3D Memory Channel Programming Direction Control
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Solution Overview
Problem
In channel-stacked 3D memory devices, determining an appropriate pre-charge voltage for the well region is challenging due to variations in threshold voltages between cells, affecting programming efficiency.
Innovation Solution
Programming the first group of cells in a bottom-to-top direction and the second group of cells in a top-to-bottom direction, with a control unit managing the bit lines and dummy layers to optimize electron drainage and boosting voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If bit line pre-charge or well region pre-charge is performed to increase boosting voltage of unselected memory strings, then the boosting voltage increases, but it becomes difficult to decide an appropriate pre-charge voltage due to threshold voltage variations between cells
Solution Approach 1:
The memory device is divided into two separate channels (first channel and second channel) stacked vertically, with each channel processed independently during programming. This segmentation allows different programming directions to be applied to each channel, resolving the voltage control issues caused by threshold variations across all cells.
Solution Approach 2:
Instead of programming all cells in a uniform bottom-to-top direction, the invention programs the first channel in bottom-to-top direction while programming the second channel in top-to-bottom direction. This inverted approach in one channel compensates for voltage distribution issues, providing better control over boosting voltage without requiring complex pre-charge voltage decisions.
2Quantity of substance
If channel-stacked 3D memory device is fabricated with middle dummy layer to maximize memory density, then memory density increases, but programming complexity increases due to need for bidirectional programming
Solution Approach 1:
The programming operation is segmented into two independent directional processes: bottom-to-top programming for the first channel and top-to-bottom programming for the second channel. The control unit manages these separate programming sequences, making the complexity of bidirectional programming systematic and manageable rather than chaotic.
Solution Approach 2:
The control unit is configured to coordinate the programming sequences in advance, determining which channel receives bottom-to-top programming and which receives top-to-bottom programming. This preliminary organization of programming directions simplifies the overall control logic despite the increased structural complexity from the stacked channel configuration.
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 allows for more precise control of electron drainage and increased boosting voltage for unselected memory strings, enhancing programming efficiency and flexibility in pre-charge voltage selection.
Implementation Method 1
the cells are programed in a direction from bottom to top with the middle dummy layer biased at a specific voltage level, thereby allowing the electrons to be drained by the bit line
Data Source
AI summary
In a channel-stacked memory device which includes a first channel stacked on a second channel, the first channel is programmed in a bottom-to-top direction and the second channel is programmed in a top-to-bottom direction. The electrons in the first channel may be drained by a bit line, while the electrons in the second channel may be drained by a well region.