data of memory cells belonging to the selected memory block are erased by a voltage difference between the word lines and the substrate, i.e., a difference between the ground voltage applied to the word lines and the erase voltage applied to the substrate
Data Source
AI summary
A nonvolatile memory device includes a plurality of memory blocks and a high voltage application unit configured to apply a high voltage to a word line of a memory block unselected from among the plurality of memory blocks and float the word line, during the erase operation.