Wide Word Lines in 3D Nonvolatile Memory
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Solution Overview
Problem
Conventional three-dimensional nonvolatile memory devices face performance degradation and increased fabrication difficulties due to word lines with smaller widths, which lead to higher resistance values.
Innovation Solution
The implementation of a nonvolatile memory device design where all word lines within memory blocks are shared and formed with a large width, connecting complete and half strings through pipe transistors, eliminating the need for insulators between adjacent blocks and allowing for broader word lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If word lines are made narrower to reduce area, then integration density is improved, but resistance increases and performance degrades
Solution Approach 1:
The patent transitions from two-dimensional word line arrangement to three-dimensional stacked arrangement. Multiple word lines are stacked vertically in the Z-direction, allowing narrow word lines in the planar view while maintaining large total width through vertical stacking. This resolves the contradiction by utilizing the third dimension to achieve both low area and low resistance.
Solution Approach 2:
The patent merges multiple word lines into a single stacked structure. Instead of having separate wide word lines, multiple narrow word lines are combined vertically through stacking, creating a unified three-dimensional word line structure that achieves both area efficiency and electrical conductivity.
2Area of moving object
If word lines are stacked to increase integration, then area utilization is improved, but fabrication difficulty increases
Solution Approach 1:
The patent segments the memory device into multiple memory blocks arranged in the X-Y plane, with each block containing complete and half strings. This segmentation allows independent fabrication and testing of each block while maintaining overall integration. The pipe transistors provide clear segmentation points for manufacturing processes.
Solution Approach 2:
The pipe transistors serve multiple functions: they connect complete strings to half strings, enable independent operation of memory blocks, and facilitate shared word line access. This multi-functionality simplifies the overall fabrication process by reducing the need for separate connection structures.
3Quantity of substance
If word lines have smaller width, then integration density is improved, but resistance increases
Solution Approach 1:
The patent uses vertical stacking in the Z-dimension to compensate for reduced planar width. Multiple narrow word lines stacked vertically provide sufficient total cross-sectional area to maintain low resistance while achieving high integration density in the planar view.
Solution Approach 2:
The patent creates a composite word line structure combining multiple conductive elements stacked vertically. This composite structure achieves both high integration density (narrow planar footprint) and low resistance (accumulated cross-sectional area) by combining the advantages of different dimensional configurations.
Data Source
AI summary
A nonvolatile memory device includes first to N-th memory blocks, wherein N is an integer and N≧3. Each memory block, of the first to N-th memory blocks comprises first to (M−1)-th strings, wherein each string, of the first to (M−1)-th strings, includes drain-side memory cells, source-side memory cells, and a pipe transistor connecting the drain-side memory cells and the source-side memory cells, where M is an integer and M≧2, and an M-th string, including drain-side memory cells formed adjacent to the first string, of a first to (M−1)-th strings, and including source-side memory cells formed adjacent to an (M−1)-th string of the first to (M−1)-th strings.