Vibration-compensated optical system with reaction mass
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithography apparatuses face challenges in minimizing vibrations that cause image distortions and unsharpnesses, particularly in the 10 nm-technology node, due to external and internal forces affecting the positioning of optical elements, which existing solutions struggle to adequately compensate for.
Innovation Solution
A vibration-compensated optical system is designed with an optical element, a carrying element, and an actuator, where a first elastic element couples the optical element to the carrying element, and a reaction mass is supported by a second elastic element, with specific mass and stiffness ratios (m1m2=k1k2) to cancel out supporting forces during actuation, allowing for zero resulting force on the carrying element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a reaction mass is supported very softly on the carrying element to minimize transmitted forces, then the forces transmitted to the carrying element are reduced, but the natural frequency of the reaction mass becomes too low to provide effective vibration compensation
Solution Approach 1:
The patent applies the counterweight principle by introducing a reaction mass that generates opposing forces to cancel out the disturbing forces from optical element actuation. The reaction mass is actuated in opposition to the optical element's movement, creating force cancellation that protects the carrying element from vibration while maintaining a sufficiently high natural frequency through optimized mass ratio and stiffness parameters.
2Force
If the mass of the reaction mass is increased to improve force compensation, then the force cancellation effectiveness increases, but the space required and system complexity increase
Solution Approach 1:
The patent employs parameter optimization by establishing specific relationships between the mass of the optical element, the mass of the reaction mass, and the stiffness of the elastic elements. By tuning these parameters according to the formula m1/m2=k1/k2, the system achieves effective force compensation with a compact reaction mass, avoiding the need for oversized components while maintaining vibration suppression performance.
3Force
If very soft elastic elements are used to support the reaction mass, then force transmission to the carrying element is minimized, but the structural space required increases and manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The patent transforms the design approach by optimizing the stiffness parameter k2 of the second elastic element based on the mass ratio and force cancellation requirements. This parameter optimization allows the use of elastic elements with moderate stiffness rather than extremely soft elements, making the system easier to manufacture and assemble while maintaining effective vibration compensation through the coordinated mass-stiffness relationships.
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 effectively minimizes the forces transmitted to the carrying element, reducing the need for very soft elastic elements and saving space, while maintaining precise control over the optical element's position, thus enhancing the accuracy of the lithography process.
Implementation Method 1
a first elastic element (218), which couples, in particular directly, the optical element (216) to the carrying element (206)
Implementation Method 2
a second elastic element (222), which couples, in particular directly, the reaction mass (220) to the carrying element (206)
Implementation Method 3
an actuator (224) for actuating the optical element (216) relative to the carrying element (206), wherein the actuator (224) couples the optical element (216) to the reaction mass (220)
Data Source
AI summary
A vibration-compensated optical system for a lithography apparatus includes an optical element, a carrying element, an actuator for actuating the optical element relative to the carrying element, a first elastic element which directly couples the optical element to the carrying element, a reaction mass, and a second elastic element. The actuator couples the optical element to the reaction mass. The second elastic element directly couples the reaction mass to the carrying element. For a mass (m1) of the optical element, a stiffness (k1) of the first elastic element, a mass (m2) of the reaction mass and a stiffness (k2) of the second elastic element the following holds true:m1m2=k1k2.