Recently, there has been a surge in the number of applications that require ultra-fast I-V measurements, which involve generating pulsed waveforms, then measuring the resulting signals before the DUT has an opportunity to relax. The reason for this growth is simple: using pulsed I-V signals rather than DC signals makes it possible to study or reduce the effects of self-heating (joule heating) or to minimize current drifting in measurements due to trapped charge.
Transient I-V measurements allow scientists and engineers to capture ultra-fast current or voltage waveforms in the time domain or to study dynamic test circuits. Other applications include using pulsed sourcing to stress test a device using an AC signal during reliability cycling or in a multi-level waveform mode to program/erase non-volatile memory (such as flash and PCRAM devices).
Ultra-fast I-V sourcing and measurement are important capabilities for many device technologies, including compound semiconductors, non-volatile memory, MEMs (micro-electro-mechanical devices), nanodevices, solar cells, and CMOS devices. Applications include single-pulse charge trapping (SPCT), charge-based capacitance measurement (CBCM), Silicon-On-Insulator (SOI), isothermal testing of medium-sized power devices and LDMOS/GaAs, charge pumping, thermal impedance, MEMs cap, and RTS CMOS testing, and NBTI/PBTI reliability tests.
As you can see, the question “Who needs pulsed I-V testing?” has a very simple answer: just about anyone responsible for developing new materials, devices, or processes. Fortunately, instrumentation vendors are developing integrated solutions to support these emerging applications.
For example, Keithley’s Model 4200-SCS (pictured right) integrates pulsed I-V test with DC I-V and C-V measurements in a single system, which can be invaluable for applications that involve multiple measurement types, such as characterizing solar cells, which typically involves measuring current and capacitance as a function of an applied DC voltage.
Lee Stauffer (firstname.lastname@example.org) is Senior Staff Technologist for Keithley Instruments' Semiconductor Measurements Group, based in Cleveland, Ohio. Prior to joining Keithley, his career included designing satellite communication systems, as well as equipment and product engineering in semiconductor fabs.
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