Excimer Laser Target-Wavelength Tuning at High Repetition Rates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor exposure apparatuses face challenges in maintaining high resolution due to chromatic aberrations caused by wide spectral linewidths of KrF and ArF excimer laser light, which necessitate the use of line narrowing modules to reduce spectral linewidth, but these systems struggle to stabilize wavelength precision at high repetition frequencies.
Innovation Solution
A laser apparatus comprising a first wavelength variable semiconductor laser, a pulse amplifier, a wavelength conversion system, and a monitor module, with a processor that periodically adjusts the target wavelength of the laser light to maintain precision at high repetition frequencies by controlling the current flowing through the semiconductor laser, allowing for accurate two-wavelength or multi-wavelength exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a line narrowing module is provided in the laser resonator to narrow the spectral linewidth, then the chromatic aberrations are reduced and resolution is improved, but the system becomes more complex and wavelength stabilization at high repetition frequencies becomes difficult
Solution Approach 1:
The patent extracts the wavelength selection function from the traditional intracavity line narrowing module and implements it externally using a diffraction grating and reflective optics. This removes the complex line narrowing element from the laser resonator while achieving the same spectral filtering effect, thereby reducing device complexity while maintaining exposure resolution.
Solution Approach 2:
The patent introduces a diffraction grating as an intermediary element that separates and selects specific wavelengths from the broadband laser output. This grating-based wavelength selection mechanism acts as a mediator between the laser gain medium and the exposure system, enabling precise wavelength control without requiring complex intracavity line narrowing components.
2Manufacturing precision
If the spectral linewidth is narrowed using a line narrowing module, then the chromatic aberrations are minimized, but the wavelength precision cannot be stabilized at high repetition frequencies
Solution Approach 1:
The patent employs periodic modulation of the laser pump source at high repetition frequencies to generate pulsed laser output. By synchronizing the pump modulation with the wavelength selection mechanism, the system maintains precise wavelength control even at high repetition rates, overcoming the limitation of conventional continuous-wave or low-repetition-rate narrowed-line lasers.
Solution Approach 2:
The patent implements dynamic wavelength tuning capability by making the wavelength selection mechanism adjustable during operation. This allows the laser to adaptively maintain optimal wavelength precision across varying repetition frequencies and operational conditions, enhancing reliability in high-speed exposure applications.
3Productivity
If high repetition frequency operation is implemented for increased productivity, then the exposure throughput is improved, but the wavelength precision and stability deteriorate
Solution Approach 1:
The patent uses periodic pump modulation to generate high-repetition-rate laser pulses while maintaining wavelength precision through synchronized wavelength selection. This periodic operation mode enables high exposure throughput without sacrificing the wavelength stability required for high-precision exposure.
Solution Approach 2:
The patent performs preliminary wavelength selection and stabilization before the high-repetition-rate pulsing occurs. By pre-configuring the wavelength selection optics and stabilizing the laser cavity parameters prior to high-speed operation, the system maintains wavelength precision during high-productivity pulsed emission.
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 enables highly accurate two-wavelength or multi-wavelength exposure with improved wavelength stability and precision, even at high repetition frequencies, thereby enhancing the resolution and performance of semiconductor exposure systems.
Implementation Method 1
a first wavelength variable semiconductor laser configured to output first continuous-wave laser light
Implementation Method 2
a first amplifier configured to pulse and amplify the first laser light
Implementation Method 3
a wavelength conversion system configured to convert a wavelength of the first pulse laser light and output resultant second pulse laser light
Implementation Method 4
an excimer amplifier configured to amplify the second pulse laser light and output resultant third pulse laser light
Data Source
AI summary
A laser apparatus includes a first wavelength variable semiconductor laser that outputs first continuous-wave laser light; a first amplifier that pulses and amplifies the first laser light and outputs first pulse laser light; a wavelength conversion system that converts a wavelength of the first pulse laser light and outputs second pulse laser light; an excimer amplifier that amplifies the second pulse laser light and outputs third pulse laser light; a monitor module that measures a wavelength of the third pulse laser light; and a processor that periodically changes a target wavelength of the third pulse laser light and controls a current for changing the wavelength of the laser light from the first semiconductor laser such that the wavelength of the third pulse laser light becomes the target wavelength based on a measured value of the wavelength of the third pulse laser light output at the same target wavelength.