Test and Measurement
Enhancing measurement capacity
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Measurement
Flexibility?
Maybe You
M
any different types of conductors. Two cables are necessary in order to
measurements go into achieve a remote sense, or Kelvin, connection on
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characterizing an electrical device and the each device terminal. Remote sense cables allow
Flexible
processes involved in its manufacture. However, the instrument to sense the voltage at the
current-voltage (I-V), capacitance-voltage (C-V), device accurately. In this figure, the device to be
Cabling. By and pulse-based measurements are the most characterized has two terminals.
Wayne Goeke,
commonly made measurement types in these Figure 2 illustrates the cabling for C-V
applications. As a result, semiconductor device measurements using four coaxial cables. The
Senior Staff characterization systems typically include outer shells are connected together to control
26
Technologist
capabilities for making these measurements, the characteristic impedance the signals see. The
with some more successful than others in outer shells of all four cables must be inter-
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and Lee integrating these measurements in a way that connected near the device under test (DUT).
.eur
Stauffer,
reduces the time and effort required to make Pulsed measurements require the highest
oasiasemiconductor
them. Perhaps the greatest challenge associated bandwidth of the three measurement types, so
Senior Staff with integrating these measurements is the to prevent reflections off the DUT from reflecting
Technologist,
fundamentally different cabling requirements for off the source, the cable must have a
each measurement type. Although the cabling characteristic impedance that matches the
Keithley
from the instrument to the probe station source impedance. Pulsing does not use a
Instruments.
bulkhead and feedthrough is fairly remote sense cable. Figure 3 illustrates a typical
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straightforward, many users find the process of connection to a two-terminal DUT. Pulsing is the
connecting the cabling from the bulkhead to the only one of the three measurement types that
probe tips to be confusing and difficult. This connects the DUT to the outer shield of the
square4
Issue VIII 2009
article explains the different cabling cable.
requirements associated with each measurement
type (Table 1) and describes a new approach to
multi-measurement cabling that combines high
signal integrity with excellent ease of use.
Measurement 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 center
conductor, the inner shield is driven as a guard
for the signal, and the outer shield is used for
safety to shield the user from high voltages that Figure 1: I-V measurement connection scheme
may be applied to the guard and signal for Kelvin connections
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