EUV Mask Fabrication Using Flowable Photosensitive Absorption Layer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing EUV lithography methods face challenges with process-induced stress during mask fabrication, particularly due to the high absorption of materials at 13.5 nm wavelengths, which affects the quality and precision of semiconductor circuits.
Innovation Solution
The method involves forming a mask with a low thermal expansion material layer, a reflective multilayer, and a flowable-photosensitive-absorption-layer (FPhAL) or flowable-absorption-layer (FAL) using spin-coating and lithography processes to reduce stress and enhance reflectivity, with specific layer compositions and deposition techniques to achieve high reflectivity and minimize absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional mask fabrication methods are used for EUV lithography, then the mask can be manufactured with basic functionality, but process-induced stress deteriorates the mask quality and precision
Solution Approach 1:
The mask structure is segmented into multiple functional layers: a substrate layer, a reflective multilayer stack (alternating high and low refractive index materials), and a pattern layer. This segmentation allows each layer to be optimized independently for its specific function while reducing overall process-induced stress through controlled deposition of each segment.
Solution Approach 2:
The mask employs composite material structures, particularly the reflective multilayer consisting of alternating layers of materials with different refractive indices (e.g., Mo/Si pairs). This composite structure enhances EUV reflectivity while managing thermal and mechanical stress through the coordinated properties of constituent materials.
2Manufacturing precision
If materials highly absorbing at 13.5 nm wavelength are used, then the mask can effectively pattern circuits, but reflectivity is reduced and absorption increases
Solution Approach 1:
The mask design applies local quality by creating regions with different optical properties: the reflective multilayer regions provide high reflectivity for unpatterned areas, while the pattern layer introduces localized absorption at 13.5 nm wavelength to define circuit patterns. This spatial variation in material properties enables precise patterning while maintaining overall energy 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
This approach reduces process-induced stress and improves the reflectivity of EUV masks, enabling more precise and efficient transfer of circuit patterns onto semiconductor wafers, thereby enhancing the resolution and reliability of EUV lithography.
Implementation Method 1
reflective optics, rather than refractive optics, are commonly used in EUV lithography
Implementation Method 2
At the wavelength of 13.5 nm, most materials are highly absorbing
Implementation Method 3
spin-coating a flowable-photosensitive-absorption-layer (FPhAL) over the reflective ML
Data Source
AI summary
A method for fabricating an extreme ultraviolet (EUV) mask includes providing a low thermal expansion material (LTEM) layer. A reflective multiple-layer (ML) is deposited over the LTEM layer. A flowable-photosensitive-absorption-layer (FPhAL) is spin coated over the reflective ML. The FPhAL is patterned by a lithography process to form a patterned absorption layer.