OAP Mirror Collimator Angular Alignment for Wafer Measurement
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Solution Overview
Problem
Optical monitoring systems in semiconductor processes face challenges due to variable planarity and orientation of workpieces, leading to errors in film thickness measurements and other properties, as angular misalignments result in chromatic variations and signal distortions, impacting the accuracy and precision of measurements.
Innovation Solution
The implementation of an off-axis parabolic (OAP) mirror collimator with a fiber optic cable, where the optical axes of the fibers are aligned to reduce angular sensitivity, allowing for precise light delivery and detection, minimizing the impact of misalignments and improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional optical system with standard fiber alignment is used, then the system structure is simple, but the measurement precision deteriorates due to angular sensitivity to workpiece orientation changes
Solution Approach 1:
The patent applies asymmetry by deviating the optical axes of the first and second optical fibers from parallel alignment with each other and from perpendicular alignment with the workpiece surface. Specifically, the optical axis of the first fiber is angled at 0.5-2 degrees relative to the workpiece normal, while the second fiber is angled at 0.1-0.5 degrees. This asymmetric angular configuration compensates for angularly-driven signal variations caused by workpiece orientation changes, thereby improving measurement precision without requiring complex additional components.
Solution Approach 2:
The patent changes the angular parameters of the optical fiber axes relative to the workpiece surface normal. By setting specific angle ranges (first fiber: 0.5-2 degrees, second fiber: 0.1-0.5 degrees), the system optimizes the collection of reflected light despite variations in workpiece orientation. This parameter adjustment allows the optical system to maintain measurement accuracy under varying angular conditions, improving precision while keeping the device structure relatively simple.
2Ease of operation
If the optical fibers are aligned perpendicular to the workpiece surface, then the alignment is simple, but the system becomes highly sensitive to angular variations caused by workpiece curvature or tilt
Solution Approach 1:
The patent introduces asymmetric angular deviations for the optical fibers relative to the workpiece surface normal. The first fiber is positioned at 0.5-2 degrees and the second at 0.1-0.5 degrees, creating an asymmetric configuration that reduces sensitivity to angular variations. This maintains ease of operation during workpiece handling while improving reliability by compensating for orientation changes and surface curvature effects.
Solution Approach 2:
The patent creates a dynamically adaptive optical system where the fixed angular offsets of the fibers (0.5-2 degrees for first fiber, 0.1-0.5 degrees for second fiber) allow the system to naturally accommodate varying workpiece orientations. This dynamic compensation mechanism improves reliability under varying operational conditions without requiring active adjustment mechanisms, maintaining ease of operation.
3Manufacturing precision
If standard optical fiber alignment is used, then the device structure is simple, but measurement accuracy deteriorates under conditions of workpiece tilt or curvature
Solution Approach 1:
The patent implements asymmetric angular positioning of optical fibers to improve manufacturing precision measurements. The first fiber is angled at 0.5-2 degrees and the second at 0.1-0.5 degrees relative to the workpiece normal, creating an asymmetric configuration that compensates for angular variations due to workpiece tilt or curvature. This approach enhances measurement accuracy while maintaining relatively simple device structure.
Solution Approach 2:
The patent modifies the angular parameters of the optical fiber configuration to optimize manufacturing precision measurements. By setting specific angle ranges for the first (0.5-2 degrees) and second (0.1-0.5 degrees) fibers, the system achieves better measurement accuracy under varying workpiece conditions without requiring complex additional components or adjustment mechanisms.
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 reduces the sensitivity to angular variations, enabling accurate and precise measurement of workpiece properties during semiconductor processes, even under conditions of tilt or curvature, thereby improving the reliability of film thickness and other property determinations.
Implementation Method 1
an off-axis parabolic (OAP) mirror collimator... an OAP mirror within the housing and having an optical axis, a fold plane, and a focal point
Implementation Method 2
A fiber optical cable is coupled to the housing, the fiber optical cable comprising first and second optical fibers
Data Source
AI summary
An optical system having an OAP mirror collimator is disclosed with a housing, an OAP mirror located within the housing and has an optical axis, a fold plane and a focal point. A fiber optical cable is coupled to the housing and has first and second optical fibers, each having an exit end that form a common end face of the fiber optic cable, wherein the fiber optical cable is rotationally and translationally aligned to the OAP mirror such that the common face is perpendicular to and centered upon the optical axis of the OAP mirror and positioned a fixed distance from the focal point, and wherein the optical axes of the first and second optical fibers are jointly angularly aligned to the fold plane, and the optical axes of the first and second optical fibers deviate from being parallel to the optical axis by no more than 0.15 degrees.