Please read the General Presentation of ECR prior to reading this manual to understand the basics of ECR measurement.
Keithley 2450 (SMU) – General Presentation
The Keithley 2450 is composed of:
- Output status: The ON/OFF button will be lit up when source output is on.
- Sense probes: The terminal connections measure the voltage difference between the red and black probe. This measurement of the voltage drop on the DUT is done independently from the current sourcing.
- Force terminals: The terminal connections are used to source current to the device under test (DUT).
- Keithley ground: The terminal can be used to connect the ground of the Keithley to the instrument.
- I/O Power Switch: Turns the instrument on or off. The instrument in on when the button is pressed down.
Advanced ECR Measurement
To realize an ECR measurement, you find need to configure the software to properly communicate with your Keithley.
Turn on the Keithley, start the instrument, the software and then go to the Configuration tab.
Activate your Keithley under the Corrosion tab by selecting “Keithley” in “Type” and your specific Keithley in “Options”.
Once it is done, the software will restart, if the status shows an error message under “Initializing Keithley”, verify that the Keithley is ON and that the communication cable between the PC and the Keithley is properly connected.
It is only possible to activate an ECR measurement in a standard step. To do so, go under the “Corrosion” tab and change the action from idle to any other option.
The options are custom SCPI commands which we will introduce later. To modify those options, you need to go back to the Configuration window and click on “CONFIG” next to the Keithley selected. The following window will appear:
- Commands Window:
- CustomCmd(1/2/3/4): To modify the content of the command sent, you need to modify the content of “CustomCmd(1/2/3/4)”.
- CC(1/2/3/4)Display: To modify the name that appears during the recipe creation, you need to modify the content of “CC(1/2/3/4)Display”.
- Commands Update:
- Write and Read: If you enter a command on a line of the “Write” Column, by pressing “Write”, then “Read”, the line in the “Read” column will be automatically updated.
The command sent to the instrument can be customized based on the requirements of the tests. The next part will explain how to customize the commands to fit your requirements.
Keithley 2450 – Advanced ECR Command control
When setting a range, you should first set the limit to a value higher than the measure range you intend to set.
Making resistance measurements
Resistance Measurement Methods
From a remote interface, you can use one of the following methods to measure resistance with the Model 2450:
- Set the measure function to resistance. When the measure function is set to resistance, the instrument sets the source current and source values automatically.
For most samples:
- Source voltage, measure current, and set measure units to ohms
For high resistance samples:
For low resistance samples: Source current, measure voltage, and set •
measure units to ohms
Measure resistance using resistance function
When the measurement function is set to resistance, the Model 2450 measures resistance by sourcing current. The instrument automatically sets the magnitude of the current source, voltage limit, and the measure range.
This is the easiest method to measure resistance of the device under test and can be used in most cases.
SCPI command
To select this type of measurement, click on “AUTO Resistance”.
The SCPI Command of the auto resistance does not need to be modified.
- AUTO Resistance - 2Wire: One cable to the upper sample, one to the lower sample. Less precise measurement.
- AUTO Resistance - 4Wire: Two cables to the upper sample, two to the lower sample. Less precise measurement.
Sourcing current, measuring voltage, and reading in ohms
This measurement method is useful for low resistance samples.Low-resistance materials allow more current to pass easily. A higher current ensures accurate resistance measurements without excessive voltage drops.
SCPI command
To select this type of measurement, click on “CONTROL Current”.
The SCPI Command of the CONTROL Current needs to be modified with the desired parameters. The user needs to replace the 3 dots with the desired parameters.
SOUR:CURR ...➔ Sets the sourcing current (in Amps)
SOUR:CURR:VLIM …➔ Sets the voltage limit (in Volts)
If you need any additional information regarding the other parameters in the SCPI commands, please contact your Rtec-Instruments representative.
Sourcing voltage, measuring current, and reading in ohms
This measurement method is useful for high resistance samples.High-resistance materials allow only small currents to flow. Applying a higher voltage ensures you get a measurable current, improving signal-to-noise ratio.
SCPI command
To select this type of measurement, click on “CONTROL Voltage”.
The SCPI Command of the CONTROL Voltage needs to be modified with the desired parameters. The user needs to replace the 3 dots with the desired parameters.
SOUR:VOLT …➔ Sets the sourcing voltage (in Volts)
SOUR:VOLT:ILIM …➔ Sets the current limit (in Amps)
If you need any additional information regarding the other parameters in the SCPI commands, please contact your Rtec-Instruments representative.
Wire Measurement reading
Once the ECR measurement wiring is done and the appropriate resistance measurement method has been selected in the recipe, you can add the Keithley Resistance reading in “Data Logging”.
To select the 4 Wire Measurement reading, click on “OHM4W”.
If the resistance reading has been properly selected, it should appear in the “Run” tab.
Please refer to the General software manual for further explanations regarding the “Data Logging” and “Run” windows.
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