Composite Metal Mask for High Aspect Ratio Etching
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Solution Overview
Problem
Current semiconductor manufacturing techniques face challenges in achieving high aspect ratio patterning and etching with non-metallic hardmasks, which often result in incomplete etching and pattern distribution issues due to low etching selectivity and thick mask layers.
Innovation Solution
A method using a metal mask with a lower tungsten metal layer and an upper titanium metal layer, where the etching selectivity is high, allowing for precise patterning and etching of the etching object layer with a CCP chamber, reducing the thickness of the hardmask and improving etching uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If non-metallic hardmasks are used for patterning, then the etching process can be performed, but the etching selectivity is low and the mask layer thickness is excessive, resulting in incomplete etching and pattern distribution issues
Solution Approach 1:
The patent uses a composite metal mask structure consisting of a tungsten layer and a titanium layer. The tungsten layer provides high etching selectivity and structural support, while the titanium layer enhances pattern definition and etching uniformity. This composite material approach resolves the contradiction by combining materials with complementary properties to achieve both complete etching and high selectivity.
Solution Approach 2:
The mask layer is segmented into multiple functional layers: a lower tungsten metal layer and an upper titanium metal layer. Each layer performs a specific function - the tungsten layer primarily provides etching selectivity and structural integrity, while the titanium layer optimizes pattern distribution and etching uniformity. This segmentation allows each layer to be optimized independently for its specific function.
2Strength
If the hardmask layer thickness is increased to improve pattern definition, then the mask durability is improved, but the etching selectivity decreases and pattern distribution issues occur
Solution Approach 1:
The composite metal mask structure with tungsten and titanium layers allows the mask to have sufficient thickness for durability while maintaining good pattern distribution. The tungsten layer provides structural strength and durability, while the titanium layer ensures uniform pattern distribution during etching, resolving the contradiction between mask durability and pattern distribution.
Solution Approach 2:
Different regions of the mask structure have different material compositions optimized for their specific functions. The lower tungsten layer is optimized for structural integrity and etching selectivity, while the upper titanium layer is optimized for pattern definition and uniform distribution. This local quality differentiation allows the mask to simultaneously achieve durability and precise pattern distribution.
3Device complexity
If a single metal layer is used for patterning, then the process complexity is reduced, but the etching selectivity and pattern uniformity are insufficient
Solution Approach 1:
The patent employs a composite metal mask structure with two distinct metal layers (tungsten and titanium) to achieve superior etching uniformity and selectivity. While the structure is more complex than a single layer, the combination of materials with different etching rates and properties enables precise control over the etching process, resulting in significantly improved manufacturing precision that justifies the increased complexity.
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 enables efficient and uniform etching of high aspect ratio features in semiconductor devices, reducing the thickness of the hardmask and mitigating pattern distribution issues, while ensuring complete etching of the lower metal layer and exposing the etching object layer effectively.
Implementation Method 1
disposing an etch structure, in which a lower metal layer and an upper metal layer are sequentially stacked, on an etching object layer in a capacitively coupled plasma (CCP) chamber
Data Source
AI summary
A patterning method using a metal mask includes sequentially forming a lower metal layer and an upper metal layer on an etching object layer, forming an upper metal mask, forming the upper metal mask including patterning the upper metal layer, forming a lower metal mask, forming the lower metal mask including patterning the lower metal layer using the upper metal mask, and patterning the etching object layer using the upper metal mask.