EUV Photomask Capping Structure for Low-Stray Reflective Openings
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing EUV photomasks face issues with damage to the reflective multilayer sidewalls and high reflectivity of silicon dioxide capping layers, leading to undesirable stray reflections and reduced effectiveness in EUV lithography processes.
Innovation Solution
The use of a silicon dioxide capping layer is replaced with a protective layer made of materials like ruthenium or ruthenium alloys to prevent oxidation and enhance durability, combined with a sacrificial layer and protective layers on the sidewalls to maintain reflectivity and prevent damage during photomask manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon dioxide capping layer is used to protect the reflective multilayer, then oxidation protection is provided, but high reflectivity causes undesirable stray reflections
Solution Approach 1:
The patent changes the material parameter of the capping layer from silicon dioxide to ruthenium or ruthenium alloys, which have different optical properties including lower reflectivity in the EUV range, thereby eliminating stray reflections while maintaining protective functions
Solution Approach 2:
The patent employs a composite structure with multiple layers including ruthenium-based capping layer, absorber layer, and optional intermediate layers, where each layer is specifically designed to address different functional requirements simultaneously
2Ease of manufacture
If the reflective multilayer sidewalls are exposed during manufacturing, then manufacturing simplicity is maintained, but sidewall damage occurs reducing service life
Solution Approach 1:
The patent applies a protective capping layer of ruthenium or ruthenium alloy over the reflective multilayer before manufacturing processes, providing preliminary protection against oxidation and damage during subsequent manufacturing steps
Solution Approach 2:
The ruthenium-based capping layer serves as a cushioning protective barrier that prevents direct exposure of the fragile reflective multilayer sidewalls to damaging environments during manufacturing and operation
3Reliability
If ruthenium or ruthenium alloy protective layers are applied, then durability and oxidation resistance are enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent uses a thin-film ruthenium or ruthenium alloy capping layer that can be deposited using standard sputtering techniques, providing effective protection at minimal material cost and thickness
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 protective layers effectively prevent damage to the reflective multilayer sidewalls, maintaining high reflectivity and extending the service life of the EUV photomask, thereby enhancing the performance and reliability of EUV lithography processes.
Implementation Method 1
The use of a silicon dioxide capping layer is replaced with a protective layer made of materials like ruthenium or ruthenium alloys to prevent oxidation
Implementation Method 2
maintaining high reflectivity and extending the service life of the EUV photomask
Data Source
AI summary
A method of manufacturing a reflective mask includes forming a sacrificial layer over a substrate and forming a reflective multilayer over the sacrificial layer. A capping layer is formed over the reflective multilayer. An absorber layer is formed over the capping layer. An opening is formed in the absorber layer, the capping layer, and the reflective layer exposing a portion of the sacrificial layer, and a protective layer is formed along sidewalls of the opening. The protective layer is made of material from the sacrificial layer.