3D Memory Programming Method for Hot Electron Injection Control
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Solution Overview
Problem
Three-dimensional semiconductor memory devices face challenges in maintaining reliability due to varying channel hole sizes caused by the etching process, leading to differences in electric fields across memory cells, which can result in hot electron injection (HCI) during programming operations.
Innovation Solution
A program method that prioritizes programming memory cells distant from the substrate first, adjusting word line voltages to prevent HCI by applying different pass voltages to unselected word lines based on their location relative to the selected word line, and incorporating a recovery phase to initialize channels and reduce negative boosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If memory cells are programmed in conventional order (closer to substrate first), then programming can proceed systematically, but hot electron injection occurs due to varying electric fields from different channel hole sizes
Solution Approach 1:
The patent inverts the conventional programming sequence by programming memory cells distant from the substrate first, then progressively programming cells closer to the substrate. This reversal of the programming order compensates for the varying channel hole sizes caused by etching, as cells farther from the substrate have larger channel holes and require different electric field conditions for successful programming.
Solution Approach 2:
The patent applies different pass voltages to different groups of unselected word lines based on their location relative to the selected word line. Specifically, a first pass voltage is applied to unselected word lines in a first group (distant from substrate) and a second pass voltage is applied to unselected word lines in a second group (closer to substrate). This local differentiation of voltage conditions addresses the spatial variation in channel hole sizes and prevents hot electron injection.
2Productivity
If uniform pass voltage is applied to all unselected word lines, then circuit operation is simplified, but programming efficiency varies across memory cells due to geometrical differences
Solution Approach 1:
The patent segments the unselected word lines into different groups based on their spatial location relative to the selected word line. The first group includes unselected word lines distant from the substrate, while the second group includes unselected word lines closer to the substrate. Each group receives a different pass voltage level, allowing optimized programming efficiency for each spatial zone without requiring completely individualized control of every word line.
Solution Approach 2:
The patent changes the pass voltage parameter applied to unselected word lines based on their location. By adjusting the voltage level (first pass voltage for distant word lines, second pass voltage for closer word lines), the patent compensates for the geometrical variations in channel hole sizes, ensuring consistent programming efficiency across all memory cells in the stack.
3Manufacturing precision
If memory cells closer to substrate are programmed first, then programming follows conventional sequence, but channel holes of different sizes experience inconsistent electric fields leading to HCI
Solution Approach 1:
The patent inverts the programming sequence to address the etching-induced geometrical variations. By programming cells distant from the substrate first and progressing toward cells closer to the substrate, the patent compensates for the systematic size variation in channel holes caused by the etching process, ensuring that each cell experiences appropriate electric field conditions for reliable programming.
Solution Approach 2:
The patent applies preliminary voltage conditions to unselected word lines before programming the selected memory cell. By pre-applying appropriate pass voltages to different groups of unselected word lines based on their location, the patent prepares the electric field environment in advance, preventing hot electron injection and ensuring programming reliability from the outset.
Data Source
AI summary
A program method of a non-volatile memory device, the non-volatile memory device including a peripheral circuit region and a memory cell region including a cell substrate and a cell string having memory cells stacked perpendicular to a surface of a cell substrate, the method includes performing a first program phase including programming a first memory cell connected to a first word line and applying a first pass voltage to other word lines above or below the first word line, and performing a second program phase including programming a second memory cell being connected to a second word line closer to the cell substrate, applying a second pass voltage to a first word line group below the second word line and applying a third pass voltage to a second word line group above the second word line, the second pass voltage being lower than the third pass voltage.