Unveiling the secrets of Wei'an's SGT MOSFET, three major advantages and a promising future

     MOSFET can be roughly divided into the following categories: planar MOSFET; Trench MOSFET, mainly used in low voltage fields; SGT (Shielded Gate Transistor, shielded gate trench) MOSFET, mainly used in medium voltage and low voltage fields; SJ- (super junction) MOSFET, mainly used in high voltage fields.

      With the rise of mobile phone fast charging, electric vehicles, brushless motors and lithium batteries, the demand for medium-voltage MOSFETs is increasing, and medium-voltage power devices are booming. Due to their huge market share, many domestic and foreign manufacturers are continuously increasing their investment in the research and development of corresponding new technologies. As a representative of medium-voltage MOSFETs, SGT MOSFETs are widely used as switching devices in motor drive systems, inverter systems and power management systems, and are core power control components.

      The SGT MOSFET structure has a charge coupling effect. On the basis of the vertical depletion of the PN junction of the traditional trench MOSFET device, horizontal depletion is introduced, and the device electric field is changed from a triangular distribution to an approximately rectangular distribution. Under the condition of using the same doping concentration of the epitaxial material specifications, the device can obtain a higher breakdown voltage. The deeper the trench depth, the more silicon volume can be used to absorb the EAS energy, so the SGT can do better in avalanche and can better withstand avalanche breakdown and surge current. In the application fields of switching power supplies, motor control, power battery systems, etc., SGT MOSFET combined with advanced packaging is very helpful to improve the efficiency and power density of the system.

Figure 1: Trench MOS and SGT MOS device structures

SGT technical advantages are embodied in:

Advantage 1: Improve power density

      SGT结构相对传统的Trench结构，沟槽挖掘深度深3-5倍，可以横向使用更多的外延体积来阻止电压，显著降低了MOSFET器件的特征导通电阻(Specific Resistance)，例如相同的封装外形PDFN5*6，采用SGT芯片技术，可以得到更低的导通电阻。

Figure 2: Comparison of characteristic resistance between Trench MOS and SGT MOS

Figure 3: Comparison of minimum on-resistance of PDFN5*6 package

Advantage 2: Extremely low switching losses

      Compared with the traditional Trench structure, SGT has the characteristics of low Qg. The introduction of the shielded gate structure can reduce the Miller capacitance CGD of the MOSFET by more than 10 times, which helps to reduce the switching loss of the device in the switching power supply application. In addition, the low ratio of CGD/CGS is also a key indicator for suppressing shoot-through in the current synchronous rectification application. The use of the SGT structure can obtain a lower CGD/CGS ratio.

Figure 4: Comparison of gate charge between Trench MOS and SGT MOS

Advantage 3: Better EMI advantage

      The built-in resistor-capacitor buffer structure in the SGT MOS structure can suppress transient oscillation when the DS voltage is turned off. As shown in Figure 5, in the switching power supply application, the parasitic CD-shield and Rshield in the SGT structure can absorb the spikes and oscillations caused by the dv/dt changes when the device is turned off, further reducing the application risk.

Figure 5: SGT MOS built-in Sunbber structure

      It is worth mentioning that, relying on the huge local market demand for medium-voltage MOSFET, domestic devices have great potential to replace imported brands in the medium and low voltage fields. Wei'an is actively deploying high-power density, low-internal resistance SGT MOSFET, combining market and customer needs, and continuing to innovate in product technology and packaging.

      For different application scenarios, the recommended selection in terms of product series, specifications and sizes are as follows:

(1) PC, laptop, wireless charging, etc.

(2) PD and adapter synchronous rectification

(3) BMS and motor control

(4) Communication power supply, 5G base station

      WAYON is a provider of circuit protection components and power semiconductors. WAYON always adheres to the core values ​​of "customer-oriented, technology-oriented, and hardworking spirit". It is committed to leading the market through technological innovation and strives to become a leading brand of circuit protection components and power semiconductors in the world.