Faceted Mirror Element With Asymmetric Tilt Range Control
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Solution Overview
Problem
Existing displaceable individual mirrors in microlithographic projection exposure apparatuses exhibit non-isotropic tilt angle ranges and maximum tilt angles that vary directionally, leading to inefficiencies in achieving desired illumination settings.
Innovation Solution
The design of individual mirrors with mounts and actuator devices that have direction-dependent properties, utilizing springs with varying stiffness, materials, and actuator elements with irregular distributions to achieve asymmetric tilt angle ranges and improved torque generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional mounts with uniform stiffness are used, then the structure is simple and easy to manufacture, but the tilt angle range is isotropic and cannot be optimized for specific directions
Solution Approach 1:
The mount is designed with direction-dependent stiffness properties, where the stiffness varies depending on the pivot axis direction. This allows optimization of tilt angle range in specific directions while maintaining simplicity in other directions, resolving the contradiction between adaptability and complexity.
Solution Approach 2:
The mount structure employs asymmetric stiffness distribution across different pivot axes, creating non-isotropic tilt angle ranges. This asymmetric design enables tailored optical performance for specific illumination settings while avoiding the need for completely complex structures.
2Force
If actuators with high torque generation capability are used, then the maximum tilt angle is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The actuator device is designed with direction-dependent properties, where different regions or elements provide different torque capabilities aligned with specific pivot axes. This local optimization allows high torque generation where needed without requiring uniformly complex structures throughout the entire actuator.
3Measurement precision
If the tilt angle range is made direction-dependent to match illumination requirements, then the illumination control precision is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The design systematically varies key parameters (stiffness, torque capability) across different directions to achieve the desired non-isotropic tilt angle range. By changing these parameters in a controlled manner during manufacturing, the system achieves precise illumination control while managing manufacturing precision requirements through standardized parameter variations rather than custom asymmetric features.
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 allows for more precise and flexible control of illumination settings, enhancing thermal and mechanical stability while reducing electrical resistance and simplifying actuator design.
Implementation Method 1
The mount may comprise springs with different stiffnesses
Implementation Method 2
springs with varying stiffness
Implementation Method 3
the maximum torque that can be generated with the actuator device and is applied to the mirror body
Data Source
AI summary
A pivotably mounted individual mirror for a facet mirror of an illumination optics unit of a projection exposure apparatus has a direction-dependent pivot range.