Curve Tracers Information
Curve tracers are electronic test devices similar to oscilloscopes. They operate by varying a parameter then measuring a separate one to produce data for analysis referencing the characteristics of semiconductor instruments such as diodes, transistors, and thyristors. Curve tracers feature time sampling, list sweep, and multichannel sweep functionality. They assist in semiconductor failure analysis as well as semiconductor device curve characterization.
Curve tracers involve voltage and current sources capable of stimulating a device under test (DUT). By applying voltage sweeps, the components display X-Y output signals on a scope. The scope shows graphics with one or more curves designating the typical behavior of a particular work area belonging to the DUT.
Modern curve tracers are solid state and involve significant automation allowing for simplified operation of the tools as well as the automatic data capture. Automation helps prevent damage to the curve tracer and DUT while the equipment is running.
Many current versions are modular, facilitating configuration of the setup for unique applications. The modular design permits the use of several types of instrumentation creating a broader selection of tasks. Systems of this category are deployed in semiconductor research, device modeling, reliability measurements, die sort engineering, and process development.
There are three primary classifications of curve tracers:
- Pulsed current-voltage (fast IV)
- Current-voltage (IV)
- Capacitance-voltage (CV)
The features supported by an individual machine distinguish the mechanisms categorized within these general classes.
Construction and Operation
A curve tracer works by applying a swept voltage, one involving continuous variation over time, to two separate terminals subject to testing. It measures the amount of current the DUT allows to flow at each voltage. This voltage (known as V-I or voltage versus current) graph is then placed for display on an oscilloscope screen. For a configured element, the maximum voltage applied is included along with the voltage's polarity (positive and negative) and resistance placed in the unit in serial form. The voltage from the primary terminal may be as high as several thousand volts. Load currents in the range of tens of amps are available at lower voltages.
The technology fully characterizes instruments with two terminals, including diodes and DIACs. The tracers display parameters, including reverse leakage current, forward voltage, and reverse breakdown voltage. The products display both forward and reverse trigger voltages in items capable of triggering, such as DIACs. Furthermore, they show the discontinuity resulting from negative resistance tools, including tunnel diodes.
Circuits with three terminals, including FETs and transistors, engage connections to a control terminal of an apparatus subject to testing, for example, a base or gate terminal. In terms of transistors and other components based on current, a base terminal, or any other control terminal, will be stepped. Field effect transistors rely on a stepped voltage. Voltage is swept through a configured section of main terminal voltages, with each voltage step of the control signal generating a group of V-I curves. The resulting group aids the process of determining a transistor's gain or trigger voltage attributed to a thyristor or TRIAC.
Connections for two or three terminal elements are common on curve tracers. These links adopt the form of sockets designed for connection via plug-ins employed with transistors and diodes. In addition, the majority of the configurations enable simultaneous linking with two DUTs. This facilitates the matching of DUTs such as differential amplifiers to provide optimal circuit performance with circuits dependent on the close alignment of tool specifications. A toggle switch permits rapid switching between DUTs while the operator compares the corresponding curve families attributed to each unit.
Curves classified as I-V serve for characterizing equipment and materials with DC source-measure testing. Calculations related to resistance and derivation of additional measurements are required with activities of this type. A set of I-V data is usable in the study of anomalies, locating maximum or minimum slopes for curves, and performing reliability analyses. One application using this procedure is identifying of the reverse bias leakage of a semiconductor in order to create its curve.
Units categorized by high current, and sometimes lower current models as well, are equipped with semiconductor test fixture adapters capable of Kelvin sensing. Analog versions with low-current sensitivity allow manual control to balance capacitive "bridge" circuits for compensating stray capacitance applicable to the test setup. The modification is achieved by mapping the empty test setup's curve and altering the balance control sufficient to present the I curve at a uniform zero level.
Curve tracers possess numerous attributes, including:
- Fully programmable operation
- Waveform comparison and averaging
- High-resolution parametric measurements
- Built-in cursor measurements
- List sweep
- Direct third party printer hard copy functionality
- Digital acquisition and display
- Push-button source and measurement configuration
- Time sampling
Curve tracers are employed in researching and developing electronic equipment. They are found in many research and industrial laboratories specializing in electronics as well as in the workshops of electronics hobbyists. Some of the functions they perform include:
Data sheet generation
Parametric characterization of semiconductors including:
Manufacture and testing of ICs, transistors, and other devices
Process monitoring and quality control
Selecting Curve Tracers
Curve tracers support an extensive selection of types with a vast array of characteristics. Check the manufacturer's specifications to ensure a system under consideration for purchase has the appropriate functionality for any intended use.