Adjustable Retardance Compensator Flexure Mechanism
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Solution Overview
Problem
Optical stages holding retardance compensators in lithographic apparatuses are prone to backlash and overdriving, leading to errors and potential damage, and are unsuitable for high-tolerance applications due to limitations in adjusting path length differences and ensuring accurate retardance correction.
Innovation Solution
A compensator apparatus with adjustable supports and flexures that provide translational and rotational adjustments with reduced backlash, dynamically adjusting the effective thickness and retardance using live optical feedback, allowing for precise correction of path length differences in optical assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an optical stage is used to hold and adjust the retardance compensator, then the compensator can be positioned and adjusted, but backlash and overdriving occur causing errors and potential damage
Solution Approach 1:
The patent replaces the traditional mechanical optical stage with a flexure-based mechanical system. The flexures provide precise motion control through elastic deformation, eliminating backlash and overdriving issues inherent in conventional mechanical stages with gears and bearings. This substitution maintains adjustability while dramatically improving reliability for high-tolerance applications.
Solution Approach 2:
The invention changes the mechanical parameters of the support system by using flexures with specific elastic properties. The flexures are designed with controlled stiffness and range of motion parameters that enable precise positioning without the drawbacks of traditional mechanical stages. This parameter optimization allows the system to achieve both ease of operation and high reliability.
2Stability of the object's composition
If a fixed waveplate is used, then the retardance value is stable, but path length differences cannot be compensated
Solution Approach 1:
The patent transforms the static fixed waveplate into a dynamic adjustable system using two optical wedges that can move relative to each other. This dynamic configuration allows the effective retardance to be continuously varied by changing the overlap and orientation of the wedges, enabling path length compensation while maintaining stable optical properties. The system adapts to different path length differences through controlled motion of the wedges.
Solution Approach 2:
The invention divides a single fixed waveplate into two separate optical wedges that can be independently positioned and oriented. This segmentation allows each wedge to contribute differently to the overall retardance, enabling continuous adjustment of the effective retardance value. The segmented design provides adaptability for compensating various path length differences while maintaining the stability of individual wedge components.
3Length of moving object
If the stage range of travel is increased to compensate for larger path length differences, then more adjustment range is available, but alignment precision decreases
Solution Approach 1:
The patent introduces an additional degree of freedom by allowing the optical wedges to rotate relative to each other in addition to translating. This dimensional addition enables path length compensation through rotational adjustment of the wedges' orientation, providing a second mechanism for achieving the required adjustment range without compromising alignment precision through translational motion alone.
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
The solution enables high-resolution and large-range retardance compensation with reduced backlash, ensuring accurate and continuous adjustments, making it suitable for high-tolerance applications in lithographic apparatuses.
Implementation Method 1
An optical retarder changes the polarization of an incident wave through a relative phase shift (e.g., retardance) between two polarization components
Implementation Method 2
A retardance compensator or variable retarder is an optical device that is capable of introducing a controllable retardance on an incident wave
Data Source
AI summary
A compensator for manipulating a radiation beam traveling along an optical path. The compensator includes a fixed support holding a first optical wedge and an adjustable support holding a second optical wedge. The adjustable support includes a base, a stage holding the second optical wedge, first and second flexures, and a drive block. The stage defines a cavity and is movable relative to the base and the fixed support. The first and second flexures couple the stage to the base such that the stage translates along a stage path. The drive block is disposed in the cavity of the stage and is configured to translate along a drive block path perpendicular to the optical path and perpendicular to the stage path. The drive block includes first and second drive bearing surfaces configured to translate the stage in first and second stage directions, respectively, along the stage path.