Phase Shift Laser Structure for Narrower Excimer Linewidth
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Solution Overview
Problem
In semiconductor exposure apparatuses, the shortening of light wavelength for improved resolving power leads to chromatic aberration due to wide spectrum line widths in KrF and ArF excimer laser apparatuses, potentially decreasing resolving power.
Innovation Solution
A laser apparatus is designed with a master oscillator, an amplifier with an optical resonator, and a phase shift structure comprising cells with different phase shift amounts, disposed on the optical path between the master oscillator and the amplifier. The phase shift structure has a specific disposition interval to reduce chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the wavelength of light is shortened to improve resolving power, then resolving power is improved, but chromatic aberration occurs due to wide spectrum line width
Solution Approach 1:
The phase shift structure is divided into multiple cells arranged in a specific pattern, where each cell introduces a different phase shift amount. This segmentation approach narrows the spectrum line width by creating interference patterns that suppress spectral broadening, thereby reducing chromatic aberration while maintaining the short wavelength for high resolving power
Solution Approach 2:
The invention changes the phase shift parameter by introducing a phase shift structure with cells having different phase shift amounts (e.g., 0 and π phase shifts). This parameter modification narrows the spectrum line width of the laser beam, reducing chromatic aberration effects on the projection lens while preserving the ultraviolet wavelength needed for high resolving power in semiconductor exposure
2Object-affected harmful factors
If a line narrowing module is provided in the laser resonator to narrow the spectrum line width, then chromatic aberration is reduced, but device complexity increases
Solution Approach 1:
The invention extracts the line narrowing function from the traditional line narrowing module (etalon or grating) and implements it through a phase shift structure with a specific cell arrangement. This approach achieves spectrum line width narrowing without requiring complex optical components, thereby reducing device complexity while effectively minimizing chromatic aberration
Solution Approach 2:
The phase shift structure acts as an intermediary element that mediates between the laser resonator and the projection lens. By introducing controlled phase shifts through the cell pattern, it narrows the spectrum line width and reduces chromatic aberration without requiring additional complex optical components in the optical path
3Object-affected harmful factors
If the phase shift structure is disposed closer to the amplifier than the middle point of the optical path, then spectrum line width is narrowed, but the optical path configuration becomes more constrained
Solution Approach 1:
The phase shift structure is positioned in advance (closer to the amplifier) in the optical path to perform spectrum narrowing before the light reaches the projection lens. This preliminary action ensures that the spectrum line width is narrowed early in the optical path, allowing for more flexible system design and reducing constraints on subsequent optical components
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 implementation of the phase shift structure in the laser apparatus effectively narrows the spectrum line width, reducing chromatic aberration and enhancing the resolving power of the semiconductor exposure apparatus.
Implementation Method 1
a phase shift structure disposed on an optical path between the master oscillator and the amplifier at a position closer to the amplifier than a middle point of the optical path. The phase shift structure includes a plurality of cells having different phase shift amounts for the laser beam
Implementation Method 2
an amplifier including an optical resonator and configured to amplify the laser beam emitted by the master oscillator in the optical resonator
Data Source
AI summary
A laser apparatus according to an aspect of the present disclosure includes a master oscillator configured to emit a laser beam, an amplifier including an optical resonator and configured to amplify the laser beam emitted by the master oscillator in the optical resonator, and a phase shift structure disposed on an optical path between the master oscillator and the amplifier at a position closer to the amplifier than a middle point of the optical path. The phase shift structure includes a plurality of cells having different phase shift amounts for the laser beam. The cells have a disposition interval of 80 μm to 275 μm inclusive.