Variable Angle Refractive Index Measurement for Thin Films
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Solution Overview
Problem
Current spectroscopic ellipsometry systems face difficulties in measuring the refractive index of thin films with thickness less than 10 nm and those with small light absorption coefficients, requiring oblique incident angles and struggling with materials of multiple phases or amorphous materials.
Innovation Solution
The system employs a setup with a first and second distributed Bragg reflector, a light source directing incident light at a flexible angle between 0° to 85°, and a processor to calculate the refractive index of thin films with thickness ranging from 1 nm to 50 μm and light absorption coefficients from 10 cm−1 to 105 cm−1, using wavelengths from 50 nm to 50 μm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectroscopic ellipsometry systems use oblique incident angles (70-80°) to measure refractive index, then measurement capability for thin films is improved, but measurement flexibility and ease of operation deteriorate due to difficulty in optimizing incident angle for materials with multiple phases or amorphous materials
Solution Approach 1:
The patent changes the incident angle parameter from fixed oblique angles (70-80°) to a variable range (0°-85°), allowing optimization for different material types. This parameter change enables the system to adapt to various materials including amorphous materials and materials with multiple phases, resolving the contradiction between measurement precision and operational flexibility.
2Measurement precision
If spectroscopic ellipsometry systems use fixed oblique incident angles, then measurement for specific material types is optimized, but adaptability to measure thin films with wide range of thickness and absorption coefficients deteriorates
Solution Approach 1:
The patent introduces dynamic adjustment capability for incident angle within the range of 0° to 85°, allowing the system to adapt to different measurement requirements. This dynamic parameter adjustment enables accurate measurement of thin films with wide thickness ranges (1 nm to 50 μm) and varied absorption coefficients, enhancing both precision and adaptability simultaneously.
3Measurement precision
If spectroscopic ellipsometry systems require oblique incident angles for measurement, then thin film measurement capability is improved, but device complexity and difficulty of detecting and measuring increase
Solution Approach 1:
The patent creates a universal measurement system that can handle various thin film characteristics (thickness from 1 nm to 50 μm, absorption coefficients from 10 to 10^5 cm^-1) using a single configurable setup with incident angles from 0° to 85°. This multi-functional capability reduces device complexity by eliminating the need for multiple specialized configurations while maintaining high measurement precision.
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 allows for accurate refractive index measurement of thin films across a wide thickness and absorption range without the need for oblique incident angles, enhancing measurement flexibility and precision.
Implementation Method 1
a first light probe comprising a first distributed Bragg reflector which reflects light having a wavelength in a range of from 50 nm to 50 μm; a second light probe comprising a second distributed Bragg reflector which reflects light having a wavelength in a range of from 50 nm to 50 μm
Data Source
AI summary
Apparatus, methods and are disclosed for measuring refractive index of a material film. The method and apparatus utilize a reference measurement and as series of reflectance measurements at a range of wavelengths and thickness values for the material film to determine the refractive index of the material film.