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Calibration

SPM Calibration Overview

308 Dimension 3100 Manual Rev. D

Table 17.1a Calibration Schedule

Note: Small Scan Size Calibration: If using scan sizes of 5µm or smaller, Veeco

recommends calibrating the scanner for small scan sizes. Contact Veeco for

further instructions.

17.1.1 Theory Behind Calibration

Scanners typically consist of a hollow tube made of piezoelectric material such as PZT (lead

zirconium titanate). Piezo materials contract and elongate when voltage is applied, according to

whether the voltage is negative or positive, and depending upon the orientation of the material’s

polarized grain structure. Scanners are used to precisely manipulate sample-tip movement in order

to scan the sample surface. In Dimension SPMs, the sample is stationary while the scanner moves

the tip.

Not all scanners react exactly the same to a voltage. Because of slight variations in the orientation

and size of the piezoelectric granular structure (polarity), material thickness, etc., each scanner has

a unique “personality.” This personality is conveniently measured in terms of sensitivity, a ratio of

piezo voltage-to-piezo movement. Sensitivity is not a linear relationship, however. Because piezo

scanners exhibit more sensitivity (i.e., more movement per volt) at higher voltages than they do at

lower voltages, the sensitivity curve is just that—curved. This non-linear relationship is determined

for each scanner crystal and follows it for the life of the scanner. As the scanner ages, its sensitivity

will decrease somewhat, necessitating periodic recalibration.

The diagram below depicts scanner crystal voltage versus photodiode voltage (see Figure 17.1a). In

this instance, detector sensitivity is given as volt per volt, a parameter provided in the Force

Calibration screen.

Calibration Routine Time Frame Frequency

Fine-Tuning Calibration

(or Full X-Y Calibration if required)

First Year Every 3 months

Subsequent Years Every 6 months

Z Calibration

(for General Applications)

First Year Every 3 months

Subsequent Years Every 6 months

Critical Height Measurements All Years Monthly

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