Processing and Analysis of Long-Range Scans with an Atomic Force Microscope (AFM) in Combination with Nanopositioning and Nanomeasuring Technology for Defect Detection and Quality Control

Abstract

This paper deals with a planar nanopositioning and -measuring machine, the so-called nanofabrication machine (NFM-100), in combination with a mounted atomic force microscope (AFM). This planar machine has a circular moving range of 100 mm. Due to the possibility of detecting structures in the nanometre range with an atomic force microscope and the large range of motion of the NFM-100, structures can be analysed with high resolution and precision over large areas by combining the two systems, which was not possible before. On the basis of a grating sample, line scans over lengths in the millimetre range are demonstrated on the one hand; on the other hand, the accuracy as well as various evaluation methods are discussed and analysed.

Demystifying data evaluation in the measurement of periodic structures

“…The optimum of 20-30 samples per period may depend on the defects present in the data. Nevertheless, it seems quite consistent over two orders of magnitude of N. It also agrees with the study of scanning speed influence [41] where the profile length was kept fixed and N decreased with increasing scanning speed. The variance of results did not change much for more than 20 samples per period, but it started to increase sharply when less than 20 points were measured (one needs to combine tables 1 and 2 in [41] to compute N/P).…”

“…by evaluating the position of the profile at some height, interpolating or fitting the points near to this position to obtain the position more accurately. This is called the zero crossing method and is also often used [39,41,42]. To use only points related to a special feature and throw away the rest of the structure might be not very efficient, so the centre of gravity evaluated from whole structures can be used in order to include all of the data [11,35,[41][42][43].…”

“…This is called the zero crossing method and is also often used [39,41,42]. To use only points related to a special feature and throw away the rest of the structure might be not very efficient, so the centre of gravity evaluated from whole structures can be used in order to include all of the data [11,35,[41][42][43].…”

“…Next class of methods is based on the spectral density of spatial frequencies that can be obtained using FT. A 1D or 2D discrete FT (DFT) is run on the measured topography and from the frequencies corresponding to the peaks the period is evaluated [41,45]. As the lateral size of the scan is limited, the frequency resolution can be very coarse, which can be handled using different approaches for calculating a refined FT [35,46], e.g.…”

“…Their average was processed using a low-pass Gaussian filter (0.5 T) and subtracted from the data. The mid-height was located by finding the two main peaks in the height distribution and taking their midpoint [41].…”