Reflective Optical Element Thermal Deformation Control
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Solution Overview
Problem
Reflective optical elements in EUV microlithographic systems experience thermal deformation due to EUV light absorption, leading to imaging quality issues, and existing solutions complicate the system with additional components for deformation compensation.
Innovation Solution
Incorporating a porous outgassing layer to release absorbed particles during EUV radiation, a heat radiation layer for efficient IR dissipation, and a Peltier element or heat buffer layer for active cooling, which reduces peak temperatures and minimizes thermal deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If reflective optical elements are used in EUV systems, then imaging is enabled in the EUV range, but thermal deformation occurs due to light absorption
Solution Approach 1:
The patent changes the physical-chemical parameters of the substrate by incorporating a porous outgassing layer with specific pore structures and material compositions. This layer is designed to undergo controlled outgassing at operating temperatures, releasing absorbed gases and preventing pressure buildup that would cause deformation. The pore size, distribution, and material properties are optimized to balance radiation reflection, heat management, and structural stability
Solution Approach 2:
The patent employs a composite structure combining the reflective optical element substrate with a porous outgassing layer. This composite material system integrates the high reflectivity properties needed for EUV imaging with the thermal and pressure management capabilities of the porous structure, creating a multi-functional component that simultaneously enables imaging while preventing thermal and pressure-induced deformation
2Temperature
If additional appliances are used for rigid body movements and temperature changes, then element heating is overcome, but system complexity increases
Solution Approach 1:
The patent implements a self-regulating system where the porous outgassing layer automatically manages thermal and pressure effects through its inherent physical properties. The layer performs self-cooling via evaporative outgassing and self-adjusts to thermal expansion without requiring external control systems, actuators, or additional appliances, thereby maintaining imaging quality while minimizing system complexity
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
Effectively reduces thermal deformations and maintains imaging quality by managing heat dissipation and absorption, protecting temperature-sensitive layers and reducing system complexity.
Implementation Method 1
at least one porous outgassing layer, which at least intermittently releases particles adsorbed in the outgassing layer when the optically effective surface is irradiated by electromagnetic radiation
Implementation Method 2
the heat induced by the electromagnetic radiation (i.e., during a light pulse) in the reflective optical element being used in part to release particles absorbed in a porous outgassing layer
Implementation Method 3
a heat radiation layer for efficient IR dissipation
Implementation Method 4
a Peltier element or heat buffer layer for active cooling
Data Source
AI summary
A reflective optical element, in particular for a microlithographic projection exposure apparatus or a mask inspection apparatus. According to one aspect, the reflective optical element has an optically effective surface, a substrate (405, 505), a reflection layer system (410, 510) and at least one porous outgassing layer (450, 550), which at least intermittently releases particles adsorbed in the outgassing layer (450, 550) when the optically effective surface (400a, 500a) is irradiated by electromagnetic radiation.