Multi-Wavelength Height Sensing for Multiple Working Distances
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Solution Overview
Problem
Traditional working distance systems in specimen characterization systems, such as optical and electron beam review and inspection systems, are unable to maintain specimens at multiple working distances, leading to decreased resolution and throughput due to the lack of feedback loops for continuous adjustment.
Innovation Solution
A multi-height Z-height sensor (ZHS) system that utilizes optical dispersion to direct multiple wavelengths to a specimen at varying working distances, enabling continuous feedback loops for precise height adjustments using a controller and actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional working distance systems are used, then the system structure is simple, but the system cannot maintain specimens at multiple working distances
Solution Approach 1:
The Z-height sensor is divided into multiple independent height detection channels, each dedicated to a specific working distance. Each channel includes its own illumination source and detector positioned at appropriate angles, enabling simultaneous measurement of specimen height at multiple working distances without interference between channels.
Solution Approach 2:
The system uses a single specimen stage and illumination system that serves multiple functions: the same stage accommodates specimens at different working distances, and the illumination source provides lighting for both the specimen and the height measurement process, reducing the need for separate dedicated systems for each function.
2Productivity
If traditional single working distance systems are used, then the device complexity is low, but the productivity decreases due to lack of continuous adjustment
Solution Approach 1:
Each height detection channel is connected to a feedback control system that continuously monitors the specimen height at its designated working distance and provides real-time feedback signals to adjust the stage position, ensuring continuous maintenance of the correct working distance during specimen scanning and inspection operations.
Solution Approach 2:
The system maintains continuous height measurement and adjustment across multiple working distances simultaneously through parallel detection channels, eliminating the need for sequential switching between different working distances and ensuring uninterrupted inspection operations.
3Measurement precision
If traditional working distance systems are used, then the illumination system is simple, but the measurement precision decreases
Solution Approach 1:
Different wavelengths are assigned to different working distance ranges based on their optimal measurement characteristics. Shorter wavelengths are used for closer working distances where higher resolution is needed, while longer wavelengths are used for farther working distances, optimizing measurement precision for each specific range.
Solution Approach 2:
The system changes the wavelength parameter of illumination light based on the required working distance and measurement precision needs. By selecting appropriate wavelengths from multiple available sources, the system optimizes the measurement precision for different working distances while managing the complexity of the illumination system.
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
Enables accurate and efficient characterization processes by maintaining specimens at multiple working distances, improving image quality and throughput by eliminating the need for 'periscope moves' and providing active working distance control.
Implementation Method 1
directing illumination of a first wavelength to a specimen at a first working distance and directing illumination of a second wavelength, different from the first wavelength, to the specimen at a second working distance different from the first working distance
Data Source
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AI summary
A system is disclosed. The system includes a stage assembly configured to receive a specimen and maintain a height of the specimen at a first working distance height during a first characterization mode and an additional working distance height during an additional characterization mode. The system further includes an illumination source configured to generate an illumination beam. The system further includes an illumination arm including a set of optical elements configured to direct a portion of the illumination beam including illumination of a first wavelength to the specimen during the first characterization mode, and direct a portion of the illumination beam including illumination of an additional wavelength to the specimen during the additional characterization mode. The system further includes a detector assembly configured to receive illumination emanated from the specimen, and a controller configured to determine a specimen height value based on the illumination received by the detector assembly.