Strip Process for High Aspect Ratio Structures
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Solution Overview
Problem
The removal of carbon hard masks from high aspect ratio structures during etching processes is challenging due to differences in mask thickness between patterned and unpatterned areas, leading to overstrip in patterned areas and damage to underlying layers, especially when using doped amorphous carbon masks which require higher selectivity.
Innovation Solution
A strip process involving the deposition of a polymer layer on high aspect ratio structures followed by a plasma strip process to remove both the polymer and doped amorphous carbon layers, reducing selectivity requirements and preventing overstrip by protecting the underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If doped amorphous carbon masks are used to enhance mask selectivity during etching, then etching selectivity is improved, but mask removal rate during traditional strip processes becomes much lower
Solution Approach 1:
The patent changes the chemical parameters of the strip plasma by introducing oxygen-containing gas (O2, O2/Ar, or O2/CF4 mixture) combined with reducing gas (H2, CH4, or C2H4). This parameter change enables efficient removal of doped amorphous carbon masks while maintaining the benefits of using doped masks during etching, thus resolving the contradiction between improved mask selectivity and reduced mask removal rate
Solution Approach 2:
The patent uses a composite plasma chemistry approach by combining oxygen-containing gas with reducing gas in specific ratios. This composite approach creates a plasma environment that can effectively strip doped amorphous carbon masks at high rates without damaging underlying layers, solving the removal rate problem while preserving the selectivity benefits of doped masks
2Reliability
If traditional strip processes are used to remove carbon hard masks, then complete mask removal is achieved, but overstrip occurs in patterned areas causing damage to underlying layers
Solution Approach 1:
The patent applies local quality control by using polymer deposition to selectively protect high aspect ratio structures in patterned areas during the strip process. The polymer coating is deposited only where needed (on the structures themselves) while leaving other areas exposed, enabling differentiated treatment that prevents overstrip damage to underlying layers while still achieving complete mask removal
Solution Approach 2:
The patent introduces polymer as an intermediary protective layer between the strip plasma and the high aspect ratio structures. This intermediary polymer layer acts as a sacrificial barrier that prevents the strip plasma from causing overstrip damage to the underlying structures, while allowing complete mask removal to occur
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 allows for efficient removal of doped amorphous carbon masks with reduced overstrip in patterned areas, maintaining the integrity of high aspect ratio structures and enhancing the feasibility of using doped amorphous carbon layers by enlarging the process window and lowering costs.
Implementation Method 1
removing at least a portion of the polymer layer and the doped amorphous carbon layer from the substrate using a plasma strip process
Implementation Method 2
depositing a polymer layer on at least a portion of a top end of a high aspect ratio structure on the substrate
Data Source
AI summary
Processes for removing a mask layer (e.g., doped amorphous carbon mask layer) from a substrate with high aspect ratio structures are provided. In one example implementation, a process can include depositing a polymer layer on at least a portion of a top end of a high aspect ratio structure on a substrate. The process can further include removing at least a portion of the polymer layer and the doped amorphous carbon film form the substrate using a plasma strip process. In example embodiments, depositing a polymer layer can include plugging one or more high aspect ratio structures with the polymer layer. In example embodiments, depositing a polymer layer can include forming a polymer layer on a sidewall of one or more high aspect ratio structures.