LAwave

The measurement method LAwave, developed at the Fraunhofer IWS with Fraunhofer CCD, 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.

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

© Fraunhofer CCD

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

© Fraunhofer CCD

Principle of the LAwave method using laser induced surface waves

Services and Examples of Application

Customized development

The Fraunhofer CCD 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.