As per a recent announcement by Nanjing Release, the National Third-Generation Semiconductor Technology Innovation Center (Nanjing) has successfully developed a key technology for the manufacturing of trench-type silicon carbide (SiC) MOSFET chip after four years of independent research. This breakthrough surpasses the performance limitations of planar SiC MOSFET chip, marking the first achievement of its kind in China.

SiC is one of the main representatives of wide bandgap semiconductor materials, characterized by its wide bandgap, high critical breakdown electric field, high electron saturation velocity, and high thermal conductivity. SiC MOSFET primarily comes in two structures: planar and trench, predominantly the former in current SiC MOSFET chip field.

Planar SiC MOS structure features simple process, good cell consistency, and relatively high avalanche energy. However, it faces the issue of JFET effect caused when current is confined to a narrow N-region near the P-body, which increases the on-resistance, and the large parasitic capacitance.

Trench structure refers to embedding the gate into the substrate to form a vertical channel, which allows for increased cell density, elimination of the JFET effect, optimal channel mobility, and significantly reduced on-resistance compared to planar structure. However, the trench process is more complex, with poorer cell consistency and lower avalanche energy.

“The key lies in the process,” explained Huang Runhua, Technical Director at the National Third-Generation Semiconductor Technology Innovation Center (Nanjing).

He noted that SiC is extremely hard, so converting from a planar to a trench structure means “digging a trench” in the material, which must be done with precision to avoid unevenness. During fabrication, the etching process’s precision, etching damage, and residual surface materials critically impact the development and performance of SiC devices.

To address these issues, the Innovation Center organized a core R&D team along with a full support team, and finally established a novel process flow following four years of continuous experimentation with new processes.

They overcame the challenges of precise, stable trench etching and successfully manufactured trench-type SiC MOSFET chip, improving conduction performance by about 30% compared to planar type.

The center is currently developing trench-type SiC MOSFET chip, with the goal of launching trench-type SiC power devices within a year, which are expected to be introduced to applications such as electric vehicle drivetrains, smart grids, photovoltaic energy storage.

What impact does this breakthrough have on our lives and the semiconductor industry? Huang explained, using electric vehicle as an example, that SiC power devices inherently offer power-saving advantages over silicon devices, potentially increasing lifespan by about 5%, and trench structure allows for designs with even lower resistance.

With the same conduction performance, this enables a higher-density chip layout, reducing chip usage costs.

Now, the National Third-Generation Semiconductor Technology Innovation Center (Nanjing) has already started research on SiC superjunction devices. “This structure outperforms the trench-type structure and is currently under development,” Huang Runhua revealed.

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(Photo credit: DRAMeXchange)