Metrology Support Substructures for EUV 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 and vibration-induced distortions due to large optical elements and rigid support structures, which are difficult to manufacture and control effectively.
Innovation Solution
The metrology support structure is split into smaller substructures to increase rigidity and resonant frequency, reducing susceptibility to low-frequency vibration disturbances and improving imaging accuracy by actively controlling optical elements in all six degrees of freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single rigid metrology support structure is used, then manufacturing difficulty increases, but vibration susceptibility decreases
Solution Approach 1:
The patent divides the single metrology support structure into multiple separate metrology support substructures. Each substructure supports a specific metrology device or group of devices, allowing them to be manufactured and aligned independently. This segmentation reduces the manufacturing difficulty of each individual substructure while collectively providing the necessary stability for high-precision imaging.
2Reliability
If a single large metrology support structure is used, then vibration resistance improves, but resonant frequency decreases
Solution Approach 1:
By dividing the large support structure into smaller substructures, each substructure has higher natural resonant frequencies due to their reduced mass and size. These smaller substructures can respond more quickly to control inputs and are less prone to low-frequency vibrations, while collectively providing the necessary vibration resistance through their distributed arrangement.
Solution Approach 2:
The patent implements active control of the optical elements and metrology devices mounted on the substructures. This dynamic control allows the system to compensate for vibrations and maintain imaging accuracy by actively adjusting the positions of components in response to detected disturbances, effectively increasing the system's resonant characteristics.
3Measurement precision
If optical elements are actively controlled in all six degrees of freedom, then imaging accuracy improves, but system complexity increases
Solution Approach 1:
The patent assigns specific control functions to individual metrology devices and support substructures. Each metrology device measures specific parameters (position, orientation) of associated optical elements, and each support substructure provides controlled adjustment for specific degrees of freedom. This segmentation of control functions reduces the complexity of the overall control system by localizing measurement and control tasks.
Solution Approach 2:
The patent implements a feedback control system where metrology devices continuously measure the position and orientation of optical elements, and this information is used to actively adjust the elements' positions. The feedback loop compensates for disturbances and maintains imaging accuracy by dynamically correcting deviations from the desired optical configuration.
Data Source
AI summary
An optical imaging arrangement includes an optical projection system and a support structure system. The optical projection system includes a group of optical elements 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 support structure system includes an optical element support structure and a metrology support structure. The optical element support structure supports the group of optical elements, while the metrology support structure supports a group of metrology devices associated with the group of optical elements and configured to capture status information representative of at least one of a position and an orientation of each of the optical elements in at least one degree of freedom up to all six degrees of freedom.