EUV Light Shielding Unit with Gas-Tight Case and Bellows
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Solution Overview
Problem
In EUV exposure apparatuses, foreign matters from the driving mechanism of the variable blind can adhere to optical members, reducing light transmittance and reflectance, leading to decreased exposure efficiency and potential pattern transfer errors, as well as thermal deformation due to heat generated from the driving mechanism, which is exacerbated by the vacuum environment.
Innovation Solution
A light shielding unit with a gas-tight case and bellows mechanism to isolate the driving mechanism from the optical path, combined with a tilt mechanism for precise control of light shielding members, mitigates the influence of foreign matters and heat, allowing for accurate adjustment of the illumination area's edge portion and maintaining high optical member reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a variable blind with movable blades is used to define the illumination area, then the shape of the illumination area can be controlled, but foreign matters are generated from the driving mechanism and adhere to optical members, reducing transmittance and reflectance
Solution Approach 1:
The patent extracts the harmful driving mechanism from the optical path by placing it in a separate chamber. The blade is driven by a motor located outside the optical path, and the driving force is transmitted through a magnetic coupling mechanism, so that no mechanical contact occurs within the optical path, eliminating the source of foreign matter generation.
Solution Approach 2:
The patent introduces a magnetic coupling mechanism as an intermediary between the motor and the blade. The motor rotates a magnet, which induces rotation in a ferromagnetic material coupled to the blade, thereby transmitting rotational force without direct mechanical contact. This intermediary mechanism eliminates wear and foreign matter generation while maintaining blade control capability.
2Productivity
If the driving mechanism operates in the vacuum environment, then the exposure process can proceed, but heat generated from the driving mechanism causes thermal deformation
Solution Approach 1:
The patent divides the system into two separate chambers: a vacuum chamber for the optical path and a non-vacuum chamber for the driving mechanism. This segmentation allows the driving mechanism to operate in atmospheric conditions where heat dissipation is more efficient, while the optical path maintains vacuum for exposure process continuity.
Solution Approach 2:
The patent uses a magnetic coupling mechanism as a thermal and physical barrier between the heat-generating motor and the optical components. The magnetic coupling transmits rotational force while preventing heat transfer, acting as a thermal intermediary that protects the optical path from thermal deformation.
3Manufacturing precision
If foreign matters adhere to the pattern surface of the reticle, then the wafer is exposed with incorrect patterns, but attaching a pellicle is not possible in EUV exposure apparatus
Solution Approach 1:
The patent removes the source of foreign matters (the driving mechanism) from the optical path, eliminating the need for protective measures like pellicles. By extracting the harmful element, the reticle surface remains clean without requiring additional protective components.
Solution Approach 2:
The patent replaces the mechanical driving system (which generates foreign matters) with a magnetic coupling system. This substitution eliminates mechanical wear and particle generation, thereby protecting the reticle surface without requiring a pellicle.
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 effectively reduces the impact of foreign matter and heat on the exposure process, ensuring high accuracy and efficiency by preventing contamination and thermal deformation, thus maintaining high resolution and throughput in EUV exposure applications.
Implementation Method 1
a bellows mechanism which gas-seals the case with respect to the light shielding member
Implementation Method 2
the transmittance or the reflectance of the certain optical member(s) is gradually lowered
Implementation Method 3
in the EUV exposure apparatus, any optimum pellicle, through which the EUV light is transmissive, is not present
Data Source
AI summary
A light shielding unit, which shields a part of an exposure light with a light shielding member, includes a sensor which detects displacement of the light shielding member, a driving device which drives the light shielding member based on a detection result obtained by the sensor, a case which accommodates the sensor and the driving device, and a bellows mechanism which gas-seals the case with respect to the light shielding member. When the illumination area of the illumination light is defined, it is possible to mitigate the influence of the foreign matters and/or the heat generated from the driving mechanism.