Lateral Calibration

There are a number of different calibration standards for SPM available in the market. One of the most widely used is a diffraction grating with a submicron pitch. But manufacturing technology for those structures cannot usually provide edge roughness better than tens of nanometers. A large number of grooves have to be measured to get reasonable accuracy, which complicates the calibration procedure and demands additional mathematical calculations. MikroMasch has developed gratings with edge shape determined by the silicon crystal structure. This ensures that the edge roughness value is about several nanometers, which is far below the typical tip radius (10 to 40 nm), so one scan is enough for lateral calibration of the scanner (Fig. 1).

The TGX01 test grating comprises a chessboard-like array of square pillars with a 3 µm pitch. This arrangement permits calibration of scanners with a lateral scanning range of about 3 µm or more.

Use calibration gratings of TGX series for lateral calibration. Make sure that your SPM measures the period of the grating correctly (Fig. 1). Update the calibration factors if necessary. For lateral SPM calibration, you can also use TGG01.

Fig.1 Image of TGX01 taken by P4-SPM-MDT model of SOLVER. For lateral calibration of your microscope, measure the pitch of the grating. It should be equal to 3 microns.

Verify that your microscope is correctly calibrated in both the fast-scan and slow-scan directions. Determine how scanning speed and feedback parameters influence the imaging. Pay close attention to distortions caused by such parasitic effects as nonlinearity, hysteresis, and creep.

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