Laser Beam Relay Optics for Stable Lithography Output
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Solution Overview
Problem
Lithographic apparatuses face challenges in maintaining stable laser beam characteristics, such as size and shape, due to divergence and pointing errors, which affect the minimum feature size and stability of patterns projected onto substrates, particularly as semiconductor manufacturing advances and feature sizes decrease.
Innovation Solution
A laser system incorporating an optical system with two optical elements of equal focal lengths spaced two focal lengths apart, which reduces the effective propagation length of the laser beam, thereby stabilizing beam size and position, and allowing for improved flexibility in positioning optical components, including pulse stretchers, to enhance beam stability and characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the laser beam propagates a long distance from the laser to the output, then more physical space is available for optical components, but the beam size and position become unstable due to divergence and pointing errors
Solution Approach 1:
The patent introduces an optical system comprising a first optical element and a second optical element as intermediaries between the laser and the output. These optical elements work together to reduce the effective propagation length of the laser beam, thereby stabilizing beam characteristics while allowing the physical distance to be extended for component placement
Solution Approach 2:
The patent changes the optical parameters of the beam by using an optical system with specific focal length relationships. The first optical element with focal length f1 and the second optical element with focal length f2 (where f2 ≥ f1) transform the beam propagation characteristics, reducing the effective propagation length while maintaining physical spacing
2Adaptability or versatility
If the propagation distance is increased to accommodate optical components like pulse stretchers, then component placement flexibility improves, but beam characteristics become less stable
Solution Approach 1:
The optical system acts as a mediator that decouples the physical distance requirement from the effective propagation length. This allows optical components to be placed at greater physical distances while the optical system maintains stable beam characteristics by reducing the effective propagation length through its focal length configuration
Solution Approach 2:
The patent segments the propagation path into distinct optical stages with the first and second optical elements. This segmentation allows for the insertion of additional optical components between these elements while maintaining overall beam stability, as each segment contributes to the overall reduction of effective propagation length
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 improves the stability and characteristics of the laser beam, enabling more precise and consistent pattern projection, reducing the effects of divergence and pointing errors, and allowing for increased physical space for optical components, thus enhancing lithographic performance.
Implementation Method 1
The optical system can be used to form an image of a first plane (located between the first optical element and the laser) in a second plane. The first plane and second plane are separated by a distance (in the direction of propagation of the laser beam) of four times the first focal length.
Implementation Method 2
the first optical element has a first focal length, the second optical element has a second focal length equal to the first focal length, and the second optical element is spaced from the first optical element by a distance of two times the first focal length
Data Source
AI summary
A laser system comprising: a laser operable to generate a laser beam; an optical system comprising a first optical element and a second optical element; and an output through which the laser beam exits the laser system; the laser, optical system and output arranged such that the laser beam travels to the first optical element, the second optical element and the output sequentially; wherein the first optical element has a first focal length, the second optical element has a second focal length equal to the first focal length, and the second optical element is spaced from the first optical element by a distance of two times the first focal length.