Sensor Frame Sub-frames for Lithographic Apparatus Position Monitoring
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Solution Overview
Problem
Lithographic apparatuses face challenges in accurately monitoring the position of optical elements due to deformations in the sensor frame, which can lead to overlay errors during pattern transfer, as existing sensor frames are prone to deformation under applied forces and vibration isolators may not adequately mitigate these issues.
Innovation Solution
The apparatus employs a sensor frame subdivided into N sub-frames, coupled together with a coupling system and equipped with a second position measurement system to monitor the relative position of the sub-frames, allowing for controlled deformation and improved positional accuracy, or uses a sensor frame supported by M vibration isolators and vertically oriented actuator forces to stabilize the frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sensor frame is used to monitor optical element positions, then the monitoring system is simple, but the frame deforms under forces causing measurement errors
Solution Approach 1:
The sensor frame is divided into multiple sub-frames (first sub-frame, second sub-frame, etc.) that can move independently relative to each other. This segmentation allows each sub-frame to accommodate local deformations without affecting the entire frame, thereby maintaining measurement precision while managing structural complexity.
Solution Approach 2:
A coupling system is introduced as an intermediary between the sub-frames. This coupling system allows controlled relative movement between sub-frames while maintaining their coordinated operation, enabling the system to absorb deformation forces without compromising the overall measurement accuracy.
2Object-affected harmful factors
If vibration isolators are used to support the sensor frame, then external vibrations are reduced, but the frame remains prone to deformation under applied forces
Solution Approach 1:
The sensor frame transitions from a rigid static structure to a dynamic system with multiple sub-frames that can move independently. This dynamic configuration allows the frame to adapt to applied forces by distributing movements across sub-frames, improving reliability while maintaining vibration isolation.
Solution Approach 2:
The system changes the degrees of freedom of the sensor frame by introducing independent movement capabilities to each sub-frame. This parameter change allows the frame to respond to forces in multiple directions, reducing deformation while maintaining stability through the coupling system.
3Measurement precision
If the sensor frame is made more rigid to prevent deformation, then measurement accuracy improves, but the frame becomes more susceptible to stress and damage
Solution Approach 1:
Dividing the frame into multiple sub-frames reduces the size and stress concentration in each individual sub-frame. This segmentation maintains measurement precision through the coupling system while improving overall durability by distributing mechanical stresses across multiple smaller components.
Solution Approach 2:
The coupling system acts as a cushioning mechanism between sub-frames, absorbing and distributing stress before it can concentrate and cause damage. This beforehand cushioning protects the frame structure while maintaining the precision needed for position monitoring.
Data Source
AI summary
A lithographic apparatus is described, the apparatus comprising:a projection system configured to project a patterned beam of radiation onto a substrate; the projection system comprising a plurality of optical elements;a sensor frame;a first position measurement system configured to measure a position of the plurality of optical elements relative to the sensor frame; wherein the sensor frame comprises:N sub-frames, N being an integer >1,a coupling system coupling the N sub-frames anda second position measurement system configured to determine a relative position of the N sub-frames.