3D Memory Stack Composition to Prevent Tier Collapse
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing memory array architectures face challenges in maintaining structural integrity and preventing tier collapse during the replacement of sacrificial silicon nitride with conducting material, particularly in regions near trenches, which can lead to electrical connectivity issues and reduced memory cell performance.
Innovation Solution
The method involves forming a vertical stack with alternating tiers of different compositions, including carbon-doped silicon nitride and silicon nitride, where carbon-doped silicon nitride is selectively etched and replaced with conducting material through trenches, while silicon nitride is replaced with conductive material, ensuring direct electrical coupling of channel material with the conductor tier and mitigating tier collapse risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sacrificial silicon nitride layers are replaced with conducting materials in existing memory array architectures, then electrical connections between memory cells are established, but structural integrity deteriorates leading to tier collapse
Solution Approach 1:
The patent applies local quality by differentiating the composition of silicon nitride layers across different vertical tiers. Lower tiers use carbon-doped silicon nitride while upper tiers use conventional silicon nitride. This local differentiation allows the lower tiers to provide structural support where it is most needed during the replacement process, while upper tiers maintain their original electrical functionality. The carbon doping specifically enhances the mechanical properties of the silicon nitride in critical support regions.
Solution Approach 2:
The patent employs composite materials by creating silicon nitride layers with carbon doping. This composite structure combines the electrical insulation properties of silicon nitride with the enhanced mechanical strength provided by carbon doping. The resulting material maintains the necessary electrical isolation while providing superior structural support during the conducting material replacement process, preventing tier collapse.
2Ease of manufacture
If conventional silicon nitride is used throughout the vertical stack, then manufacturing process is simplified, but tier collapse occurs during conducting material replacement
Solution Approach 1:
The patent implements local quality by applying carbon doping selectively to lower-tier silicon nitride layers while leaving upper-tier silicon nitride undoped. This approach maintains manufacturing simplicity for the majority of the structure while providing enhanced stability only where required. The selective doping process adds minimal complexity to the overall manufacturing workflow while dramatically improving tier stability during the critical replacement phase.
3Reliability
If carbon-doped silicon nitride is used in lower tiers, then resistance to etching increases preventing tier collapse, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by restricting carbon doping to only the lower-tier silicon nitride layers that require enhanced etch resistance. This localized approach provides the necessary protection against tier collapse during conducting material replacement in critical regions while avoiding unnecessary complexity in upper tiers. The selective application minimizes the overall manufacturing complexity increase.
Solution Approach 2:
The patent utilizes parameter changes by modifying the chemical composition of silicon nitride through carbon doping. This changes the material's etching resistance parameter, making it more resistant to the etching processes used during conducting material replacement. The parameter change is applied selectively to lower tiers, providing enhanced protection where the etching process poses the greatest risk of tier collapse.
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 enhances the structural integrity and electrical connectivity of memory arrays by preventing tier collapse and maintaining efficient channel-material coupling, thereby improving the performance and reliability of memory cells.
Implementation Method 1
carbon-doped silicon nitride in lower tiers and using selective etching to form etch-resistant materials alongside silicon nitride, followed by replacing these layers with conducting materials, thereby stabilizing the vertical stack and preventing tier collapse
Data Source
AI summary
A memory array comprising strings of memory cells comprises laterally-spaced memory blocks individually comprising a first vertical stack comprising vertically-alternating insulative tiers and conductive tiers. Strings of memory cells comprise channel-material strings that extend through the insulative tiers and the conductive tiers. A second vertical stack is aside the first vertical stack. The second vertical stack comprises insulative tiers collectively comprising at least two different compositions relative individual of the insulative tiers. Individual of the at least two different compositions comprise silicon nitride. One of the individual different compositions comprise carbon-doped silicon nitride having at least 0.5 atomic percent more carbon than atomic percent of carbon, if any, in the silicon nitride of another of the individual different compositions. Other embodiments, including method, are disclosed.