Multibeam Optical Lever Profiling for Displacement Error Compensation
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Solution Overview
Problem
Existing optical lever profilers are limited by errors due to sample displacement and a restricted range of angle measurement, which are unsuitable for high-accuracy applications like semiconductor and x-ray mirror measurements.
Innovation Solution
A multibeam optical lever profiler system using a set of convergent beams extends the measurement range and reduces errors by employing triangulation methods and multiple beams to compensate for sample displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single beam optical lever profiler is used, then the device complexity is low, but the measurement precision and range are limited due to errors from sample displacement
Solution Approach 1:
The patent divides the single optical beam into multiple discrete beams (typically 3-5 beams) that are spatially separated and directed at different angles toward the sample surface. Each beam independently probes the surface, and their combined measurements are used to calculate slope and position with higher precision, eliminating the limitations of single-beam methods while maintaining manageable system complexity through modular beam generation and detection architecture.
2Adaptability or versatility
If the optical lever length is increased to improve measurement range, then the measurement range increases, but the measurement precision decreases due to amplified displacement errors
Solution Approach 1:
The patent introduces angular dimension by directing multiple beams at different incidence angles relative to the sample surface normal. This angular diversity allows the system to measure slope and position independently of the optical lever length, as the angular information provides an additional measurement dimension that decouples the relationship between lever length and measurement precision. The beams are arranged to cover a wide angular range, enabling extended measurement capability without sacrificing precision.
3Adaptability or versatility
If multiple beams are used to extend measurement range, then the measurement range and precision improve, but the device complexity increases
Solution Approach 1:
The patent combines multiple optical beams and their corresponding detection paths into a unified measurement system where all beams converge on or near the sample surface and their reflected paths are collected by a single or few position-sensitive detectors. The multibeam arrangement is integrated with the optical lever mechanism, and all beams are processed simultaneously through a common computational algorithm that analyzes the angular positions and intensities to determine surface slope and position, thereby achieving extended measurement range without proportionally increasing system complexity.
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 enhances measurement accuracy and range without compromising precision, making it suitable for precise applications such as semiconductor and x-ray mirror measurements.
Implementation Method 1
The optical beam 101 produces reflected beam 102 impinging position detector 1000 at a point at the distance x from the intersection of the detector 1000 and normal 10
Data Source
AI summary
We present a novel optical lever surface slope metrology tool employing a plurality of optical beams converging and crossing at the point close to the measured surface. The system increases the range and accuracy of the measurement.