Self-Aligned Layer Patterning for Wider Dummy Gate Lines
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Solution Overview
Problem
Current lithographic processes and SAMP methods struggle to form lines wider than the spaces between them at a pitch not accessible by direct lithography, leading to irregular dummy gate profiles and issues with epitaxial growth in FinFET fabrication, where the hard mask spacers are exposed during fin recessing.
Innovation Solution
The SAMP process is modified by skipping the mandrel removal step, allowing the whole assembly of hard mask spacers and mandrels to be transferred, resulting in lines thicker than the spaces between them, which helps maintain the dummy gate's uniformity and protects it from etching during fin recessing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If standard SAMP process is used to form lines at sub-lithographic pitch, then line density is increased, but line width becomes equal to space width which is not always desired
Solution Approach 1:
The patent segments the patterning process into multiple stages: first forming mandrels at a relaxed pitch, then depositing spacers on mandrel sidewalls, and finally selectively removing either mandrels or spacers based on the desired final geometry. This segmentation enables independent control of line width and spacing, resolving the contradiction between manufacturing precision and adaptability.
Solution Approach 2:
The patent inverts the traditional approach by making the mandrels wider than the spacers, rather than making spacers equal to or narrower than mandrels. This inversion allows the final pattern to have lines wider than the spaces between them, achieving the desired geometry while maintaining sub-lithographic pitch.
2Manufacturing precision
If mandrels are removed after spacer deposition, then pattern transfer is achieved, but dummy gate profile becomes irregular and etching protection is lost
Solution Approach 1:
The patent performs preliminary actions by forming the mandrel-spacer assembly with mandrels intentionally made wider than the final desired line width. The mandrels serve as both the initial pattern definition and as ongoing protection for the dummy gate during subsequent etching steps, eliminating the need for separate protection layers and ensuring uniform dummy gate profiles.
Solution Approach 2:
The mandrels serve multiple functions: they define the initial pattern, provide sidewall support during spacer deposition, and continue to protect the dummy gate from etching during fin recessing. This multi-functionality resolves the contradiction between achieving accurate pattern transfer and maintaining dummy gate uniformity throughout the process.
3Productivity
If hard mask spacers are exposed during fin recessing, then etching protection is lost, but parasitic epitaxial growth occurs
Solution Approach 1:
The patent provides beforehand cushioning by designing the mandrel width to be greater than the spacer width, creating an overlapping region where mandrels extend beyond the spacers. This overlapping region acts as a protective cushion during fin recessing, preventing direct exposure of the dummy gate and eliminating the conditions that would lead to parasitic epitaxial growth.
Data Source
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AI summary
A method comprising the steps of: a. forming, by self-aligned multiple patterning, a first pattern of regularly spaced mandrels (4) on a layer (3) to be patterned, b. subsequently, forming hard mask spacers (5) on sidewalls of the mandrels (4), thereby forming a second pattern formed of assemblies (4,5) comprising a mandrel (4) and hard mask spacers (5) on sidewalls thereof, and c. subsequently, etching the second pattern in the layer (3) to be patterned.