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Tips, Tools and Techniques that
Simplify I-V and C-V Characterization


A G R E AT E R M E A S U R E O F C O N F I D E N C E



T O O L S , T I P S , A N D T E C H N I Q U E S T H AT S I M P L I F Y I -V A N D C -V C H A R A C T E R I Z AT I O N
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Tools, Tips, and Techniques that Simplify I-V and C-V Characterization




Introduction
Semiconductor characterization presents a wide range of test challenges. This e-Guide offers
an overview of advanced tools, tips, and techniques that you can use to simplify the I-V and C-V
measurements that are essential to characterizing emerging semiconductor materials, devices,
and processes.



Table of Contents
Making Accurate I-V and C-V Measurements ............................................................................................... 3

Ensuring C-V Measurement Integrity ....................................................................................................... 4-5

Preventing C-V Measurement Errors While Reducing Test Times.................................................................. 6

New C-V Measurement Techniques for High Impedance Devices ................................................................. 7

Measuring Sub-Picoamp Currents Accurately .............................................................................................. 8

Combining I-V, C-V, and Pulse I-V Measurements in One System ................................................................. 9




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Making Accurate I-V and C-V Measurements for Semiconductor Research,
Design, Development, and Test
I-V Measurements Capacitance-Voltage (C-V) Measurements
Making low current measurements presents a variety of measurement challenges. Error sources such Capacitance measurements have been used to determine a variety of semiconductor parameters
as leakage currents, noise, offset currents, piezoelectric currents, and environmental conditions can on many different devices and structures. Three measurement techniques are used to derive critical
have a serious impact on measurement accuracy. Precision DC I-V measurements are the foundation parameters from a wide range of new materials, processes, devices. Multi-frequency capacitance
of electrical characterization for cutting-edge devices, materials, and semiconductors. With proper provides capacitance vs. voltage (C-V), capacitance vs. frequency (C-f), and capacitance vs. time
measurement techniques and practices, these critical measurement challenges can be met. (C-t) measurements to evaluate at frequencies ranging from 10-MHz down to 1-kHz. Sometimes
even lower frequency capacitance measurements are necessary to evaluate test parameters of thin
film transistors, MEMS structures, and other high impedance devices. Called very low frequency
Ultra-Fast Pulsed I-V Measurements (VLF) C-V, this newer technique performs C-V measurements in the range of 10-mHz to 10-Hz.
To characterize slow trapping and de-trapping phenomenon in some materials, a capacitance
Today, many parametric measurements require a fast, pulsed I-V measurement. Using pulsed I-V measurement technique called quasistatic (or almost DC) measurements can be used.
signals to characterize devices rather than DC signals makes it possible to study or reduce the
effects of self-heating (joule heating) or to minimize current drift/degradation in measurements. Many
applications require pulsed I-V along with C-V and DC I-V measurements. Learn how to combine all
three measurement types into one test system while maintaining the measurement performance.




Want to learn more about Keithley's
powerful characterization solutions?
Download our Applicaton Guies for DC I-V
Testing, Pulsed I-V Testing, and C-V Testing.




Get advice on optimizing your I-V/C-V characterization applications.
Send us your question or join the discussion on our application forum.
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Ensuring C-V Measurement Integrity
Capacitance measurements at the wafer level are often plagued by preventable measurement errors. Ensuring
the accuracy of capacitance measurements can be challenging due to parasitic capacitance from cable,
switch matrix, and fixturing combined with small capacitance values, often in the picofarad or femtofarad
range. These values are typically far lower than most LCR meters can resolve. Additionally, measuring
capacitance on a semiconductor wafer is very different from measuring a packaged device due to the effects
of the probe station's chuck.
To ensure measurement integrity, it's important to
understand how a capacitance measurement is made.
A typical capacitance meter will apply a DC bias
voltage across the device under test while measuring
the AC signal at a frequency between 1-kHz to 10-
MHz. For MOScap structures, the DC voltage is swept,
which causes the device under test to pass through
accumulation into the depletion region and then into the
inversion region.
Keithley's Model 4200-SCS Parameter Analyzer
Interconnect Capatitance includes an extensive set of sample programs, The optional Model 4210-CVU C-V Meter plugs
test libraries, and built-in parameter extraction directly into the Model 4200-SCS chassis for
examples to simplify C-V measurements. measuring capacitances from femtofarads to
microfarads at frequencies from 1kHz to 10MHz.
Users can quickly configure linear or custom C-V,
C-f, and C-t sweeps with up to 4096 data points.




Get advice on optimizing your I-V/C-V characterization applications.
Send us your question or join the discussion on our application forum.
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Ensuring C-V Measurement Integrity HCUR


HPOT
Most capacitance measurements are performed on a probe station, which is the source of many errors. A probe CDUT
station's chuck can act as a large antenna that collects random noise. Since a wafer's substrate is connected V
LPOT
electrically to the prober's noisy ground, the AC ammeter circuitry used in the capacitance meter can pick up
this noise, which adds errors to measurements. Therefore, it's essential to connect the terminals of your meter to
LCUR
the DUT terminal with the least noise, which generally means the terminal with the least amount of capacitance A CCHUCK
to ground. Unfortunately, stopping a test and changing the setup to do this is time-consuming and increases
the opportunity for reconnection errors. To ensure your C-V measurements, the Model 4200-SCS Parameter
Analyzer software allows switching the AC ammeter with a simple mouse click, without the need to change
the test setup.
The DC bias required to make a C-V measurement creates an electric field that pushes or pulls the mobile carriers When measuring capacitance on a wafer and probe station, it is essential to connect AC ammeter circuitry to the least
noisy DUT terminal.
closer to or farther away from the DUT's oxide layer. Precise control over that electrical field requires the ability
to switch the DC bias from one device terminal to another. Similarly. the Model 4200-SCS Parameter Analyzer Simplified Test Circuit

software makes switching the DC bias to the desired DUT terminal fast and easy. There's no need to change the Simplified Test Circuit
test setup, which saves time and eliminates inadvertent misconnections, that can cause errors and require extra + Source
ACV
A B Measure
ACI
+