Bipolar Electromagnet Actuator for EUV Lithography
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Solution Overview
Problem
In EUV lithography, actuation mechanisms for optical components face challenges in achieving precise, multi-degree of freedom movement within a vacuum environment while maintaining compactness, cost-effectiveness, and heat dissipation, especially when dealing with numerous individual facets that require accurate positioning and feedback control.
Innovation Solution
The development of an actuation mechanism using bipolar electromagnets with ferromagnetic shields and an optical position sensor to enable compact, elongate actuators suitable for close packing, allowing for precise control of movable optical components in EUV illumination systems, including a suspension section and a stiffness compensation arrangement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional actuators are used for EUV lithography, then basic actuation function is achieved, but precision and reliability are insufficient for extreme accuracy requirements
Solution Approach 1:
The actuator is divided into separate functional modules: a motor module containing bipolar electromagnets for generating motion, and a suspension module with bellows and tendons for providing controlled degrees of freedom. This segmentation allows each module to be optimized independently for precision and reliability
Solution Approach 2:
An optical position sensor is integrated into the actuator to provide real-time feedback on the position of the movable optical component. This closed-loop feedback system enables precise positioning by continuously comparing actual position with target position and making corrective adjustments
2Adaptability or versatility
If actuators with multiple degrees of freedom are provided for extended illumination profiles, then versatility is improved, but device complexity increases
Solution Approach 1:
The actuator is designed with two bipolar electromagnets that can independently control motion in two orthogonal directions, enabling a single actuator to provide multiple degrees of freedom. This multi-functionality allows one actuator to replace what would traditionally require multiple separate actuators, reducing overall system complexity while maintaining versatility for extended illumination profiles
Solution Approach 2:
The suspension system incorporates flexible bellows and tendons that dynamically adapt to provide controlled rotational and translational degrees of freedom. This dynamic suspension mechanism allows the actuator to achieve complex motion patterns required for various illumination profiles without requiring rigid, complex mechanical linkages
3Volume of moving object
If compact actuators are used for close packing, then space efficiency is improved, but heat dissipation becomes more difficult
Solution Approach 1:
A non-magnetic, thermally conductive intermediary material is introduced between the electromagnet coils and the movable components. This intermediary serves dual functions: it provides a thermal pathway for heat dissipation from the coils while maintaining the magnetic field integrity and electrical insulation, enabling compact design without compromising heat management
4Volume of moving object
If bipolar electromagnets are used for compact design, then space efficiency is improved, but magnetic interference between adjacent actuators increases
Solution Approach 1:
Ferromagnetic shielding elements are extracted and strategically positioned around the bipolar electromagnets. These shields capture and contain the magnetic flux generated by the electromagnets, preventing magnetic field leakage into adjacent actuators. This extraction of magnetic interference from the operational space allows compact actuator packing while maintaining independent control of each actuator
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 EUV-compatible actuators that enable precise, multi-degree of freedom movement of optical components, enhancing the range of achievable illumination profiles while maintaining compactness and reducing heat dissipation, thus addressing the stringent requirements of EUV lithography.
Implementation Method 1
The static part of the actuator comprises a bipolar electromagnet
Implementation Method 2
Each of the pole pieces comprises a ferromagnetic shield
Implementation Method 3
The actuator also comprises an optical position sensor
Data Source
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AI summary
An actuator (300) to displace, for example a mirror, provides movement with at least two degrees of freedom by varying the currents in two electromagnets (370, 372, 376, 378). A moving part includes a permanent magnet (362) with a magnetic face constrained to move over a working area lying substantially in a first plane perpendicular to a direction of magnetization of the magnet. The electromagnets have pole faces (380, 382) lying substantially in a second plane closely parallel to the first plane, each pole face substantially filling a quadrant of the area traversed by the face of the moving magnet. An optical position sensor (390) may direct a beam of radiation (398) at the moving magnet through a central space between the electromagnets. The sizes of facets in a pupil mirror device may be made smaller in a peripheral region, but larger in a central region, thereby relaxing focusing requirements.