Model 6485 Picoammeter Instruction Manual Applications Guide I-25
Figure I-23
Basic connection scheme
NOTE The details on page I-12 concerning range change transients may be particu-
larly relevant to this application
Focused ion beam applications
Focused Ion Beam (FIB) systems have been developed to perform nanometer-scale imag-
ing, micro machining, and mapping in the semiconductor industry. Typical applications
include mask repair, circuit modification, defect analysis, and sample preparation of site-
specific locations on integrated circuits.
FIB systems use a finely focused ion beam for imaging, or for site specific sputtering or
milling. The magnitude of the beam current determines what type of operation is per-
formed. A low beam current results in very little material being sputtered, and is therefore
ideal for imaging applications. Utilization of high beam currents resulting in a great deal
of material being removed by sputtering, and is subsequently well suited for precision
milling operations.
Therefore, whether the application calls for imaging, or a complete circuit modification,
monitoring and control of the beam current is critical to the success of the process. The ion
beam current cannot be measured directly, but requires the use of an ion detector. There
are several detectors commonly used throughout the industry including Channeltron®,
Daly, Microchannel plate, and the Faraday cup. The Faraday cup can only be used in an
analog mode, and is therefore not as sensitive as newer current pulse devices.
Calibrated Light Source
Wafer
Model 2400
Bias Voltage
Probe Needles
Model 6485
Pads
Probe Needles
Photo Diode
Trigger Link Cable
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