Projection Exposure Tool Thermal Deformation Compensation
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Solution Overview
Problem
High radiation intensities used in projection exposure tools for microlithography cause radiation-induced changes in optical elements, leading to aberrations and image errors due to thermal deformations, which are difficult to control and correct during the imaging process.
Innovation Solution
Determining thermal expansion coefficients at multiple locations of the optical elements, calculating the changes in optical properties caused by heat emission, and adapting the imaging characteristics in real-time to compensate for these changes, using a control apparatus that includes manipulation devices to adjust the optical elements and correct image errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high radiation intensities are used to achieve high throughput, then productivity increases, but thermal deformations of optical elements occur leading to image errors
Solution Approach 1:
The patent determines thermal expansion coefficients at multiple locations of optical elements before the imaging process begins. This preliminary characterization allows the system to predict and compensate for thermal deformations that will occur during high-intensity radiation exposure, enabling both high throughput and maintained imaging precision
Solution Approach 2:
The system adapts imaging characteristics by applying correction values derived from the determined thermal expansion coefficients. These corrections dynamically adjust optical parameters to compensate for thermal deformations, allowing the system to maintain imaging precision even when operating at high radiation intensities for increased productivity
2Stability of the object's composition
If thermal expansion coefficients are determined at multiple locations of optical elements, then imaging stability improves, but measurement and processing complexity increases
Solution Approach 1:
The patent divides the optical element surface into multiple measurement locations and determines thermal expansion coefficients at each location separately. This segmentation approach captures local variations in thermal properties, enabling more accurate prediction and compensation of thermal deformations, thereby improving imaging stability despite the increased measurement complexity
3Manufacturing precision
If correction values are applied to compensate for thermal deformations, then imaging precision is maintained, but control system complexity increases
Solution Approach 1:
The system uses determined thermal expansion coefficients to calculate correction values that compensate for thermal deformations. This feedback mechanism continuously adjusts imaging characteristics based on the pre-characterized thermal properties of optical elements, maintaining imaging precision while using a control approach that is systematic rather than overly complex
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 maintains stable imaging characteristics with high precision, effectively mitigating image errors caused by thermal deformations and improving the stability of the projection exposure tool, even with materials having local variations in thermal expansion coefficients.
Implementation Method 1
which, during an imaging process, convey electromagnetic radiation
Implementation Method 2
All of the surfaces of the optical elements interact with the electromagnetic radiation during the imaging process
Implementation Method 3
determining respective individual thermal expansion coefficients at least two different locations of the overall optical surface; calculating a change to an optical property of the optical surface brought about by heat emission of the electromagnetic radiation
Implementation Method 4
variations in temperature occur on the mirror surface which lead to deformations of the mirror surface
Data Source
AI summary
A method for operating a projection exposure tool for microlithography is provided. The projection exposure tool includes an optical system which includes a number of optical elements which, during an imaging process, convey electromagnetic radiation. All of the surfaces of the optical elements interact with the electromagnetic radiation during the imaging process to form an overall optical surface of the optical system. The method includes: determining respective individual thermal expansion coefficients at least two different locations of the overall optical surface; calculating a change to an optical property of the optical system brought about by heat emission of the electromagnetic radiation (during the imaging process upon the basis of the thermal expansion coefficients; and imaging mask structures into an image plane via the projection exposure tool with adaptation of the imaging characteristics of the projection exposure tool so that the calculated change to the optical property is at least partially compensated.