Optical Integrator Reducing Light Loss in Modified Illumination
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Solution Overview
Problem
Conventional exposure apparatuses experience significant light-quantity loss and reduced illuminance due to the aperture stop in modified illumination techniques, such as annular or multi-pole illumination, which affects the throughput and accuracy of exposure processes in device manufacturing.
Innovation Solution
The use of an optical integrator with refracting and deflecting surface regions of specific arcuate contours, which form a far field pattern localized in an annular region, minimizing light loss at the aperture stop and maintaining desired illuminance distribution on the mask and wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an aperture stop is used to limit the secondary light source shape in modified illumination (annular or multi-pole), then the depth of focus and resolving power are improved, but a considerable amount of light is blocked causing light-quantity loss and reduced illuminance on the mask and wafer
Solution Approach 1:
The optical integrator is divided into multiple refracting surface regions arranged in specific patterns (annular, multi-pole, or other desired shapes). Each region refracts light independently to form a segmented secondary light source that directly matches the desired illumination pattern, eliminating the need for an aperture stop to block unwanted light.
Solution Approach 2:
The optical integrator acts as an intermediary between the light source and the aperture stop/illumination system. By pre-shaping the light into the desired pattern through its refracting surfaces, it mediates the light distribution so that no additional blocking is required, thus preserving light quantity while achieving the desired illumination shape.
2Ease of operation
If a rectangular secondary light source is formed by the first fly's eye lens, then a rectangular illumination field is formed on the entrance surface of the second fly's eye lens, but the aperture stop must block considerable light to achieve annular or multi-pole illumination
Solution Approach 1:
The optical integrator uses segmented refracting surfaces arranged in annular or multi-pole patterns to directly form the desired secondary light source shape. This segmentation approach eliminates the need to start with a rectangular light source and block portions of it, thereby preventing light-quantity loss while achieving the target illumination pattern.
Solution Approach 2:
Instead of forming a rectangular secondary light source and then blocking light to achieve annular or multi-pole patterns, the invention inverts the approach by directly forming the annular or multi-pole secondary light source through specifically arranged refracting surfaces, thus eliminating the blocking step entirely.
3Manufacturing precision
If the aperture stop blocks light to achieve modified illumination patterns, then the illumination shape is controlled, but the illuminance on the mask and wafer is reduced and throughput decreases
Solution Approach 1:
The optical integrator employs segmented refracting surfaces arranged in the desired illumination pattern (annular, multi-pole, etc.). This segmentation allows direct formation of the controlled illumination shape without blocking, thereby maintaining high light throughput while achieving precise illumination shape control for high-quality exposure.
Solution Approach 2:
The optical integrator serves as an intermediary that pre-shapes the light distribution into the desired pattern before it reaches the exposure system. This mediation eliminates the need for subsequent light blocking, thereby preserving light quantity and maintaining high throughput while achieving the required illumination shape control.
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 reduces light-quantity loss and ensures stable, high-contrast illumination, enhancing the exposure process and manufacturing throughput by maintaining desired illuminance and resolving power in device manufacturing.
Implementation Method 1
a plurality of refracting surface regions which refract incident light
Implementation Method 2
a plurality of deflecting surface regions provided corresponding to the plurality of refracting surface regions and adapted for changing a traveling direction of the incident light
Data Source
AI summary
An optical integrator is able to keep down a light-quantity loss in modified illumination with an illumination optical apparatus. An optical integrator of a wavefront division type according to the present invention has a plurality of refracting surface regions which refract incident light, and a plurality of deflecting surface regions provided corresponding to the plurality of refracting surface regions and adapted for changing a traveling direction of the incident light. The plurality of refracting surface regions include a plurality of first refracting surface regions includes an arcuate contour with the center projecting in a first direction, and a plurality of second refracting surface regions includes an arcuate contour with the center projecting in a second direction.