Terahertz Thickness Measurement for Multilayer Thin Films
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current thickness measurement technologies face challenges in accurately measuring the thickness of each layer in multilayer thin film specimens, especially when these specimens include metals and non-metals, as the reflection of light from metals complicates the determination of the index of refraction in transmission mode.
Innovation Solution
A thickness measurement device and method utilizing terahertz waves in reflection mode, which includes a terahertz wave emitter, a detector, and a calculator. The device emits terahertz waves towards the edge of a second layer, detecting waves reflected from the second layer, the first layer, and their interface. The calculator determines the index of refraction and thickness of the second layer based on detection time differences and signal intensities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transmission mode measurement is used to measure the index of refraction of thin films, then the index of refraction can be obtained, but accurate measurement becomes difficult when the multilayer thin film includes metals due to light reflection from metals
Solution Approach 1:
The patent changes the measurement parameter from optical transmission mode to terahertz reflection mode. By using terahertz waves instead of visible light and switching from transmission to reflection measurement, the harmful effect of metal reflection is eliminated while enabling accurate measurement of both metal and non-metal layer thicknesses in multilayer structures
Solution Approach 2:
The patent substitutes the optical measurement system with a terahertz wave measurement system. By replacing visible light with terahertz waves and using reflection mode instead of transmission mode, the system overcomes the limitation of metal reflection and enables non-destructive measurement of multilayer thin films containing metals
2Adaptability or versatility
If the specimen includes multiple layers of thin films, then the specimen structure becomes complex, but it becomes difficult to measure the thickness of each layer separately during the manufacturing process
Solution Approach 1:
The patent applies segmentation by analyzing reflected terahertz waves from different interfaces within the multilayer structure. Each layer interface produces a distinct reflection signal with unique time delay and amplitude characteristics, allowing the system to separately identify and measure the thickness of each individual layer even in complex multilayer configurations
Solution Approach 2:
The patent introduces time domain analysis as an additional dimension for measurement. By measuring the time delay of reflected terahertz waves from different layer interfaces and converting this temporal information into spatial thickness information, the system can distinguish and measure each layer in multilayer structures without physical separation
3Reliability
If terahertz waves are used in reflection mode to measure thickness, then non-destructive testing is enabled, but reliable thickness information is difficult to obtain
Solution Approach 1:
The patent uses feedback by analyzing the reflected terahertz wave signals that contain information about the sample structure. By measuring the time delay and amplitude of reflections from different interfaces and using this feedback information to calculate layer thicknesses and material properties, the system obtains reliable thickness information while maintaining non-destructive testing
Solution Approach 2:
The patent performs preliminary calibration and characterization of the terahertz wave interaction with different materials. By establishing reference data and measurement protocols before actual measurement, the system ensures reliable thickness information can be extracted from reflection mode measurements of unknown samples
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 approach allows for accurate and reliable measurement of the thickness of the second layer in specimens with multiple layers, even when the first layer is composed of metal, by overcoming the limitations of transmission mode measurements.
Implementation Method 1
a terahertz wave emitter emitting terahertz waves toward an edge of the second layer such that the first layer and the second layer are directly irradiated with the terahertz waves at the same time by single irradiation
Implementation Method 2
a terahertz wave detector detecting, with reference to a reflected location of the terahertz waves, a first terahertz wave (R1) reflected from a surface of the second layer, a second terahertz wave (R2) reflected from an exposed surface of the first layer, and a third terahertz wave (R3) reflected from an interface between the first layer and the second layer
Data Source
AI summary
A thickness measurement device includes: a terahertz wave emitter emitting terahertz waves toward an edge of the second layer; a terahertz wave detector detecting, with reference to a reflected location of the terahertz waves, a first terahertz wave (R1) reflected from a surface of the second layer, a second terahertz wave (R2) reflected from an exposed surface of the first layer, and a third terahertz wave (R3) reflected from an interface between the first layer and the second layer; and a calculator calculating an index of refraction of the second layer based on a detection time difference (Δt1) between a detection time of the first terahertz wave (R1) and a detection time of the second terahertz wave (R2) and a detection time difference (Δt2) between the detection time of the first terahertz wave (R1) and a detection time of the third terahertz wave (R3).