EUV Mask Blank Multilayer Absorber for Overlay Error Reduction
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Solution Overview
Problem
Extreme ultraviolet lithography systems face challenges in reducing overlay errors and three-dimensional mask effects due to the limitations of reflective multilayer masks with absorber layers, which affect the precision and flatness required for future semiconductor production.
Innovation Solution
The development of an extreme ultraviolet (EUV) mask blank with a multilayer stack of reflective layers and a capping layer, combined with a multilayer stack of absorber layers comprising pairs of different absorber materials with distinct extinction coefficient and refractive index values, to enhance reflectivity and reduce errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-layer absorber is used in EUV reflective masks, then the mask structure is simple, but overlay errors and three-dimensional mask effects increase
Solution Approach 1:
The single absorber layer is segmented into multiple absorber layers with different materials and thicknesses. Each layer is optimized to address specific optical challenges, collectively reducing overlay errors and three-dimensional mask effects while maintaining etch selectivity
Solution Approach 2:
The patent employs composite absorber structures combining multiple materials (e.g., platinum, nickel, molybdenum, tantalum) with distinct optical and etch properties. This composite approach enables simultaneous optimization of absorption characteristics, etch selectivity, and reduction of mask effects
2Object-affected harmful factors
If absorber layer thickness is increased to improve absorption, then absorption efficiency improves, but three-dimensional mask effects worsen
Solution Approach 1:
The total absorber thickness is segmented across multiple layers rather than using a single thick layer. This distribution maintains sufficient absorption efficiency while reducing the height variations that cause three-dimensional mask effects
Solution Approach 2:
The patent optimizes the thickness parameters of individual absorber layers to achieve the desired balance between absorption efficiency and mask flatness, rather than simply increasing the total thickness
3Manufacturing precision
If etch selectivity between absorber and capping layer is improved, then pattern transfer accuracy improves, but manufacturing complexity increases
Solution Approach 1:
The patent assigns specific materials to specific layers based on their local functional requirements. The absorber layer material is selected to provide optimal etch selectivity against the capping layer, enabling accurate pattern transfer while keeping the manufacturing process manageable
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 improves the reflectivity and reduces overlay errors and three-dimensional mask effects, enabling more precise image placement and adherence to stringent flatness specifications for future semiconductor production.
Implementation Method 1
a reflective multilayer stack 12 on a substrate 14, which reflects EUV radiation at unmasked portions by Bragg interference
Implementation Method 2
each pair comprising two different absorber materials having extinction coefficient (k) values that are different
Data Source
AI summary
Extreme ultraviolet (EUV) mask blanks, methods for their manufacture and production systems therefor are disclosed. The EUV mask blanks comprise a multilayer stack of absorber layers on the capping layer, the multilayer stack of absorber layers including a plurality of absorber layer pairs.