Keithley's four-probe test system realizes material resistivity measurement

Resistivity is an important parameter that determines the electrical properties of semiconductor materials. In order to characterize the process quality and the doping of the material, the resistivity of the material needs to be tested.

The four-probe method is currently a commonly used method for testing the resistivity of semiconductor materials because this method has simple equipment, easy operation, high measurement accuracy and no strict requirements on the shape of the sample.

Operating specifications of the four-probe method: It is required to use four probes to contact the material surface at equal intervals; while outputting current between the two outer probes, test the voltage difference between the two middle probes; finally, through the geometry of the sample parameters, the output current source and the measured voltage value to calculate the resistivity.

1. What equipment is required for the four-probe method test system?

Four-probe method test system structure

The four-probe method test system introduced to you today mainly consists of Keithley source meter, four-probe station and host computer software. The four probes can be connected to the source meter through the front panel banana connector or the rear panel cable connector.

2. Why can Keithley source meters be used in the four-probe method?

Keithley's smart touch screen interface provides IV chart function

Many engineers choose the high-precision source meter developed by Keithley Company because it can simplify test connections and obtain accurate test results. Keithley source meters can test voltage while outputting current, and can also test current while outputting voltage. The output current range is controllable from picoamp level to ampere level, and the measurement voltage resolution is up to microvolt level. Keithley SourceMeter supports four-wire Kelvin mode, so it is very suitable for four-probe method testing. What is configured here is the Keithley 2400 series source meter (2450/2460).

3. What benefits can the four-probe method test solution bring?

Convenient reading: The system provides host computer software with built-in resistivity calculation formula, which complies with the national silicon single crystal resistivity test standards. After the test, the calculation results are read directly from the computer to facilitate subsequent data processing and analysis.

High accuracy: Provides forward/reverse current commutation testing, which can eliminate the influence of thermoelectric potential error through current commutation and improve measurement accuracy.

Strong applicability: The four probe heads are made of tungsten carbide, with a spacing of 1 mm, and the probe positions are precise and stable. Adopting a cantilever structure, the probe has a pressure stroke. Provides a variety of needle options with different spacing and different tip diameters for parts under test of different materials.

Good flexibility: The probe station has two levels of coarse/fine height adjustment. During fine adjustment, the height resolution is as high as 2 microns. The distance between the probe head and the object being measured is precisely controlled to prevent the needle from damaging the object.

Smaller errors: The surface of the carrier plate adopts an insulating Teflon layer to reduce test errors caused by leakage current.