Will This Be the World’s Largest Silicon-Carbide Materials Factory?

This article is part of the TechXchange: Power Supply Design.

Wolfspeed will invest up to $5 billion to construct what it claims will be the largest silicon-carbide (SiC) materials factory in the world, in a move to shore up its supply of a semiconductor key to the future of electric vehicles (EVs).

The company said the new facility will be located on the outskirts of Raleigh, N.C., close to its corporate headquarters in Research Triangle Park.

The new plant will help the company keep up with rising demand for SiC wafers for the next few years, internally and externally. Power MOSFETs forged from SiC have special physical properties that make it possible it to pump out more power and dissipate less heat when regulating or converting electricity. That results in better power density and system-level efficiency—particularly at higher voltages.

The company is struggling to keep up with a rise in demand for power MOSFETs and other chips based on SiC, largely due to a lack of raw materials and capacity at facilities that can process them into chips.

Said Wolfspeed President and CEO Gregg Lowe, “Demand for our products continues to grow at a rapid pace, and the industry continues to be supply constrained. Expanding our materials production will further our market leadership and allow us to better serve the growing needs of our customers.”

The first phase of construction will be wrapped up in 2024 at a cost of approximately $2 billion, said the company. Wolfspeed will add more capacity as necessary in a second phase expected to be done in 2030.

The new facility could eventually occupy more than one million square feet on the 450-acre site, creating 1,800 jobs by 2030. According to Wolfspeed, its investment in the site could hit up to $5 billion.

Beside EVs, power devices based on SiC are also seen as key building blocks for photovoltaic (PV) inverters for solar panels, fast-charging stations, high-voltage industrial motor drives, and railway infrastructure.

Material Differences

The potential for SiC in the world of power electronics is largely credited to the material itself.

SiC is a wide-bandgap semiconductor, a property that enables it to tolerate higher breakdown voltages—thousands of volts or roughly 10X what a standard silicon chip can endure—and higher temperatures—more than 500°C in some cases—than the silicon MOSFETs and IGBTs that have dominated for decades.

Power MOSFETs based on SiC are alternatives to IGBTs at higher voltages, due to their decreased turn-on and turn-off losses in switches. That contributes to its superior energy-efficiency compared to silicon chips.

SiC offers better on-resistance (R_DS(on)) at high voltage levels, leading to lower power loss and higher current density, and resulting in less heat when regulating and converting power from one level to another.

Switching speeds are also faster than silicon MOSFETs and IGBTs that they’re replacing. This feature allows you to surround the immediate power stage with smaller transforms and other passives. When coupled with its better energy efficiency, they can help reduce the weight and bulkiness of power supplies.

With its ability to handle high voltages efficiently and tolerate intense heat, SiC is gaining ground as more electric cars hit the road. Tesla pioneered the use of SiC chips in a mass-produced vehicle. Now, other major car manufacturers are following in its footsteps.

Early this year, Wolfspeed hammered out a deal to supply U.S. auto giant GM with SiC devices that will control the integrated power electronics in future EV models.

Every EV contains several major power building blocks. But many want to use SiC in the inverter that converts dc from the battery to ac to propel the electric motor turning the wheels, where even small energy-efficiency gains pay huge dividends.

In turn, it reduces power losses for power electronics, and thus, extends the range of EVs. As an alternative, car companies could build EVs with smaller, cheaper batteries without sacrificing range.

These chips are also being tapped for the on-board charger (OBC) in electric vehicles. Their power-saving capabilities translate to faster charging rates because the chips can transfer considerably more electricity.

Incredibly Hard

The new Wolfspeed facility will grow SiC ingots and transform them into 200-mm wafers, which are 1.7X larger than the 150-mm wafers that have long been the dominant format for SiC.

The larger format translates into more power semiconductors per wafer and, in the process, reduces the higher per-device costs for SiC MOSFETs. One of the major challenges for the company is making sure the higher system-level efficiency possible with SiC chips outweigh the higher cost of making them.

Despite its valuable power-handling properties, SiC is one of the hardest materials in the world and manipulating it is a challenge. To grow the ingots that it slices into wafers and transforms into chips, Wolfspeed uses custom furnaces that heat the raw material to several thousands of degrees—so hot that it vaporizes the raw silicon and carbon material used in the process.

The compound coalesces around a so-called “seed” that forms a cylindrical bar of SiC—all a single crystal—called a boule. The ingot is then sliced into discs that are polished mirror-smooth to remove as many irregularities and impurities as possible. This is far from a simple procedure: the hardiness and brittleness of silicon carbide means it’s more difficult to polish the surface of the wafer without ruining it.

The company touts itself as the world’s largest supplier of SiC, with it responsible for about 60% of the global output. The expansion, Wolfspeed claims, will increase its capacity to produce the raw material tenfold.

Federal Funding?

These wafers will be used to supply Wolfspeed’s recently completed fab in upstate New York, which opened early this year as the world’s first capable of rolling out SiC devices with 200-mm wafers. Customer shipments of SiC-based devices from the Mohawk Valley fab are expected to start before the end of this year. 

Wafers from the plant will likely be used primarily to fill Wolfspeed's internal manufacturing needs. But the company also has supply agreements in place with external partners such as STMicroelectronics.

The announcement comes as the U.S. prepares to dole out tens of billions in subsidies, grants, and other incentives under the recently passed CHIPS and Science Act, signed into law by President Biden last month.

Wolfspeed stands to win a slice of the approximately $39 billion in manufacturing-related subsidies and a 25% investment tax credit on new U.S. fabs under the legislation, also called the CHIPS+ Act. It hopes to apply for and obtain funding made possible by the bill to accelerate the construction and build-out of the plant.

While it remains to be seen how much assistance it gets from the U.S., Wolfspeed’s plan to build in North Carolina likely came down to non-federal incentives. To support development of the facilities’ first phase, Wolfspeed said that it landed $1 billion in incentives from state, county, and local governments.

Read more articles in the TechXchange: Power Supply Design.