First of all, it should be explained that SiC can also be used as an
IGBT Module. There is a problem with the Mosfet of Si material, that is, the chip will become thicker if the voltage withstand capability is high, and the conduction loss is also very high. Therefore, the Mosfet of silicon material can generally only be used as a low-voltage device. In order to improve the withstand voltage of silicon-based devices, the
IGBT is designed. SiC is a wide-bandgap semiconductor material that can achieve high withstand voltage. The chip is still very thin. Now SiC's Mosfet can achieve 6500V withstand voltage, which can already cover the current
IGBT withstand voltage level, and Mosfet's The chip structure is simpler than
IGBT, so there is no need to use SiC to make IGBT waste cost at present.
There are three main reasons why SiC IGBTs cannot be marketed at present.
1. For application scenarios, only SiC IGBTs in the high-voltage and high-power field are valuable. Because of the wide band gap of SiC material, the emitter-collector voltage is turned on until close to 3V. In this way, at a lower voltage level, the conduction characteristics of SiC IGBT devices are worse than Si IGBTs and silicon carbide MOSFETs, and the switching loss is also greater than Silicon carbide MOSFET. At present, there are fewer high-voltage and high-power application scenarios that require the use of silicon carbide IGBTs.
2. The problem of carrier lifetime. The conductance modulation ability of IGBT devices depends on the carrier lifetime in the drift region. In fact, for a silicon carbide IGBT device with a voltage level of 10-20kV, a carrier lifetime of 3us-5us is sufficient. However, the current thermal oxidation method and C ion implantation annealing method for improving the carrier life of silicon carbide are difficult to achieve a stable carrier life increase, and the inter-chip uniformity of the experimental results is very poor, so it is difficult to form a commercial device product.
3. The problem of yield rate. The yield rate of the terminals of high-voltage devices above 10kV, the yield problem caused by the influence of the bimetal ohmic contact on the previously formed gate oxide, etc.
