Movable Element Support with Gravity and Torque Compensation
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Solution Overview
Problem
Conventional lithographic or exposure apparatuses face challenges in accurately positioning movable elements due to parasitic forces caused by magnetization errors in permanent magnets and the non-linear relationship between gravity-opposing force and current in reluctance actuators, leading to positioning errors and stray fields that disrupt other apparatus elements.
Innovation Solution
A support system for movable elements using a stator element with a gravity compensator field inducing element and torque compensator field inducing elements, which control magnetic fields in a gap between the stator and movable elements to apply translational and torque forces, respectively, to compensate for gravity and torque, thereby reducing parasitic forces and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a permanent magnet is used to compensate gravity, then the constant gravitational force is compensated, but magnetization errors cause parasitic forces that lead to positioning errors and stray fields
Solution Approach 1:
The support system is divided into separate functional components: a gravity compensator for constant force compensation and torque compensators for dynamic torque control. This segmentation allows each component to be optimized for its specific function, with the gravity compensator using permanent magnets for DC compensation and torque compensators using electromagnetic actuators for AC compensation, thereby eliminating the parasitic force problem while maintaining positioning accuracy
Solution Approach 2:
The patent introduces torque compensator actuators as intermediary elements between the gravity compensator and the movable element. These torque compensators generate counteracting torques to neutralize the parasitic forces produced by the gravity compensator's magnetization errors, thereby protecting the positioning system from accuracy degradation while preserving the gravity compensation function
2Object-generated harmful factors
If a reluctance actuator is used to compensate gravity, then parasitic forces are reduced, but the non-linear relationship between force and current makes control difficult
Solution Approach 1:
The patent replaces the non-linear reluctance actuator with an electromagnetic actuator that produces a linear relationship between control current and generated force. This substitution eliminates the control difficulty associated with non-linearity while maintaining the low parasitic force characteristic, as the electromagnetic actuator can be precisely controlled through current regulation
Solution Approach 2:
The patent changes the operating parameters of the support system by using electromagnetic actuators instead of reluctance actuators. This parameter change enables linear control through direct current-to-force proportionality, while the system maintains low parasitic forces through proper electromagnetic design and control algorithms
3Force
If a permanent magnet and Lorentz actuator are used, then gravity compensation is achieved, but significant stray fields disrupt other apparatus elements
Solution Approach 1:
The patent extracts the stray field problem from the gravity compensation function by separating the DC gravity compensation (using permanent magnets) from the AC torque compensation (using electromagnetic actuators). The electromagnetic actuators are designed with magnetic shielding and optimized geometry to minimize stray fields, thereby eliminating the disruption to other apparatus elements while preserving gravity compensation
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 effectively reduces parasitic forces and stray fields, enhancing the accuracy of movable element positioning and reducing the complexity of corrective measures, while also providing independent control over translational and torque forces, thus improving the overall performance of the exposure apparatus.
Implementation Method 1
a gravity compensator field inducing element mounted on the stator element, the gravity compensator field inducing element configured to apply a translational force to the movable element by controlling a magnetic field in a gap between the stator element and the movable element
Implementation Method 2
a plurality of torque compensator field inducing elements mounted on the stator element, the torque compensator field inducing elements configured to apply a torque to the movable element by controlling a magnetic field in the gap between the stator element and the movable element
Data Source
AI summary
A support for a movable element includes a stator element, a gravity compensator field inducing element mounted on the stator element, the gravity compensator field inducing element configured to apply a translational force to the movable element by controlling a magnetic field in a gap between the stator element and the movable element, and a plurality of torque compensator field inducing elements mounted on the stator element, the torque compensator field inducing elements configured to apply a torque to the movable element by controlling a magnetic field in the gap between the stator element and the movable element, the torque being about a first axis substantially perpendicular to the direction of the translational force applied by the gravity compensator field inducing element.