Measurement of surface roughness by AFM

Project Description

AFM as high resolution instruments are used very often to determine roughness parameters of technical surfaces. However, up to now - as for the optical microscope - there exit no rules or guidance how to perform the measurements and how to analyze them in order to achieve a satisfying degree of comparability. Furthermore our experience e.g. among members of the German VDI FA 3.41 guideline committee has shown that the determined parameters depend critically on the properties of the tip, the digital resolution of the area investigated as defined by the scan range and the number of data points and lines, the dynamic behaviour of the instrument and the settings of the control parameters, plus the data treatment prior to the roughness analysis, e.g. leveling and filtering, and finally the software used for the determination of the roughness parameters.

Within this project we will investigate some samples which might be useful to verify the instruments' properties for areal measurements. A draft guideline under development in VDI FA 3.41 committee is available for this European comparison in this field. In order to exclude the influence of different approaches to AFM image analysis, the raw data of the participants' measurements will be sent to the coordinator for central analysis with the same software and the same analysis strategy. Additionally, it might be agreed to send the used cantilevers to the coordinators for high-resolution SEM inspection.

The samples and the guidelines investigated within this project should be a good base to set-up international standards in ISO/TC 201 or ISO/TC213.

Investigation of roughness measurement will be done by using two artifacts of step hight (PTB step height standards of nom. heights of 20 nm and 40 nm), a flatness sample, two samples with Ge-Si-nanodots (nearly isotropic roughness), lapped Si chips (three samples of the novel RnS-series by Simetrics company, with nominal Sq-values from some ten to a few hundred nm), Si chip with monoatomic steps. Optionally: an ion-track membrane (nom. diameter of holes 50 nm), resolution standard of type RS-N by Simetrics (chip with 9 one-dimensional gratings of different pitch, the finest nom. 300 nm)

Progress Report 2018-10-31

The progress report can be downloaded here >>.