By analyzing a semiconductor’s performance parameters, much can be learned about how it will behave under different conditions. Whether for designing a circuit, validating performance claims, or monitoring process quality, semiconductor parameter analysis at various levels of current (I), voltage (V), and power can provide invaluable insights into a semiconductor device’s expected behavior. Analysis is performed by applying test signals and studying the device’s responses to the signals. It requires a source of test signals and an analyzer sensitive enough to detect low-level signals but robust enough to handle high-power signals from a device under test (DUT). Testing can be performed with a digital multimeter or test equipment as basic as an inductance-capacitance-resistance (LCR) meter. But faster measurements, with less setup time by the operator, require test equipment designed for the task, such as a curve tracer or a semiconductor parameter analyzer. The latest computerized semiconductor parameter analyzers are programmable and even capable of helping create device models for simulation when analyzing test results.
The world of electronics has never seen as many different semiconductor devices in use as at present. The world runs on semiconductors, from amplifiers in car radios to home/office computer to transceivers in 5G smart phones. Many different semiconductors power these products, including diodes, discrete transistors, integrated circuits (ICs), memory devices, and photonic devices. They are tested at separate times to verify quality and performance, and in different forms, such as within a package such as a ball-grid-array (BGA) housing placed within a test fixture, and in chip form using an advanced wafer probe station.
Parameters to be measured are related to the semiconductor device under test (DUT) and depend on the type of device to be analyzed. A semiconductor will provide different responses to distinct levels of applied I and V and those responses must be measured. Some semiconductor parameter analyzers feature built in supplies of I and V, some test methods require an external test signal source. Built-in sources are often supplied as part of a module or assembly that combines power source and measurement capability into what is known as a source measure unit (SMU).
The device parameters to be measured vary device by device and will change according to the device to be characterized. A bipolar transistor’s I-V characteristics, for example, are related to its collector, emitter, and base structure. Its parameters are functions of how I and V flow through the device and include DC current gain, emitter current, collector current, breakdown voltage, PN junction forward bias, PN junction reverse bias, and resistivity. In contrast, semiconductor parameters for a nonvolatile memory device are completely different due to its different device structure, and include threshold voltage, capacitance (C), and endurance time.
Curve tracers have been used for many years to characterize semiconductor devices in the laboratory and on the production floor. They generate plots of a device’s responses to changing current and voltage and can provide a great deal of information about a semiconductor’s capabilities. However, faster, more automated measurements are possible with modern, “intelligent” semiconductor parameter analyzers. With their embedded computers, they can be programmed to perform repetitive measurements and even interpret results. For simpler test requirements, curve traces still provide viable test solutions for such tasks as incoming inspection, design prototype testing, and manufacturing/process testing.
The Tektronix 371B is an example of a curve tracer well suited for plotting a semiconductor’s I-V characteristics even at high power levels. It can operate in a high voltage (continuous) mode or a high current (pulsed) mode. It has maximum continuous power rating of 30 W (CW) and maximum peak power of 3 kW. The curve tracer is capable of measuring semiconductor responses at peak voltages of 3 kV and higher and current as high as 400 A in pulsed mode. It features high measurement resolution courtesy of 10-b analog-to-digital conversion of measured results and provides many automatic functions, such as the capability to compare different curves for averaging and statistical analysis. For flexibility in connecting a computer, it features GPIB and USB interfaces. The model 371B can even connect directly to a thermal printer to generate hard-copy curves.
Many semiconductor parameter analyzers are designed with modular architectures to simplify upgrades in test capability as needed. The Keithley 4200A-SCS Parameter Analyzer can be equipped with multiple SMU modules with different ratings as needed. Available SMU modules include modules capable of ±210 V and as much as 100 mA current and modules rated for ±210 V and as much as 10 A current for high peak power (pulsed) measurements. Both types of SMU modules are available with two- and four-wire connections for different test configurations. In addition, this analyzer can be fit with capacitance-voltage-unit (CVU) modules for multiple-frequency (from 1 kHz to 10 MHz) C-V device measurements, and the analyzer can be equipped with an optional switch to speed and simplify testing between I-V and C-V modes.
The Keysight B1500A Semiconductor Device Analyzer is also designed as a mainframe with ten slots for slide-in modules. Results are shown on a bright, 15-in. diagonal touch screen and the analyzer is quite versatile, capable of performing I-V, C-V, C-vs.-time, and C-vs.-frequency (1 kHz to 5 MHz) measurements. An optional switching module is also available for this analyzer, for switching between different measurement modes. The analyzer performs continuous or pulsed I-V measurements and can generate ±40-V pulses as well as arbitrary waveforms as test signals. The analyzer is equipped with GPIB, USB, and LAN interfaces and measurement results are sampled at rates to 5 ns and 200 MSamples/s.
The Keysight 4155C Semiconductor Parameter Analyzer is also modular, with available SMUs, voltage monitor units (VMUs), voltage source units (VSUs), and pulse generator units (PGUs) allowing a user to configure a mainframe analyzer as needed. A standard model 4155C is supplied with four medium-power SMUs, two VMUs, and two VSUs. Source modules can supply as much as 100 mA at 100 V continuously for medium-power modules and as much as 1 A at 200 V for high-power (pulsed) modules. The analyzer, which includes GPIB and USB interfaces, is equipped with Agilent Technology’s I/CV 2.1 Lite software for computer automation of I-V and C-V measurements.
When impedance measurements are needed over a wider frequency range, the Keysight E4990A Impedance Analyzer is available for a frequency range as wide as 20 Hz to 120 MHz. In addition to LCR, it measures I and V as well as complex impedance, with impressive accuracy of 0.045%, making it well suited for dielectric and magnetic material measurements when teamed with the proper test fixture.
Specialized components can require specialized equipment, like the Wayne Kerr 3260B Precision Magnetics analyzer. It operates measurements in modular form with 0.1% basic accuracy. It operates at frequencies from 20 Hz 3 MHz in an impedance mode to measure L, C, and R and has a transformer mode to evaluate the resistance of each transformer’s windings. In yet another mode, the telecom mode, it can measure the insertion loss and return loss of components commonly used in telecommunications applications. The basic analyzer provides current capability from 1 mA to 1 A and can extended that range to as high as 125 A by adding five DC bias modules. This analyzer includes a GPIB port for computer control and a copy of the driver for LabVIEW™ test software from National Instruments (now known as NI).
Semiconductor parameter analysis takes work, but it provides insights that lead to better devices, processes, even better electronic materials. It is possible to perform some semiconductor testing with a basic LCR meter, but the accuracy will suffer even as test leads are jiggled compared to using a higher-level curve tracer or dedicated semiconductor parameter analyzer. More information on any of the test equipment featured here, and many others, is available on the Axiom site or by contacting a sales rep for advice on the best unit for your application, by calling 760-806-6600 or emailing firstname.lastname@example.org.