Solid Immersion Lens Position Control for Lithography Metrology
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Solution Overview
Problem
Current techniques face challenges in maintaining accuracy and reducing the size of metrology targets in lithographic processing, particularly in controlling the position of optical components relative to surfaces at solid immersion gap distances, which are crucial for precise measurement and inspection in lithographic techniques.
Innovation Solution
A method involving the use of a solid immersion lens (SIL) with a high numerical aperture, where the gap between the SIL and the substrate is controlled using position measurement signals from first and second position measurement processes, and radiation detection signals to adjust the position of the optical component relative to the surface, allowing for precise positioning and measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gap between the solid immersion lens and the substrate is reduced to increase numerical aperture, then measurement precision is improved, but the difficulty of detecting and measuring the gap position increases
Solution Approach 1:
The patent employs feedback control by detecting the gap between the solid immersion lens and substrate using optical means (reflective or transmissive sensors) and adjusting the lens position accordingly. The detection system provides real-time feedback on gap distance, enabling automated positioning to maintain the optimal gap for maximum numerical aperture while avoiding contact with the substrate surface.
Solution Approach 2:
The patent introduces an intermediary detection system that uses optical sensors (reflective or transmissive types) as mediators to measure the gap distance. These sensors act as intermediaries between the solid immersion lens and substrate, converting the physical gap into detectable optical signals that can be processed to control lens positioning.
2Area of stationary object
If the target size is reduced to decrease space occupation, then area is reduced, but measurement accuracy deteriorates
Solution Approach 1:
The patent changes the optical parameters of the measurement system by introducing a solid immersion lens with high numerical aperture and adjusting the gap distance parameter. This optical parameter change enables the system to achieve high measurement accuracy on much smaller targets compared to conventional optical systems, as the enhanced numerical aperture provides superior light collection and resolution capabilities.
Solution Approach 2:
The patent replaces conventional mechanical measurement systems with an optical measurement system utilizing a solid immersion lens. This substitution enables non-contact measurement with higher precision, allowing accurate measurement of microscopic features on reduced-size targets without the mechanical constraints that would limit target size reduction.
3Measurement precision
If the solid immersion lens is positioned closer to the substrate to increase numerical aperture, then measurement precision is improved, but the stability of the optical component position deteriorates
Solution Approach 1:
The patent uses feedback control to maintain stable positioning of the solid immersion lens relative to the substrate. Optical sensors continuously monitor the gap distance and provide feedback to the positioning system, enabling real-time adjustments to compensate for vibrations and drift, thereby maintaining both close proximity for high numerical aperture and positional stability.
Solution Approach 2:
The patent implements dynamic positioning control that allows the solid immersion lens to be adjusted in real-time to maintain the optimal gap distance. The system dynamically responds to changes in conditions (such as thermal expansion or mechanical vibrations) to keep the lens-stabilized at the desired position, combining the benefits of close proximity with positional stability.
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 enables accurate and precise control of the optical component's position, enhancing measurement accuracy and allowing for the use of smaller targets, thereby improving the efficiency and precision of lithographic processes.
Implementation Method 1
The extreme proximity of the SIL with the substrate surface (e.g., target surface) results in near-field radiation with a very high effective numerical aperture (NA) larger than 1
Implementation Method 2
a scatterometer in which a beam of radiation is directed onto a target on the surface of the substrate and properties of the scattered or reflected beam are measured
Implementation Method 3
comparing one or more properties of the beam before and after it has been reflected or scattered by the substrate
Implementation Method 4
obtaining a first signal by a first position measurement process; controlling relative movement between the optical component and the surface for a first range of motion using the first signal
Data Source
AI summary
A method of position control of an optical component relative to a surface is disclosed. The method may include: obtaining a first signal by a first position measurement process; controlling relative movement between the optical component and the surface for a first range of motion using the first signal; obtaining a second signal by a second position measurement process different than the first position measurement process; and controlling relative movement between the optical component and the surface for a second range of motion using the second signal, the second range of motion being nearer the surface than the first range of motion.