Perpendicular SRAFs for Lithography Mask Artifacts
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Solution Overview
Problem
Current lithography masks face challenges in producing semiconductor devices with small dimensions due to discrepancies between mask topography and semiconductor device topography, particularly with phase shifting masks, where sub-resolution assist features (SRAFs) do not effectively prevent artifacts from printing in the photoresist layer, interfering with further fabrication processes.
Innovation Solution
The use of horizontal sub-resolution assist features (SRAFs) on the lithography mask, oriented perpendicular to the patterning features, which are dimensioned less than the resolution limit of the lithography system, allowing for the selective removal of photoresist patterns corresponding to SRAFs and improving the contrast and definition of the printed image without SRAF artifacts in the photoresist layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional SRAFs are used in phase shifting masks, then the resolution of small features is improved, but SRAF artifacts are printed in the photoresist layer interfering with fabrication processes
Solution Approach 1:
The patent applies local quality by making the SRAFs transparent in specific regions where they would otherwise create artifacts. The mask structure includes transparent regions positioned at locations corresponding to where SRAF artifacts would form, allowing light to pass through and prevent unwanted photoresist patterns while maintaining the beneficial resolution enhancement effects of the SRAFs in other areas.
Solution Approach 2:
The patent extracts or removes the harmful artifact-forming portions of the SRAFs by creating transparent regions in the mask at those specific locations. This separates the useful function (resolution enhancement) from the harmful function (artifact creation) by taking out only the problematic parts while retaining the beneficial parts of the SRAF structure.
2Manufacturing precision
If mask topography is modified to achieve desired semiconductor device topography, then fabrication precision is improved, but mask design complexity increases
Solution Approach 1:
The patent applies local quality by modifying only specific regions of the mask (adding transparent regions at artifact locations) rather than redesigning the entire mask structure. This localized modification approach achieves the desired topography correction while minimizing the increase in overall mask design complexity.
Solution Approach 2:
The patent segments the mask into distinct functional regions: opaque patterning features for primary pattern definition, SRAF regions for resolution enhancement, and transparent regions for artifact prevention. This segmentation allows each region to be optimized independently, managing complexity through modular design.
3Length of moving object
If features with smaller dimensions are produced, then device scaling is achieved, but discrepancies between mask and device topography increase
Solution Approach 1:
The patent applies parameter changes by introducing transparent regions with specific optical properties (different transmission characteristics from opaque regions) at critical locations. This changes the local optical parameters of the mask to compensate for scaling effects, maintaining topography correspondence even as feature dimensions decrease.
Solution Approach 2:
The patent addresses scaling-induced topography discrepancies by applying local quality modifications - transparent regions are strategically placed at specific locations where artifacts would form due to scaling effects, allowing differential correction across the mask structure to maintain accuracy at smaller dimensions.
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 the printing of features with 38 nm size and 76 nm pitch in the photoresist layer without SRAF artifacts, enhancing the precision and accuracy of semiconductor device fabrication by preventing SRAF artifacts from interfering with subsequent processes.
Implementation Method 1
The first plurality of SRAFs are dimensioned less than a resolution limit of the lithography system used with the lithography mask
Implementation Method 2
interference (e.g., using phase shifting masks)
Data Source
AI summary
A lithography mask includes a plurality of patterning features formed on a mask substrate and a first plurality of sub-resolution assist features (SRAFs) formed substantially perpendicular to the patterning features on the mask substrate.