Application of high precision digital source meter in field effect transistor test

FET mainly includes two types, JFET and MOSFET. The unipolar transistor is a transistor in which the majority of carriers participate in the conduction. It has the advantages of high input resistance, low noise, low power consumption, large dynamic range, easy integration, no secondary breakdown phenomenon, and wide safe working area. It has become a strong competitor of bipolar transistors and power transistors.
FET is a unipolar semiconductor device that controls the current size with voltage. It basically does not take current or takes very small current at its input end. It has gradually replaced triodes in integrated circuits.

In order to ensure that FET can work normally during use, it is necessary to perform multiple tests on the performance of FET, and IV characteristics are the most comprehensive and effective test method. IV characteristic test analysis for FET is conducive to obtaining various parameters of related devices, and can be used as an important reference for studying manufacturing technology and process changes.

Basic characteristic curve of ideal field effect tube

Test items related to IV characteristics generally include gate leakage current, breakdown voltage, threshold voltage, transmission/transfer characteristics, drain current, on-resistance, etc. In traditional test scenarios, multiple instruments are usually required to complete the test, including high-precision ammeters, multiple voltage sources and voltmeters.

FET is a majority carrier device whose current carrying capacity changes by changing the applied voltage. FET has three main terminals: gate, drain and source. The voltage applied to the gate (VG) controls the current flowing from the source IS to the drain ID.
The following is a schematic diagram of the NGI N2600 series high-precision digital source meter for field effect tube IV characteristic testing

The positive terminal of SMU CH1 is connected to the gate of the FET, and the positive terminal of SMU CH2 is connected to the drain of the FET. If it is necessary to source and measure from all three terminals of the FET, the source of the FET is connected to the negative terminals of two SMU channels or a third SMU can be used.

Common IV characteristic curves of FETs are such as the drain characteristic curve (VDS-ID). Through this test, the gate voltage (VG) is adjusted on SMU CH1, and SMU CH2 sweeps the drain-source voltage (VDS) and measures the resulting drain current (ID). Once the two SMUs are configured for synchronous triggering, IV data can be generated and displayed on the screen in real time, and can be directly saved and exported in table form. For each SMU channel, current, voltage, and time data can also be saved separately.

N-channel junction field effect transistor drain output characteristic curve and transfer characteristic curve

The NGI 2600 series high-precision digital source meter (SMU) integrates the functions of 5 instruments (voltage source, current source, I/V/R measurement), which can output ultra-high-precision voltage source and current source and provide high-precision measurement functions. Its resolution can reach 6.5 digits, the basic accuracy is 1μV, 10pA, 10μΩ, and it supports 2/4/6-wire resistance measurement. It can work in four quadrants, can be used as a source or load, and integrates multiple scanning modes such as linear scanning and logarithmic scanning. The scanning scheme runs automatically after setting the function relationship and protection point. The two basic scanning waveform can be set to single event or continuous operation, which is very suitable for IV characteristic analysis of FET testing. It can trigger multiple units synchronously, supports seven current range settings, has a maximum sampling speed of 100ksps, and a scanning speed of 1ms per point. It can quickly establish a scan, greatly improving test efficiency, and can well meet the needs of FET for IV characteristic test analysis in R&D and production.