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6.4 CD Measurement Function (Option)
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6.4.5.5 Calibration
The accuracy of measured values depends on the accuracy of image magnification unless
calibration has been made. Factors that affect the accuracy include accelerating voltage, scan
speed, magnification setting, working distance, raster rotation angle and others. By fixing these
parameters and conducting calibration with a sample of known dimensions, measurement can
be made with an even higher accuracy.
(1) Using Registered Calibration factor
Calibration is specified by means of the Calibration selector box on CD Measurement window.
The modes of calibration are selectable from the following.
(a) Auto Select
Automatically selects calibration that matches the measurement parameters. When a
number of calibrations have been registered under the same parameters, the
calibration registered at the maximum Entry No. among the relevant parameters will
be selected.
(b) Entry No.
Calibration is applied only when the SEM parameters of the specified calibration match
the SEM parameters of the object image. Specifying an Entry No. displays the
corresponding SEM parameters. An Entry No. for which calibration is not registered
cannot be specified.
(c) Not Apply
Calibration is not applied.
(2) Applied Parameters for Calibration
Calibration is made when the present SEM parameters are within the following ranges as
compared with the calibrated condition.
• Accelerating voltage : Same as calibrated condition
• Viewing magnification : ±1% of calibrated mag.
• Working distance : ±0.5mm of calibration working distance
• Detector : Same as calibrated condition
• Probe Current : ±1.0 of calibrated condition
• Vacuum : Same as calibrated condition
• Scan speed : Same as calibrated condition