Microlithography Illumination System with Raster Elements
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Solution Overview
Problem
Current illumination systems for microlithography, particularly at wavelengths less than 193 nm, face challenges in achieving uniformity and high geometric filling factor in the exit pupil, leading to suboptimal performance in microlithography processes.
Innovation Solution
The proposed illumination system employs a combination of first and second optical components with raster elements that deflect incoming ray bundles to create a non-rectangular intensity profile, optimizing the shape and arrangement of these elements to achieve a geometric filling factor greater than 70%, preferably higher than 80%, and ensuring nearly point-symmetric illumination of the exit pupil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional illumination systems are used, then the system structure is simpler, but the geometric filling factor in the exit pupil is insufficient
Solution Approach 1:
The illumination system is divided into multiple independent optical components: a first optical component with first raster elements and a second optical component with second raster elements. Each component handles a specific function in the light path, allowing the system to achieve high geometric filling factor through coordinated action of segmented elements rather than a single complex structure.
Solution Approach 2:
The patent introduces a second optical component that operates in a different dimensional plane of the optical path. The first optical component creates a preliminary light distribution, and the second optical component further processes this distribution in a subsequent dimensional space, thereby achieving high geometric filling factor through multi-dimensional light manipulation.
2Manufacturing precision
If conventional illumination systems are used, then the device complexity is lower, but the uniformity in the exit pupil is insufficient
Solution Approach 1:
The first and second raster elements have different shapes and are positioned at different locations within their respective optical components. This local differentiation allows each element to contribute specifically to uniformizing the light distribution in its local region, with the second raster elements being shaped to match the light distribution pattern created by the first raster elements.
Solution Approach 2:
The design of the second optical component is based on the light distribution pattern created by the first optical component. The second raster elements are shaped to compensate for non-uniformities introduced by the first component, creating a feedback mechanism where each component is optimized based on the output of the previous component to achieve overall uniformity.
3Productivity
If conventional illumination systems are used, then the system is easier to manufacture, but the filling degree in the exit pupil is insufficient
Solution Approach 1:
The complex function of achieving high filling degree is segmented across two separate optical components with raster elements. Each component can be manufactured independently using standard optical fabrication techniques, and their coordinated action achieves the high filling degree that would be difficult to accomplish in a single monolithic component.
Solution Approach 2:
The second optical component replicates and refines the light distribution pattern created by the first optical component. The second raster elements are shaped to match the light distribution pattern, effectively copying and optimizing the illumination pattern through a second stage of light manipulation.
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 enhances the uniformity and filling factor of the exit pupil, improving the overall performance of the microlithography process by ensuring a high percentage of the exit pupil is illuminated, thereby optimizing the light distribution and energy distribution within the scanning direction.
Implementation Method 1
The invention relates to an illumination system for wavelengths ≦193 nm... which uses EUV radiation... An illumination system for a lithographic device, which uses EUV radiation, has been made known from U.S. Pat. No. 5,339,346... U.S. Pat. No. 5,737,137, an illumination system with a plasma light source including a condenser mirror is shown, in which an illumination of a mask or a reticle to be illuminated is achieved by way of spherical mirrors... U.S. Pat. No. 5,361,292 shows an illumination system, in which a plasma light source is provided, and the point plasma light source is imaged in an annular illuminated surface by way of a condenser, which has five aspherical mirrors arranged off-center
Data Source
AI summary
An illumination system for scannertype microlithography along a scanning direction with a light source emitting a wavelength especially ≦193 nm. The illumination system includes a plurality of raster elements. The plurality of raster elements is imaged into an image plane of the illumination system to produce a plurality of images being partially superimposed on a field in the image plane. The field defines a non-rectangular intensity profile in the scanning direction.