Chapter 5
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FIGURE 5-7 Errors in surface texture calculations can occur if (Top) the probe is not sharp enough to correctly track the surface topography and (Bottom) the scan range is not long enough to sample the extremes of the surface texture. In this case if the scan range is L2 a different value will be reached than if the scan range is L1. |
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5.3.3 Height Analysis |
Many applications for AFMs require measuring the heights of features and the features have one or more distinct levels. It is critical that the image be properly leveled to obtain reliable and accurate step height measurements. |
Figure 5-8 A is an example of measuring heights from a histogram. Histogram measurements are the most accurate because the histogram is comprised of data from the entire image, which provides an averaging effect. |
Figure 5-8 B shows one of the pitfalls of measuring step heights from a line profile. If only a single point is selected at the bottom of the profile and at the top of the profile, the step height value can vary dramatically. The error is a result of either the surface texture of the sample or noise in
the image. This error may be minimized by averaging several lines that are in sequence in the image. |
Figure 5-8 C illustrates a step height measurement technique where the average signal at the top and bottom of the profile are used. This technique is typically used when the type of sample under analysis is well characterized. |
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