Line Narrowed Laser Apparatus Spectral Width Control
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Solution Overview
Problem
Current semiconductor exposure technologies face challenges in narrowing the spectrum line width of excimer laser apparatuses, leading to chromatic aberration and reduced resolving power due to the wide natural oscillation spectrum widths of KrF and ArF excimer lasers, which necessitate the development of a line narrowed laser apparatus capable of controlling spectral width and wavelength to improve exposure performance.
Innovation Solution
A line narrowed laser apparatus is configured with a laser resonator, a chamber, electrodes, a pulsed voltage source, a wavelength-selecting element, a spectral width varying unit, and a controller that performs feedforward and feedback control of spectral width and wavelength, allowing for precise adjustment during burst oscillations and suspension periods to maintain optimal spectral characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the natural oscillation spectrum width of excimer laser apparatus is used, then the laser output power is maintained, but the chromatic aberration increases and resolving power decreases
Solution Approach 1:
An etalon is introduced as an intermediary component in the laser resonator to selectively filter and narrow the spectrum width of the laser beam. The etalon acts as a mediator between the broad-spectrum laser source and the exposure system, allowing only a narrow wavelength band to pass through, thereby reducing chromatic aberration while maintaining laser output power
Solution Approach 2:
The spectrum width parameter of the laser beam is actively changed from a broad natural oscillation width (approximately 350-400 pm) to a narrowed width (100 pm or less) by controlling the etalon's optical properties. This parameter change is achieved by adjusting the etalon's orientation angle and position, which modifies the transmitted wavelength band and reduces chromatic aberration
2Adaptability or versatility
If the etalon is fixed in position and orientation, then the spectral width is stable, but the wavelength cannot be adjusted for different exposure requirements
Solution Approach 1:
The etalon is transformed from a fixed component to a dynamically adjustable element. By introducing drive mechanisms that can change the etalon's orientation angle and position during operation, the system achieves wavelength tunability. This dynamic adjustment allows the laser to adapt to different exposure requirements while maintaining a relatively simple control structure
Solution Approach 2:
The etalon serves multiple functions: it narrows the spectrum width, stabilizes the wavelength, and enables wavelength adjustment for different exposure conditions. This multi-functionality reduces the need for separate components for each function, thereby managing device complexity while enhancing adaptability
3Manufacturing precision
If the burst oscillation period is extended, then the spectral width can be narrowed more effectively, but the productivity of the exposure apparatus decreases
Solution Approach 1:
The etalon is pre-positioned and pre-oriented during the suspension period between burst oscillations to prepare for the next exposure sequence. This preliminary action allows the system to maintain narrow spectrum width without extending the actual burst oscillation duration, thereby preserving productivity while achieving effective spectral control
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 apparatus effectively narrows the spectral width and stabilizes the wavelength, reducing chromatic aberration and enhancing the resolving power of the laser beam, thereby improving the precision and quality of semiconductor exposure processes.
Implementation Method 1
a wavelength-selecting element provided in the laser resonator
Implementation Method 2
a spectral width varying unit provided in the laser resonator
Implementation Method 3
a pair of electrodes provided in the chamber, an electric power source configured to apply a pulsed voltage to the pair of electrodes
Data Source
AI summary
The line narrowed laser apparatus configured to perform a plurality of burst oscillations including a first burst oscillation and a second burst oscillation next to the first burst oscillation to output a pulse laser beam. The line narrowed laser apparatus comprises a laser resonator, a chamber provided in the laser resonator, a pair of electrodes provided in the chamber, an electric power source configured to apply a pulsed voltage to the pair of electrodes, a wavelength-selecting element provided in the laser resonator, a spectral width varying unit provided in the laser resonator, a wavelength variable unit configured to change a selected wavelength selected by the wavelength-selecting element, and a controller. The controller is configured to control the wavelength variable unit based on an amount of control of the spectral width varying unit in a period from a time of ending the first burst oscillation to a time of starting the second burst oscillation.