3D NAND Fabrication via Composite Mask Etching
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Solution Overview
Problem
Conventional methods for fabricating 3D NAND flash memory cells are complex and costly, limiting the efficiency and cost-effectiveness of semiconductor device production.
Innovation Solution
A method involving the formation of composite structures with laminated layers and the use of multiple mask layers for controlled etching, creating a stepped structure that reduces the number of etching steps and simplifies the fabrication process, while maintaining precise control over layer thickness and morphology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional methods are used for fabricating 3D NAND flash memory cells, then the fabrication process can be completed, but the process complexity and cost increase significantly
Solution Approach 1:
The patent combines multiple etching operations into a single etching step by using a composite mask structure with first and second mask layers having different etch selectivities. This allows simultaneous formation of contact holes through the first laminated layers and trench structures through the second laminated layers, reducing the number of separate etching steps and simplifying the overall fabrication process.
Solution Approach 2:
The composite mask structure serves multiple functions: it acts as an etch mask for different materials with different selectivities, defines multiple pattern geometries (contact holes and trenches), and enables sequential etching of different layer stacks. This multi-functional mask reduces the need for multiple separate masking and etching operations.
2Productivity
If multiple separate etching steps are performed, then precise control over different structures is achieved, but the fabrication time and cost increase
Solution Approach 1:
The patent enables continuous etching action by using a composite mask structure that allows a single etching step to simultaneously process multiple layer stacks with different etch rates. The first etch selectively removes material through the first mask layer while the second etch selectively removes material through the second mask layer, maintaining continuous productive action without interrupting for multiple separate etching cycles.
Solution Approach 2:
Multiple etching operations are merged into one continuous etching step by designing the composite mask with first and second mask layers that have different etch selectivities relative to their respective underlying layers. This allows simultaneous etching of contact holes and trenches in a single process step, doubling the productivity of the etching operation.
3Manufacturing precision
If simplified fabrication methods are used, then cost and time are reduced, but control over layer thickness and morphology may be compromised
Solution Approach 1:
The composite mask structure provides local quality control by having different mask layers with different etch selectivities for different underlying materials. The first mask layer provides precise control for etching through the first laminated layers, while the second mask layer provides precise control for etching through the second laminated layers. Each mask layer is optimized for its specific local etching requirement, maintaining high manufacturing precision.
Solution Approach 2:
The patent utilizes parameter changes in etch selectivity between different mask layers and their underlying substrates. By selecting materials with appropriate etch selectivity ratios, the process achieves precise control over etching depth and morphology for different layer stacks simultaneously. The etch selectivity parameters enable differentiated control without requiring separate etching steps.
Data Source
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AI summary
A semiconductor device and a method for fabricating the semiconductor device are provided. The method includes forming a first composite structure, including a plurality of first composite layers, on a substrate, and forming a second composite structure, including a plurality of second composite layers on a surface portion of the first composite structure. The method also includes forming a first mask layer covering a sidewall of the second composite structure and a surface portion of the first composite structure and exposing at least another surface portion of the first composite structure. In addition, the method includes forming a second mask layer, on a surface portion of the second composite structure and spaced apart from the first mask layer by a first annular opening. Further, the method includes etching a top first layer of the first composite layers and a top first layer of the second composite layers.