Sweep Concepts; Source-Delay-Measure Cycle; Sweep Waveforms - Keithley 4200-SCS Reference Manual

Model 4200-SCS Reference Manual

Sweep concepts

Source-delay-measure cycle

Although the SMU can be used for static source or measure operation, SMU operation usually
consists of a series of source-delay-measure (SDM) cycles (see
(refer to
1.
2.
3.
The delay phase of the SDM cycle, which is programmed by software, allows the source and
external circuitry to settle before the measurement is performed. Although the source itself settles
quite quickly (provided the unit is not in compliance), external V or I settling may take considerably
longer due to interaction between the DUT and the SMU.
When there is more capacitance seen at the output, there will be more settling time required for
the source signal. The actual delay period needed can be calculated or determined by trial and
error. For purely resistive loads and at higher current levels, the programmable delay can be set to
a minimum.
The measure time depends on the selected integration period, and it also can be extended by
autorange.
Figure 5-12
SDM cycle
Source
Value
Trigger

Sweep waveforms

There are three general sweep types: linear staircase, logarithmic staircase, and custom (refer to
Figure
steps. The logarithmic staircase sweep is similar, except it is done on a log scale with a specified
number of steps per decade. The custom sweep lets you construct your own sweep by specifying
the number of measure points and the source level at each point.
An SDM cycle is performed on each step (or point) of the sweep; one measurement will be
performed at each step (level). The time spent at each step depends on how the SDM cycle is
configured for such aspects as the programmed delay.
Typical applications for staircase sweeps include: I-V curves for two- and three-terminal
semiconductor devices, characterization of leakage versus voltage, and semiconductor
breakdown.
4200-901-01 Rev. S / May 2017
Sweep waveforms). During each SDM cycle, the following occurs:
The source output level is set.
There is a wait for the source delay.
The measurement is made.
Trigger
Delay
Latency
5-13). The linear staircase sweep goes from the start level to the stop level in equal linear
Return to
Start of A/D Conversion
Measure
Section Topics
Section 5: Source-Measure Concepts
Figure 5-12) as part of a sweep
End of A/D
Conversion
5-15