EUV Reflectometer Parallel Kinematic Positioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current EUV reflectometers face challenges in measuring large and heavy test objects with high accuracy due to limitations in motor torque, heat dissipation, and positioning precision, especially in vacuum environments, which affect the measurement accuracy and reliability of reflectivity measurements.
Innovation Solution
The development of a parallel kinematic multi-axis positioning device with a rotatable main carrier and a tripod arrangement, combined with an independent measuring system for load-independent pose determination, allows for precise positioning and orientation of test objects in six degrees of freedom, using multiple actuators and drives to distribute loads effectively and minimize heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional motor-driven positioning systems are used for heavy test objects, then the system structure is simple, but the motor torque is insufficient and heat dissipation is poor in vacuum environments
Solution Approach 1:
The positioning system is divided into multiple independent actuators (at least three) that work together in a parallel configuration. Each actuator independently controls a degree of freedom, distributing the positioning task and reducing the burden on individual motors, thereby improving reliability without requiring oversized single motors that would suffer from torque and heat dissipation issues in vacuum.
Solution Approach 2:
The system incorporates a non-contact measurement system that independently measures the actual pose of the test object and compensates for positioning deviations through feedback control. This pre-compensation mechanism cushions against positioning errors caused by load-dependent deformations, ensuring measurement accuracy despite the complexity of the parallel positioning system.
2Measurement precision
If single-axis or simple multi-axis positioning systems are used, then the device complexity is low, but the positioning precision and orientation precision cannot achieve 100 μm and 0.01°
Solution Approach 1:
A non-contact measurement system continuously monitors the actual position and orientation of the test object during positioning. The measured data is fed back to the control system, which adjusts the actuator commands to compensate for deviations. This closed-loop feedback mechanism enables sub-100 μm positioning precision and sub-0.01° orientation precision by constantly correcting errors rather than relying solely on open-loop actuator precision.
Solution Approach 2:
The system replaces contact-based mechanical measurement methods with non-contact optical or electromagnetic measurement techniques. This substitution eliminates mechanical interference and loading effects on the test object while providing high-precision pose data for feedback control, enabling the system to achieve the required precision without over-complicating the mechanical positioning structure.
3Measurement precision
If multiple actuators are used to distribute loads, then the positioning precision improves, but the heat generation from multiple drives increases
Solution Approach 1:
The positioning function is segmented across multiple actuators that share the positioning task and associated heat generation. By distributing the work load, each actuator operates at lower power levels and generates less heat individually. The vacuum environment naturally aids heat dissipation through radiation, and the segmented approach prevents any single actuator from becoming a heat concentration point that would compromise measurement accuracy.
Data Source
AI summary
An EUV reflectometer includes a radiation source, a beam shaping unit (130) generating a measurement beam (190) from the radiation; a positioning device (500) for holding and positioning a test object (110) relative to the measurement beam in plural degrees of freedom; and a detector that detects the EUV radiation reflected by the test object. The positioning device has a main carrier (520), which is rotatable about a vertical rotation axis and on which a parallel kinematic multi-axis system (530) having a multiplicity of actuators is arranged. A common platform (540) movable in three linear and three rotational degrees of freedom carries a holding device (550) for holding the test object and a rotary drive for rotating the holding device about a rotation axis. An associated measuring system (700) determines the location and position of the test object in space and/or in relation to the measurement beam.