How is Gate Leakage Measured?

How to Measure Gate Leakage

Measuring gate leakage typically refers to measuring the leakage current between the gate and source or drain in a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) or similar devices. Gate leakage is an important parameter for assessing device reliability and performance, especially in high-voltage and high-frequency applications. Below are some common methods and techniques for measuring gate leakage:

1. Using a Precision Current Meter (Picoammeter)

Precision current meters (such as the Keithley 6517B Electrometer/Picoammeter) can measure very small currents and are suitable for measuring gate leakage.

Steps:

Prepare Test Equipment: Ensure you have a high-precision current meter connected to a power supply and the Device Under Test (DUT).

Connect the Circuit:

Connect the gate of the DUT to one input terminal of the current meter.

Connect the other input terminal of the current meter to ground (typically the source).

If needed, connect a voltage source in series between the gate and the current meter to apply the desired gate voltage.

• Set Up the Current Meter: Set the current meter to an appropriate range (usually in the nanoampere or picoampere range) and ensure its sensitivity is high enough to detect small leakage currents.

• Apply Voltage: Use an external power supply to apply the required gate voltage.

• Record Current Readings: Observe the current meter readings and record the gate leakage current.

2. Using an IV Curve Tracer

An IV curve tracer can be used to plot the relationship between current and voltage, helping to analyze gate leakage at different voltages.

Steps:

• Prepare Test Equipment: Connect the IV curve tracer to the gate, source, and drain of the DUT.

• Set Up the IV Curve Tracer: Select an appropriate voltage range and current resolution.

• Apply Voltage and Record Data: Gradually increase the gate voltage while recording the corresponding leakage current values.

• Analyze Data: By plotting the IV curve, you can visually see the trend of gate leakage with respect to voltage.

3. Using a Semiconductor Parameter Analyzer (SPA)

A semiconductor parameter analyzer (such as the Agilent B1500A) is a specialized device for analyzing semiconductor device characteristics and can precisely measure gate leakage current.

Steps:

• Prepare Test Equipment: Connect the semiconductor parameter analyzer to the gate, source, and drain of the DUT.

• Set Up the Parameter Analyzer: Configure the appropriate voltage and current ranges, ensuring the instrument's sensitivity is sufficient.

• Perform the Test: Follow the instrument’s guidelines to conduct the gate leakage test, gradually increasing the gate voltage and recording the corresponding leakage current.

• Data Analysis: Use the software provided with the instrument to analyze the data, generate reports, and create charts.

4. Using an Oscilloscope and Differential Probes

For certain high-frequency applications, it may be necessary to use an oscilloscope and differential probes to measure gate leakage current.

Steps:

• Prepare Test Equipment: Connect the oscilloscope and differential probes to the gate and source of the DUT.

• Set Up the Oscilloscope: Adjust the time base and vertical scale of the oscilloscope to capture small current fluctuations.

• Apply Voltage: Use an external power supply to apply the required gate voltage.

• Observe Signals: Observe the signals on the oscilloscope screen and record the changes in gate leakage current.

5. Considerations

• Environmental Control: When measuring gate leakage, try to keep environmental conditions (such as temperature and humidity) stable, as these factors can affect the measurement results.

• Shielding Interference: To reduce the impact of external electromagnetic interference on measurements, use shielded cables and shielding boxes.

• Calibrate Equipment: Regularly calibrate measurement equipment to ensure accuracy and reliability.

• Prevent Electrostatic Damage: When handling sensitive devices, take anti-static measures (such as wearing an anti-static wrist strap) to avoid electrostatic damage.

6. Typical Application Scenarios

• MOSFET Testing: Measure the gate leakage current of MOSFETs to assess their quality and reliability.

• Integrated Circuit Testing: During chip design and manufacturing, measure gate leakage current to ensure process quality.

• High-Voltage Equipment Testing: In high-voltage applications, measure gate leakage current to ensure safe operation of the equipment.

By using the above methods and techniques, you can effectively measure gate leakage current, thereby evaluating the performance and reliability of the device.