Test & Measurement
Flexible cabling
Manufacturing semiconductors requires the ability to accurately and astutely
measure electrical characterization right along the manufacturing process. There are
a wide range of possibilities for any manufacturer but one issue that can be
Issue VI 2009
overlooked is the specific cabling requirements for each type. Wayne Goeke and
square4
Lee Stauffer, Senior Staff Technologists at Keithley Instruments, discuss the different
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cabling requirements associated with each measurement type and describes an
approach to multi-measurement cabling that combines high signal integrity with
excellent ease of use.
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any different types of conductor, the inner shield is driven as a guard
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measurements go into for the signal, and the outer shield is used for
characterizing an electrical safety to shield the user from high voltages that
device and the processes involved in its may be applied to the guard and signal
manufacture. However, current-voltage (I-V), conductors. Two cables are necessary in order to Figure 1: I-V
capacitance-voltage (C-V), and pulse based achieve a remote sense, or Kelvin, connection on measurement
measurements are the most commonly made each device terminal. Remote sense cables allow connection scheme for
measurement types in these applications. As a the instrument to sense the voltage at the Kelvin connections
result, semiconductor device characterization
systems typically include capabilities for making
these measurements, with some more successful
than others in integrating these measurements in
a way that reduces the time and effort required
to make them.
Perhaps the greatest challenge associated
with integrating these measurements is the
fundamentally different cabling requirements for
each measurement type. Although the cabling
from the instrument to the probe station
bulkhead and feed through is fairly
straightforward, many users find the process of
connecting the cabling from the bulkhead to the
probe tips to be confusing and difficult.
Cabling Requirements
Guarding is crucial to making high integrity low
current I-V measurements, so it’s essential to use
triaxial cables for these measurements. Figure 1
illustrates how these measurements can be
made using four triaxial cables. The
measurement signal is carried on the centre
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