Thin Film Measurement

For both creative and technical applications, thin films are playing an increasingly key role. The functionality of the coating can be significantly influenced by its thickness, depending on the application. The exact determination of the coating thickness is critical both in development and in process and quality control.

FRT supplies the ideal surface measuring tool for every coating: Whether development, laboratory, quality assurance or production. The MicroProf® series’ multi-sensor measuring tools can measure coatings easily and non-contact.

Establishing the coating thickness can be combined with topography measurements and can also be completely automated.

In addition to the analysis of complex multilayer structures with high resolution, the FTR sensor was developed in-house for the determination of thin films in the sub-micrometer range, from a few tens of nanometers up to several tens of micrometers.

PVA film measured with FTR sensor

Image Credit: FormFactor

The FTR is an optical thin-film reflectometer for the thickness measurement of transparent, thin films and layer stacks. The reflectometric technique is characterized by non-destructive, non-contact measurement with very high resolution.

The thin-film sensor is utilized in variants with different wavelength ranges depending on the requirements. This means that optimum measuring conditions are provided for different materials and layer thicknesses. The lateral resolution can be increased up to 5 µm for small structures.

The sensor is employed for measurement tasks in:

  • MEMS
  • Semiconductors
  • Solar technology
  • Optical and metal processing
  • Medical applications.

Some application examples include thickness measurements of nitrides, oxides, photoresists and other optically transparent layers. 

The measurement of thin layers with the FTR is based on the superposition of partial waves reflected at the interfaces of a layer. Assessing the reflection spectra of the interferometric sensor is performed using a powerful software developed together with our film thickness experts. 

An evaluation by means of FFT (Fast Fourier Transformation) and a model-based fit based on the material data or a combination of both techniques are utilized depending on the thickness of the film and the layer system. 

It is for this reason that extremely thin layers in the nanometer range can be analyzed with high resolution and fast measurement results can be gathered. 

An extensive database with refractive indices and absorption coefficients of a large variety of materials such as polymers, glasses, oxides, and semiconductors is included, which can be expanded easily by the user. 

The FTR can be used to generate layer thickness profiles and mappings with high lateral resolution in addition to point measurements when used together with the measuring tools. The sensor is also ideally suited for integration into in-line control. 

This sensor also enables the analysis of multilayer systems with up to ten layers and transparent substrates coated on both sides can also be modeled.

Components can be characterized in which the layer system is located between thicker materials, like OLEDs which are encapsulated with glass on one side and have a metal electrode on the other.

The CWL FT is an interferometric film thickness sensor that is specially designed to measure the thickness of products like films or coatings which are transparent to visible light. The film thickness can be evaluated at a given position, along a profile or over the entire surface with the CWL FT, as a mapping to assess the coating homogeneity. 

The sensor is also suitable for the characterization of multilayer systems. FFT (Fast Fourier Transformation) can be employed to measure layer thicknesses of up to two layers in the range from approximately 2 to 250 μm with a resolution of approximately 10 nm. 

The CWL FT is based on the spectral assessment of the superposition of partial waves of a white light source reflected at the interfaces of a transparent layer. The intensity of the superimposed partial beams varies with the wavelength at a given film thickness and refractive index. The spectrum then exhibits a typical interference pattern. 

The sensor is able to calculate the thickness using this spectrum and the refractive index of the coating material. The analysis program FRT Mark III is employed to assess the measured film thickness. The powerful software is utilized in the FRT measuring tools to display and evaluate topography data and film thickness measurements. 

The multi-sensor measuring tools of the MicroProf® series provide the possibility to combine the film thickness sensor with a chromatic distance sensor. This enables the film thickness measurements described in addition to topography and profile measurements with a height resolution of a few nanometers in one measuring tool. 

This supplies the user with an extremely powerful measuring tool for highly accurate, fast film thickness and topography measurements. The exact transfer of the leather pattern to the artificial leather skin should be ensured for the process control during the production of artificial leather skins. 

The forming tools have metal surfaces; artificial leather skins are soft and very soft silicone imprints should also be taken. In addition to the rough leather structure, the microstructure on the nubs and in the scars should be measured. All measurements should be carried out with the same sensor. 

The surface is scanned mechanically by conventional stylus tools. They cannot measure the soft surfaces without interaction and they are too slow to take 3D measurements. A lens in the sensor follows the height of the object being measured in non-contact autofocus systems. The highly structured artificial leather surfaces can only be measured very slowly. 

Artificial leather surfaces for car interiors should not be reflected in the windshield of the car as this would mean that incident light would be absorbed to a high degree. An optical sensor has to be extremely sensitive to be able to reliably establish the topography from the small amount of light scattered on a black artificial leather surface. 

The MicroProf® utilizes a confocal, chromatic distance sensor. Using the spectral distribution of the light scattered on the surface, the CWL sensor focuses white light on the measuring object and determines the height of the measuring object in the measuring spot. 

For different measuring tasks, there are different measuring heads with measuring ranges of up to 10 mm and a height resolution from 3 nm. The system can be employed to measure the entire spectrum of materials utilized (silicone, leather, metal, plastic). 

The full resolution (2 μm lateral, 3 nm in height) is available for every possible measuring field size for measurements with the MicroProf®

The SLS is an optical line sensor that can be used for extremely fast measurements. It works according to the principle of chromatic distance measurement. This sensor generates 192 measuring spots, which are lined up equidistantly along a line. 

A distance value with a resolution in the nm range is produced for each measuring point in this way. It is possible to generate a 3D measurement immediately while scanning along a measurement direction perpendicular to it due to the line arrangement of the measuring points. 

The scanning of a measurement object is thus possible in a fraction of the time required for point sensors as measurement rates of up to 2 kHz can be achieved. 

Utilized in MicroProf® to assess the measured data, the Mark III software determines the width of the scars, the height of the nubs, and the slope of the flanks. The roughness of the surface is determined in small areas between the scars. 

Authentic Haptics for Modern Imitation Leather Cover in Cars

The haptic in cars is important; the appearance and touch of the matt black imitation leather cover are both key factors. 

Slush Skins

The automotive industry is always developing new materials that look great, are durable and feel good. The majority of these are leather-like surfaces, known as slush skins, which exact contour images of leather structures and real-looking decorative seams. They do not fade and do not become brittle like real leather. 

The Automotive Industry Wishes

The high quality demands of the automotive industry are met with regard to color embossing and gloss. They also create a range of design possibilities, as complex geometries with large undercuts, but also small radii can be generated with high precision. 

Example: Imitation of the Leather Structure

The topography measurement of slush skin for automotive interiors is one specific example. In this instance, the height and diameter of the grains are measured in large surface areas, and the high resolution micro-roughness of the individual grains is established. 

Artificial leather measurement

Image Credit: FormFactor


In this case, it is crucial to be able to dynamically adjust the measuring range from the millimeter range to the micrometer range. These measurements are vital for the manufacture of tools, the design of structures, production monitoring and quality control. 

The aim is to optimize the structures to attain the best possible imitation of the leather structure through synthetic surfaces. The result must have the desired characteristics when touched, but it must also be as resistant as possible to dirt and effects like heat or humidity. 

Slush Skin Determines the Function of the Airbag

Slush skins must have a certain thickness since they also cover the areas under which the airbag is located. It must not be so thin that it collapses and the perforation of the underlying material becomes visible and also so thin that the cover of the airbag tears open in an emergency. 

This information has been sourced, reviewed and adapted from materials provided by FormFactor.

For more information on this source, please visit FormFactor.

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