Visible Laser Alignment for UV Lithography Beam Shaping
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Solution Overview
Problem
Existing methods for testing the optical performance of diffractive optical elements in ultraviolet lithography systems are costly, inconvenient, and difficult to align due to the use of expensive ultraviolet equipment and toxic fluorine-containing gases, making it challenging to achieve precise off-axis illumination and high energy efficiency.
Innovation Solution
A detection apparatus using a visible wavelength laser and optical units such as beam expanders, splitters, imaging lenses, and energy sensors, with a central obscuration on the CCD image sensor, allows for the detection of far field optical intensity distribution and energy efficiency, enabling quick and cost-effective testing of diffractive optical elements suitable for ultraviolet wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultraviolet equipment is used for testing, then measurement precision is improved, but device cost increases and ease of operation deteriorates
Solution Approach 1:
A visible light optical path is introduced as an intermediary to guide and align the ultraviolet optical path. The visible light path serves as a mediator that makes the invisible UV path adjustable and observable, allowing operators to align mirrors, lenses, and detectors by following the visible light trajectory before switching to UV mode for actual measurement.
Solution Approach 2:
The system uses visible light (typically green or red laser) to trace the optical path during alignment, which appears as colored visible beams. This color change from invisible UV to visible light enables operators to see and adjust the optical path components. Once alignment is complete, the system switches to ultraviolet wavelength for the actual performance measurement.
2Measurement precision
If ultraviolet laser and sensors are used, then measurement precision is improved, but device cost increases
Solution Approach 1:
The system creates an optical copy by using visible light to reproduce the same optical path geometry as the ultraviolet light would follow. By measuring the visible light path through the same optical components (mirrors, lenses, beam shaping elements), the system obtains measurement data that accurately represents the UV performance without requiring expensive UV-specific detectors and light sources for the actual measurement process.
3Power
If fluorine-containing mixed gas is used, then laser performance is improved, but harmful factors increase
Solution Approach 1:
The system replaces the expensive and hazardous fluorine-containing mixed gas with a simple, safe, and inexpensive visible light laser source. The visible light laser does not require special gas mixtures and produces no corrosive or toxic byproducts. This substitution maintains sufficient laser power for optical path alignment and measurement while eliminating the harmful chemical properties of the UV laser medium.
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 provides a low-cost, easy-to-operate method for testing diffractive optical elements, allowing for convenient optical path adjustments and safe operation, while maintaining the ability to assess performance across various ultraviolet bands with high accuracy.
Implementation Method 1
a beam splitter, a first far field imaging lens
Implementation Method 2
the output beam of beam shaping element is detected by ultraviolet CCD imaging camera at far field (the focal plane of far field imaging lens)
Implementation Method 3
diffractive optical method is usually adopted for the beam shaping element
Implementation Method 4
the output beam is focused on the ultraviolet energy sensor to detect the energy efficiency
Data Source
Figure 1~2
AI summary
A detection apparatus and method for testing optical performance of beam shaping element used in ultraviolet lithography machine; The apparatus comprises visible wavelength laser and other optical units placed along the optical axis including, in order from laser side, (a) beam expander lens group, (b) beam splitter, (c) first far field imaging lens, (d) adjustable aperture or (e) CCD image sensor, (f) second far field imaging lens and (g) energy sensor. The detection apparatus is suitable be employed to detect the optical performance of beam shaping element working at any ultraviolet band, and provides the features of low cost, easy operation and quick measurement.