Semiconductor curve tracer
Encyclopedia
A semiconductor curve tracer is a specialised piece of electronic test equipment
used to analyse the characteristics of discrete semiconductor device
s such as diode
s, transistor
s, and thyristor
s. Based on an oscilloscope
, the device also contains voltage and current source
s that can be used to stimulate the device under test
(DUT).
For two terminal devices (such as diodes and DIAC
s), this is sufficient to fully characterize the device. The curve tracer can display all of the interesting parameters such as the diode's forward voltage, reverse leakage current
, reverse breakdown voltage, and so on. For triggerable devices such as DIACs, the forward and reverse trigger voltages will be clearly displayed. The discontinuity caused by negative resistance
devices (such as tunnel diode
s) can also be seen.
The main terminal voltage can often be swept up to several thousand volts with load currents of tens of amps available at lower voltages.
Three-terminal devices require an additional connection; this is usually supplied from a stepped voltage or current source attached to the control terminal of the DUT. By sweeping through the full range of main terminal voltages with each step of the control signal, a family of V-I curves can be generated. This family of curves makes it very easy to determine the gain of a transistor or the trigger voltage of a thyristor or TRIAC
. For most devices, a stepped current is used. For field effect transistors, a stepped voltage is used instead.
Curve tracers usually contain convenient connection arrangements for two- or three-terminal DUTs, often in the form of sockets arranged to allow the plugging-in of the various common packages used for transistors and diodes. Most curve tracers also allow the simultaneous connection of two DUTs; in this way, two DUTs can be "matched" for optimum performance in circuits (such as differential amplifier
s) which depend upon the close matching of device parameters. This can be seen in the image to the right where a toggle switch allows the rapid switching between the DUT on the left and the DUT on the right as the operator compared the respective curve families of the two devices.
I-V curves are used to characterize devices and materials through DC source-measure testing. These applications may also require calculation of resistance and the derivation of other parameters based on I-V measurements. For example, I-V data can be used to study anomalies, locate maximum or minimum curve slopes, and perform reliability analyses. A typical application is finding a semiconductor diode’s reverse bias leakage current and doing forward and reverse bias voltage sweeps and current measurements to generate its I-V curve.
.
curve tracers (e.g., Tektronix 570). Early semiconductor curve tracers themselves used vacuum tube circuits, as semiconductor devices then available could not do everything required in a curve tracer.
The Tektronix
model 575 curve tracer shown in the gallery was a typical early instrument.
Nowadays, curve tracers are entirely solid state
(except for the CRT
, if used) and are substantially automated to ease the workload of the operator, automatically capture data, and assure the safety of the curve tracer and the DUT.
Recent developments in semiconductor curve tracer systems now allow three core types of curve tracing: current-voltage (I-V), capacitance-voltage (C-V), and ultra-fast transient or pulsed current-voltage (I-V). Modern curve tracer instrument designs tend to be modular, allowing system specifiers to configure them to match the applications for which they will be used. For example, new mainframe-based curve tracer systems, can be configured by specifying the number and power level of the Source Measure Units (SMUs) to be plugged into the slots in the back panel of the chassis. This modular design also provides the flexibility to incorporate other types of instrumentation to handle a wider range of applications. These mainframe-based systems typically include a self-contained PC to simplify test setup, data analysis, graphing and printing, and on-board results storage. Users of these types of systems include semiconductor researchers, device modeling engineers, reliability engineers, die sort engineers, and process development engineers.
In addition to mainframe-based systems, other curve tracer solutions are available that allow system builders to combine one or more discrete Source-Measure Units (SMUs) with a separate PC controller running curve tracer software. Discrete SMUs offer a broader range of current, voltage, and power levels than mainframe-based systems permit and allow the system to be reconfigured as test needs change. New Wizard-based user interfaces have been developed to make it easy for students or less experienced industry users to find and run the tests they need, such as the FET curve trace test.
http://www.abielectronics.co.uk
hazard for the operator. Modern curve tracers often contain mechanical shields and interlocks
that make it more difficult for the operator to come into contact with hazardous voltages or currents. Power DUTs can become dangerously hot during testing.
Electronic test equipment
Electronic test equipment is used to create signals and capture responses from electronic Devices Under Test . In this way, the proper operation of the DUT can be proven or faults in the device can be traced and repaired...
used to analyse the characteristics of discrete semiconductor device
Semiconductor device
Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide, as well as organic semiconductors. Semiconductor devices have replaced thermionic devices in most applications...
s such as diode
Diode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
s, transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
s, and thyristor
Thyristor
A thyristor is a solid-state semiconductor device with four layers of alternating N and P-type material. They act as bistable switches, conducting when their gate receives a current trigger, and continue to conduct while they are forward biased .Some sources define silicon controlled rectifiers and...
s. Based on an oscilloscope
Oscilloscope
An oscilloscope is a type of electronic test instrument that allows observation of constantly varying signal voltages, usually as a two-dimensional graph of one or more electrical potential differences using the vertical or 'Y' axis, plotted as a function of time,...
, the device also contains voltage and current source
Current source
A current source is an electrical or electronic device that delivers or absorbs electric current. A current source is the dual of a voltage source. The term constant-current sink is sometimes used for sources fed from a negative voltage supply...
s that can be used to stimulate the device under test
Device under test
Device under test , also known as unit under test , is a term commonly used to refer to a manufactured product undergoing testing.-In semiconductor testing:...
(DUT).
Operation
The basic operating principle of the device is to apply a swept (automatically varying) voltage to the main terminals of the device under test while measuring the amount of current that the device permits to flow. This so-called V-I (voltage versus current) graph is displayed on an oscilloscope screen. The operator can control the maximum amount of voltage applied to the device, the polarity of the voltage applied (including the automatic application of both positive and negative polarities), and the load resistance inserted in series with the device.For two terminal devices (such as diodes and DIAC
DIAC
The DIAC, or 'diode for alternating current', is a diode that conducts current only after its breakover voltage has been reached momentarily....
s), this is sufficient to fully characterize the device. The curve tracer can display all of the interesting parameters such as the diode's forward voltage, reverse leakage current
Reverse leakage current
Reverse leakage current in a semiconductor device is the current from that semiconductor device when the device is reverse biased.When a semiconductor device is reverse biased it should not conduct any current at all, even though, as a temperature effect, it will form electron-hole pairs at both...
, reverse breakdown voltage, and so on. For triggerable devices such as DIACs, the forward and reverse trigger voltages will be clearly displayed. The discontinuity caused by negative resistance
Negative resistance
Negative resistance is a property of some electric circuits where an increase in the current entering a port results in a decreased voltage across the same port. This is in contrast to a simple ohmic resistor, which exhibits an increase in voltage under the same conditions. Negative resistors are...
devices (such as tunnel diode
Tunnel diode
A tunnel diode or Esaki diode is a type of semiconductor diode which is capable of very fast operation, well into the microwave frequency region, by using quantum mechanical effects....
s) can also be seen.
The main terminal voltage can often be swept up to several thousand volts with load currents of tens of amps available at lower voltages.
Three-terminal devices require an additional connection; this is usually supplied from a stepped voltage or current source attached to the control terminal of the DUT. By sweeping through the full range of main terminal voltages with each step of the control signal, a family of V-I curves can be generated. This family of curves makes it very easy to determine the gain of a transistor or the trigger voltage of a thyristor or TRIAC
TRIAC
TRIAC, from Triode for Alternating Current, is a genericized tradename for an electronic component that can conduct current in either direction when it is triggered , and is formally called a bidirectional triode thyristor or bilateral triode thyristor.TRIACs belong to the thyristor family and are...
. For most devices, a stepped current is used. For field effect transistors, a stepped voltage is used instead.
Curve tracers usually contain convenient connection arrangements for two- or three-terminal DUTs, often in the form of sockets arranged to allow the plugging-in of the various common packages used for transistors and diodes. Most curve tracers also allow the simultaneous connection of two DUTs; in this way, two DUTs can be "matched" for optimum performance in circuits (such as differential amplifier
Differential amplifier
A differential amplifier is a type of electronic amplifier that amplifies the difference between two voltages but does not amplify the particular voltages.- Theory :Many electronic devices use differential amplifiers internally....
s) which depend upon the close matching of device parameters. This can be seen in the image to the right where a toggle switch allows the rapid switching between the DUT on the left and the DUT on the right as the operator compared the respective curve families of the two devices.
I-V curves are used to characterize devices and materials through DC source-measure testing. These applications may also require calculation of resistance and the derivation of other parameters based on I-V measurements. For example, I-V data can be used to study anomalies, locate maximum or minimum curve slopes, and perform reliability analyses. A typical application is finding a semiconductor diode’s reverse bias leakage current and doing forward and reverse bias voltage sweeps and current measurements to generate its I-V curve.
Kelvin sensing
Curve tracers are usually supplied with various semiconductor device test fixture adapters http://www.tek.com/site/ps/0,,76-15104-INTRO_EN,00.html that have Kelvin sensingFour-terminal sensing
Four-terminal sensing , 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements than traditional two-terminal sensing...
.
History
Before the introduction of semiconductors, there were vacuum tubeVacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
curve tracers (e.g., Tektronix 570). Early semiconductor curve tracers themselves used vacuum tube circuits, as semiconductor devices then available could not do everything required in a curve tracer.
The Tektronix
Tektronix
Tektronix, Inc. is an American company best known for its test and measurement equipment such as oscilloscopes, logic analyzers, and video and mobile test protocol equipment. In November 2007, Tektronix became a subsidiary of Danaher Corporation....
model 575 curve tracer shown in the gallery was a typical early instrument.
Nowadays, curve tracers are entirely solid state
Solid state (electronics)
Solid-state electronics are those circuits or devices built entirely from solid materials and in which the electrons, or other charge carriers, are confined entirely within the solid material...
(except for the CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
, if used) and are substantially automated to ease the workload of the operator, automatically capture data, and assure the safety of the curve tracer and the DUT.
Recent developments in semiconductor curve tracer systems now allow three core types of curve tracing: current-voltage (I-V), capacitance-voltage (C-V), and ultra-fast transient or pulsed current-voltage (I-V). Modern curve tracer instrument designs tend to be modular, allowing system specifiers to configure them to match the applications for which they will be used. For example, new mainframe-based curve tracer systems, can be configured by specifying the number and power level of the Source Measure Units (SMUs) to be plugged into the slots in the back panel of the chassis. This modular design also provides the flexibility to incorporate other types of instrumentation to handle a wider range of applications. These mainframe-based systems typically include a self-contained PC to simplify test setup, data analysis, graphing and printing, and on-board results storage. Users of these types of systems include semiconductor researchers, device modeling engineers, reliability engineers, die sort engineers, and process development engineers.
In addition to mainframe-based systems, other curve tracer solutions are available that allow system builders to combine one or more discrete Source-Measure Units (SMUs) with a separate PC controller running curve tracer software. Discrete SMUs offer a broader range of current, voltage, and power levels than mainframe-based systems permit and allow the system to be reconfigured as test needs change. New Wizard-based user interfaces have been developed to make it easy for students or less experienced industry users to find and run the tests they need, such as the FET curve trace test.
List of curve tracer models
Although many of the older analog type curve tracers are no longer manufactured, they may be available on the used equipment market. Modern chassis-based systems, like Keithley Instrument’s Model 4200-SCS Semiconductor Characterization System and Scientific Test's 5000 Series of Curve Tracers, are more generally commercially available. Scientific Test additionally offers other curver tracer systems including the 5000E and 5300HX semiconductor testers; and Keithley also offers other curve tracing solutions, including the ACS Basic Edition package and the Series 2400 and Series 2600A SourceMeter instruments.ABI Electronics Ltd
- CircuitMaster 4000M (main function circuit analysis, available )
- Counterfeit IC Detectorhttp://www.abielectronics.co.uk/Products/SENTRYCounterfeitICDetector.php, available
- System 8 Range of V-I Testers (main function board fault-finding, available )
http://www.abielectronics.co.uk
Agilent Technologies
- B1505A http://www.agilent.com/find/b1505a, available
Keithley Instruments
- Model 4200-SCS Semiconductor Characterization System http://www.keithley.com/products/semiconductor/parametricanalyzer/4200scs/?mn=4200-SCS
- Series 2400 SourceMeter instruments http://www.keithley.com/products/dcac/currentvoltage/gpmp/?mn=2400
- Series 2600A System SourceMeter instruments http://www.keithley.com/products/dcac/currentvoltage/gpmp/?mn=2602A
- ACS Basic Edition http://www.keithley.com/products/semiconductor/parametricanalyzer/acsbasic/?mn=ACSBasicEdition
Scientific Test, Inc.
Series 5000 Curver Tracers http://www.scitest.com and http://www.curve-tracer.net- Model 5000C1 Curve Tracer: 50A, 1Kv
- Model 5000C2 Curve Tracer: 50A, 2Kv
- Model 5000C2-1 Curve Tracer: 100A, 2Kv
- Model 5000C2-5 Curve Tracer: 500A, 2Kv
- Model 5000C2-10 Curve Tracer: 1000A, 2Kv
- Curve Tracer Software http://www.curve-tracer.net/curve-tracer-software.html
Tektronix
- 570 - vacuum tube curve tracer, discontinued
- 575, discontinued
- 576, discontinued
- 577, 577D1, 577D2, discontinued
Telequipment
- CT71, c1974, discontinued. CT71 Manual
Sony/Tektronix
- 370, 370A and 370Bhttp://www2.tek.com/cmswpt/psdetails.lotr?ct=PS&cs=psu&ci=13558&lc=EN, discontinued
- 371, 371A and 371B (high power)http://www2.tek.com/cmswpt/psdetails.lotr?ct=PS&cs=psu&ci=13558&lc=EN, discontinued
Safety
Curve tracers are capable of generating lethal voltages and currents and so pose an electrocutionElectric shock
Electric Shock of a body with any source of electricity that causes a sufficient current through the skin, muscles or hair. Typically, the expression is used to denote an unwanted exposure to electricity, hence the effects are considered undesirable....
hazard for the operator. Modern curve tracers often contain mechanical shields and interlocks
Interlock (engineering)
Interlocking is a method of preventing undesired states in a state machine, which in a general sense can include any electrical, electronic, or mechanical device or system....
that make it more difficult for the operator to come into contact with hazardous voltages or currents. Power DUTs can become dangerously hot during testing.