Keithley curve tracers, SMUs augment power-device test

The August print issue of EE-Evaluation Engineering includes a special report on power electronics test. In preparation for that article, we asked test equipment vendors to provide information on their products and strategies. Lee Stauffer, senior staff technologist; Robert Green, senior market development manager; Jonathan Tucker, senior marketing manager; and Ming Wang, product manager—all of Keithley—provided extensive feedback. In the Q&A below, they elaborate on points raised in the print article.

Question: What configurations of the Parametric Curve Tracer (PCT) are available for power test?

Answer: Four standard configurations (low power, high current, high voltage, and high current and high voltage) are available, as well as a variety of test fixture and interface options. These systems include the key elements necessary for power device characterization. PCT measurement channels are configured from Keithley Series 2600B and Series 2650A SourceMeter source measure unit (SMU) Instruments and an optional Model PCT-CVU multifrequency capacitance-voltage (C-V) meter. They offer dynamic range and accuracy that is orders of magnitude beyond what a traditional curve tracer could provide. The C-V meter is designed for C-V measurements on two-, three- or four-terminal devices. Capacitances from picofarads to 100 nF can be measured, with test frequencies from 10 kHz to 2 MHz, which makes it well suited for applications like measuring the parasitic capacitances on a high voltage SiC transistor.

Could you elaborate on the source-measure units?

Series 2600B SMU Instruments offer single- and dual-channel models that combine the capabilities of a precision power supply, true current source, 6½-digit DMM, arbitrary waveform generator, pulse generator, and electronic load—all into one tightly integrated instrument. This family of models offers the test and measure industry’s widest dynamic range: 10-A pulse to 0.1 fA and 200 V to 100 nV. The result is a powerful solution that significantly boosts productivity in applications ranging from bench-top I-V characterization through highly automated production test.

The Model 2651A high-power system SourceMeter instrument is designed to characterize and test high current and high power electronics, including those fabricated from compound semiconductors like SiC and GaN. Its wide dynamic range (50 A, 40 V, 100 fA) helps improve productivity in applications across the R&D, reliability, and production spectrums. It can be combined with another Model 2651A to increase the maximum current range to 100 A, with other Series 2600B SourceMeter SMU instruments to create SMU-per-pin test systems, or with the Model 2657A high power system SourceMeter instrument to configure a high-power PCT test system capable of 3000 V and 100 A.

The Model 2657A high power system SourceMeter instrument has the ability to source, sink, and measure up to 3 kV/1 fA for precise characterization of a wide variety of power semiconductors in applications across the R&D, reliability, and production spectrums, including those fabricated from compound semiconductors like SiC and GaN.

With its 7-A DC and pulse current capability, the Model 2460 SourceMeter SMU is optimized for characterizing and testing the operating performance of high power materials, devices, and modules such as SiC and GaN devices, DC/DC converters, power MOSFETs, solar cells and panels, LEDs and lighting systems, electrochemical cells and batteries, and much more.

At what stage of the design, development, and production process are these products used (for example, debug, validation, characterization, production, failure analysis)?

Keithley’s Parametric Curve Tracer configurations, SourceMeter SMU instruments, and power supplies are widely used in design and development:

• During the design stage, given that engineers are trying to gather as much information as possible on a new device, they need to acquire a broad range of parameters. These include breakdown voltage, on-state current (DC), on-state current (pulse), drain/collector leakage current, gate/base leakage current, on-state threshold voltage or cutoff voltage, forward transfer admittance or forward transconductance, on-state resistance, input capacitance, output capacitance, and reverse transfer capacitance.
• During the development stage, engineers tend to focus more on how their devices will be commercialized, and how they might fail. Here, the PCT configurations, SMU instruments, and power supplies are often used in characterization applications designed for developing device specifications and for failure analysis.

Series 2600B SourceMeter SMU Instruments, and the Series 2650A SourceMeter instruments are also well suited for use in production test because of their high test throughput and high measurement speeds when configured in systems that include an appropriate probing system (for testing on wafers) or test fixture (for testing packaged parts). Although the Model 2460 doesn’t offer quite the speed of the Series 2600B instruments, it is also appropriate for some production test applications because of its 7-A DC and pulse current capability.

Keithley’s Parametric Curve Tracer configurations (including the Models 2657A and Model 2651A) offer the power required for the vast majority of high-power device design and development applications and are optimized to address the characterization and test needs of research, reliability, failure analysis, and power device applications engineers; power device designers; incoming inspection technicians; and many others. Applications include

• power semiconductor device characterization and testing at both the wafer and packaged parts level,
• characterization of GaN and SiC, LDMOS and other devices,
• reliability studies on power devices, and
• incoming inspection and device qualification.

Series 2290 high-voltage power supplies are often used in characterization applications in research, design, and reliability labs for the following types of tests:

• high voltage device breakdown testing,
• high voltage component testing,
• insulation testing, and
• high voltage resistivity measurements.

Series2600B SourceMeter instruments and the Series 2650A SourceMeter instruments are also suited for use in production test because of their high test throughput and high measurement speeds when configured in systems that include an appropriate probing system (for testing on wafers) or test fixture (for testing packaged parts). Although the Model 2460 doesn’t offer quite the speed of the Series 2600B instruments, it is also appropriate for some production test applications because of its 7A DC and pulse current capability.

Keithley’s Parametric Curve Tracer configurations (including the Models 2657A and Model 2651A) offer the power required for the vast majority of high power device design and development applications and are optimized to address the characterization and test needs of research, reliability, failure analysis, and power device applications engineers; power device designers; incoming inspection technicians; and many others. Applications include

power semiconductor device characterization and testing at both the wafer and packaged parts level;

characterization of GaN and SiC, LDMOS, and other devices;

reliability studies on power devices, and

incoming inspection and device qualification.

Series 2290 high-voltage power supplies are often used in characterization applications in research, design, and reliability labs for the following types of tests:

• high-voltage device breakdown testing,
• high-voltage component testing,
• insulation testing, and
• high-voltage resistivity measurements.

What types of measurements are your instruments making (for example, I-V or other electrical parameters or thermal or other parameters?

Keithley test instruments primarily perform I-V measurements. The Parametric Curve Tracer can also be configured to perform capacitance and C-V measurements.

A Parametric Curve Tracer configuration can, depending upon the exact instrument configuration chosen, extract these power transistor parameters:

• breakdown voltage (Bvdss, Bvceo);
• on-state DC current (Vdson, Vcesat, Vf);
• on-state pulse current (Vdson, Vcesat, Vf);
• drain/collector leakage current (Idss, Ir/Icbo, Iceo);
• gate/base leakage current (Igss, Ib);
• on-state threshold voltage or cutoff voltage (Vth, Vf, Vbeon, Vcesat);
• forward transfer admittance or forward transconductance;
• on-state resistance (RDS(on), Vcesat);
• input capacitance (Ciss);
• output capacitance (Coss); and
• reverse transfer capacitance (Crss).

The Model 2460 SourceMeter instrument and Model 2651A and Model 2657A High Power System SourceMeter instruments are well suited for high power testing, especially in the areas of the characterization of new materials (such as SiC and GaN) and components and module testing.

Do you offer any options (for example, software or fixturing) that are particularly applicable for power electronics test applications?

Keithley’s ACS Basic Edition software (included in PCT configurations) provides complete device characterization, including both real-time trace mode for quickly checking fundamental device parameters like breakdown voltage and full parametric mode for extracting precise device parameters. ACS Basic Edition goes beyond traditional curve-tracer interfaces by offering a broad array of parametric test libraries. Users have complete control of all test resources, allowing the creation of more advanced tests than previously possible on a curve tracer.

The Model 8010 High Power Device Test Fixture provides safe and easy connections for testing packaged high power devices at up to 3000 V or 100 A. The Model 8010 provides connections for a high-voltage SourceMeter instrument (Model 2657A), one or two high current SourceMeter instruments (Model 2651A), and three low-power SourceMeter instruments. This allows devices with two terminals (diodes) or three terminals (transistors) or even four or five terminals to be characterized safely and accurately. The Model 8010 has full interlock capability for up to six SourceMeter SMU instruments. Integrated protection circuits protect the low voltage SourceMeter SMU instruments from high voltages that the Model 2657A can output should a device fault occur. It includes both a high current (100 A) and a high voltage (3,000 V) test socket. Various replacement test socket modules are available, including TO-247, TO-220, axial lead, and a blank socket module that allows building a custom socket. In addition to standard banana jumpers, the Model 8010 has rear-panel scope and thermal probe ports to simplify system integration. The new Model 8010-DTB-CT Tektronix Curve Tracer Adapter Module supports the use of Tektronix curve tracer test modules with the Model 8010 fixture.