Optical End Stop With Variable Stiffness for Tremor Protection
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Solution Overview
Problem
In EUV lithography apparatuses, the use of reflective optical units is prone to damage due to tremors, which can cause direct contact between metallic components, leading to excessive forces and particle abrasion.
Innovation Solution
An optical system with a bending element that allows movement within an actuation region and abruptly increases stiffness at its limit, preventing direct contact and force transfer between components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional end stop device with bolt and sleeve is used, then the movement of the sensor frame is delimited, but direct contact between metallic components occurs causing excessive forces and particle abrasion
Solution Approach 1:
The patent introduces a bending element as an intermediary component between the force frame and sensor frame. This bending element absorbs the mechanical stress during tremors by deforming elastically, preventing direct contact between the metallic bolt and sleeve components. The bending element acts as a mediator that protects the optical units from damage while avoiding the harmful direct contact that generates particles and excessive forces.
Solution Approach 2:
The patent employs a bending element with variable stiffness characteristics. The bending element has a first stiffness value during normal operation and a second, higher stiffness value when the actuation region limit is reached. This parameter change allows the element to permit movement within the actuation region while automatically stiffening to block movement outside the actuation region, preventing component contact and particle generation.
2Reliability
If the bending element allows movement within the actuation region, then component damage is prevented, but movement blocking is required outside the actuation region
Solution Approach 1:
The bending element is designed with variable stiffness parameters that change based on the deflection state. Within the actuation region, the element maintains a first stiffness value that allows controlled movement. When the limit of the actuation region is reached, the element's stiffness automatically increases to a second value, blocking further movement. This parameter change is achieved through the element's geometric design and material properties, eliminating the need for additional control mechanisms.
Solution Approach 2:
The bending element performs the dual function of allowing movement and blocking movement automatically based on its own deflection state. When the actuation region limit is reached, the element self-stiffens through its geometric configuration, eliminating the need for external control systems. The element serves itself by using its own deformation to trigger the stiffness change that blocks movement outside the actuation region.
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
Prevents component damage and particle formation by allowing controlled movement within the actuation region and blocking movement outside it, ensuring stable operation under tremors.
Implementation Method 1
a bending element, whose stiffness increases abruptly upon reaching a limit of the actuation region so as to block the movement of the second component relative to the first component
Data Source
AI summary
An optical system for a projection exposure apparatus comprises: a first component; a second component which is actuable within an actuation region relative to the first component; and an end stop device which permits a movement of the second component relative to the first component within the actuation region and which blocks it outside the actuation region. The end stop device comprises a bending element having a stiffness which increases abruptly upon reaching a limit of the actuation region to block the movement of the second component relative to the first component.