Four-Point Probe User Manual

Ossila Four-Point Probe User Manual (PDF)

Four-Point Probe

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1. EU Declaration of Conformity (DoC)

We

declare that the DoC is issued under our sole responsibility and belongs to the following product:

Object of Declaration

Four-Point Probe System (T2001A4)

The object of declaration described above is in conformity with the relevant Union harmonisation legislation:

Signed:

Name: Dr James Kingsley

Place: Leiden

Date: 16/11/2021

2. Safety

2.1 Warning

2.2 Use of Equipment

The Ossila Four-Point Probe System is designed to be used as instructed. It is intended for use under the following conditions:

• Indoors in a laboratory environment (Pollution Degree 2).
• Altitudes up to 2000m.
• Temperatures of 5°C to 40°C; maximum relative humidity of 80% up to 31°C.

The unit is supplied with a 24 VDC power adapter with a power cord for the country of purchase, in accordance with European Commission regulations and British Standards. Use of any other electrical power cables, adaptors, or transformers is not recommended.

2.3 Hazard Icons

The following symbols can be found at points throughout the rest of the manual.

Table 2.1 Hazard warning labels used in this manual.

Symbol	Associated Hazard
	Electrical shock

2.4 General Hazards

Before installing or operating the Ossila Four-Point Probe System there are several health and safety precautions which must be followed and executed to ensure safe installation and operation.

2.5 Power Cord Safety

Emergency power disconnect options: use the power cord as a disconnecting method and remove from wall. To facilitate disconnect, make sure the power outlet for this cord is readily accessible to the operator.

2.6 Servicing

If servicing is required, please return the unit to Ossila Ltd. The warranty will be invalidated if:

• Modification or service has been carried out by anyone other than an Ossila engineer.
• The Unit has been subjected to chemical damage through improper use.
• The Unit has been operated outside the usage parameters stated in the user documentation associated with the Unit.
• The Unit has been rendered inoperable through accident, misuse, contamination, improper maintenance, modification, or other external causes.

2.7 Health and Safety - Servicing

Servicing should only be performed by an Ossila engineer. Any modification or alteration may damage the equipment, cause injury, or death. It will also void your equipment’s warranty.

3. Requirements

Table 3.1 details the power requirements for the system, and the minimum computer specifications for the Ossila Sheet Resistance software.

Four-Point Probe System requirements.

4. Unpacking

4.1 Packing List

The standard items included with the Ossila Four-Point Probe System are:

• The Ossila Four-Point Probe.
• 24 VDC power adapter.
• USB-B cable.
• USB memory stick pre-loaded with the user manual, software installer, QC data, and USB drivers.
• 400 - 450 nm FTO coated glass substrate (60 x 60 x 2.2 mm).
• 10 kΩ resistor test head.

4.2 Damage Inspection

Examine the components for evidence of shipping damage. If damage has occurred, please contact Ossila directly for further action. The shipping packaging will come with a shock indicator to show if there has been any mishandling of the package during transportation.

5. Specifications

The Four-Point Probe System measurement specifications are shown in Table 5.1 and Table 5.2, and the physical specifications are shown in Table 5.3.

Table 5.1 Four-Point Probe System measurement specifications.

Table 5.2 Accuracy and precision of the Four-Point Probe System at each resistance range. Accuracy is the maximum deviation from the true value. Precision is the maximum deviation between identical measurements (useful for comparative measurements).

Table 5.3 Four-Point Probe System physical specifications.

6. System Components

The Four-Point Probe System is comprised of: the Ossila Four-Point Probe System (Figure 6.1) and the Ossila Sheet Resistance Software (Figure 6.2).

7. Installation

1. Install the Ossila Sheet Resistance Lite software on your PC.
1. Run the file ‘Ossila-Sheet-Resistance-Lite-Installer-vX-X-X.exe’ on the USB memory stick provided.
2. Follow the on-screen instructions to install the software.
2. Connect the 24 VDC power adaptor to the power socket on the rear of the unit.
3. Connect the unit to your PC using the provided USB-B cable, or an Ethernet cable if preferred. If you are using a USB connection and the unit is not detected, please refer to the SMU USB Driver Installation Guide found on the USB memory stick.

8. Operation

8.1 Taking a Measurement

1. Place your sample in the centre of the vertical stage.
2. Raise the platform until the probes have retracted approximately half-way into their housing.
1. One full turn of the micrometer (after initial contact is made) is a good way to ensure that there is good electrical contact between the probes and your sample.
2. Ensure that the probes make contact with the centre of the sample.
3. For rectangular samples, the longest edge should be aligned parallel to the probes.
3. Start the Ossila Sheet Resistance Lite software. The window shown in Figure 8.1 will open.
4. Set the appropriate settings in the software (explained in more detail in Section 8.2).
5. Click the on/off toggle button.
1. The system will attempt to pass a current between through the sample.
2. If a current can be passed though the sample, the system will measure the sheet resistance, which will be displayed in the program.
3. If a thickness has been provided, the resistivity and conductivity will also be displayed.
4. The measurement will continue until the on/off toggle button is clicked or the software is closed.

8.2 Software Settings

There are several settings in the program which must be filled in before taking a measurement. These are found in the column on the left of the window, as shown in Figure 8.1.

8.2.1 Basic Settings

(I) System Address

Select the COM port or IP address of the connected unit you intend to use (USB and Ethernet connection respectively). This box will be populated automatically with the addresses of any units connected to the computer or network.

(II) Geometry

Select the geometry of the sample being measured. This is required to calculate the geometrical correction factor for the current sample.

If the shape of the sample is irregular, consider whether it is closer to rectangular or circular and then estimate what size of that shape could fit within the sample

(III) Long Side (Rectangular Sample)

Sets the length of the long side of the sample in mm (if the sample is rectangular). This is required for calculating the appropriate geometrical correction factor.

(IV) Short Side (Rectangular Sample)

Sets the length of the short side of the sample in mm (if the sample is rectangular). This is required for calculating the appropriate geometrical correction factor.

(V) Diameter (Circular Sample)

Sets the diameter of the sample in mm (if the sample is circular). This is required for calculating the appropriate geometrical correction factor.

(VI) Thickness (Optional)

Sets the thickness of the conductive layer being measured in µm.

This enables the calculation of the resistivity and conductivity of the sample, as well as calculating a thickness correction factor for samples with a thickness greater than 40% of the probe spacing. It is not needed for sheet resistance measurements of samples with a thickness less than 40% of the probe spacing, thus can be set to 0 if not known.

8.2.2 Saving Results

(I) Readings to Save

Set the number of measurements to save.

(II) Save

Opens a file dialog window to choose where to save the data.

(III) Saved Data Format

The applied current, measured voltage, and measured sheet resistance are saved to the file. The mean and standard deviation of the sheet resistance measurements are saved to the same file, placed after the data readings.

If a thickness is provided, the resistivity and conductivity values are also saved.

8.2.3 Advanced Settings

Advanced settings can be found by checking the “Use Advanced Settings” box below the basic settings. This will also show the voltage and current set between the outer probes, and voltage measurements between the inner probes. Note that these settings will only be used whilst “Use Advanced Settings” box is ticked, default settings will be used when not ticked.

(I) Probe Spacing

Sets the spacing between each of the probes in mm. This is required to determine the appropriate geometric correction factors for the sample being measured.

(II) Samples per Point

Select the number of samples to be taken for each measurement. A higher number of samples per point will improve the accuracy and precision of the measurement. However, this will increase the time taken for it to be performed.

(III) Current Range

Select whether the appropriate range should be automatically determined or whether a specific range of currents is used. This defines the upper limit and accuracy of current measurements that can be performed by the unit.

Autorange will enable the measurement to automatically switch ranges as needed. The maximum current values for each range are shown in the range selection box.

(IV) Polarity

Sets whether the measurement polarity is positive or negative.

(V) Voltage Limit

Sets the maximum voltage the measurement can apply to the sample in volts. If the voltage limit is exceeded the measurement will stop.

(VI) Current Limit

Sets the maximum current the measurement can apply to the sample in mA. If the current limit is exceeded the measurement will stop.

(VII) Reset to Default

Clicking this button will reset all advanced settings to their default values.

9. Test Head

The system is shipped with a test head that can be used to verify the correct operation the system by providing a reference measurement. It is designed to give a response of 10 kΩ when a sheet resistance measurement is performed on it using the system.

9.1 Taking a Measurement

1. Replace the four-point probe head on the system with the test head.
1. Remove the 3 screws attaching the head to the system.
2. Lift the probe head and unscrew the cables from the underside.
3. Remove the four-point probe head.
4. Attach the cables to the underside of test head.
5. Fasten the test head to the unit using the 3 screws.
2. Plug in and switch on the system.
3. Allow at least 30 minutes for the system to warm up.
4. Start the Sheet Resistance Lite software and enter the settings in Figure 9.2. The Long Side and Short Side can be any value greater than 55 mm, this is to ensure that no correction factor is applied to the measurement.

1. Start the measurement.
2. The system should measure a sheet resistance between 9.9 and 10.1 kΩ/square (within 1% of 10 kΩ/square).

10. Troubleshooting

Most of the issues that may arise will be detailed here. However, if you encounter any issues that are not detailed here, then please contact Ossila.

10.1 Installation and Setup

10.2 Error Messages and Warnings

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