Radiation Conditioning System With Chaotic Mixing Stages
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Solution Overview
Problem
Current metrology systems, particularly scatterometers, face challenges in achieving complete homogeneity of radiation beams, both spatially and angularly, which is crucial for accurate measurements in lithographic processes.
Innovation Solution
A system comprising multiple mixing stages with a transformation stage in between, utilizing chaotic mixing rods or similar elements, to condition the radiation beam, ensuring both spatial and angular homogenization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single mixing stage is used to homogenize the radiation beam, then the device complexity is reduced, but the homogeneity of angular distribution is insufficient
Solution Approach 1:
The mixing process is divided into multiple stages: a first mixing stage that homogenizes spatial distribution, followed by a transformation stage that converts spatial homogeneity to angular homogeneity, and then a second mixing stage that further homogenizes the angular distribution. This segmentation allows each stage to specialize in a particular aspect of homogenization, achieving complete angular homogeneity that would be difficult with a single stage.
2Manufacturing precision
If a transformation stage is added between mixing stages, then the angular homogeneity is improved, but the device complexity increases
Solution Approach 1:
The transformation stage acts as an intermediary between the first and second mixing stages. It receives radiation with homogenized spatial distribution from the first mixing stage and transforms it into radiation with homogenized angular distribution, which is then further processed by the second mixing stage. This intermediary transformation is essential for achieving complete angular homogeneity.
3Manufacturing precision
If multiple mixing stages with transformation are used, then the beam homogeneity is improved, but the measurement throughput is reduced
Solution Approach 1:
The transformation stage changes the parameters of the radiation beam by transforming spatial distribution characteristics into angular distribution characteristics. This parameter transformation allows the system to achieve complete angular homogeneity without requiring an excessive number of mixing stages, thereby balancing measurement precision with acceptable throughput.
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 results in a more complete homogenization of the radiation beam, enhancing measurement accuracy and throughput in lithographic processes by achieving uniform spatial and angular distributions.
Implementation Method 1
The chaotic mixing rod effectively homogenizes the spatial distribution of radiation across the illuminating beam
Implementation Method 2
The mixing element has a form that causes multiple internal reflections of radiation passing through it
Implementation Method 3
The provisional patent application 62/299,723 proposes to use a filter element in a pupil plane of the optical system, to modulate the angular distribution of radiation
Data Source
AI summary
Disclosed are an optical system for conditioning a beam of radiation, and an illumination system and metrology apparatus comprising such an optical system. The optical system comprises one or more optical mixing elements in an optical system. The optical system defines at least a first optical mixing stage, at least a second optical mixing stage, and at least one transformation stage, configured such that radiation entering the second optical mixing stage includes a transformed version of radiation exiting the first optical mixing stage. The first and second optical mixing stages can be provided using separate optical mixing elements, or by multiple passes through the same optical mixing element. The transformation stage can be a Fourier transformation stage. Both spatial distribution and angular distribution of illumination can be homogenized as desired.