Reflective Beam Combining Optics for High-Intensity Spot Metrology
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Solution Overview
Problem
Existing broadband light sources struggle to efficiently combine sources for high-intensity, small-spot-size illumination, particularly for examining small features in semiconductor manufacturing, as refractive lenses introduce aberrations and reduce light intensity.
Innovation Solution
A system using a long-wavelength and a short-wavelength source with reflective beam combining optics, including a concave reflector with broadband coating, to shape and combine radiation into a high-intensity broadband beam, focused to a small spot size using reflective optics, and a sampling pinhole for precise detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If refractive lenses are used to focus broadband light to a small spot size, then the spot size is reduced, but light intensity is reduced and aberrations are introduced
Solution Approach 1:
The patent replaces refractive optical systems with reflective optical systems. Specifically, it uses a compound parabolic reflector (CPR) and off-axis parabolic mirrors to focus broadband light, eliminating the need for refractive lenses that cause aberrations and intensity loss. The reflective system achieves the same focusing function without the harmful effects of refraction.
Solution Approach 2:
The patent employs curved reflective surfaces including a compound parabolic reflector and off-axis parabolic mirrors to focus light. The curved geometry of these reflectors enables efficient light collection and focusing across the entire broadband spectrum, achieving both small spot size and high intensity without the aberrations inherent in refractive systems.
2Area of stationary object
If refractive lenses are used to focus broadband light to a small spot size, then the spot size is reduced, but optical aberrations are introduced
Solution Approach 1:
The patent replaces refractive optical systems with reflective optical systems. Specifically, it uses a compound parabolic reflector (CPR) and off-axis parabolic mirrors to focus broadband light, eliminating the need for refractive lenses that cause aberrations and intensity loss. The reflective system achieves the same focusing function without the harmful effects of refraction.
Solution Approach 2:
The patent employs curved reflective surfaces including a compound parabolic reflector and off-axis parabolic mirrors to focus light. The curved geometry of these reflectors enables efficient light collection and focusing across the entire broadband spectrum, achieving both small spot size and high intensity without the aberrations inherent in refractive systems.
3Adaptability or versatility
If individual light sources are combined to create broadband output, then wavelength coverage is improved, but system complexity increases
Solution Approach 1:
The patent combines multiple individual light sources (e.g., deuterium lamp for UV, halogen lamp for visible, and infrared source) into a single integrated broadband illumination system. The compound parabolic reflector acts as a unifying optical element that collects and directs light from all sources through a common path to the sample, creating a unified broadband output while managing the complexity through systematic integration.
Solution Approach 2:
The compound parabolic reflector serves multiple functions simultaneously: it collects light from different wavelength sources, directs them through a common optical path, focuses them to a small spot size, and maintains high intensity across the entire broadband spectrum. This multi-functional design reduces overall system complexity despite the multiple sources involved.
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 system achieves higher intensity and better-focused broadband illumination across the spectrum, enabling precise examination of small features with reduced aberrations and increased light efficiency.
Implementation Method 1
A reflective beam combining optics is provided for shaping the long-wavelength radiation to enter the short-wavelength source via the passage and also for shaping the short-wavelength radiation that exits through the passage and propagates to the long-wavelength source
Implementation Method 2
beam steering optics for projecting the broadband beam to a spot on the sample
Implementation Method 3
a sampling pinhole that passes a test portion of the signal beam on to a detector for performing optical examinations
Data Source
AI summary
An apparatus and method for examining features of a sample with a broadband beam of light obtained from a long-wavelength source that may include two distinct emitters that emit a long-wavelength radiation and a short-wavelength source that emits a short-wavelength radiation. A passage is positioned between the sources and a reflective beam combining optics is provided for shaping the long-wavelength radiation to enter the short-wavelength source via the passage and also for shaping the short-wavelength radiation that exits through the passage and propagates toward the long-wavelength source. The reflective beam combining optics shape the short-wavelength radiation such that it re-enters the short-wavelength source via the passage and is combined with the long-wavelength radiation into the broadband beam that exits the short-wavelength source. A beam steering optics projects the broadband beam to a spot on the sample, and a scattered broadband radiation from the spot is intercepted and shaped to a broadband signal beam, which is passed through a sampling pinhole that passes a test portion of it on to a detector for optical examination; the test portion that is passed can correspond to a center portion of the spot.