Nonvolatile Memory Selection Line Profile Control
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Solution Overview
Problem
The integration density of nonvolatile memory devices, particularly flash memory, is limited by the difficulty in controlling the depth and profile of channel holes with high aspect ratios, leading to performance deterioration and variations in memory cell performance.
Innovation Solution
A stacked structure with alternating conductive films and interlayer insulating films is used, where the selection line has distinct lower and upper portions with different sidewall profiles, and a method involving a mold structure with sacrificial films and etching stop films is employed to form a vertical channel structure, allowing precise control of channel hole formation and conductive film placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional channel hole formation methods are used, then manufacturing process is simpler, but manufacturing precision deteriorates due to difficulty in controlling depth and profile of high aspect ratio channel holes
Solution Approach 1:
The fabrication process is segmented into multiple sequential steps: forming the mold structure with sacrificial films, creating the trench, selectively removing portions of the mold structure, and forming conductive films in the resulting openings. This segmentation allows precise control of channel hole depth and profile at each stage, resolving the contradiction between manufacturing precision and process complexity.
Solution Approach 2:
The mold structure with sacrificial films is formed preliminarily before channel hole formation. This preliminary action establishes precise depth and profile control parameters that guide subsequent etching and conductive film formation, enabling high aspect ratio channel holes with controlled geometry without requiring complex real-time adjustment mechanisms.
2Quantity of substance
If channel holes with high aspect ratios are formed, then integration density is improved, but manufacturing precision deteriorates due to performance variations in memory cells
Solution Approach 1:
Different regions of the mold structure are assigned different local qualities through the use of sacrificial films with specific etch selectivity. The trench formation and selective removal steps create locally optimized conditions for channel hole formation, ensuring consistent depth and profile control across high aspect ratio structures, thereby maintaining manufacturing precision while achieving high integration density.
Solution Approach 2:
The invention utilizes parameter changes in the etching process by selectively removing portions of the mold structure based on etch selectivity differences between sacrificial films and other layers. This parameter-based control enables precise depth and profile formation in high aspect ratio channel holes, maintaining manufacturing precision while enabling higher integration density through increased vertical stacking.
3Ease of manufacture
If the selection line has uniform profile, then manufacturing is easier, but device complexity increases due to performance deterioration from inability to control channel hole formation
Solution Approach 1:
The selection line is segmented into a lower portion and an upper portion with different profiles. The lower portion extends deeper to enable precise channel hole formation, while the upper portion provides standard connectivity. This segmentation resolves the contradiction by maintaining ease of manufacture for the upper portion while achieving precise control for channel hole formation through the extended lower portion.
Solution Approach 2:
Different portions of the selection line are assigned different local qualities: the lower portion has extended depth for precise channel hole formation control, while the upper portion maintains standard profile for ease of manufacture and connectivity. This local differentiation resolves the contradiction between ease of manufacture and manufacturing precision by optimizing each portion for its specific function.
Data Source
AI summary
Nonvolatile memory devices and methods of fabricating the nonvolatile memory devices are provided. The nonvolatile memory devices may include a stacked structure including a plurality of conductive films and a plurality of interlayer insulating films stacked in an alternate sequence on a substrate and a vertical channel structure extending through the stacked structure. The plurality of conductive films may include a selection line that is closest to the substrate among the plurality of conductive films. The selection line may include a lower portion and an upper portion sequentially stacked on the substrate, and a side of the upper portion of the selection line and a side of the lower portion of the selection line may have different profiles.