Reflective Optical Element Electrode Integration for Lithography
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithographic apparatuses face challenges in reliably determining the degradation of reflective optical elements, which affects the dosage and profile of electromagnetic radiation projected onto the patterning device, leading to potential inaccuracies and downtime due to reliance on a secondary optical reference.
Innovation Solution
An optical apparatus for a reticle stage of a lithographic apparatus, featuring a reflective optical element with at least two electrodes at its surface, and a measurement system that measures electrical characteristics between these electrodes, allowing for direct assessment of reflectivity degradation without relying on additional optical references.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a secondary optical reference is used to measure degradation of the reflective optical element, then the measurement can be performed, but the system complexity increases and downtime increases due to need for reference replacement
Solution Approach 1:
The patent extracts the measurement function from the optical domain and places electrodes directly on the reflective optical element surface. This eliminates the need for separate optical reference elements and sensors, reducing system complexity while maintaining measurement capability through direct electrical contact with the element being measured.
Solution Approach 2:
The reflective optical element serves dual functions: it performs its primary optical function of reflecting radiation, and simultaneously serves as the measurement sensor itself through the electrodes integrated on its surface. This eliminates the need for separate reference elements, reducing both system complexity and downtime.
2Measurement precision
If a secondary optical reference is used to determine degradation, then degradation can be measured, but downtime increases due to replacement of the reference
Solution Approach 1:
The reflective optical element performs self-diagnosis through integrated electrodes that directly measure its own degradation state. This self-service capability eliminates the need for separate reference elements that would require periodic replacement, thereby reducing downtime while maintaining accurate degradation measurement.
3Measurement precision
If optical characteristics are measured to assess reflectivity degradation, then degradation can be detected, but the measurement is indirect and less reliable
Solution Approach 1:
The patent replaces indirect optical measurement methods with direct electrical measurement through electrodes contacted with the reflective optical element surface. This substitution of measurement modality provides more reliable and direct information about degradation, such as changes in electrical conductivity or resistance that correlate with surface condition.
Data Source
AI summary
An optical apparatus for a reticle stage of a lithographic apparatus is disclosed. The optical apparatus comprises: a reflective optical element comprising a surface for exposure to radiation; at least two electrodes located at the surface; and a measurement system configured to measure one or more electrical characteristics of the reflective optical element between the at least two electrodes. Also disclosed is a method of measuring a degradation of a reflective optical element having a surface for exposure to radiation in a lithographic apparatus, the method comprising: providing at least two electrodes at the surface of the reflective optical element; and measuring one or more electrical characteristics of the reflective optical element between the at least two electrodes.