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Testing modern power semiconductor devices requires modern

curve tracers

Researchers are looking to new semiconductor materials for enhanced performance. To quantify the performance advantages, devices must be thoroughly characterized. The traditional curve tracer has significant limitations when it comes to testing modern power semiconductor devices. The Source Measure Unit (SMU) offers a more capable test solution; David Wyban, Applications Engineer at Keithley Instruments tells us why.

CURVE TRACERS have been widely used in the electronics and semiconductor industries since the late 1950s, originally for characterizing vacuum tubes, later for characterizing transistors. A curve tracer incorporates power supplies for stimulating the device under test, a scope-like display for visualizing the collected data, a knob for real- time adjustment of the peak voltage across the device, and a test fixture for making connections to packaged devices both safely and easily. A curve tracer is relatively simple in design (Figure 1). It has two power supplies for stimulating the device under test (DUT). A step generator stimulates

the device’s control terminal with either DC current or DC voltage; the collector supply stimulates the device’s channel with DC voltage. Two amplifiers monitor the voltage across and the current through the device and put a charge on the vertical and horizontal deflection plates to move the electron beam on screen and thus display different readings. Two 10-bit ADCs read the voltage from the amplifiers and convert them into a digital reading.

Curve tracers allow rapid characterization of two- and three-terminal semiconductor devices like diodes, BJTs, MOSFET, IGBTs, etc. They can be used to create characteristic current-voltage (I-V) curves on these devices using high current and high voltage. Once the curves have been traced, the built-in on- screen cursors allow extracting device parameters.

Curve tracers allow extracting parameters ranging from the reverse breakdown voltage on a diode to the family of curves on a MOSFET to the DC current gain on a BJT. Although some form of parametric analysis is required at every stage of the semiconductor device design, development, and fabrication sequence, traditional curve tracers are primarily used for device-level characterization in device development, failure analysis and for incoming inspection.

42 Issue IV 2013

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