Excimer Laser Prism-Grating Control for Narrow Spectral Width
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Solution Overview
Problem
Current 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 not adequately addressed by existing line narrowing modules.
Innovation Solution
A laser apparatus with an optical resonator configuration including an output coupling mirror, grating, laser chamber, prism, rotary stage, wavelength measuring unit, angle sensor, and control units that adjust the incident angle of the laser beam to narrow the spectral width and maintain target wavelength accuracy, even at high speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional gas laser apparatus (KrF or ArF excimer laser) is used as an exposure light source, then high power output is achieved, but chromatic aberration occurs due to large spectral line width (350-400 pm), reducing resolution
Solution Approach 1:
The optical resonator is divided into multiple sections with different functional elements: a first optical resonator for generating high power laser output, and a second optical resonator containing line narrowing elements (etalon or grating) for reducing spectral width. This segmentation allows simultaneous achievement of high power and narrow spectral width that cannot be obtained in a single resonator configuration.
Solution Approach 2:
Line narrowing elements (etalon or grating) are introduced as intermediary components between the laser chamber and the output coupling mirror. These intermediaries selectively filter the laser spectrum to narrow the spectral width while maintaining the high power output from the excimer laser, thereby reducing chromatic aberration without sacrificing power.
2Manufacturing precision
If a line narrowing module is added to narrow the spectral width, then chromatic aberration is reduced, but the system complexity increases
Solution Approach 1:
The line narrowing function is merged into the optical resonator structure itself rather than being added as a separate external module. The etalon or grating is integrated within the resonator cavity, combining the resonator's light amplification function with the line narrowing function in a unified structure, thereby reducing overall system complexity.
Solution Approach 2:
The optical resonator is designed to perform multiple functions simultaneously: light amplification, wavelength selection, and line narrowing. By making the resonator multi-functional, separate dedicated modules for each function are eliminated, reducing the number of components and simplifying the overall system structure.
3Measurement precision
If the incident angle of the laser beam on the grating is adjusted to control wavelength, then wavelength accuracy is improved, but the response speed is limited
Solution Approach 1:
The incident angle of the laser beam on the grating is made dynamically adjustable during laser operation. By enabling real-time angle adjustment, the system can rapidly respond to wavelength control requirements while maintaining high wavelength accuracy, resolving the contradiction between speed and precision in wavelength tuning.
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
The solution effectively reduces chromatic aberration, enabling precise control of the laser beam's wavelength and improving the resolution of semiconductor exposure, allowing for accurate exposure of semiconductor wafers.
Implementation Method 1
a grating that constitutes an optical resonator together with the output coupling mirror
Implementation Method 2
at least one prism arranged in an optical path between the laser chamber and the grating
Data Source
AI summary
A laser apparatus includes an output coupling mirror; a grating that constitutes an optical resonator together with the output coupling mirror; a laser chamber in an optical path of the optical resonator; at least one prism in an optical path between the laser chamber and the grating; a rotary stage including an actuator that rotates the prism to change an incident angle of a laser beam from the laser chamber on the grating; a wavelength measuring unit that measures a central wavelength of the laser beam from the laser chamber through the output coupling mirror; an angle sensor that detects a rotation angle of the prism; a first control unit that controls the actuator at a first operation frequency; and a second control unit that controls the actuator at a second operation frequency.