EUV Lithography Optical System Charge Compensation Flood Gun
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Solution Overview
Problem
EUV lithography apparatuses face significant challenges in maintaining high reflectivity over time due to contamination and oxidation of reflective optical elements caused by secondary electrons and reactive fragments in the residual gas atmosphere, especially when the substrate is made of insulating or poorly conductive materials.
Innovation Solution
An optical system for EUV lithography that incorporates a flood gun as the sole charge carrier compensation source, applying low-energy electrons uniformly across the reflective optical element to prevent local charging and sputtering effects, ensuring effective charge carrier compensation independent of substrate material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the substrate is made of insulating or poorly conductive material, then the mechanical and thermal properties are improved, but charge carrier compensation becomes insufficient leading to electrical charging and sputtering effects
Solution Approach 1:
A conductive coating layer is introduced as an intermediary between the insulating substrate and the EUV radiation field. This coating layer serves as a charge carrier compensation mechanism, collecting secondary electrons and preventing electrical charging of the substrate surface, thereby eliminating sputtering effects while preserving the mechanical and thermal advantages of the insulating substrate material
2Object-affected harmful factors
If electrode arrangements are used to remove secondary electrons, then carbon contamination and oxidation are reduced, but device complexity increases
Solution Approach 1:
The complex electrode arrangement system is extracted and replaced by a simple conductive coating layer applied directly to the substrate. This coating layer passively performs the electron collection function without requiring external electrodes, power supplies, or control systems, thereby dramatically simplifying the device structure while maintaining protection against carbon contamination and oxidation
Solution Approach 2:
The conductive coating layer provides self-service charge carrier compensation by inherently collecting secondary electrons through its conductive properties. The system requires no external control or additional components - the coating itself serves as the complete charge management solution, eliminating the need for complex electrode arrangements
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 solution maintains high, uniform reflectivity of reflective optical elements over extended periods by controlling charge carrier compensation, reducing sputtering effects, and minimizing the risk of degrading the highly reflective coatings, thus enhancing the stability and throughput of EUV lithography processes.
Implementation Method 1
a source of electrically charged particles, which is arranged in such a manner that electrically charged particles can be applied to the reflective optical element
Implementation Method 2
a substrate with a highly reflective coating emitting secondary electrons when irradiated with EUV radiation
Implementation Method 3
applying low-energy electrons uniformly across the reflective optical element to prevent local charging and sputtering effects
Data Source
AI summary
To prevent reflective optical elements (2) for EUV lithography from becoming electrically charged as they are irradiated with EUV radiation (4), an optical system for EUV lithography is proposed, having a reflective optical element (2), including a substrate (21) with a highly reflective coating (22) emitting secondary electrons when irradiated with EUV radiation (4), and a source (3) of electrically charged particles, which is arranged in such a manner that electrically charged particles are applied to the reflective optical element (2), wherein the source (3) for the charge carrier compensation is exclusively a flood gun applying electrons to the reflective optical element (2).