Adjustment Surfaces for Uniform Pupil Luminance in Exposure Systems
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Solution Overview
Problem
In exposure apparatus for manufacturing microdevices, achieving uniform pupil luminance distribution across the wafer surface is challenging, leading to variations in pattern line width, which affects the accurate transfer of microscopic mask patterns.
Innovation Solution
The illumination optical apparatus incorporates adjustment surfaces with specific transmittance or reflectance distributions to independently adjust pupil luminance at various points, ensuring uniformity while maintaining desired illuminance distribution, using a combination of correction filters and diffractive optical elements to form and adjust the secondary light source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional illumination optical systems are used without adjustment surfaces, then the device complexity is low, but the pupil luminance distribution uniformity across the wafer surface deteriorates
Solution Approach 1:
The adjuster is divided into multiple adjustment surfaces (first adjustment surface 8 and second adjustment surface 9) positioned at different locations in the optical path. Each adjustment surface independently modifies the light intensity distribution for specific regions, enabling localized control of pupil luminance without requiring a complete system redesign.
Solution Approach 2:
Each adjustment surface is designed with specific transmittance distributions tailored to correct luminance variations in particular regions of the wafer surface. The first adjustment surface 8 corrects luminance for one region while the second adjustment surface 9 corrects luminance for another region, allowing localized optimization of pupil luminance uniformity.
2Manufacturing precision
If adjustment surfaces with specific transmittance distributions are introduced, then the pupil luminance distribution uniformity improves, but the device complexity increases
Solution Approach 1:
Adjustment surfaces with specific transmittance distributions are introduced as intermediary elements in the optical path between the illumination source and the wafer. These intermediaries modify the light intensity distribution to achieve uniform pupil luminance without requiring changes to the primary illumination or projection systems.
3Manufacturing precision
If multiple adjustment surfaces are used to independently adjust pupil luminance at respective points, then the illuminance distribution uniformity improves, but the manufacturing complexity increases
Solution Approach 1:
The adjustment function is segmented across multiple adjustment surfaces, each responsible for correcting luminance in specific regions. This segmentation allows for independent optimization of different areas of the wafer surface without requiring complex integrated adjustments.
Solution Approach 2:
Each adjustment surface is designed with localized transmittance characteristics optimized for its specific region. This local optimization approach simplifies the manufacturing process by allowing each component to be designed and adjusted independently rather than requiring complex global optimization.
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 allows for accurate and uniform transfer of microscopic patterns across the entire exposure region, ensuring high precision in manufacturing microdevices by adjusting pupil luminance distributions and maintaining uniform illuminance.
Implementation Method 1
an adjuster for independently adjusting each of pupil luminance distributions about respective points on the surface to be illuminated, wherein the adjuster has a plurality of adjustment surfaces each of which is disposed in an optical path between the pupil distribution forming means and the surface to be illuminated
Implementation Method 2
each of the adjustment surfaces outputs light with a light intensity distribution different from a light intensity distribution of incident light
Implementation Method 3
a light beam emitted from a light source is guided through a fly's eye lens (or microlens array) as an optical integrator to form a secondary light source as a substantive surface illuminant consisting of a lot of light sources
Implementation Method 4
Light beams from the secondary light source are incident to a condenser lens. The light beams converged by the condenser lens illuminate a mask with a predetermined pattern thereon in a superposed manner
Data Source
AI summary
An illumination optical apparatus is able to adjust each of pupil luminance distributions at respective points on a surface to be illuminated to being almost uniform, while maintaining or adjusting an illuminance distribution on the surface to be illuminated to being almost uniform. The illumination optical apparatus illuminates the surface to be illuminated (M, W), with a light beam from a light source (1). The apparatus is provided with a pupil distribution forming device (1-4) for forming a pupil luminance distribution with a predetermined luminance distribution on an illumination pupil plane; and an adjuster (8, 9) for independently adjusting each of pupil luminance distributions about respective points on the surface to be illuminated. The adjuster has a plurality of adjustment surfaces each of which is disposed in an optical path between the pupil distribution forming device and the surface to be illuminated and has a predetermined transmittance distribution or reflectance distribution.