Compensating Force Control for Lithographic Illumination Stability
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Solution Overview
Problem
Lithographic apparatuses face instability in controlling spatial intensity distribution due to radiation bursts, which can alter the orientation of controllable optical elements, leading to unwanted changes in illumination modes and affecting critical dimensions.
Innovation Solution
An array of individually controllable optical elements, with a controller that applies a compensating force to stabilize their orientation during radiation bursts, either by feed-forward correction or pre-adjusting to offset orientations, and optionally surrounding elements with ionized gas to reduce charge-induced movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If individually controllable optical elements are used to form desired illumination modes, then adaptability and versatility are improved, but stability deteriorates due to radiation bursts altering element orientations
Solution Approach 1:
The controller applies a compensating force to the optical elements before radiation bursts occur, pre-counteracting the expected radiation pressure effects. This preliminary anti-action prevents the radiation bursts from altering element orientations, thereby maintaining stability while preserving the adaptability of illumination mode control.
Solution Approach 2:
The system implements feedback control by monitoring the orientations of optical elements and adjusting compensating forces in real-time. This feedback mechanism detects deviations caused by radiation bursts and automatically corrects them, ensuring stable element orientations while maintaining the ability to switch between different illumination modes.
2Stability of the object's composition
If compensating force is applied to maintain element orientations during radiation bursts, then stability is improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The control system automatically adjusts optical element orientations without requiring external intervention. The controller autonomously detects radiation bursts and applies appropriate compensating forces, making the system self-regulating. This self-service approach maintains stability while minimizing the need for complex external control infrastructure.
Solution Approach 2:
The system changes operational parameters dynamically by adjusting the orientation of optical elements in response to radiation bursts. By modifying these parameters in real-time through automated control, the system maintains stability without requiring fundamentally complex additional hardware, leveraging parameter adaptation instead.
3Stability of the object's composition
If optical elements are pre-adjusted to offset orientations before radiation bursts, then stability is improved, but productivity decreases due to additional positioning steps
Solution Approach 1:
The system performs preliminary positioning of optical elements to offset orientations before radiation bursts occur. This preliminary action prepares the elements in advance so that when radiation bursts hit, the elements are already in the correct compensated positions, maintaining stability while minimizing disruption to the overall process flow.
Solution Approach 2:
The control system continuously monitors and adjusts element orientations without interrupting the illumination process. By maintaining continuous control rather than discrete positioning steps, the system preserves stability while ensuring uninterrupted productivity, as the adjustments occur seamlessly during normal operation.
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 approach enhances the accuracy and stability of illumination modes, maintaining desired orientations during radiation bursts and improving the consistency of critical dimensions in lithographic processes.
Implementation Method 1
a controller to control orientation of one or more of the elements, the controller configured to apply force to the one or more of the elements which at least partially compensates for force applied to the one or more elements by a burst of radiation incident upon the one or more elements
Implementation Method 2
one or more of the elements are surrounded by an ionized gas
Data Source
AI summary
An illumination system having an array of individually controllable optical elements is disclosed, wherein each element is moveable between a plurality of orientations which may be selected in order to form desired illumination modes. The illumination system includes a controller to control orientation of one or more of the elements, the controller configured to apply force to the one or more elements which at least partially compensates for force applied to the one or more elements by a burst of radiation incident upon the one or more elements.