Solid-State Laser Source for Air-Propagating UV Inspection
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Solution Overview
Problem
Ultraviolet light sources with wavelengths shorter than 193 nm, such as 177 nm, are attenuated by oxygen in the air, requiring expensive vacuum-tight structures and complex optical components, which increase device cost and maintenance time due to the need for nitrogen filling and evacuation.
Innovation Solution
A solid-state laser device generating a sixth harmonic of pulsed laser light with a fundamental wave center wavelength within specific bands, allowing efficient propagation through air without significant absorption by oxygen molecules, eliminating the need for vacuum-tight structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultraviolet light sources with wavelength shorter than 193 nm (e.g., 177 nm) are used, then the resolution is improved, but the laser light is attenuated by oxygen in the air
Solution Approach 1:
The patent changes the wavelength parameter of the laser light from conventional 193 nm to specifically 176-178 nm, which falls within an atmospheric transmission window where oxygen absorption is minimized. This parameter change allows the laser light to propagate through air without significant attenuation while maintaining the resolution improvement benefit of shorter wavelength
Solution Approach 2:
The patent employs pulsed laser operation with specific pulse widths (1-100 ps) and repetition rates (100 kHz - 10 MHz). This periodic action allows the laser to deliver high peak power for improved resolution while the pulsed nature reduces average power exposure to oxygen, minimizing attenuation and enabling air propagation without vacuum
2Loss of energy
If vacuum-tight structures are used to prevent laser light attenuation, then the laser light propagation is maintained, but the device complexity and cost increase
Solution Approach 1:
Instead of treating oxygen as a harmful factor that must be excluded through vacuum systems, the patent identifies and exploits the beneficial property that certain wavelength ranges (176-178 nm) have minimal oxygen absorption. This converts the previously harmful atmospheric oxygen into a non-interfering medium, eliminating the need for vacuum-tight structures
Solution Approach 2:
The patent effectively uses air as an inert atmosphere for the specific wavelength range of 176-178 nm, where oxygen does not significantly absorb the laser light. This allows the inspection device to operate in normal atmospheric conditions without requiring vacuum or nitrogen-filled environments
3Loss of energy
If nitrogen filling and evacuation procedures are implemented, then the laser light propagation is protected, but the maintenance time increases
Solution Approach 1:
The patent extracts and eliminates the problematic procedure of nitrogen filling and evacuation by selecting a wavelength (176-178 nm) that is naturally compatible with atmospheric propagation. This removes the maintenance burden entirely, allowing the device to operate continuously in air without periodic atmospheric replacement
4Measurement precision
If complex optical components are used for short wavelength operation, then the laser light generation is achieved, but the device cost increases
Solution Approach 1:
The patent uses a frequency-multiplied Nd:YAG laser system that can operate at multiple wavelengths (1064 nm fundamental, 532 nm second harmonic, 355 nm third harmonic, and 176-178 nm sixth harmonic). This multi-functional laser source can serve different inspection requirements without requiring separate laser systems, reducing overall device complexity and cost
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
Enables a simpler, cost-effective inspection device configuration with high sensitivity and reduced laser light fluctuations, allowing for accurate pattern inspection without the need for vacuum conditions.
Implementation Method 1
a solid-state laser device that oscillates laser light including a fundamental wave with its center wavelength being included in one of first to fourth wavelength bands
Implementation Method 2
means for generating a sixth harmonic of pulsed laser light having a pulse width equal to or greater than 2 picoseconds extracted from the solid-state laser device
Implementation Method 3
it is possible to oscillate (i.e., generate) laser light that can efficiently propagate through the air
Data Source
AI summary
A laser light source device having a simple configuration and an inspection device are provided. A laser light source device 200 according to an exemplary embodiment in accordance with the present invention has a repetition frequency of 1 MHz or higher, and includes fundamental wave generation means 201 for oscillating laser light including a fundamental wave with its center wavelength being included in one of first to fourth wavelength bands, and means 205 for generating a sixth harmonic of pulsed laser light extracted from the fundamental wave generation means 201. The first wavelength band is 1064.326 nm to 1064.511 nm. The second wavelength band is 1064.757 nm to 1064.852 nm. The third wavelength band is 1063.805 nm to 1063.878 nm. Further, the fourth wavelength band is 1063.962 nm to 1064.031 nm.