Excimer Laser Wavelength Conversion for Stable Narrowband Exposure
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Solution Overview
Problem
The existing semiconductor exposure apparatuses face challenges in achieving high resolution due to chromatic aberration caused by the large spectral line width of KrF and ArF excimer laser apparatuses, which is exacerbated by the difficulty in rapidly changing the incident angle on nonlinear crystals for phase matching to maintain high wavelength conversion efficiency, especially when fine-tuning the wavelength for image formation and correcting for environmental changes.
Innovation Solution
A laser system comprising a wavelength-variable solid-state laser device, a nonlinear crystal for wavelength conversion, and a control unit that adjusts the incident angle to optimize wavelength conversion efficiency, allowing for precise control of the excimer laser beam's wavelength and angle to minimize chromatic aberration and maintain high pulse energy stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the spectral line width of excimer laser is reduced using a line narrowing module, then chromatic aberration is reduced and resolution is improved, but the device complexity and cost increase
Solution Approach 1:
The patent extracts and removes the line narrowing module (LNM) from the excimer laser system, replacing it with a solid-state laser source that inherently provides narrow spectral width without requiring additional chromatic aberration correction components
Solution Approach 2:
The solid-state laser source serves multiple functions: it provides the necessary narrow spectral width for high-resolution exposure, eliminates chromatic aberration, and removes the need for separate line narrowing modules, thereby simplifying the overall system
2Measurement precision
If the incident angle on nonlinear crystal is rapidly changed to fine-tune wavelength, then wavelength precision is improved, but the difficulty of operation and response time increase
Solution Approach 1:
The patent replaces the mechanical adjustment system (rotating the nonlinear crystal) with a direct solid-state laser source that achieves wavelength tuning through electrical or optical control mechanisms, eliminating the need for rapid mechanical rotation and improving both ease of operation and response time
3Stability of the object's composition
If the incident angle on nonlinear crystal is adjusted to correct environmental changes, then wavelength stability is improved, but the response time and operational complexity increase
Solution Approach 1:
The patent eliminates the mechanical angle adjustment system and uses a solid-state laser source with inherent wavelength stability, allowing for rapid environmental compensation without the time delays associated with mechanical rotation and alignment
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 resolution and stability of the excimer laser beam by optimizing wavelength conversion efficiency, reducing chromatic aberration, and ensuring consistent pulse energy output, even under rapid wavelength changes and environmental variations.
Implementation Method 1
a wavelength conversion system including a first nonlinear crystal configured to wavelength-convert the first pulse laser beam output from the first solid-state laser device
Data Source
AI summary
A laser system according to one aspect of the present disclosure includes a wavelength-variable first solid-state laser device configured to output a first pulse laser beam; a wavelength conversion system including a first nonlinear crystal configured to wavelength-convert the first pulse laser beam and a first rotation stage configured to change a first incident angle of the first pulse laser beam on the first nonlinear crystal; an excimer amplifier configured to amplify a pulse laser beam wavelength-converted by the wavelength conversion system; and a control unit configured to receive, from an external device, data of a target center wavelength of an excimer laser beam output from the excimer amplifier, control a wavelength of the first pulse laser beam in accordance with the instructed target center wavelength, and control the first incident angle on the first nonlinear crystal in accordance with an average value of the target center wavelength.