Atomic force microscopy (AFM) and atomic force acoustic microscopy (AFAM)


Atomic force microscopy – AFM


With atomic force microscopy (AFM), Fraunhofer IKTS offers an imaging technique for high-resolution surface analysis. AFM can reach a lateral size of one to 90 micrometers, with a resolution in the nanometer range. This makes AFM an important tool in surface chemistry, surface mechanics and topography. Its purpose is to mechanically scan surfaces and measure atomic forces on the nanometer scale. The imaging technique is performed in contact mode and semi-contact mode. Both available AFM systems can also provide PFM (piezoresponse force microscopy) analyses of the magnetic and piezoelectric properties of surfaces. For instance, it is possible to analyze the structure size and the step height and surface roughness of 300 mm wafers.

© Fraunhofer IKTS
Example of a surface analysis based on a topography measurement for CU/SiO2 on silicon waver substrate (Figures 1 to 3).
© Fraunhofer IKTS
© Fraunhofer IKTS

Atomic force acoustic microscopy – AFAM


Another option for surface analysis is atomic force acoustic microscopy (AFAM), also offered at Fraunhofer IKTS. With AFAM it becomes possible to analyze changes of elastic properties within the range of three to 300 GPa. This is done by ultrasonic excitation, with which the elastic properties are extracted with high-precision and high-lateral resolution. In addition, a calibration method developed at Fraunhofer IKTS increases further the accuracy of the calculated elastic properties. This optimized calibration enables the researchers to reliably measure the elastic properties of thin layers with a thickness as low as 100 nanometers.

© Fraunhofer IKTS
Results of a comparison between conventional calibration methods and the method developed by Fraunhofer IKTS. The results show that the improved calibration outmatches the existing calibration methods as the material gets stiffer.
© Fraunhofer IKTS
The indentation modulus measured for thin layers depends on the ratio between AFM tip radius and coat thickness. If the radius of the AFM tip is larger than the coat thickness, this will affect the calculation of the film’s indentation modulus. The Fraunhofer IKTS calibration method ensures that this ratio remains below 0.5 for thin-film measurements.
© Fraunhofer IKTS
AFM of aluminum nitride (AlN). Topography (left), piezo mode, 20 kHz (right).

Porosity [%] Layer thickness [nm] Indentation module [GPa]
Indentation module [GPa]
40 650 3.8±0.2 3.8±0.2
27 627 6.8±0.2 6.9±0.4
30 716 5.7±0.2 5.5±0.3
30 350 6.7±0.1 -
30 200 7.4±0.1 -
30 46 8.2±0.2 -

The table shows the measuring results of a comparison of methods performed on porous organosilicate thin films. The comparison pitched atomic force acoustic microscopy (AFAM) against the nanoindentation method. As the results show, AFAM and nanoindentation deliver similar measuring results for coat thicknesses up to 700 nanometers. When it comes to thin films, however, nanoindentation reaches its limits, whereas smaller thicknesses are no problem for AFAM thanks to the sharp tip, the tip geometry and the special calibration method. AFAM delivers precise results even for a coat thickness of 46 nanometers.

Services offered for AFM and AFAM


  • Topography characterization for process optimization (including large 300 mm wafers)
  • Determination of Young’s modulus/indentation modulus in the range of 3 to 300 GPa
  • Mechanical characterization of thin films
  • Representation of the mechanic properties of composite materials
  • Characterization of piezoelectric thin films on the nanoscale (identification of piezoactivity and representation of piezoelectric domains)
  • Development of client-specific methods for the characterization of structures and materials on the nanoscale

AFM and AFAM equipment


  • Agilent LS5600 atomic force microscope for measuring the topography and the piezo mode and lateral force mode
  • Atomic force acoustic microscopy system for the local determination of Young’s modulus/indentation modulus, for representing stiffness and generating calibrated images of Young’s modulus