Thin Film Adhesion Measurement via Surface Wave Dispersion
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Solution Overview
Problem
Existing methods for measuring the adhesive strength of thin films are destructive, making it impossible to reuse samples and leading to defects in electronic devices due to weak adhesion, and they fail to accurately compare adhesion between thin films deposited through the same process.
Innovation Solution
A non-destructive method using the dispersion characteristic of surface waves, where an electronic calculator receives input values such as thickness, density, longitudinal wave velocity, and shear wave velocity of a thin film and substrate, calculates a virtual second thin film's properties, and uses a transfer matrix to determine the adhesive strength by matching the surface wave propagation speed with a dispersion curve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If destructive testing methods (pull-off test, scratch test, indentation test) are used to measure adhesive strength, then measurement precision is improved, but the sample is damaged and cannot be reused
Solution Approach 1:
The patent replaces mechanical destructive testing methods with acoustic wave-based measurement. Surface waves (Rayleigh waves) are generated on the thin film surface, and their propagation characteristics are measured to determine adhesive strength. This substitutes mechanical contact and damage with non-contact or minimal-contact acoustic field interaction, enabling non-destructive measurement while maintaining measurement capability.
Solution Approach 2:
The patent utilizes the relationship between acoustic wave phase velocity and material properties. By measuring the phase velocity of surface waves at different frequencies and analyzing the dispersion characteristics, the adhesive strength is determined without mechanical damage. The phase information of the acoustic waves serves as the measurement parameter instead of mechanical deformation.
2Measurement precision
If mechanical evaluation methods are used to measure adhesion, then adhesive strength can be quantified, but the testing process damages the sample making it unusable for subsequent processes
Solution Approach 1:
The patent replaces mechanical evaluation systems with acoustic wave-based measurement systems. Surface acoustic waves interact with the thin film-substrate interface, and their propagation characteristics reveal adhesive strength information without causing mechanical damage. This allows the same sample to proceed through subsequent manufacturing processes.
Solution Approach 2:
The patent introduces acoustic waves as an intermediary medium to probe the adhesive strength. Instead of directly applying mechanical forces that damage the sample, acoustic waves serve as a gentle probe that interacts with the interface properties, extracting measurement information without compromising sample integrity.
3Measurement precision
If conventional measurement methods are applied to thin films deposited through the same process, then individual samples can be tested, but samples not undergoing inspection cannot have their adhesion verified
Solution Approach 1:
The patent creates a universal measurement method that can be applied to any thin film on a substrate regardless of whether it has undergone inspection before. The surface wave measurement technique works on any such structure, allowing both inspected and uninspected samples to be evaluated using the same approach, thereby expanding inspection coverage to all 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
Enables accurate, non-destructive measurement of adhesive strength, allowing for iterative calculations and comparison of adhesion between thin films without damaging the samples, thereby preventing defects in electronic devices.
Implementation Method 1
calculating, by the electronic calculator, a dispersion characteristic of a velocity of a surface wave using the transfer matrix
Implementation Method 2
receiving, by the electronic calculator, a thickness, a density, a longitudinal wave velocity, and a shear wave velocity of each of a first thin film and the substrate
Implementation Method 3
receiving, by the electronic calculator, a thickness, a density, a longitudinal wave velocity, and a shear wave velocity of each of a first thin film and the substrate
Data Source
AI summary
Disclosed are a method for measuring the adhesive strength of a thin film using surface waves, and a computer-readable recording medium having a program for performing same recorded thereon. The method for measuring the adhesive strength of a thin film measures the adhesive strength between a substrate and a thin film by means of an electronic calculator, using sound waves measured from a thin film structure having a thin film formed on a substrate. The method, which is performed by the electronic calculator, comprises the steps of: receiving, as a first input value, the thickness, density, longitudinal wave velocity, and shear wave velocity of a first thin film and a substrate the adhesive strength between which is to be measured; calculating, from the first input value, the thickness and density of a second thin film virtually configured between the first thin film and substrate, and setting as a second input value; calculating the longitudinal wave velocity and shear wave velocity of the second thin film according to the stiffness constant of the second thin film, while varying the stiffness constant, and setting as a third input value; using the first to third input values to acquire a transfer matrix between the first thin film, second thin film, and substrate; using the transfer matrix to calculate the dispersion characteristics of the speed of surface waves; and substituting, to dispersion curves, the propagation speed of the surface waves measured from the substrate having the first thin film formed thereon, in order to acquire the stiffness constant matching the propagation speed of the measured surface waves and measure the adhesive strength between the substrate and the thin film.