Phase-Modulated Semiconductor Laser Pulses for Narrow Spectral Linewidth
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Solution Overview
Problem
Existing gas laser devices, such as KrF and ArF excimer lasers, suffer from significant chromatic aberration due to their wide spectral line widths, which can lead to decreased resolution in semiconductor exposure applications.
Innovation Solution
A laser device configuration that includes a semiconductor laser, a first amplifier to convert continuous light to pulse light, an optical phase modulator, a modulation signal generator, and a processor to control the modulation signal generator. The processor generates a modulation signal with an identical pattern synchronized with a light emission trigger signal to modulate the wavelength of continuous light and adjust the spectral line width of pulse light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a gas laser device (KrF or ArF excimer laser) is used to output ultraviolet light for semiconductor exposure, then the wavelength can be shortened to improve resolution, but the spectral line width becomes large causing chromatic aberration
Solution Approach 1:
The patent applies preliminary action by generating a modulation signal before the light emission trigger signal and pre-modulating the continuous light from the semiconductor laser. This pre-modulation ensures that when the pulse light is generated through amplification, the spectral line width is already narrowed, preventing chromatic aberration from occurring in the first place during the exposure process
Solution Approach 2:
The patent implements dynamics by using a time-varying modulation signal that changes its frequency content over time. The modulation signal has different spectral characteristics at different time points within the pulse duration, allowing dynamic control of the spectral line width to match the requirements of the amplification process and reduce chromatic aberration
2Object-affected harmful factors
If a line narrowing module (LNM) including etalon or grating is provided in the laser resonator to narrow spectral line width, then chromatic aberration can be reduced, but the device complexity increases
Solution Approach 1:
The patent replaces the mechanical/optical line narrowing module (etalon, grating) with an electronic modulation system. Instead of using physical components to filter and narrow the spectral line width, the invention uses electrical modulation signals applied to the semiconductor laser to achieve spectral narrowing through frequency modulation, thereby eliminating complex mechanical/optical narrowing components
Solution Approach 2:
The patent changes the operational parameters of the semiconductor laser through electrical modulation. By applying a time-varying modulation signal with specific frequency characteristics, the laser's optical spectrum is dynamically controlled to achieve narrow spectral line width without requiring additional optical filtering components, thus simplifying the overall device structure
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 configuration effectively narrows the spectral line width of the laser light, reducing chromatic aberration and enhancing the resolution of the laser device, thereby improving the performance in semiconductor exposure applications.
Implementation Method 1
an optical phase modulator arranged on an optical path of the continuous light between the semiconductor laser and the first amplifier, a modulation signal generator configured to output a modulation signal to be provided to the optical phase modulator
Data Source
AI summary
A laser device includes a semiconductor laser outputting continuous light, a first amplifier amplifying the continuous light and converting the continuous light to pulse light in synchronization with a light emission trigger signal received from an external apparatus, an optical phase modulator arranged on an optical path of the continuous light between the semiconductor laser and the first amplifier, a modulation signal generator outputting a modulation signal to be provided to the optical phase modulator, and a processor controlling the modulation signal generator. The processor causes the modulation signal generator to generate the modulation signal having an identical pattern in synchronization with the light emission trigger signal and provide the modulation signal to the optical phase modulator so as to modulate a wavelength of the continuous light within a time period corresponding to one pulse of the pulse light and adjust a spectral line width of the pulse light.