Labview Program for remote interfacing of keithley 2612A Source Meter

Acknowledgement

Abstract

The programs are created for testing, verification and analysis of semiconductor components in such a manner that suits the need of user instead of being limited to functions developed by vendor. The programs can be changed, as required by user, easily. In other case we have to replace hardware to fulfill our new need. User is able to analyze acquired data in more detailed and friendly manner. Required characteristics can also be analyzed with the help of graphs. Readings can also be stored in files in PC.

Table of contents 1) Keithley 2612A source meter2) Requirement of interfacing3) Virtual instrumentation?4) Remote interface5) Test script processor6) Command reference7) Labview?8) How to give commands in

labview9) Programs10) Bias source

11) Bias source12) Linear staircase sweep13) Logarithmic staircase sweep14) Pulsed linear staircase sweep15) Pulsed logarithmic staircase

sweep16) Results

Keithley 2612a Source Meter

Series 2600A System Source Meter instruments are Keithley's latest I-V source measurement unit (SMU) instruments for use as either bench-top I-V characterization tools or as building block components of multi-channel I-V test systems.

• For system level applications, the Series 2600A's Test Script Processor (TSP) architecture, along with other new capabilities such as parallel test execution and precision timing, provides the highest throughput in the industry, lowering the cost of test.

•For bench-top use, Series 2600A instruments feature an embedded TSP Express Software Tool that allows users to quickly and easily perform common I-V tests without programming or installing software.

Requirement of interfacing for keithley source meter

• If a need arises to extend the set of functions of source meter, it can be done cost effectively and easily by software running on the PC processor.

• Results can be displayed in desired format on front panel of labview( for example in table, graph, etc.). I-V characteristics can be analyzed by plotting current and voltage on ‘X-Y Graph’ simultaneously.

Importance and significance of virtual instruments

• With virtual instruments, engineers and scientists build measurement and automation systems that suit their needs exactly (user-defined) instead of being limited by traditional fixed-function instruments (vendor-defined).

• You can adapt a virtual instrument to your particular needs without having to replace the entire device because of the application software installed on the PC and the wide range of available plug-in hardware.

• A traditional instrument might contain an integrated circuit to perform a particular set of data processing functions; in a virtual instrument, these functions would be performed by software running on the PC processor. You can extend the set of functions easily, limited only by the power of the software used.

•By employing virtual instrumentation solutions, you can lower capital costs, system development costs, and system maintenance costs, while improving time to market and the quality of your own products.

Remote interface Connecting to the interface

Use a shielded IEEE-488 cable to connect the 2612A IEEE-488 connector to the GPIB connector on the host PC.

Remote operation•Keithley Instruments Test Script Processor (TSP) enabled instruments operate like conventional instruments by responding to a sequence of commands sent by the controller.

•You can send individual commands to the TSP-enabled instrument the same way you would using any other instrument.

•Unlike conventional instruments, TSP-enabled instruments can execute automated test sequences independently, without a controller.

•In the instrument, the Test Script Processor (TSP) scripting engine processes and runs scripts.

•You can load a series of remote commands into the instrument and store these commands as a script that can be run later by sending a single command message to the instrument.

•You do not have to choose between using “conventional” control or “script” control. You can combine these forms of instrument control in the way that works best for your particular test application.

Test Script Processor (TSP)•The Test Script Processor (TSP) is a scripting engine that runs inside the instrument.

•It is capable of running code written in a scripting language called Lua. Lua is referred as the Test Scripting Language for this instrument.

•The TSP runs portions of TSL code formally known as chunks. Most messages sent to the instrument are directly executed by the TSP as TSL chunks.

What is a script?

•A script is a collection of instrument control commands and programming statements. Scripts that you create are referred to as user scripts.

•Your scripts can be interactive. Interactive scripts display messages on the front panel of the instrument to prompt the operator to enter parameters.

Command reference•There is a huge collection of remote commands to control the instruments. It is classified in groups according to their functions or in alphabetical order.

•Example of commands:--- to source a voltage of 10 volts across DUT on channel A“ smua.source.levelv = 10”

-- to measure current across DUT on channel B“smub.measure.i()”

-- to automatically detect the power line frequency“localnode.autolinefreq”

Labview •LabVIEW is a graphical programming language that uses icons instead of lines of text to create applications. In contrast to text-based programming languages, where instructions determine program execution, LabVIEW uses dataflow programming, where the flow of data determines execution.

•In LabVIEW, you build a user interface with a set of tools and objects. The user interface is known as the front panel. You then add code using graphical representations of functions to control the front panel objects. The block diagram contains this code. In some ways, the block diagram resembles a flowchart.

In LabVIEW, you build a user interface with a set of tools and objects. The user interface is known as the front panel.

You then add code using graphical representations of functions to control the front panel objects. The block diagram contains this code. In some ways, the block diagram resembles a flowchart.

Why Labview?• Labview is an integral part of virtual instrumentation because

it provides an easy-to-use application development environment designed specifically with the needs of engineers and scientists in mind. LabVIEW offers powerful features that make is easy to connect to a wide variety of hardware and other software.

• We can customize front panels with knobs, buttons, dials and graphs to emulate control panels of traditional instruments, create custom test panels, or visually represent the control and operation of processes.

How to give commands to instrument through Labview

To write a command into the instrument a “GPIB WRITE” Icon is used.

GPIB WRITE iconAddress of instrument

Commands given to instrument

Error out of function

To read data from instrument “GPIB READ” icon is used.

GPIB WRITE icon

Address of instrument

Data taken from instrument

GPIB READ icon

No. of bytes of data to be read

PROGRAMSThere are five type of source required to analyze the characteristic of DUT. There is a program for each type of sourcing.

Types of source input are:-

1. Bias voltage/current2. Linear staircase sweep voltage/current3. Logarithmic staircase sweep voltage/current4. Pulse linear staircase sweep voltage/current5. Pulse logarithmic staircase sweep voltage/current

•Quantities to measure1. Voltage across DUT2. Current through DUT3. Resistance of DUT4. Power dissipated across DUT

•I-V characteristics of DUT

•Readings are also saved into memory of PC in folder specified by the user.

1.Bias source

• A constant voltage of desired amount is sourced to the DUT by inserting the value through front panel.

• Number of readings taken is also decided by the user. Default is 1.

• Type of source and measure are selected from options in combo boxes.

Case # 1

Front panel

• Here the readings are taken across resistor of 674ohm.

• A source voltage of 5 volts is given and the measurement is done 5 times.

• All measurements are shown in table and they are also stored in PC in the folder specified by user.

Block diagram

Linear staircase sweep source• this sweep type steps from a start voltage or current value to an

ending (stop) value.• A measurement is made at each point after source and

measurement settling time.

Case # 2

•A linear staircase sweep is configured using a start level, a stop level, and the total number of points, including the start and stop points.

•The step size is determined by the start and stop levels, and the number of sweep points: step = (stop - start) / (points - 1)

•The sweep can be either positive-going or negative-going, depending on the relative values of the start and stop parameters.

•When the sweep starts, the output will go to the start source level. The output will then change in equal steps until the stop level is reached.

Front panel

•Here readings are taken around a 674 ohm resistor.

•Voltage is sourced from 1.3v to 6.7v with a step size of 0.4v.

•Current values through the DUT are measured at every step.

•Readings are also stored in specified folder in PC with the help of icon ”write to spreadsheet file”.

•Graph of source values, measure values and I-V characteristics can also be observed.

Block diagram

Logarithmic staircase sweep

• This type of sweep is similar to the linear staircase sweep.• The steps, however, are done on a logarithmic scale.• Like a linear staircase sweep, logarithmic sweeps are

configured using a start level, stop level, and the number of points.

• The step size is determined by the start and stop levels, and the number of sweep points.

• However, in a logarithmic sweep step size increases or decreases exponentially.

• An asymptote is used to change the inflection of a sweep curve and allow it to sweep through zero.

Case # 3

•The formula for a logarithmic sweep is: vi = A + kb^i

Where:vi = The source value at source point ii = The index of points in the sweep (ranges from 0 to N-1)N = The number of points in the sweepk = The initial source value as an offset from the asymptoteb = The step size ratioA = The asymptote value

The following figure is an example of a five-point logarithmic sweep from 1v to 10v.

The five log steps for this sweep are listed in the Logarithmic sweep points table below.

When this sweep starts, the output will go to the start level (1 V) and sweep through the symmetrical log points.

Front panel

Block diagram

Pulsed linear staircase sweep

• Pulsed linear staircase sweeps function the same way that DC linear staircase sweeps function, except pulsed linear staircase sweeps return to the idle level between pulses.

Case # 4

Front panel

Block diagram

Pulsed logarithmic staircase sweep• Pulsed logarithmic staircase sweeps function the same way

that DC logarithmic staircase sweeps function, except pulsed logarithmic staircase sweeps return to the idle level between pulses.

Front panel

Block diagram

Conclusion

The five cases for testing and analysis of semiconductor devices by sourcemeter(by sourcing and measuring) can be done easily by just entering the details. Results are expressed in all required formats and can also be saved in specified folder in PC. This is much more efficient, flexible and user friendly than performing the experiment without interfacing.