The SiC substrate and SiC homoepitaxy from PAM-XIAMEN can be provided for the fabrication of MOSFET devices. Silicon carbide (SiC) MOSFET structure is mainly manufactured by imitating the process of Si MOSFET structure. In terms of configuration, MOSFET structures are generally divided into two types: plane gate and groove gate. Below is the typical epi structure of SiC MOSFETs. More details of epitaxial SiC MOSFET structure on SiC substrate please consult us. Or you can send us your SiC epi wafer design to grow.
1. Typical SiC Epi Structure for MOSFET
|Epi Layer||Material||Thickness||Carrier Concentration|
|1||SiC N– Drift Layer||10 um||6 x 1015cm-3|
|0||4H-SiC N+ Substrate||–||–|
The SiC epitaxy wafer can be used for fabricating vertical trench SiC MOSFET and planar SiC MOSFET devices.
2. SiC MOSFET Working Principle
SiC-MOSFET is a device that has received a lot of attention in the research of silicon carbide power electronic devices. SiC MOSFET N+ source region and P well doping are both ion implanted and annealed and activated at a temperature of 1700 °C.
The working principle of SiC power MOSFET structure is:
Off: positive power supply is applied between the drain and source, and the voltage between the gate and source is zero. The PN junction J1 formed between the P base region and the N drift region is reverse biased, and no current flows between the drain and source electrodes.
Conduction: A positive voltage UGS is applied between the gate and the source, and the gate is insulated, so no gate current flows. However, the positive voltage of the gate will push the holes in the P-region below it away, and attract the minority-electrons in the P-region to the surface of the P-region under the gate.
When UGS is greater than UT (turn-on voltage or threshold voltage), the electron concentration on the surface of the P region under the gate will exceed the hole concentration, so that the P-type semiconductor is inverted into N-type and becomes an inversion layer, which forms an N-channel The channel makes the PN junction J1 disappear, and the drain and source conduct electricity.
3. SiC MOSFET Applications
MOSFET modules manufactured on SiC homoepitaxy is the most widely used in high frequency, medium and small power applications (voltage below 600V), especially in consumer electronics.
In addition, SiC based MOSFETs have great advantages in medium and high power electric system applications, such as photovoltaics, wind power, electric vehicles and rail transit. The advantages of high voltage, high frequency and high efficiency of silicon carbide devices can break through the limitations of the existing electric vehicle motor design due to device performance, which is the focus of research and development in the field of electric vehicle motors at home and abroad. For example, the power control unit (PCU) in the hybrid electric vehicle (HEV) and pure electric vehicle (EV) jointly has started using modules fabricated on SiC MOSFET structure, and the volume ratio is reduced to 1/5.
4. Advantages of Devices based on Epitaxial SiC MOSFET Structure
Compared with the widely used Si material, the higher thermal conductivity of SiC material determines its high current density, and the higher forbidden band width determines the high breakdown field strength and high operating temperature of SiC devices. The advantages of SIC MOSFETs can be summarized as follows:
1) High temperature work: SiC material has a highly stable crystal structure in physical properties, and its energy band width can reach 2.2eV to 3.3eV, which is almost more than twice that of Si material. Therefore, the temperature that SiC can withstand is higher. Generally speaking, the maximum operating temperature that SiC devices can reach can reach 600 °C.
2) High blocking voltage: The breakdown field strength of SiC is more than ten times that of Si, so the blocking voltage of MOSFET based on SiC epi wafer is much higher than that of Si.
3) Low loss: At a similar power level, the conduction loss of a SiC MOSFET is much smaller than that based on Si. Moreover, the conduction loss of SiC based devices has little dependence on temperature, and will change very little with temperature.
4) Fast switching speed: SiC MOSFET vs Si MOSFET, in the development and application of SiC MOSFETs, compared with Si epitaxial MOSFETs of the same power level, the on-resistance and switching loss of epitaxial SiC MOSFET structure are greatly reduced, which is suitable for higher operating frequencies. In addition, due to its high-temperature operating characteristics, the high-temperature stability is greatly improved.
5. FAQ of SiC MOSFET Epitaxy
Q: What dopant level could be offered for the SiC substrate? We would like to get a highly doped N++ substrate if possible (<0.005Ohm-cm). Would this be possible for 1200V power MOSFET application?
A: 1) At present, the resistivity of commercial SiC substrate is 0.015 ~ 0.028 ohm, and the resistivity of epitaxial layer is higher than that of substrate, so it is impossible to achieve the requirement of epitaxial layer resistivity < 0.005 (unit Ohm).
2) For 1200V devices, the recommended parameters are XXum thickness and XX concentration (about 1 ohm resistivity for epitaxial layer). Please contact email@example.com for the specific values.