DUV AOD Beam Shaping for Longer Sweep Length Scanning
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Solution Overview
Problem
Existing acousto-optical deflectors are not sufficiently transmissive in the deep ultraviolet spectrum, limiting their angular deflection range and scan lengths, which results in low printing speeds for pattern generators.
Innovation Solution
An optical train design with expanders before and after the AOD that reshapes the radiation beam into a high aspect ratio, allowing it to fill the AOD aperture, and then reshapes it back to a writing spot, effectively increasing the deflection angle and scan length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If legacy acousto-optical media are used, then the system is simpler and cheaper, but the media are not sufficiently transmissive in the deep ultraviolet spectrum, limiting angular deflection range and scan lengths
Solution Approach 1:
The patent introduces an optical train with expanders and lenses as intermediary components between the radiation source and the AOD, and between the AOD and the substrate. These intermediaries reshape the beam into a high aspect ratio format that fills the AOD aperture, enabling effective DUV transmission while maintaining system functionality. The expander optics act as mediators to bridge the limitations of DUV-transmissive AODs.
Solution Approach 2:
The patent changes the beam parameters by reshaping the radiation into a high aspect ratio beam that fills the AOD aperture. This parameter change optimizes the interaction between the DUV radiation and the acousto-optical medium, maximizing deflection efficiency while maintaining transmissivity. The beam aspect ratio is specifically adjusted to match the AOD aperture geometry.
2Length of moving object
If the AOD aperture is filled with high aspect ratio beam, then the angular deflection range and scan length are increased, but the optical train complexity increases
Solution Approach 1:
The patent transforms the beam from a conventional circular cross-section to a high aspect ratio rectangular cross-section by introducing expander optics. This dimensional transformation allows the beam to fill the AOD aperture more effectively, maximizing the utilization of the acoustic wave interaction region and thereby increasing the angular deflection range and scan length.
Solution Approach 2:
The optical train is segmented into distinct functional components: expanders before the AOD to shape the beam, the AOD itself for acoustic-optical interaction, and additional optics after the AOD to reshape the deflected beam. This segmentation allows each component to be optimized independently for its specific function while working together to achieve extended scan length.
3Productivity
If the beam is reshaped into high aspect ratio to fill AOD aperture, then the number of resolved spots and writing speed are increased, but the device complexity increases
Solution Approach 1:
The expander optics perform preliminary beam shaping before the radiation reaches the AOD. By pre-shaping the beam into a high aspect ratio format that fills the aperture, the system maximizes the effective interaction area and deflection efficiency from the outset. This preliminary action ensures that when the acoustic wave modulates the refractive index, the maximum number of resolved spots are generated across the scan length.
Solution Approach 2:
The patent replaces mechanical scanning methods with acousto-optical deflection using high-frequency acoustic waves in the crystal medium. This substitution enables rapid scanning at speeds unachievable by mechanical means, while the optical train components facilitate the beam shaping needed to maximize the resolution and speed performance.
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 design significantly increases the number of resolved spots and writing speed, achieving high-resolution patterning with improved printing speed using commercially available AODs, while maintaining a lower material cost and complexity.
Implementation Method 1
An AOD periodically applies a high-frequency acoustic wave, over one million Hz, to a crystal to modify its optical properties
Implementation Method 2
an optical train design with expanders before and after the AOD that reshapes the radiation beam into a high aspect ratio
Implementation Method 3
then reshapes it back to a writing spot, effectively increasing the deflection angle and scan length
Data Source
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AI summary
The technology disclosed uses extreme beam shaping to increase the amount of energy projected through an AOD. First and second expanders and are described that are positioned before and after the AOD. In one implementation, the optical path shapes energy from a source, such as a Gaussian laser spot, deflects it, then reshapes it into a writing spot. In another implementation for image capture, rather than projection system, the disclosed optics reshape a reading spot from an imaged surface to a high-aspect ratio beam at an AOD exit, subject to deflection by the AOD. The optics reshape the radiation relayed by the high-aspect ratio beam through the AOD to a detector. Since light can travel in both directions through an optical system, the details described in terms of projecting a writing spot onto a radiation sensitive surface also apply to metrology sweeping a reading spot over an imaged surface. The most significant difference is using multiple detectors, such as a line camera, an area camera, a spectrometer, scatterometer or an interferometer could be used in a system that read from the workpiece instead of writing to it. All of the references that follow to a laser spot or writing spot are hereby extended to a reading spot.