Using high-power digital source meter to build a multi-source measurement unit (SMU) system - Part 1

The design and construction of a power semiconductor device DC characteristic analysis test system using a high voltage, high current source measure unit (SMU) includes the following steps:

• Select equipment that meets the test requirements

• Select cables and fixtures to connect the device under test (DUT) to the instrument

• Check system safety and instrument protection

• Optimize instrument setup to ensure measurement integrity

• Control instrument hardware

The design of power semiconductor devices ensures that: in the ON state, it can provide a lot of power to the load while consuming minimal power itself (high efficiency); in the OFF state, it provides almost zero power to the load while consuming minimal power itself (high efficiency) (standby current is very small). Therefore, the characterization or DC parameter testing of power semiconductor devices can be divided into two types: ON state characterization and OFF state characterization. This application note describes these two test applications and gives examples of building test systems using various Keithley SourceMeter source measure unit (SMU) instruments.

Select equipment that meets your test requirements

Power device testing usually requires high-power instrumentation at only one or two ports. For example, high-voltage N-channel MOSFET off-state characterization requires high-voltage power at the drain; all other ports only need to be driven by lower voltage power supplies. Conversely, when characterizing its on-state performance, a large current needs to be applied to the source, so only these two ports are required to maintain the rated maximum power. If test researchers move from testing lower-power devices to testing higher-power devices, they can reuse some existing test equipment at the gate and substrate ports. If multiple devices can share the same test instrument, users can maximize their return on investment.

To select the appropriate test equipment, it is important to understand the minimum and maximum currents required to source and measure. If possible, select equipment with scalable minimum and maximum values ​​to accommodate the development of new device testing requirements.

Keithley's Series 2600A Source Measure Units (SMUs) are designed with evolving test systems in mind. The TSP-Link® inter-device communication bus enables the creation of "mainframeless" systems while achieving sub-microsecond synchronization across multiple SMU channels.

One of the most powerful features of the 2600A Series is the ability to build systems that meet a wide variety of application test needs while maintaining seamless system performance. The 2600A Series Source Measure Units (SMUs) include eight models that offer a variety of features and capabilities:

• When the pulse power is 2000W, the current range is 50A (using two SMUs in parallel, 100A can be achieved)

• Voltage source up to 3kV at 60W, up to 1500V at 180W

• Sub-Amp measurement capability

• Provides 1A or 3A DC source for lower power SMUs. Ideal for testing high power transistors with large base currents.

This capability is often unavailable in existing commercial test mainframes and previously required the configuration of custom or semi-custom automated test equipment. In addition, utilizing standalone instruments allows test engineers to add new capabilities as test requirements evolve. Standalone high-power source-measure units (SMUs) can extend the current and voltage capabilities of semiconductor parameter analyzers, thereby expanding the range of testable devices.