Electrostrictive Mirror Actuator for Lithography Aberration Control
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Solution Overview
Problem
Lithography apparatuses face challenges in implementing feedback control for mirror surface deformation due to limited installation space and high costs, making it impractical to incorporate additional optical measurement systems for aberration correction.
Innovation Solution
An optical system with a mirror coupled to an actuator device comprising electrostrictive elements for deformation and sensing, allowing for closed-loop control of the mirror surface without the need for separate measurement systems, using the same mechanism for actuation and detection, such as the piezo effect, to maintain system simplicity and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an additional optical measurement system is arranged in the lithography apparatus to scan the mirror surface, then the mirror surface deformation can be detected for feedback control, but the installation space requirement increases and the system complexity and cost increase
Solution Approach 1:
The patent combines the actuator element and sensor element into a single integrated unit. The sensor element is arranged to directly adjoin the actuator element or is positioned such that it detects the mechanical stress produced by the actuator element. This merging eliminates the need for separate measurement systems, reducing installation space and system complexity while maintaining the capability to detect mirror surface deformation for feedback control
Solution Approach 2:
The actuator element serves dual functions: it both deforms the mirror surface (actuation) and enables detection of the deformation (sensing). The sensor element utilizes the same mechanical stress field produced by the actuator, making the system multi-functional. This universal approach allows a single component to perform multiple roles, reducing the overall number of components needed in the lithography apparatus
2Measurement precision
If an additional optical measurement system is arranged in the lithography apparatus to scan the mirror surface, then the mirror surface deformation can be detected for feedback control, but the installation space requirement increases
Solution Approach 1:
The patent merges the actuator and sensor into a single integrated element, eliminating the need for separate measurement systems. The sensor element is positioned to directly detect the mechanical stress produced by the actuator element, allowing both actuation and sensing to occur at the same location. This significantly reduces the installation space required while maintaining the capability to detect mirror surface deformation
3Adaptability or versatility
If different physical mechanisms are used for actuation and sensing, then the functional capabilities are enhanced, but the system complexity increases and manufacturing becomes more difficult
Solution Approach 1:
The patent employs the same physical mechanism (electrostriction) for both actuation and sensing. The actuator element and sensor element are both based on electrostrictive material, allowing them to respond to electrical signals in the same way. This homogeneity simplifies manufacturing processes, reduces the number of different material types needed, and lowers production costs while maintaining full functional capabilities for both deforming and detecting mirror surface deformation
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
Enables precise correction of imaging errors and aberrations within a compact and cost-effective framework, suitable for high-precision applications like lithography, astronomy, and military optics, with reduced complexity and susceptibility to defects.
Implementation Method 1
The actuator device comprises at least one electrostrictive actuator element for producing mechanical stress in the mirror body for deforming the mirror surface in dependence on an electrical drive voltage
Implementation Method 2
The actuator device comprises at least one electrostrictive sensor element for outputting a sensor signal in dependence on a deformation of the sensor element
Data Source
AI summary
An optical system comprises at least one mirror having a mirror body and a mirror surface, and at least one actuator device coupled to the mirror body and serving for deforming the mirror surface. The actuator device comprises at least one electrostrictive actuator element for generating a mechanical stress in the mirror body for deforming the mirror surface depending on an electrical drive voltage, and at least one electrostrictive sensor element for outputting a sensor signal depending on a deformation of the sensor element. The at least one sensor element is arranged directly adjacent to the actuator element and/or is arranged in such a way that it is configured at least partly for transferring the mechanical stress generated by the actuator element to the mirror body.