Deep UV Laser Wavelength Conversion for Wafer Inspection
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Solution Overview
Problem
The semiconductor industry faces challenges in detecting defects on reticles and wafers due to the increasing sensitivity of devices to smaller defects, requiring improved inspection techniques and apparatus with sub-200 nm light sources for effective defect detection.
Innovation Solution
A laser apparatus is developed that generates output radiation with a wavelength below 208 nm by using seed radiation sources, amplifiers, and a wavelength conversion module comprising crystals for frequency multiplication and mixing, producing a fifth harmonic beam suitable for inspecting reticles and wafers, which includes specific implementations using different crystal types and amplifiers to achieve wavelengths between 180-199 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical inspection systems are used, then inspection capability is limited, but detecting small defects becomes increasingly difficult
Solution Approach 1:
The patent changes the wavelength parameter of the light source from conventional visible or near-UV ranges to deep UV range (below 200 nm, specifically around 193 nm). This parameter change enables higher measurement precision for detecting small defects because the shorter wavelength light provides better resolution and can detect smaller feature sizes on reticles and wafers that are becoming increasingly miniaturized in semiconductor manufacturing
Solution Approach 2:
The patent replaces conventional light sources (such as lamps or standard lasers) with a specifically designed deep UV laser system. This substitution involves using nonlinear optical frequency multiplication processes (such as harmonic generation) to produce the required deep UV wavelength, thereby overcoming the limitations of conventional optical inspection systems and enabling detection of smaller defects
2Measurement precision
If sub-200 nm light sources are used, then defect detection sensitivity improves, but system complexity increases
Solution Approach 1:
The patent segments the light generation process into multiple stages: starting with a fundamental wavelength laser source, then using a series of nonlinear optical crystals to progressively multiply the frequency (e.g., second harmonic generation, third harmonic generation, fifth harmonic generation). Each stage produces an intermediate wavelength that is then fed into the next stage, ultimately achieving the deep UV wavelength below 200 nm. This segmentation makes the complex process manageable and allows for optimization at each stage
Solution Approach 2:
The patent uses nonlinear optical crystals as intermediary elements to convert the fundamental laser wavelength to the desired deep UV wavelength. These crystals act as mediators in the frequency multiplication process, enabling the transformation from a more readily available fundamental wavelength source to the required sub-200 nm deep UV radiation through processes like harmonic generation
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 efficient detection of defects on reticles and wafers by providing a high-quality, high-power laser source with a wavelength suitable for inspecting small feature sizes, enhancing the sensitivity and accuracy of defect detection in semiconductor manufacturing.
Implementation Method 1
a wavelength conversion module comprising a plurality of crystals for frequency multiplying and mixing the amplified first and second radiation beams to produce an output beam at a fifth harmonic that is less than about 208 nm
Implementation Method 2
frequency multiplying and mixing the amplified first and second radiation beams to produce an output beam at a fifth harmonic
Data Source
AI summary
Disclosed are methods and apparatus for generating a sub-208 nm laser. A laser apparatus includes one or more seed radiation sources for generating a first radiation beam having a first fundamental wavelength on a first optical path and a second radiation beam having a second fundamental wavelength on a second optical path, a first amplifier for amplifying the first radiation beam, a second amplifier for amplifying the second radiation beam, and a wavelength conversion module comprising a plurality of crystals for frequency multiplying and mixing the amplified first and second radiation beams to produce an output beam at a fifth harmonic that is less than about 208 nm.