Hollow Waveguide Stabilizes Lithography Illumination
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Solution Overview
Problem
Illumination optical units for projection lithography are sensitive to light source instabilities, which affect the homogeneity and stability of the illumination light beam, requiring complex mirror arrays with precise control and high etendue values.
Innovation Solution
An illumination optical unit with a hollow waveguide component upstream of the mirror array for homogenizing and stabilizing the light beam, combined with a random phase element to reduce sensitivity to mode instabilities, and a relay optical unit for imaging, allowing for fewer mirrors and lower etendue values, achieving high throughput and homogenization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a complex mirror array with precise control is used to compensate for light source instabilities, then illumination homogeneity can be maintained, but device complexity increases significantly
Solution Approach 1:
The hollow waveguide component performs preliminary homogenization and stabilization of the illumination light beam before it reaches the mirror array. By pre-processing the light beam to achieve homogeneous intensity distribution and stable illumination characteristics upstream of the mirror array, the system reduces the complexity requirements for the mirror array while maintaining overall illumination homogeneity.
2Use of energy by moving object
If high etendue values are used to improve light collection, then more light can be captured, but the system becomes more sensitive to light source instabilities
Solution Approach 1:
The hollow waveguide component acts as an intermediary element between the light source and the mirror array. It mediates the light beam by homogenizing the intensity distribution and stabilizing illumination characteristics, thereby decoupling the system's reliability from sensitivity to light source instabilities while maintaining effective light collection.
3Device complexity
If fewer mirrors are used in the mirror array, then device complexity is reduced, but illumination homogeneity and stability deteriorate
Solution Approach 1:
The hollow waveguide performs preliminary stabilization of the illumination light beam before it reaches the mirror array. This pre-stabilization ensures that even with fewer mirrors in the array, the illumination maintains its homogeneity and stability characteristics, as the waveguide has already conditioned the light beam upstream.
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
The solution provides a stable and homogeneous illumination light beam with reduced sensitivity to light source instabilities, enabling the production of microstructured or nanostructured components with high precision and efficiency, such as semiconductor chips, using a simpler mirror array and minimizing losses.
Implementation Method 1
The hollow waveguide component can have a ratio of waveguide length to waveguide cross section of at least 100. This can enable a sufficiently high number of internal reflections in the hollow waveguide component and thus a good intermixing of the illumination light
Implementation Method 2
A random phase element (RPE) can be arranged between the primary light source and the optical hollow waveguide component, the random phase element supporting light mixing even in the phase space
Data Source
AI summary
An illumination optical unit for projection lithography guides illumination light toward an object field and has a mirror array including a multiplicity of individual mirrors which are tiltable independently. A condenser optical unit transfers an arrangement plane of the mirror array into a pupil plane of the illumination optical unit. An optical hollow waveguide component of the illumination optical unit is upstream of the mirror array in the beam path of the illumination light and homogenizes and stabilizes an illumination light beam incident on the mirror array. An input coupling optical unit is upstream of the hollow waveguide component and couples an incident illumination light beam into the hollow waveguide component. A relay optical unit images a beam exit surface of the hollow waveguide component onto the mirror array. The illumination optical unit is insensitive to light source instabilities.