Introduction to Atomic Force Microscopy:Theory,practice,applications

AFM University Introduction to Atomic Force Microscopy by Paul West

6.1.1 Features on a Surface Appear Too Large

6.1.2 Features in an Image Appear Too Small

6.1.3 Strangely Shaped Objects

6.1.4 Repeating Strange Patterns in an Image

6.2 Scanner Artifacts

6.2.1 Probe / Sample Angle

6.2.2 X-Y Calibration / Linearity

6.2.3 Z Calibration / Linearity

6.2.4 Background Bow / Tilt

6.2.5 Z Edge Overshoot

6.2.6 Scanner Drift

6.2.7 X-Y Angle Measurements

6.2.8 Z Angle Measurements

6.3 Image Processing

6.3.1 Leveling

6.3.2 Low Pass Filter

6.3.3 Matrix Filter / Smoothing

6.3.4 Fourier Filtering

6.3.5 Image Looks Too Good

6.4 Vibrations

6.4.1 Floor Vibrations

6.4.2 Acoustic Vibrations

6.5 Other Sources

6.5.1 Surface Contamination

6.5.2 Electronics

6.5.3 Vacuum Leaks

6.5.4 PID Settings / Scan Rate

6.5.5 Laser Interference Patterns

Chapter 6

FIGURE 6-3 The motion of an AFM probe as it moves over a hole in a surface. Because of the width of the probe, it does not reach the bottom of the hole.

FIGURE 6-4 A: Scanning electron microscope image of a test pattern of squares (NT-MDT TXO1). The sides of the squares are all equal. B: AFM image of the test pattern. Because the probe is not sharp, the test pattern squares appear much smaller than they should. The features in the AFM image appear as rectangles and not as squares.

FIGURE 6-5 This "chipped" AFM probe follows the geometry of the sample surface and creates an image with a substantial artifact.

6.1.3 Strangely Shaped Objects

If the probe gets broken or chipped before an image is measured, strangely shaped objects may be observed that are difficult to explain. For example, when scanning a semiconductor test pattern, it can appear as though the tip is at a large angle to the surface (as described in Section 6.2.1). However, the probe to sample angle would have to be extreme to explain the image artifact (see Figure 6.6).

« back

112