Optical Integrator Stabilizes Illuminance Distribution
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Solution Overview
Problem
Existing optical integrator systems in exposure apparatuses are affected by surface shape errors of wavefront dividing elements, leading to uneven illuminance distribution when there are movable optical members upstream, which can disrupt the desired illumination conditions necessary for precise device manufacturing.
Innovation Solution
The implementation of an optical integrator system comprising a combination of auxiliary and main fly's eye elements, where the auxiliary element stabilizes the angles and angular range of light incident to the main element, ensuring a uniform illuminance distribution is maintained on the surface to be illuminated, regardless of upstream optical member movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single fly's eye lens is used as the optical integrator, then the structure is simple, but the illuminance distribution becomes uneven when surface shape errors occur or movable optical members are present upstream
Solution Approach 1:
The patent divides the optical integrator into multiple fly's eye lenses (first and second optical integrators) arranged in sequence. Each lens processes a portion of the light field, and their combined effect produces a uniform illuminance distribution that is less sensitive to surface shape errors and upstream optical member movements, thereby resolving the contradiction between structural simplicity and illumination uniformity.
2Volume of moving object
If wavefront dividing elements with large numbers of microscopic refracting surfaces are used, then the optical integrator can be compact, but surface shape errors in these elements cause uneven illuminance distribution
Solution Approach 1:
The patent introduces an auxiliary optical integrator as an intermediary component between the light source and the main optical integrator. This auxiliary integrator pre-condition the light field by compensating for surface shape errors and angular variations before the light reaches the main integrator, thereby reducing the sensitivity to manufacturing errors while maintaining compact size.
Solution Approach 2:
The auxiliary optical integrator performs preliminary optical processing on the incident light, correcting angular deviations and surface error effects before the light enters the main optical integrator. This preliminary action ensures that the main integrator receives light that is already partially corrected, reducing the impact of subsequent surface shape errors.
3Adaptability or versatility
If movable optical members are placed upstream to adjust illumination, then the system becomes adaptable, but the angles and angular range of incident light vary, disrupting the desired illumination conditions
Solution Approach 1:
The auxiliary optical integrator acts as a feedback mechanism that continuously compensates for angular variations introduced by movable optical members. By monitoring and correcting the angular range of incident light in real-time, the system maintains stable illumination conditions despite the presence of adjustable components, thereby achieving both adaptability and stability.
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 configuration allows for consistent and desired illuminance distribution on the surface, even with surface shape errors, enabling good exposure conditions and improved device manufacturing quality.
Implementation Method 1
each of the first wavefront dividing elements is so constructed that rays obliquely incident to a center on an optical axis of an entrance surface of the first wavefront dividing element are emitted in parallel with the optical axis from the first wavefront dividing element
Data Source
AI summary
An optical integrator system comprises a first optical integrator including a plurality of first wavefront dividing elements two-dimensionally juxtaposed, and a second optical integrator including a plurality of second wavefront dividing elements two-dimensionally juxtaposed. Each of the first wavefront dividing elements is so constructed that rays obliquely incident to a center on an optical axis of an entrance surface are emitted in parallel with the optical axis. Each of the second wavefront dividing elements is also so constructed that rays obliquely incident to a center on an optical axis of an entrance surface are emitted in parallel with the optical axis. The system satisfies the condition of P2/(2×tan θ)<L12.