Terahertz Wave Measurement for Layered Specimens on Metal
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Solution Overview
Problem
Conventional techniques fail to measure the reflected wave by the boundary surface between layers in specimens with a layered structure, especially when the refractive indices of neighboring layers are similar or when the specimen is placed on a metal surface, leading to undetectable reflected waves.
Innovation Solution
An electromagnetic wave measurement device that outputs terahertz waves between 0.01 THz and 100 THz, detects substrate-surface-reflected waves, and derives layer thicknesses by analyzing the amplitude of frequency components, allowing for the measurement of layer thicknesses without directly measuring the boundary surface reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional reflection measurement technique is used, then layer boundary reflections can be measured, but measurement fails when refractive indices of neighboring layers are similar or when placed on metal surface
Solution Approach 1:
The patent inverts the conventional measurement approach by measuring the substrate-surface-reflected wave instead of the layer-boundary-reflected wave. The electromagnetic wave passes through the object to be measured and reflects off the substrate surface, allowing measurement of layer thicknesses even when boundary reflections are undetectable due to similar refractive indices or metal surface placement.
Solution Approach 2:
The patent introduces the substrate surface as an intermediary reflection point. By using the substrate surface as the reflection source, the system can indirectly measure the properties of the object to be measured (layer thicknesses) without requiring direct detection of weak boundary reflections between layers with similar refractive indices.
2Loss of information
If boundary surface reflection measurement is attempted, then layer interface information can be obtained, but reflected wave becomes indistinguishable from metal surface reflection
Solution Approach 1:
The patent reverses the measurement strategy by detecting the substrate-surface-reflected wave that passes through the object to be measured, rather than attempting to detect the weak boundary reflections between layers. This inversion allows clear distinction between the measured signal and metal surface reflection, as the substrate surface reflection provides a strong, distinguishable reference signal.
3Ease of manufacture
If non-destructive test is performed, then specimen integrity is maintained, but measurement accuracy decreases when boundary reflections are undetectable
Solution Approach 1:
The patent maintains non-destructive testing capability while improving measurement accuracy by inverting the measurement approach. Instead of relying on undetectable boundary reflections, the system uses the substrate-surface-reflected wave that passes through the specimen, enabling accurate layer thickness measurement without destroying the specimen or requiring detectable boundary reflections.
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 non-destructive testing of specimens with layered structures by accurately determining layer thicknesses even when boundary surface reflections are undetectable, using terahertz waves and advanced signal processing to distinguish substrate-surface-reflected waves from surface-reflected waves.
Implementation Method 1
an electromagnetic wave output device that outputs an electromagnetic wave having a frequency between 0.01 [THz] and 100 [THz] toward an object to be measured
Implementation Method 2
detects a substrate-surface-reflected electromagnetic wave which has been made incident to the object to be measured, has been reflected by the substrate, and has passed through the object to be measured
Implementation Method 3
if refractive indices of the respective neighboring layers are almost equal to each other, the reflected wave by the boundary surface between the layers may not be measured
Data Source
AI summary
According to the present invention, an electromagnetic wave measurement device includes: an electromagnetic wave detector, a frequency component acquisition unit, and a thickness indication quantity deriving unit. An object to be measured is disposed on a substrate and includes at least two layers, and the electromagnetic wave detector detects a substrate-surface-reflected electromagnetic wave which has been made incident to the object, has been reflected by the substrate, and has passed through the object. The frequency component acquisition unit acquires an amplitude of a frequency component of the substrate-surface-reflected electromagnetic wave. The thickness indication quantity deriving unit derives a thickness indication quantity based on the amplitude of the frequency component of the substrate-surface-reflected electromagnetic wave and a relationship between the thickness indication quantity and the amplitude of the frequency component of the substrate-surface-reflected electromagnetic wave.