Multilayer Spacer for Lithography Footing Reduction
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Solution Overview
Problem
The challenge in semiconductor manufacturing is the occurrence of spacer footing during the anisotropic etching process in multiple pattern photolithography, which affects the reliability of using spacers as masks for transferring patterns to underlying layers, as the bottom portions of spacers may not be perpendicular and can extend excessively, leading to reliability issues.
Innovation Solution
A multilayer spacer is formed by conformably depositing and plasma treating spacer layers over mandrels, making them more compact and easier to etch, thereby reducing spacer footing and improving the anisotropic etching process, allowing for the use of the spacer as a reliable mask for patterning underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-layer spacer is formed and anisotropically etched, then the spacer can be used as a mask for patterning, but spacer footing occurs causing reliability issues
Solution Approach 1:
The spacer structure is divided into multiple layers (first spacer layer and second spacer layer) with different etch selectivities. The first spacer layer has higher etch selectivity than the second spacer layer, allowing the etching process to selectively remove material at different rates. This segmentation enables precise control over the etching profile, preventing spacer footing while maintaining the ability to use the spacer as a reliable patterning mask.
2Ease of manufacture
If anisotropic etching is performed on a conventional spacer, then the desired pattern transfer is achieved, but excessive horizontal extension (footing) occurs at the bottom
Solution Approach 1:
The etching process parameters are changed by introducing a multi-layer spacer structure with varying etch selectivities. The first spacer layer is designed with higher etch selectivity to be removed more readily, while the second spacer layer has lower etch selectivity to maintain structural integrity. This parameter change in etch selectivity across layers allows the bottom portions to remain substantially perpendicular to the underlying layer, eliminating excessive horizontal extension while preserving pattern transfer capability.
3Measurement precision
If multiple pattern lithography is used to achieve smaller pitch, then half-pitch resolution is achieved, but spacer footing creates reliability issues
Solution Approach 1:
The spacer structure uses composite material layers with different etch selectivity characteristics. The first spacer layer material is selected to have higher etch selectivity relative to the mandrel, while the second spacer layer material has lower etch selectivity. This composite structure enables the multiple pattern lithography process to achieve half-pitch resolution while the differential etch selectivity prevents spacer footing, thereby maintaining high process reliability.
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
The multilayer spacer approach enhances the reliability of the patterning process by reducing spacer footing, enabling the achievement of smaller line spacings and improving the overall process reliability in semiconductor device manufacturing.
Implementation Method 1
The multilayer spacer may be formed by conformably depositing one or more spacer layers over the mandrels and plasma treating each spacer layer after each deposition. The plasma treatment causes the spacer layers to become more compact (i.e., thinner) and easier to etch.
Data Source
AI summary
A method embodiment for patterning a semiconductor device includes forming a plurality of mandrels over a substrate, and forming a multilayer spacer layer over the plurality of mandrels. The multilayer spacer layer is formed by conformably depositing a spacer layer over the plurality of mandrels and treating the spacer layer with plasma. The plurality of mandrels is exposed by etching a top portion of the multilayer spacer layer, thereby forming a multilayer spacer.