From Si to SiC: How to take this step in the upgrading of power electronics technology?

As we all know, in the field of power electronics, the performance of Si devices is getting closer and closer to the theoretical limit, and the “bonus” that the follow-up can provide to users is becoming more and more limited. The iterative upgrade of “quality” has become the general trend of the entire industry.

If it is said that in 2020, GaN (gallium nitride) has become a “net celebrity” in the wide bandgap (WBG) semiconductor industry by virtue of its penetration into the mobile phone fast charging market. By 2021, the focus of the market will be Turning to another wide bandgap semiconductor “new favorite” SiC (silicon carbide), this is because Tesla, a new energy vehicle company like Tesla, to traditional old car companies, have all announced the integration of pure electric vehicles. The plan to upgrade the drive system from a silicon-based inverter to a SiC inverter has triggered a global “core battle” for SiC devices.

As we all know, in the field of power electronics, the performance of Si devices is getting closer and closer to the theoretical limit, and the “bonus” that the follow-up can provide to users is becoming more and more limited. The iterative upgrade of “quality” has become the general trend of the entire industry.

From Si to SiC: How to take this step in the upgrading of power electronics technology?
Figure 1: Comparison of Si, SiC and GaN material properties (Image source: ON Semiconductor)

As can be seen from Figure 1, as a member of the wide band gap semiconductor material family, the band gap of SiC is as high as 3.26 eV, which is 3 times that of Si material (1.12 eV), which means that the electrons of SiC material are removed from the valence band. The energy required to move to the conduction band is about 3 times that of Si material, so devices made with SiC can withstand higher breakdown voltages with 10 times the dielectric breakdown field strength of Si. And higher breakdown field strength is beneficial to reduce the “thickness” of the device under the same rated voltage, thereby reducing the on-resistance of the device and improving its current carrying capacity – these characteristics are the dream of many power Electronic devices. of.

At the same time, the electron saturation speed of SiC is 2 times higher than that of Si material. The higher the value is, the faster the switching speed of power devices can be done, which makes the driving power required for high-frequency operation under high voltage smaller, and the corresponding energy Losses are also lower. And from the system point of view, the high-frequency switching circuit allows the use of smaller peripheral devices, making the entire power electronic system design more compact, which can be described as killing two birds with one stone.

Furthermore, the thermal conductivity of SiC is 3 times that of Si. At a given power consumption, higher thermal conductivity means lower temperature rise, which makes SiC devices have better thermal performance and can support more high power density. Compared to other materials, SiC can achieve a junction temperature of 600°C, so using bonding and packaging techniques to ensure high operating temperatures of 150°C to 200°C in commercial SiC devices is clearly a skill.

From Si to SiC: How to take this step in the upgrading of power electronics technology?
Figure 2: Advantages of SiC technology in power electronics applications (Source: ON Semiconductor)

It is precisely because of these characteristics and advantages that SiC has become an ideal “candidate” for power electronic systems to achieve higher power density, higher switching speed, lower power loss, higher operating temperature, and smaller system size and cost.

Although currently due to the particularity of the manufacturing process, improving the yield and productivity of SiC devices is still a big challenge, and the cost of SiC devices is relatively high, but from a system point of view, after replacing Si devices, it is possible to achieve Smaller package size and cost, improve the overall energy efficiency of the system, so the overall cost assessment is still very cost-effective. For example, some people have estimated that the use of SiC power devices can reduce the power consumption of the vehicle by 5%-10%. Although the cost of the inverter module will increase, comprehensively speaking, the battery cost, Cooling costs, as well as space usage costs, will be significantly reduced, resulting in a total vehicle cost savings of about $2,000. It is not difficult to understand why the new energy vehicle circle is so enthusiastic about SiC.

Ideal power switching device

The purpose of the power electronic system is to efficiently control and transmit high-voltage and high-current high-power energy. Therefore, in people’s minds, an ideal power electronic switching device should meet three requirements: a sufficiently high withstand voltage, the lowest possible on-resistance, and a higher switching speed.

To this end, people use Si material to create two power switching devices: MOSFET and IGBT. These two devices have their own characteristics, but due to the material properties of Si, they are still far from the goal of “ideal” power switching devices.

Specifically, silicon-based MOSFETs have the advantage of higher switching speeds (up to several hundreds of kHz), but larger on-resistance and larger recovery losses. And due to the characteristics of Si material, its withstand voltage is generally limited to less than 1,000V, so it is difficult to be competent in high-voltage and high-power applications.

Compared with MOSFET, IGBT can achieve higher withstand voltage and lower on-resistance, so it has more advantages in high-power applications; however, due to the minority carrier accumulation effect, IGBT reverse recovery is slow, making it limited in high-speed switching applications.

Therefore, silicon-based MOSFETs are generally preferred for low-voltage, high-frequency switching applications, while IGBTs are more suitable for higher-voltage, higher-current, low-frequency applications. Compared with the above-mentioned Si devices, SiC MOSFET can combine many advantages such as high withstand voltage, high frequency, low power consumption, etc., coupled with outstanding high-temperature operating characteristics, it can be said that it is an “ideal” device in terms of performance. ” of the power switching device.

From Si to SiC: How to take this step in the upgrading of power electronics technology?
Figure 3: Suitable application range for different power switching devices (Source: ON Semiconductor)

Figure 4 compares three different types of power switching devices under 1,200V withstand voltage. It can be seen intuitively that the on-resistance of SiC MOSFET devices is only 1/100 of that of SiMOSFET (SiC) and 1/1 of that of Si IGBT. 3 to 1/5, while lower switching losses can be achieved. Therefore, in the long run, in the power electronics field of 650V to 1,700V, especially 1,200V and above – such as new energy vehicles, solar energy and power systems, etc. – SiC MOSFETs have unparalleled advantages.

From Si to SiC: How to take this step in the upgrading of power electronics technology?
Figure 4: Comparison of SiC MOSFETs and silicon-based power switching devices (Source: ON Semiconductor)

Building reliable SiC MOSFETs

It is precisely because SiC MOSFET is an ideal choice for a wide range of power switching applications that in recent years, power semiconductor manufacturers have also taken it as an important market fulcrum in the future, and have continued to invest in creating commercially available SiC MOSFET devices. Among them, the M3S 1200V Si MOSFET launched by ON Semiconductor is a very good one.

From Si to SiC: How to take this step in the upgrading of power electronics technology?
Figure 5: 1200V SiC MOSFET based on M3S technology (Image source: ON Semiconductor)

In addition to the inherent advantages of SiC MOSFET devices mentioned above, M3S 1200V SiC MOSFETs have three distinct features:

• First, based on M3S technology, the device achieves an on-resistance of 22mΩ with low Eonand EoffThe characteristics of loss, according to the data provided by ON Semiconductor, in the application of hard switching, the power loss can be reduced by 20% compared with competing products.

• Second, the device achieves lower common-source inductance due to the TO247-4LD package, which allows this SiC MOSFET to support higher slew rates in system design, effectively controlling high-frequency switching operations switching losses.

• Again, this SiC MOSFET has good drive compatibility. Be aware that SiC MOSFETs have lower drift layer resistance than Si devices, but their lower carrier mobility results in higher channel resistance, so SiC MOSFETs require higher gate-source voltages than Si devices (usually 18V to 20V) before entering saturation mode to get the lowest possible on-resistance and prevent accidental switching. That is to say, in general, SiC MOSFETs are incompatible with 10V standard Si MOSFET gate drivers and 15V IGBT gate drivers, and special drive devices are often required. The 1200V MOSFET with M3S planar technology can be used with 18V dedicated gate driver for excellent performance or with 15V IGBT gate driver and is reliable with negative gate voltage drive and turn-off spikes. Work.

In short, ON Semiconductor’s M3S 1200V SiC MOSFET not only maximizes the advantages of SiC materials, but also optimizes reliability and ease of use, effectively accelerating the application of SiC MOSFETs in energy storage, Solar inverters, new energy vehicles and other fields.

Improve the design ecology of SiC

Of course, as a latecomer, SiC wants to complete the replacement of Si power devices that have been developed for decades, not overnight, nor can it be accomplished by relying on a few devices with excellent performance, but a complete technology ecosystem to support. As a major manufacturer in the field of power semiconductors, ON Semiconductor is well aware of this, and has been actively improving its product layout around the SiC state circle.

On the one hand, it can be seen from Figure 6 that ON Semiconductor has formed a rich SiC device product portfolio, covering different withstand voltage levels and different package types; including SiC diodes, SiC MOSFETs, and SiC modules; in SiC modules, both Hybrid modules including IGBT + SiC diodes, as well as full SiC modules – this can meet the needs of different customer power electronic product upgrade iterations at different stages.

From Si to SiC: How to take this step in the upgrading of power electronics technology?
Figure 6: ON Semiconductor’s SiC product line portfolio (Source: ON Semiconductor)

On the other hand, in addition to SiC devices themselves, ON Semiconductor can also provide technical resources supporting SiC devices, such as high-end gate driver ICs specially designed for SiC FETs, and SPICE physical models, which can facilitate developers to apply SiC devices. Circuits are simulated to simplify the design process and save development costs. All these efforts are making the iterative process of upgrading SiC technology smoother and faster.

According to IHS Markit’s analysis data, the market size of SiC power devices in 2020 is about 600 million US dollars, and by 2027 this figure will reach 10 billion US dollars. Faced with such a fast-growing market, how should we plan ahead and make adequate preparations? From the SiC device product portfolio to the supporting design ecology, where should more complete technical resources be obtained to support the next upgrade journey of power electronics technology?

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