Calibration
62
Scanning Probe Microscope Training Notebook
Rev. F
21.0 Calibration
Note:
This section is meant to introduce the NanoScope user to basic Calibration
procedures. For a more detailed discussion, please consult your specific
equipment manual. Please refer to your standard for step height information.
As described earlier in this manual, the sensitivity of the scanner decreases exponentially with
operation time. This will result in inaccurate dimensional measurements in the AFM image if this is
left uncorrected.
It is recommended that the X, Y, & Z calibration of the AFM be checked at least every 3 months
during the first year of operation and every six months thereafter.
This may be accomplished by imaging the 10µm x 10µm pitch grating with 200nm deep pits that is
supplied with the instrument. The 1µm x 1µm grating may be used for calibrating X & Y for small
range scanners.
Check that the spacing of the pits is the same throughout the scan at the largest scan size (440V).
This can be easily done using the Zoom box.
•
If the spacing is not consistent, go to
Microscope
>
Calibrate
>
Scanner
and adjust the
Fast Mag and Fast Arg parameters for correction in the X direction, and the Slow Mag
and Slow Arg parameters for correction in the Y direction. (see manual for instructions)
Check the dimensions in X & Y at scan sizes of 440V and 150V to see if the pitch measurement
falls within 2% (10 + 0.2µm).
•
If this needs correcting, run the automated calibration routine found under
Capture
>
Capture Calibration
. This routine captures twelve images at various scan sizes and
settings to calibrate the scanner sensitivity, sensitivity change with scan size, and
scanner rotation. The operator should watch the capture of the first four images in case
the microscope needs adjustment.
•
Once the images are acquired, go to
Utility
>
Autocalibration
in the Offline menu.
This routine will bring up each of the images and tell you to draw a vertical or
horizontal line along the pits. The computer will display what it thinks the distance of
the line is and the operator enters the distance according to the pitch of the pits. This
will calculate new sensitivity, derating, and coupling parameters in the
Microscope
>
Calibrate
>
Scanner
menu.
Check the Z calibration by scanning the same 10µm x 10µm pitch grating as used in the X and Y
calibration. The pits in this grating have a depth of 200nm.
•
Capture an image which contains a single pit. Make sure that the Z-center position in
the
Realtime
offline menu is near 0V for most of the scan (try to keep it /-
20V). A 1:4 Aspect Ratio captures the image faster.
•
Go to
Offline
and
Planefit
and/or
Flatten
the image if necessary.
•
Use the histogram in
Bearing
to perform an area depth measurement by determining
the relative depth between the histogram cursors.