Veeco Dimension 3100, Manual

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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