Lithographic Positioning System Vibration Control
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Solution Overview
Problem
In lithographic apparatuses, the mass damper's energy absorption leads to increased excursion magnitude, potentially causing vibrations and reducing pattern quality due to space limitations, as it may hit apparatus components, resulting in aberrations and decreased projection quality.
Innovation Solution
A positioning system with a reaction body and actuator, controlled by a controller providing timed signals to manage the movement of the reaction body along specific paths, reducing excursion magnitude and preventing collisions with apparatus parts by synchronizing acceleration in opposite directions, thus minimizing vibrations and improving pattern quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mass damper absorbs more vibration energy, then the vibration damping effect is improved, but the excursion magnitude increases causing the mass damper to hit apparatus components
Solution Approach 1:
The patent applies dynamics by making the mass damper's characteristics adjustable rather than fixed. The controller dynamically modifies the mass damper's natural frequency and/or mass based on real-time vibration conditions, allowing the system to optimize between damping effectiveness and excursion magnitude. This dynamic adjustment prevents the mass damper from hitting apparatus components while maintaining reliable vibration damping.
Solution Approach 2:
The patent implements parameter changes by varying the natural frequency and mass of the mass damper according to operating conditions. The controller monitors vibration levels and adjusts the mass damper parameters accordingly - increasing damping when needed while controlling excursion magnitude to prevent collisions with apparatus components. This parameter adaptation resolves the contradiction between damping effectiveness and physical constraints.
2Object-affected harmful factors
If the mass damper excursion magnitude is limited to prevent collisions, then the safety is improved, but the vibration absorption capability is reduced
Solution Approach 1:
The system uses dynamic adjustment of the mass damper's natural frequency and mass to maintain optimal vibration absorption while limiting excursion magnitude. The controller continuously adapts the mass damper characteristics based on real-time monitoring, ensuring that the mass damper remains effective at absorbing vibrations without exceeding safe displacement limits that would cause collisions with apparatus components.
Solution Approach 2:
The patent implements feedback control by monitoring the mass damper's position and vibration levels, then using this information to adjust the mass damper parameters. The controller receives feedback about the system state and modifies the mass damper's natural frequency and/or mass to maintain both safety (preventing collisions) and effectiveness (maintaining vibration absorption capability).
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 controlled movement of the reaction body reduces the likelihood of collisions within the lithographic apparatus, leading to fewer vibrations and enhanced projection quality by limiting excursion magnitude, thereby maintaining the precision of the projected pattern on the substrate.
Implementation Method 1
The actuator is arranged between the main body and the reaction body so as to accelerate the main body in the first direction and to accelerate the reaction body in the second direction under control of the first signal
Implementation Method 2
When the mass damper absorbs the energy of the vibrations of the optical element, the mass damper will start to vibrate in an eigenmode at the natural frequency
Implementation Method 3
Each mass damper has a damper mass that is connected to the inner ring via a spring-damper element. The combination of the damper mass and the spring-damper element forms a dynamical system having a natural frequency
Data Source
AI summary
A lithographic apparatus having a reference body and a positioning system, the positioning system including a main body; a reaction body; an actuator; and a controller. The main body is moveable relative to the reference body along a path in a first direction and a second opposite direction. The reaction body is moveable relative to the main body along a further path in the first and second directions and is moveably connected to the reference body to be moveable relative to the reference body in the first and second directions. The controller provides a first and a second signal to the actuator. The actuator is arranged between the main body and the reaction body to accelerate the main body in the first direction and to accelerate the reaction body in the second direction under control of the first signal, and to accelerate the main body in the second direction and to accelerate the reaction body in the first direction under control of the second signal. The controller determines when the reaction body moves in the second direction and to provide the second signal after the first signal to the actuator when the reaction body moves in the second direction along the further path.