Acoustically Tunable Filter for Lithography Alignment
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Solution Overview
Problem
Lithographic processes face limitations due to the inability to match optimal narrow-band radiation wavelengths for alignment marks, which can fall outside the discrete wavelengths provided by conventional alignment systems, leading to adverse alignment performance and reduced flexibility in modifying processes or marks.
Innovation Solution
An alignment system that includes a radiation source capable of converting narrow-band radiation into continuous, broad-band radiation, using an acoustically tunable narrow pass-band filter to generate narrow-band linearly polarized radiation, and a tunable filter to select desired wavelengths within a continuous spectral range, allowing for alignment of wafers with improved signal strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional alignment systems use discrete narrow-band wavelengths, then alignment signal quality is improved for specific alignment marks, but flexibility to match optimal wavelengths for different alignment marks or processes is reduced
Solution Approach 1:
The system employs a continuously tunable wavelength source that can dynamically adjust to any wavelength within a broad spectral range, replacing the static discrete wavelength selection of conventional systems. This allows real-time optimization of alignment signal quality for different alignment marks and processing conditions while maintaining full spectral flexibility.
Solution Approach 2:
The invention changes the fundamental parameter of wavelength selection from discrete fixed values to continuous tunable values across a broad spectrum. By using a broadly tunable laser source combined with acoustic optical filtering, the system can precisely control wavelength while maintaining narrow bandwidth, thereby achieving both high measurement precision and adaptability.
2Device complexity
If discrete wavelength sources are used, then system complexity is reduced, but the ability to provide optimal wavelength for specific alignment processes is limited
Solution Approach 1:
The system introduces an acoustic optical filter as an intermediary component between a broadly tunable laser source and the alignment mark. This filter enables precise wavelength selection and narrow bandwidth control, achieving high alignment accuracy while keeping the overall system architecture relatively simple through the use of well-established acoustic optical technology.
3Adaptability or versatility
If broadband radiation is used, then wavelength flexibility is improved, but alignment signal intensity is reduced due to energy distribution across spectrum
Solution Approach 1:
The system applies local quality by maintaining broadband capability for wavelength selection while concentrating the radiation energy into a narrow bandwidth at the selected wavelength. The acoustic optical filter ensures that only a narrow spectral band passes through, thereby concentrating the broadband source's energy into a focused, high-intensity narrow-band output that optimizes alignment signal strength.
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 solution enhances alignment performance by enabling the selection of optimal wavelengths, even within spectral gaps, thereby improving alignment accuracy and flexibility in lithographic processes and mark modifications.
Implementation Method 1
a radiation source configured to convert narrow-band radiation into continuous, flat and broad-band radiation
Implementation Method 2
photonic crystal fibers coupled to the fiber amplifier and configured to generate the continuous, flat and broad spectrum of radiation from the high intensity short pulse radiation
Implementation Method 3
An acoustically tunable narrow pass-band filter is coupled to the radiation source and is configured to filter the broad-band radiation into narrow-band linearly polarized radiation
Implementation Method 4
a tunable filter to select desired wavelengths within a continuous spectral range
Implementation Method 5
The radiation source may comprise a fiber amplifier configured to generate high intensity short pulse radiation with a high repetition rate
Data Source
AI summary
A lithographic apparatus has an alignment system including a radiation source configured to convert narrow-band radiation into continuous, flat and broad-band radiation. An acoustically tunable narrow pass-band filter filters the broad-band radiation into narrow-band linearly polarized radiation. The narrow-band radiation may be focused on alignment targets of a wafer so as to enable alignment of the wafer. In an embodiment, the filter is configured to modulate an intensity and wavelength of radiation produced by the radiation source and to have multiple simultaneous pass-bands. The radiation source generates radiation that has high spatial coherence and low temporal coherence.