Deformable EUV Obscuration Stop for Thermal Shape Compensation
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Solution Overview
Problem
In EUV lithography systems, obscuration stops in the optical beam path face challenges with thermal management due to high light absorption, leading to significant temperature changes and shape alterations that affect imaging quality, particularly in the production of microstructured components like integrated circuits.
Innovation Solution
An optical system with a deformable stop, heated by a heating device and controlled using temperature sensors and infrared cameras, allows for the compensation of temperature variations and shape changes, ensuring stable imaging behavior by adjusting the stop's geometry in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the obscuration stop is made thin to minimize light blocking, then the light transmission is improved, but the thermal management deteriorates due to insufficient heat dissipation
Solution Approach 1:
The obscuration stop is segmented into a two-layer structure: a thin functional layer that blocks light and a thick thermal management layer that dissipates heat. This segmentation allows each layer to perform its specific function optimally without compromising the other.
Solution Approach 2:
The patent merges two previously separate functions (light blocking and heat dissipation) into a single integrated obscuration stop component. The thin functional layer and thick thermal layer are combined into one piece that simultaneously achieves both light blocking and effective thermal management.
2Temperature
If the obscuration stop is made thick to improve thermal management, then the heat dissipation is improved, but the light transmission deteriorates due to increased absorption
Solution Approach 1:
The obscuration stop is segmented into a two-layer structure: a thin functional layer that blocks light and a thick thermal management layer that dissipates heat. This segmentation allows each layer to perform its specific function optimally without compromising the other.
3Manufacturing precision
If the stop geometry is fixed during manufacturing, then the manufacturing precision is improved, but the adaptability deteriorates due to temperature-induced shape changes
Solution Approach 1:
The patent employs parameter changes by utilizing the temperature-dependent physical properties of materials with different thermal expansion coefficients. The bi-metallic or multi-material construction allows the stop geometry to automatically adjust in response to temperature changes, compensating for thermal effects without requiring active control mechanisms.
Solution Approach 2:
The obscuration stop is constructed from composite materials with different thermal expansion coefficients. This composite structure enables differential expansion/contraction that compensates for temperature-induced shape changes, maintaining optical precision across varying thermal conditions.
4Temperature
If active heating and cooling systems are added to the obscuration stop, then the temperature control is improved, but the device complexity increases
Solution Approach 1:
The obscuration stop is designed to self-regulate its temperature through its inherent multi-material construction. The different thermal expansion coefficients of the combined materials create automatic geometric compensation for temperature changes, eliminating the need for external heating/cooling systems and reducing overall system complexity.
Solution Approach 2:
The patent employs parameter changes by utilizing the temperature-dependent physical properties of materials with different thermal expansion coefficients. The bi-metallic or multi-material construction allows the stop geometry to automatically adjust in response to temperature changes, compensating for thermal effects without requiring active control mechanisms.
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 solution stabilizes imaging behavior by compensating for temperature-induced shape changes in the obscuration stop, reducing structure size variations and telecentricity errors, thereby improving the precision of microstructured component production.
Implementation Method 1
Metallic coefficients of thermal expansion are in an order of magnitude of approximately 1E-5/K. The extension of an obscuration stop is in the order of magnitude of 10 mm. Hence, shape changes in the order of magnitude of micrometers or, converted to pupil coordinates, in the order of magnitude of 0.01 mσ to 0.1 mσ (1 σ=full pupil) are to be expected.
Implementation Method 2
If the stops now capture light according to the task at hand, they will absorb at least some of it and heat up as a result.
Implementation Method 3
Such an obscuration stop can be kept in position with the aid of blade-shaped holders or wires. This holder, for example in the form of the aforementioned wires, blocks used light and is therefore designed to be as thin as possible. Since thermal conduction is proportional to the material cross section, the cooling effect for the obscuration stop via this link typically acts weakly.
Implementation Method 4
Metallic coefficients of thermal expansion are in an order of magnitude of approximately 1E-5/K. The extension of an obscuration stop is in the order of magnitude of 10 mm. Hence, shape changes in the order of magnitude of micrometers or, converted to pupil coordinates, in the order of magnitude of 0.01 mσ to 0.1 mσ (1 σ=full pupil) are to be expected.
Data Source
AI summary
An optical system for a projection exposure apparatus comprises: an obscuration stop, a stop for the numerical aperture or an extraneous light stop, at least portions of which are arranged in a beam path of the optical system to shade at least portions of the beam path; a heating device for introducing heat into the stop, the stop being deformable from an initial geometry into a design geometry with the aid of the introduction of the heat; and a temperature sensor, a photo element and/or an infrared camera.