Fraunhofer USA Center Midwest CMWThe measurement method LAwave, developed at the Fraunhofer IWS with Fraunhofer USA CMW, allows non-destructive characterization of films and material surfaces. It uses short laser pulses to create surface acoustic waves. Their propagation velocity is then measured over frequency. The so-called dispersion curve depends on the elastic modulus (Young’s modulus), density, and thickness of the film. After measurement, the dispersion curve is fitted with a physical model to obtain the desired material parameters. It is also possible to characterize non-coated surfaces, for example gradients of the micro-structure such as machining layers and porosity.
LAwave
Highlights
Non-destructive
Film thickness from a few nanometers to several hundred micrometers
Film properties from polymer to diamond
Test time less than one minute
High reproducibility
Easy to use
Simple arrangement
Dimensions of the test area: minimum 5 × 5 mm
Few requirements for the sample geometry
Low effect of surface roughness
Complies with EN 15042-1
Application
In general, all coating and surface properties that affected the propagation of surface acoustic waves can be measured.
Young’s modulus, thickness and density of:
PVD coatings, e.g. DLC, nitrides, carbides, oxides, other ceramics
CVD coatings and CVD diamond
Thermal-sprayed coatings
Low-k films
Si, GaAs semiconductors
Polymeric sensor films
Bulk materials, e.g. steel, brass
Cemented carbide
Depth of:
Subsurface damage from silicon wafer processing
Work hardening zone after metal finishing
Surface hardening
Principle of the LAwave method using laser induced surface waves
Services and Examples of Application
Customized development
The Fraunhofer USA CMW looks back on many years of experience in developing LAwave measurement systems and software that are used for R&D as well as for quality control throughout the world. Based on a modular designed standard table-top unit, the device can be adapted to customer-specific tasks and sample geometries.
Distributing partners
We have distributing partners for Japan, USA, China, and Taiwan, providing sales, service and consulting for LAwave measuring systems to many international customers directly.
Examples of application
Amorphous carbon coatings (DLC): Young’s modulus correlates with hardness and wear resistance of the coating
Thermal-sprayed coating: Young’s modulus correlates with crack and pore density, and delamination can be detected. Quality of the coating can be measured on rough, as sprayed surfaces.
Depth of subsurface damage can be measured, for example on processed silicon wafers after sawing, grinding and polishing. Dispersion curve slope directly correlates with damage depth.
High-porous low-k films can be measured on suitable substrates: Young’s modulus correlates with resistance against chemical activated polishing process.