Cascaded Sum-Frequency Mixing for 193.4 nm DUV Generation
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Solution Overview
Problem
Current technologies fail to generate a continuous output deep ultraviolet (DUV) beam with a wavelength of 193.4 nm, which is essential for accurate defect evaluation in semiconductor production, due to limitations in nonlinear optical crystals and phase matching conditions.
Innovation Solution
A radiation source apparatus utilizing a series of laser beams and wavelength conversion means, including first, second, and third laser apparatuses, and corresponding wavelength conversion processes to achieve a 193.4 nm DUV beam through sum-frequency mixing with nonlinear crystals like BBO and CLBO, optimizing phase matching and conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If pulse oscillation systems are used for wavelength conversion, then 193.4 nm beam generation is achieved, but continuous output capability is lost
Solution Approach 1:
The patent divides the wavelength conversion process into multiple stages: first generating 266 nm from 1064 nm fundamental wave, then mixing with 2000-2100 nm laser to produce 235 nm, and finally mixing with 1100 nm laser to achieve 193.4 nm. This segmentation allows each stage to be optimized independently for continuous operation while maintaining phase matching stability.
Solution Approach 2:
The patent employs temperature control of nonlinear optical crystals (LBO at 50-100°C, CLBO at 80-120°C) to maintain stable phase matching conditions for continuous wave operation. By adjusting crystal temperature parameters, the system achieves reliable continuous 193.4 nm output that matches ArF excimer laser wavelengths.
2Loss of energy
If existing nonlinear optical crystals are used, then wavelength conversion is achieved, but absorption losses increase at 193.4 nm
Solution Approach 1:
The patent uses composite nonlinear optical material systems: LBO crystal for the first sum-frequency mixing stage (266 nm + 2000-2100 nm → 235 nm), and CLBO crystal for the second stage (235 nm + 1100 nm → 193.4 nm). This composite approach selects materials with complementary properties: LBO has low absorption at 235 nm, while CLBO has low absorption at 193.4 nm, minimizing total energy loss while maintaining beam quality.
3Power
If sum frequency mixing is used for wavelength conversion, then conversion efficiency improves, but device complexity increases
Solution Approach 1:
The patent uses 1064 nm laser as a universal pump source that serves multiple functions: it generates 266 nm fourth harmonic, which then participates in sum-frequency mixing to generate 235 nm, and also serves as the basis for the final 193.4 nm generation. This multi-functionality reduces the need for separate laser sources, simplifying the overall system while maintaining high conversion efficiency through cascaded sum-frequency mixing.
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 efficiently generates a high-quality, continuous 193.4 nm DUV beam, overcoming previous limitations and enabling accurate semiconductor inspection with improved resolution and reduced production time.
Implementation Method 1
first wavelength conversion means arranged to receive the first laser beam of radiation and to generate a beam of first DUV radiation having a fourth-harmonic wavelength of the first fundamental wavelength
Implementation Method 2
second wavelength conversion means arranged to receive the beam of first DUV radiation and the second laser beam of radiation and to sum-frequency mix the first DUV radiation with the second fundamental wavelength radiation to generate a beam of second DUV radiation having a wavelength between approximately 232 nm and 237 nm
Implementation Method 3
third wavelength conversion means arranged to receive the beam of second DUV radiation and the third laser beam of radiation and to sum-frequency mix the second DUV radiation with the third fundamental wavelength radiation to generate third DUV radiation having a wavelength between approximately 192.5 nm and 194.5 nm
Implementation Method 4
there be a nonlinear optical crystal which satisfies the phase matching conditions utilizing birefringence for the beam wavelengths for generation of harmonics and sum frequency mixing
Data Source
AI summary
The present invention provides a radiation source apparatus which can generate a DUV radiation beam having a wavelength of 193.4 nm efficiently. The radiation source apparatus according to the invention has first wavelength conversion means arranged to receive a first laser beam of a first fundamental wavelength and to generate a fourth-harmonic wavelength of the first fundamental wavelength, second wavelength conversion means arranged to receive the beam of the fourth-harmonic wavelength of the first fundamental wavelength (266 nm) and a second laser beam of a second fundamental wavelength and to sum-frequency mix the fourth-harmonic with the second fundamental wavelength radiation to generate a beam of second DUV radiation having a wavelength between approximately 232 nm and 237 nm, and third wavelength conversion means arranged to receive the beam of second DUV radiation and the third laser beam of a third fundamental wavelength and to sum-frequency mix the second DUV radiation with the third fundamental wavelength radiation to generate third DUV radiation having a wavelength between approximately 192.5 nm and 194.5 nm.