Flash Memory Dummy Cell Voltage Control
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Solution Overview
Problem
Flash memory devices experience program disturbance due to gate-induced drain leakage (GIDL) and hot electron injection, which affect the programming of normal memory cells when dummy memory cells are not properly managed, leading to voltage imbalances and over-erasure issues.
Innovation Solution
Incorporating dummy memory cells with a distinct dummy pass voltage different from the normal pass voltage, and controlling their programming operations before and after erase operations to prevent program disturbance by maintaining threshold voltages within a given range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dummy memory cells are programmed using the same pass voltage as normal memory cells, then the programming process is simple, but program disturbance occurs due to voltage imbalances and GIDL effects
Solution Approach 1:
The patent applies different pass voltages to different types of memory cells (normal vs. dummy) based on their specific requirements. Normal memory cells use a first pass voltage optimized for their programming characteristics, while dummy memory cells use a second pass voltage tailored to their specific function of preventing GIDL and hot electron effects. This localized differentiation resolves the contradiction by sacrificing uniformity for reliability.
Solution Approach 2:
The patent changes the electrical parameter (pass voltage) when programming dummy memory cells compared to normal memory cells. By adjusting the pass voltage parameter specifically for dummy cell programming, the system prevents voltage imbalances and associated program disturbance effects, thereby improving reliability without significantly complicating the overall programming process.
2Ease of manufacture
If dummy memory cells are not programmed, then the programming process is simpler, but GIDL and hot electron injection cause program disturbance in normal memory cells
Solution Approach 1:
The patent performs preliminary programming of dummy memory cells before or after programming normal memory cells. This preliminary action ensures that dummy cells are in the appropriate state to prevent GIDL and hot electron injection during the programming of normal cells. The dummy cells act as a buffer or control element that mitigates harmful effects before they can affect normal memory cell operation.
Solution Approach 2:
Dummy memory cells serve as an intermediary element between the programming operations and the harmful GIDL/hot electron effects. By programming dummy cells with a specific pass voltage, they create a protective state that mediates the interaction between programming signals and normal memory cells, thereby reducing harmful effects without directly participating in the main programming function.
3Device complexity
If a single pass voltage is used for all memory cells, then the control process is simpler, but threshold voltage distribution becomes uncontrolled leading to over-erasure issues
Solution Approach 1:
The patent implements different control parameters (pass voltages) for different memory cell types. Normal memory cells receive a first pass voltage optimized for their threshold voltage characteristics, while dummy memory cells receive a second pass voltage tailored to their specific control function. This local differentiation enables precise control of threshold voltage distribution for each cell type, resolving the contradiction between control simplicity and precision.
Solution Approach 2:
The patent segments the memory cell population into normal cells and dummy cells, each with distinct programming requirements. By segmenting the control process to address each segment separately with appropriate pass voltages, the system achieves precise threshold voltage control without excessive overall complexity. The segmentation allows targeted optimization for each cell type's specific needs.
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 program disturbance in normal memory cells, maintains threshold voltages of dummy memory cells within a specified range, and enhances the operating performance of flash memory devices by reducing GIDL and hot electron generation.
Implementation Method 1
programming the normal memory cells, and programming the dummy memory cells. A dummy pass voltage used for programming the dummy memory cells is different from a normal pass voltage used for programming the normal memory cells.
Implementation Method 2
Flash memory devices experience program disturbance due to gate-induced drain leakage (GIDL) and hot electron injection
Implementation Method 3
controlling their programming operations before and after erase operations to prevent program disturbance by maintaining threshold voltages within a given range
Implementation Method 4
Flash memory devices experience program disturbance due to gate-induced drain leakage (GIDL) and hot electron injection
Data Source
AI summary
Disclosed is an operating method of a flash memory device, which includes normal memory cells and dummy memory cells. The operating method includes programming the normal memory cells and programming the dummy memory cells. A dummy pass voltage used for programming the dummy memory cells is different from a normal pass voltage used for programming the normal memory cells.