Active Metrology Support for EUV Optical Imaging Accuracy
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Solution Overview
Problem
High numerical aperture optical imaging arrangements in EUV microlithography face challenges with line of sight accuracy, large optical elements leading to reduced rigidity and increased dynamic issues, and residual low-frequency vibration disturbances affecting imaging quality.
Innovation Solution
Measuring mechanical disturbances acting on a first optical element and using this information to control an active device acting on a second optical element to correct imaging errors, which is more accessible and less restricted by space, thereby maintaining imaging accuracy and reducing the impact of vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high numerical aperture reflective systems are used in EUV range to achieve enhanced resolution, then imaging resolution is improved, but line of sight accuracy deteriorates due to increased sensitivity to component position variations
Solution Approach 1:
The patent applies parameter changes by actively adjusting the position and orientation of optical elements using actuators to compensate for the inverse relationship between numerical aperture and line of sight accuracy. The control system modifies physical parameters (position, orientation) of optical components to maintain imaging accuracy despite high NA requirements.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the positions and orientations of optical elements and actively adjusting them to maintain predetermined spatial relationships. This closed-loop system compensates for position variations that would otherwise deteriorate line of sight accuracy in high NA systems.
2Manufacturing precision
If large optical elements are used to achieve high numerical aperture, then imaging accuracy is improved, but rigidity deteriorates leading to increased dynamic issues and vibration sensitivity
Solution Approach 1:
The patent applies dynamics by implementing active support units with actuators that continuously adjust the positions and orientations of large optical elements. This dynamic compensation system counteracts the reduced rigidity and vibration sensitivity of large elements, maintaining imaging accuracy despite their inherent structural challenges.
Solution Approach 2:
The patent uses feedback control to monitor and actively adjust the positions of large optical elements, compensating for their reduced rigidity. The control system detects position variations and applies corrective movements to maintain predetermined spatial relationships, effectively managing the dynamic issues associated with large element sizes.
3Measurement precision
If optical elements are supported to maintain predetermined spatial relationships, then line of sight accuracy is improved, but device complexity increases due to multiple support structures and active adjustment mechanisms
Solution Approach 1:
The patent applies universality by designing support structures that perform multiple functions: mechanical support, active position adjustment, and vibration compensation. The active support units integrate sensing and actuation capabilities, reducing the need for separate dedicated components and simplifying the overall system architecture despite the high precision requirements.
4Reliability
If vibration isolation measures are implemented to reduce mechanical disturbances, then imaging stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent implements feedback control by continuously monitoring mechanical disturbances and actively compensating for their effects on optical element positions. This active vibration compensation approach replaces passive isolation measures, achieving imaging stability through real-time correction rather than complex mechanical isolation structures.
Solution Approach 2:
The patent substitutes mechanical vibration isolation systems with an active control system using sensors and actuators. Instead of relying on complex mechanical damping structures, the system uses electronic sensing and active position adjustment to achieve the same stability goal, reducing mechanical complexity.
Data Source
AI summary
An optical imaging arrangement includes an optical projection system, a support structure system and a control device. The optical projection system includes a group of optical elements supported by the support structure system and configured to transfer, in an exposure process using exposure light along an exposure light path, an image of a pattern of a mask onto a substrate. The group of optical elements includes a first optical element and a second optical element and the control device includes a sensor device and an active device. The sensor device is functionally associated to the first optical element and is configured to capture mechanical disturbance information representative of a mechanical disturbance acting on the first optical element in at least one degree of freedom up to all six degrees of freedom.