Test & Measurement
The main advantage of Keithley’s new approach to
connecting the instrumentation to the prober is that, no matter
which type of measurement is being made, no changes
to the probe manipulator cabling are required
ground connection at the end of a short cable
might seem like a simpler alternative, this would
reduce the effective bandwidth of the ground.
To obtain a clean 10ns rise time, the ground
cable must have an electrical length that is less
than 1.5ns (approximately 30cm), which would
allow the ground to be applied at the mounting
base of the probe manipulator.
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Adding connectors in the cables near the
probe manipulator mounts allows inserting a
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shorting cap as shown in Figure 9. The shorting
.eur cap can be added without disturbing the probe
oasiasemiconductor
needle, making it possible to switch from I-V
and/or C-V measurements to pulsed
measurements without the need to re-probe a
wafer site. By allowing an operator to make
quick, easy set-up changes while the probe
needles are in contact with a wafer, the cap
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reduces pad damage and maintains the same
Figure 9: To insert a shorting cap, add connectors in the cables near the contact impedance for all three types of
probe manipulator mounts measurements.
square4
Issue VI 2009
In order to simplify switching from Kelvin to
non-Kelvin measurements, it was necessary to
allow the cables to be connected in parallel. This
means that cables do not have to be added or
removed when changing from one measurement
type to another; they can simply be moved from
one set of instrument connections to another.
Given that most fast pulse instruments require a
50Ω pathway, the parallel combination of cables
should yield 50Ω, so each cable must have a
characteristic impedance of 100Ω. Most LCR/C-V
meters are designed to function with 50( cables,
but the Keithley Model 4210-CVU instrument for
the Model 4200-SCS system is designed for use
with 100Ω cables, resulting in slightly improved
C-V results.
The main advantage of Keithley’s new
Figure 10: An I-V measurement setup for a four-terminal DUT approach to connecting the instrumentation to
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