Reflective Photomask Black Border Anneal Patterns
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Solution Overview
Problem
In extreme ultraviolet lithography, reflective photomasks face challenges in preventing overlap exposure due to extreme ultraviolet rays reflected from the edge areas, which can adversely affect pattern image transfer, especially with the limitations of existing black border areas in terms of productivity and accuracy.
Innovation Solution
A reflective photomask design featuring a black border area with first and second anneal patterns of island and line shapes, respectively, where the edge is formed using a step manner and the inside is formed using a scan manner, with a reduced reflector layer thickness in the black border area to minimize reflectance and prevent overlap exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a black border area is formed to prevent overlap exposure from reflected extreme ultraviolet rays, then pattern image transfer accuracy is improved, but manufacturing complexity and process time increase
Solution Approach 1:
The black border area is segmented into multiple functional zones: a first black border area adjacent to the pattern area with reduced reflector layer thickness, and a second black border area extending further outward. This segmentation allows different regions to serve different purposes in preventing overlap exposure while simplifying the overall structure compared to a uniformly complex design.
Solution Approach 2:
The reflector layer thickness is locally varied within the black border area, with the first black border area having a first thickness and the second black border area having a second thickness different from the first. This local quality variation optimizes reflectance control in different zones, improving pattern image transfer accuracy without requiring uniformly complex structures throughout.
2Object-affected harmful factors
If the reflector layer thickness is reduced in the black border area to minimize reflectance, then overlap exposure prevention is improved, but manufacturing precision control becomes more difficult
Solution Approach 1:
The reflector layer thickness is segmented into distinct zones: a first thickness in the first black border area and a second thickness in the second black border area. This segmentation makes thickness control more manageable by dividing a potentially complex gradient into discrete, controllable steps, reducing manufacturing difficulty while effectively minimizing reflectance to prevent overlap exposure.
Solution Approach 2:
The reflector layer thickness parameter is changed across different regions of the black border area. By varying this parameter (thickness) spatially - with the first thickness adjacent to the pattern area and the second thickness extending outward - the patent optimizes reflectance control to prevent overlap exposure while maintaining manufacturability through defined parameter transitions.
3Object-affected harmful factors
If a conventional black border area design is used, then overlap exposure prevention is achieved, but productivity decreases due to extended process time
Solution Approach 1:
The black border area is divided into two distinct segments with different reflector layer thicknesses. This segmentation enables more efficient manufacturing by allowing targeted processing in different zones, reducing overall process time compared to treating the entire black border area uniformly, thereby improving productivity while still preventing overlap exposure.
Solution Approach 2:
Different regions of the black border area are assigned different local properties (first thickness adjacent to pattern area, second thickness extending outward). This local quality differentiation allows optimization of each zone for its specific function, reducing unnecessary material and processing in regions where full thickness is not required, thus improving productivity without compromising overlap exposure prevention.
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 design enhances both the accuracy and productivity of the reflective photomask by effectively preventing overlap exposure while maintaining precise edge definition and reducing process time, thereby improving the overall performance in extreme ultraviolet lithography.
Implementation Method 1
a reflective optical system rather than a refractive optical system is used in the extreme ultraviolet lithography process
Implementation Method 2
The absorber layer may transfer a pattern image by selectively absorbing the extreme ultraviolet rays in the pattern area of the reflective photomask
Implementation Method 3
The black border area includes first and second anneal areas which are arranged along an edge of the pattern area
Data Source
AI summary
A reflective photomask includes a pattern area, a non-pattern area at least partially surrounding the pattern area, and a black border area interposed between the pattern area and the non-pattern area. The reflective photomask includes a mask substrate, a reflector layer stacked on the mask substrate, and an absorber layer stacked on the reflector layer. The black border area includes a plurality of first anneal patterns which are arranged along an edge of the pattern area and each have an island shape, and a second anneal pattern which fills inside of the black border area and has a line shape.