SiC MOSFETs: Transforming Electronic Circuit Design

Silicon carbide, or SiC, as a semiconductor material, is gradually gaining prominence and finding extensive applications in the power electronics field. Compared to other available technologies, silicon carbide MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) exhibit significant performance improvements, opening up new possibilities for numerous electronic applications.

The Essence of Silicon Carbide

While silicon carbide may not often be associated with semiconductor devices, it has been around for many years. It was used as detector devices in the era of crystal radios in the 1920s or even earlier, evolving into the first widely used silicon carbide (SiC) diodes.

Silicon carbide is formed by combining silicon dioxide (a form of silicon) with carbon at high temperatures. Through refinement and processing, the raw materials required for silicon carbide devices are prepared. These electronic components can include SiC diodes, SiC Field-Effect Transistors (FETs), or SiC MOSFETs.

Due to its unique properties, silicon carbide is now widely used as a semiconductor material in many power devices. One of its key characteristics is an extremely high breakdown electric field, enabling the manufacture of high-voltage semiconductor devices, especially SiC MOSFETs.

Adoption of Silicon Carbide MOSFETs

Silicon carbide technology did not see widespread adoption immediately; it took time to develop and mature.

Although silicon carbide has been used in the electronics field for many years, such as in the 1920s with crystal radio detectors and even earlier with radio signal detectors using silicon carbide (also known as carborundum), making this technology viable and commercially applicable required some time.

Silicon carbide is not as easily processed as silicon, so making this technology work not only involved making it function correctly but also reducing its manufacturing costs.

Over the years, manufacturing cost has been a limiting factor for the adoption of SiC technology. SiC devices have much higher substrate costs compared to equivalent silicon devices. Additionally, the inherent material properties and high defect density meant that SiC MOSFETs and SiC diodes couldn’t survive in many applications for years.

However, with time, silicon carbide technology has evolved to a level where defect density is reduced, and processing costs are lowered.

Viable SiC MOSFETs have emerged, although they are priced higher than comparable IGBTs. Nevertheless, their outstanding performance in terms of faster switching speeds, higher efficiency, and superior thermal characteristics make them an ideal choice for many new electronic circuit designs.

Advantages of Silicon Carbide MOSFETs

Silicon carbide MOSFETs have shown mature applications in many areas, especially in the field of power electronics, where their switching characteristics make them particularly suitable for numerous new electronic circuit designs.

SiC MOSFETs are similar to traditional silicon MOSFETs, but there are some design considerations to be taken into account. Here are some key advantages of SiC MOSFETs:

1. High Breakdown Voltage: Silicon carbide’s breakdown electric field is 10 times that of silicon, allowing the manufacture of smaller, higher-voltage SiC MOSFETs. This enables achieving high breakdown voltage while using thinner drift layers.
2. Current Density: SiC MOSFETs offer much higher current density than silicon MOSFETs, crucial for high-power applications.
3. High-Temperature Operation: Silicon carbide MOSFETs can operate at higher temperatures, allowing them to take advantage of higher current density without concerns about the device’s actual temperature.
4. Low Switching Losses: Silicon carbide technology gives SiC MOSFETs lower on-resistance, resulting in reduced conduction losses.
5. High Switching Frequency: SiC MOSFETs have a higher switching speed, allowing for the use of higher switching frequencies, thus reducing circuit size and costs.
6. Short Reverse Recovery Time: SiC MOSFETs have a fast reverse recovery time, in the range of tens of nanoseconds, much faster than silicon MOSFETs. This is crucial for improving circuit operation speed.

SiC MOSFET Circuit Design Considerations

While SiC MOSFETs demonstrate excellent performance in electronic circuit design, several considerations should be kept in mind:

1. Gate Drive Requirements: SiC MOSFETs require higher gate-source voltage to achieve low VDS saturation voltage. Electronic circuit designs need to ensure proper gate drive requirements are met.
2. Input and Output Isolation: As SiC MOSFETs are often used in power switching applications, isolation transformers are needed between input and output to ensure that switching signals can pass through the input side.
3. Electromagnetic Interference (EMI): The high switching speed of SiC MOSFETs can generate electromagnetic interference, so electronic circuit designs need to account for this.
4. Extra Source Pins: Some SiC MOSFET devices have extra source pins to reduce the impact of parasitic inductance and resistance, ensuring isolation between input circuits and the output.