EUV Source Property Monitoring via Thermal Load Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining properties of an EUV source in semiconductor lithography projection exposure apparatuses are cumbersome and unreliable due to the influence of multiple optical elements in the light path, requiring production interruptions and providing corrupted measurement results.
Innovation Solution
A method that determines the thermal load on components of the apparatus and uses this data to indirectly assess EUV source properties, leveraging existing sensor technology to monitor contamination and changes in source power without interrupting production or modifying the apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If properties of the source are determined indirectly from the intensity distribution of the projection light on the wafer plane, then source properties can be assessed without additional measurement devices, but the measurement results are corrupted by multiple optical elements in the light path and production must be interrupted
Solution Approach 1:
The patent extracts the measurement function from the wafer plane (downstream of optical elements) and relocates it to the illumination system (upstream of optical elements). By measuring intensity distribution at an intermediate focus or on a monitoring wafer before the projection optical system, the measurement bypasses the corrupting influence of projection optical elements while still using existing sensors in the apparatus.
Solution Approach 2:
The patent introduces an intermediate measurement plane (intermediate focus or monitoring wafer) as a mediator between the source and the final wafer plane. This intermediary location allows measurement of source properties before the light passes through the projection optical system, thus avoiding corruption by those elements while still using the existing illumination system infrastructure.
2Reliability
If measurements are performed to determine source properties, then operating parameters can be monitored, but production must be interrupted
Solution Approach 1:
The patent enables continuous monitoring of source properties by utilizing the illumination system's existing sensors and measurement capabilities during normal operation. The measurement of intensity distribution at the intermediate focus or monitoring wafer can be performed without interrupting the lithography process, as it uses light that would otherwise be used for exposure or is taken from a portion of the illumination beam.
3Device complexity
If existing sensor technology is used to monitor source properties, then no additional measurement devices are needed, but the measurement is influenced by multiple optical elements
Solution Approach 1:
The patent segments the optical path into distinct measurement and exposure regions. By measuring at the intermediate focus or monitoring wafer location, it separates the measurement function from the projection function, allowing existing sensors to be used for source property monitoring without their readings being corrupted by the projection optical elements that would otherwise be in the complete light path.
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
Enables reliable and non-intrusive monitoring of EUV source properties, particularly contamination of collector mirrors and source power changes, allowing for timely maintenance and adjustment without production interruptions or structural modifications.
Implementation Method 1
A thermal load for a component of the projection exposure apparatus is determined and the property of the source is deduced on the basis of the thermal load determined. The disclosure is based on the assumption that the thermal load acting on a component is proportional to or at least positively correlated with the intensity of the incident electromagnetic radiation
Data Source
AI summary
The disclosure provides a method for determining at least one property of an EUV source in a projection exposure apparatus for semiconductor lithography, wherein the property is determined on the basis of the electromagnetic radiation emanating from the EUV source, and wherein a thermal load for a component of the projection exposure apparatus is determined and the property is deduced on the basis of the thermal load determined.