Memory Device Dummy Cell Voltage Control
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Solution Overview
Problem
During the program operation in nonvolatile memory devices, the threshold voltage of unselected memory cells can inadvertently increase due to the application of pass voltage, leading to inefficiencies in data storage.
Innovation Solution
The memory device includes a memory cell string with first and second channel areas and dummy memory cells connected between them. A program operation controller applies a first pass voltage to dummy word lines during the program operation, followed by a second pass voltage less than the first, and then applies a program voltage to the selected word line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a pass voltage is applied to unselected memory cells during program operation, then the threshold voltage of selected memory cells can be increased, but the threshold voltage of unselected memory cells may inadvertently increase
Solution Approach 1:
The memory cell array is divided into first memory cells in a first channel area and second memory cells in a second channel area positioned on the first channel area. Dummy memory cells are inserted between them in the second channel area. This segmentation allows different voltage conditions to be applied to different regions, preventing unintended threshold voltage increases in unselected cells while maintaining program operation effectiveness.
Solution Approach 2:
Dummy memory cells are introduced as intermediary elements between the first and second memory cells. These dummy cells act as a buffer that absorbs or redirects the pass voltage effects, preventing the pass voltage from inadvertently increasing the threshold voltage of unselected memory cells while allowing the program voltage to effectively increase the threshold voltage of selected memory cells.
2Object-generated harmful factors
If the magnitude of pass voltage is adjusted to prevent threshold voltage increase in unselected memory cells, then unintended voltage increases are reduced, but program operation efficiency may decrease
Solution Approach 1:
By segmenting the memory cell array into distinct first and second channel areas with dummy memory cells inserted between them, the patent enables selective voltage application. This allows the pass voltage to be effectively managed without reducing program operation efficiency, as the dummy cells provide a pathway to maintain necessary voltage levels for programming while preventing harmful effects on unselected cells.
Solution Approach 2:
The dummy memory cells serve as intermediaries that enable the system to maintain high program operation efficiency while preventing unintended threshold voltage increases. They provide a mechanism to apply pass voltage at levels sufficient for effective programming without causing harmful effects on unselected cells, thus resolving the efficiency-preservation trade-off.
3Manufacturing precision
If dummy memory cells are inserted between first and second memory cells, then threshold voltage distribution is improved, but device structure becomes more complex
Solution Approach 1:
The memory cell string is segmented into first memory cells, dummy memory cells, and second memory cells arranged in a specific sequence. This segmentation improves threshold voltage distribution by creating distinct zones that can be independently controlled, with dummy cells acting as buffers between the functional memory cell regions.
Solution Approach 2:
Dummy memory cells are inserted as intermediary elements between the first and second memory cells. While this increases structural complexity, it provides significant benefits by improving threshold voltage distribution and preventing unintended voltage increases. The dummy cells serve as buffer zones that simplify the overall voltage management strategy.
Data Source
AI summary
The present technology relates to an electronic device. A memory device according to an embodiment includes a memory cell string including first memory cells included in a first channel area, second memory cells included in a second channel area, and dummy memory cells connected between the first memory cells and the second memory cells, a peripheral circuit configured to perform a program operation of storing data in the first and second memory cells, and a program operation controller configured to control the peripheral circuit to apply a first pass voltage to a dummy word line connected to the dummy memory cells during the program operation, apply a second pass voltage less than the first pass voltage to the dummy word line, and then apply a program voltage to a selected word line among a plurality of word lines connected to the first and second memory cells.