In-situ EUV Lithography Contamination Measurement via Reference Region
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Solution Overview
Problem
Current methods for measuring contamination in extreme ultraviolet lithography are inefficient, relying on ex-situ measurements and complex chemical analysis, which are destructive and prone to statistical variation, and require expensive recalibration procedures due to the use of reference mirrors that also contaminate over time.
Innovation Solution
A method and system for in-situ measurement of contamination in lithographical elements, where a test region and reference region on the same element are used, allowing direct optical measurement of reflectivity or transmissivity within the process chamber, reducing the need for external reference elements and minimizing manipulation of the elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ex-situ measurements with reference mirrors are used, then contamination can be measured, but measurement precision deteriorates due to statistical variation and recalibration requirements
Solution Approach 1:
The patent combines the reference region and test region measurements into a single integrated measurement process on one lithographical element. The reference beam and test beam are measured simultaneously using the same detector, eliminating the need for separate measurements with different reference mirrors. This merging approach removes the statistical variation between separate measurements and eliminates recalibration requirements, directly improving both measurement precision and reliability.
Solution Approach 2:
The patent introduces an intermediary reference region on the same lithographical element that is not exposed to the contaminant. This reference region serves as a stable reference that remains constant during the measurement process, allowing direct comparison with the contaminated test region. The intermediary reference region eliminates the need for external reference mirrors that themselves contaminate over time, providing a stable baseline for contamination measurement.
2Measurement precision
If reference mirrors are used for measurement, then contamination levels can be determined, but device complexity increases due to recalibration procedures
Solution Approach 1:
The lithographical element serves itself as both the test object and the reference object. The reference region is created by simply blocking part of the lithographical element from the contaminant, rather than requiring a separate reference mirror. This self-service approach eliminates the need for external reference standards and complex recalibration procedures, reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The patent performs preliminary action by creating the reference region before contamination occurs. The reference region is established by blocking part of the lithographical element from the contaminant source at the beginning of the process. This preliminary creation of the reference region eliminates the need for subsequent recalibration procedures, as the reference is already in place and remains stable throughout the measurement process.
3Measurement precision
If multiple measurements are performed with different reference mirrors, then contamination can be assessed, but loss of time increases due to recalibration between measurements
Solution Approach 1:
The patent enables continuous measurement by performing both reference and test measurements simultaneously in a single continuous process. The reference beam and test beam are measured at the same time using the same detector, eliminating the need to switch between different reference mirrors. This continuity of measurement action removes the time losses associated with recalibration between measurements, allowing rapid assessment of contamination levels.
4Measurement precision
If lithographical elements are manipulated for external measurement, then contamination can be measured, but reliability decreases due to element manipulation
Solution Approach 1:
The lithographical element performs self-measurement by comparing its own reference region with its contaminated test region. This self-service approach eliminates the need to remove and manipulate the element for external measurement. The element remains in place throughout the measurement process, and the measurement is performed in-situ, eliminating reliability issues associated with element manipulation and handling.
Solution Approach 2:
The patent performs preliminary action by creating both the reference region and test region on the same lithographical element before any measurement takes place. The reference region is established by blocking part of the element from the contaminant, and both regions are then measured in-situ without removing the element. This preliminary setup eliminates the need for subsequent manipulation of the element for measurement, ensuring consistent and reliable results.
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 provides more accurate and stable contamination measurements with reduced uncertainty, avoiding the need for destructive sampling and complex recalibration, and allows for precise correlation of contamination levels using the same light beam as the exposure beam, thereby improving the reliability and efficiency of contamination monitoring.
Implementation Method 1
the components contamination that outgases during the exposure may contaminate the EUV optics
Implementation Method 2
the components contamination that outgases during the exposure may contaminate the EUV optics and as a consequence diminishes both the reflectivity of the reticle as well as the reflectivity of the imaging optics
Implementation Method 3
At short wavelengths however, e.g. for extreme ultraviolet lithography and soft X-ray lithography, the electromagnetic radiation is absorbed by most materials, including glass used for conventional lenses and masks
Data Source
AI summary
A method and system for measuring contamination of a lithographic element is disclosed. In one aspect, the method comprises providing a first lithographical element in a process chamber. The method further comprises providing a second lithographical element in the process chamber. The method further comprises covering part of the first lithographical element providing a reference region. The method further comprises providing a contaminant in the process chamber. The method further comprises redirecting an exposure beam via the test region of the first lithographical element towards the second lithographical element whereby at least one of the lithographical elements gets contaminated by the contaminant. The method further comprises measuring the level of contamination of the at least one contaminated lithographical element in the process chamber.