Individual Mirror Solid-Body Joint Geometry for Microlithography
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Solution Overview
Problem
Existing facet mirrors in projection exposure systems for microlithography lack adequate adjusting forces and efficient heat dissipation, particularly when handling EUV radiation, leading to limitations in tilting angles and illumination geometry adjustments.
Innovation Solution
The design incorporates individual mirrors with compact actuator arrangements, including zipping actuators and solid-body joints with specific electrode configurations, allowing for high adjusting forces and efficient heat dissipation through microchannels and optimized joint geometry, enabling precise tilting and heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a compact actuator arrangement is used for tilting the mirror, then the device size is reduced, but the adjusting force becomes insufficient
Solution Approach 1:
The actuator is divided into multiple movement electrodes (at least three, preferably four) that can be independently controlled. Each electrode can be selectively activated to produce adjusting forces in specific directions, allowing the compact actuator arrangement to generate sufficient total adjusting force despite its small size. The segmentation enables distributed force generation across multiple independent units.
Solution Approach 2:
The patent employs electrostatic actuators where the adjusting force is controlled by changing electrical parameters (voltage applied to movement electrodes). By varying the voltage parameter, the actuator generates adjustable forces in the mN range, transforming the electrical energy into mechanical force to tilt the mirror. This parameter-based control allows compact design while maintaining adequate force output.
2Temperature
If the joint length is increased relative to joint thickness, then heat dissipation is improved, but the force required for tilting increases
Solution Approach 1:
The solid-body joint is designed with specific dimensional parameters where the joint length is greatly exceeded by the joint thickness (high length/thickness ratio). This geometric parameter change optimizes the heat conduction path from the mirror body to the carrier body, improving heat dissipation. The elongated joint structure provides a larger cross-sectional area for thermal energy transfer while maintaining mechanical functionality.
3Adaptability or versatility
If multiple movement electrodes are used to increase degrees of freedom, then the adjusting capability is improved, but the device complexity increases
Solution Approach 1:
The actuator is segmented into multiple movement electrodes (at least three, preferably four) that can be independently controlled. Each electrode corresponds to a specific degree of freedom or directional control, enabling the mirror to be tilted in multiple directions. The segmentation allows independent activation of each electrode to achieve different tilting configurations without requiring complex mechanical linkages.
Solution Approach 2:
The movement electrodes are designed to serve multiple functions: they act as both structural support elements and as electrostatic actuation elements. The same electrode structure that provides mechanical stability also generates adjusting forces when voltage is applied, eliminating the need for separate actuation mechanisms and reducing overall device complexity despite having multiple degrees of freedom.
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 provides a compact and efficient system for adjusting facet mirrors, enabling precise tilting and heat management, thereby improving the variability of illumination geometries and maintaining high structural resolution in microlithography.
Implementation Method 1
applying a voltage between the movement electrode and the counter-electrode... a high electrical field strength with a correspondingly large adjusting force results there
Implementation Method 2
adequate heat dissipation from the mirror body to the carrier body is ensured by the solid-body joint... the joint length... ensures an adequately large heat transmission cross section through the solid-body joint
Data Source
AI summary
An individual mirror is used to construct a facet mirror. A mirror body of the individual mirror is configured to be tiltable relative to a rigid carrier body about at least one tilting axis of a tilting joint. The tilting joint is configured as a solid-body joint. The solid-body joint, perpendicular to the tilting axis, has a joint thickness S and, along the tilting axis, a joint length L. The following applies: L/S>50. The result is an individual mirror to construct a facet mirror, which can be reproduced and is precisely adjustable and simultaneously ensures adequate heat removal, in particular, heat produced by residually absorbed useful radiation, which is reflected by the individual mirror, by dissipation of the heat by the mirror body.