Many important parameters of device materials are related to resistivity. Today, with the rapid development of photovoltaic and semiconductor industry processes, the resistance uniformity and electrical properties of materials have received widespread attention. When characterizing materials, accurate resistivity is critical, as it determines how well the material conducts electricity. The four-point probe measurement method has been widely used in semiconductor measurement technology. The Four-Point Probe Tester developed by Millennial Solar has an ultra-wide measurement range and ultra-high measurement accuracy, and can characterize various materials. In this issue of Millennial Solar, you will learn about the measurement methods for characterizing sheet resistance in materials.

Sheet resistance

Sheet resistance refers to the resistance from one side of a square thin film of conductive material to the other side. One characteristic of sheet resistance is that the resistance from edge to edge of a square of any size is the same, and the sheet resistance between any distance is the same. In this way, the sheet resistance is only related to factors such as the thickness of the conductive film. Sheet resistance measurements are commonly used to characterize the uniformity of conductive or semiconductive coatings and materials for quality assurance purposes. Typical applications include semiconductors and solar cells, functional materials, amorphous alloys, LCD panels, etc.

So how is the square resistance tested?

Four-probe measurement method

The most important technique for measuring sheet resistance is the four-probe measurement method. The four probes are equally spaced and shown to be in contact with the surface. Current (I) is injected through probe 1 and collected through probe 4, while the voltage between probes 2 and 3 is measured. It works by applying a DC current (I) between two external probes and measuring the resulting voltage drop between the two internal probes.

Four point probe diagram

Four-Point Probe Tester

E-mail: market@millennialsolar.com

Four-Point Probe Tester is specially designed for scientific research. It can quickly and automatically scan samples up to 220mm to obtain sheet resistance/resistivity distribution information at different locations of the sample. Dynamic test repeatability (close to real scenarios) can reach 0.2%, which is an industry-leading level. The ultra-wide measurement range of 0.1μΩ~100MΩ can cover most application scenarios and can be widely used in many fields such as photovoltaics, semiconductors, alloys, and ceramics.

● Ultra-wide measurement range of 0.1μΩ~100MΩ

● It can calculate the average sheet resistance between positive and negative currents to eliminate possible voltage deviations and improve measurement accuracy.

● Two measurement methods: "manual arbitrary point measurement" and "fully automatic multi-point scanning", multiple preset schemes

● The probe pressure is adjustable from 3-5N to prevent the probe from puncturing the film while providing good electrical contact.

Four-Point Probe Tester can perform simple and direct resistance measurements, and provides a wide range of probe types to suit and optimize the characteristic characterization measurements of different surface materials, bringing a better measurement experience to users in more industries!