Tellurium-Germanium EUV Mask Absorber for Phase Shift Reduction
Find Innovative SolutionsGenerate Solutions
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 also limits the ability to mitigate 3D mask effects.
Innovation Solution
A method of manufacturing EUV mask blanks using a multilayer stack with a capping layer and an absorber layer comprising an alloy of tellurium and germanium, which reduces the absorber thickness to minimize reflectivity and phase shift effects, while maintaining high reflectivity and etch selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional absorber layer is used in EUV mask blanks, then the absorber can effectively absorb EUV radiation, but the phase shift effects and 3D mask effects increase, reducing image placement precision
Solution Approach 1:
The patent changes the material parameters of the absorber layer by using a tellurium-germanium alloy instead of conventional absorber materials. This material substitution alters the optical properties including the index of refraction, which directly affects the phase shift characteristics. The alloy composition is specifically selected to reduce the phase shift effect while maintaining adequate absorption of EUV radiation, thereby improving image placement precision and reducing 3D mask effects.
2Reliability
If the absorber layer thickness is increased to improve absorption, then more EUV radiation is absorbed, but the 3D mask effects and phase shift effects are exacerbated
Solution Approach 1:
The patent employs a composite material approach by using a tellurium-germanium alloy in the absorber layer. This composite material combines the advantages of both tellurium and germanium to achieve optimal absorption efficiency while minimizing 3D mask effects. The specific composition ratio is optimized to balance the absorption capability with the reduction of harmful phase shift and 3D mask effects, allowing for adequate thickness without exacerbating the harmful effects.
3Object-generated harmful factors
If the absorber layer thickness is reduced to mitigate 3D mask effects, then 3D mask effects are reduced, but the absorption of EUV radiation is insufficient
Solution Approach 1:
The patent changes the material parameters by selecting a tellurium-germanium alloy with specific optical properties that have higher absorption coefficient per unit thickness compared to conventional absorber materials. This allows the absorber layer to be made thinner to reduce 3D mask effects while still achieving adequate EUV radiation absorption. The material parameter optimization ensures that the reduced thickness does not compromise the absorption efficiency.
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 alloy absorber layer in EUV mask blanks enhances the reliability and reduces 3D mask effects, improving the precision and defect tolerance of EUV mask blanks, thereby supporting more precise image placement and overlay in semiconductor manufacturing.
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
Masked (non-reflective) areas 16 of the conventional EUV reflective mask 10 are formed by etching buffer layer 18 and absorbing layer 20
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 and germanium.