EUV Lithography Mask Black Border for Pattern Accuracy
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Solution Overview
Problem
Existing EUV lithography technologies face challenges in achieving precise and high-resolution pattern formation due to issues like out-of-band light interference, residual absorber reflectivity, and REMA blade instability, which lead to inaccuracies and over-exposure around die edges.
Innovation Solution
The introduction of a non-reflective 'black border' region around the image field in EUV masks, formed without additional lithographic processing or heating steps, helps mitigate these issues by absorbing unwanted radiation and reducing exposure overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a black border area is placed between adjacent dies to reduce over-exposure, then pattern accuracy is improved, but device complexity increases
Solution Approach 1:
The patent applies local quality by creating a black border region with different optical properties (non-reflective) specifically at the periphery of the mask, while the central image field maintains its original reflective properties. This localized modification addresses the over-exposure problem at die edges without affecting the pattern formation in the main imaging area, thus improving pattern accuracy while minimizing added complexity.
2Reliability
If additional lithographic processing or heating steps are used to form the black border, then the black border effectiveness is improved, but manufacturing complexity and time increase
Solution Approach 1:
The patent employs preliminary action by incorporating the black border region formation into the existing mask manufacturing process flow without requiring separate lithographic processing or heating steps. The black border is created as an integral part of the mask structure during the standard fabrication sequence, thereby ensuring effective over-exposure prevention while maintaining high manufacturing throughput and avoiding additional process complexity.
3Measurement precision
If the black border area is increased to better block out-of-band light, then exposure accuracy is improved, but the usable image field area is reduced
Solution Approach 1:
The patent applies parameter changes by optimizing the dimensions, position, and optical properties of the black border region to achieve the minimum effective size that blocks out-of-band light and prevents over-exposure. By carefully controlling the black border parameters (width, location, reflectivity), the design maximizes the usable image field area while maintaining sufficient exposure accuracy, thus resolving the trade-off between border size and imaging area.
Data Source
AI summary
A mask for extreme ultraviolet (EUV) lithography includes a multilayer (ML) stack including alternating metal and semiconductor layers disposed over a first surface of a mask substrate, a capping layer disposed over the ML stack, and an absorber layer disposed over the capping layer. An image pattern is formed in the absorber layer. A border layer surrounding the image pattern is disposed over the absorber layer.