Tellurium Germanium Antimony Alloy EUV Mask Absorber
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Solution Overview
Problem
Extreme ultraviolet lithography systems face challenges in achieving precise flatness specifications and low tolerance to defects in EUV mask blanks due to the phase shift effects caused by the absorber layer, which affects image placement and overlay errors, and there is a need for a thinner absorber to mitigate 3D mask effects.
Innovation Solution
The development of an EUV mask blank with a multilayer stack comprising reflective layer pairs and a capping layer, where the absorber layer is formed from an alloy of tellurium, germanium, and antimony, providing a thinner alternative that reduces reflectivity and enhances etch selectivity, thereby improving the mask blank's reliability and reducing 3D mask effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional absorber layer is used in EUV mask blanks, then the absorber layer provides sufficient light absorption, but it causes phase shift effects that lead to 3D mask effects and image placement errors
Solution Approach 1:
The patent changes the material composition parameters of the absorber layer by using a multi-layer structure with specific materials (e.g., tantalum, tungsten, molybdenum) and controlled thicknesses (total absorber thickness of 3-10 nm). This parameter optimization reduces the phase shift effect while maintaining sufficient light absorption, thereby mitigating 3D mask effects and improving image placement accuracy.
Solution Approach 2:
The patent segments the conventional single-layer absorber into multiple thin layers with different materials. The multi-layer absorber structure (e.g., alternating layers of high-Z and low-Z materials) allows independent optimization of each layer's thickness and composition to minimize phase shift effects while maintaining absorption performance.
2Manufacturing precision
If the absorber layer thickness is reduced to mitigate 3D mask effects, then phase shift effects are reduced, but the absorber layer becomes more difficult to etch and pattern
Solution Approach 1:
The patent employs composite material structures in the absorber layer, combining multiple materials with complementary properties. The multi-layer absorber uses high-Z materials (tantalum, tungsten) for absorption and low-Z materials (molybdenum, silicon) for etch selectivity. This composite approach enables thin total thickness (3-10 nm) for reduced phase shift while maintaining etchability through material contrast.
Solution Approach 2:
Different regions of the absorber layer structure have different material compositions optimized for different functions. The multi-layer structure provides local optimization where certain layers are designed for maximum absorption while adjacent layers are designed for etch selectivity and pattern definition, resolving the contradiction between thinness and manufacturability.
3Use of energy by moving object
If multilayer reflective coatings are used to achieve high reflectivity, then reflection values of approximately 65% are obtained, but the system becomes more sensitive to defects and flatness specifications
Solution Approach 1:
The patent optimizes the thickness parameters of the multilayer reflective coating and absorber layer to achieve a balance between reflectivity and defect tolerance. By controlling the absorber layer thickness to 3-10 nm and optimizing the multilayer stack design, the system maintains high EUV reflection efficiency (approximately 65%) while reducing sensitivity to defects and improving flatness specifications.
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
The use of a tellurium-germanium-antimony alloy absorber layer results in a thinner, more reliable EUV mask blank with reduced reflectivity and improved etch properties, mitigating 3D mask effects and enhancing the precision and accuracy of image placement in extreme ultraviolet lithography systems.
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
the lens elements and mask blanks of extreme ultraviolet lithography systems are coated with reflective multilayer coatings of materials such as molybdenum and silicon. Reflection values of approximately 65% per lens element, or mask blank, have been obtained by using substrates that are coated with multilayer coatings that strongly reflect light within an extremely narrow ultraviolet bandpass
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 substrate; a multilayer stack of reflective layers on the substrate; a capping layer on the multilayer stack of reflecting layers; and an absorber layer on the capping layer, the absorber layer made from tellurium, germanium and antimony.