Silicon carbide shines

By IM Staff
Published: Monday, 17 May 2021

Silicon carbide demand is expected to grow as its value in components increasingly needed for power electronics is recognized, reports Cristina Belda.

As global economies shift away from fossil fuels and pursue a sustainable future, electrification will be at the top of their agendas, with investment decisions likely to focus on the raw materials that can help to speed up the transition. The United States Energy Information Administration (EIA) projects a near 50% rise in world energy use by 2050, led by growth in Asia and, ahead of that, an increasingly global effort to improve the efficiency of power electronics.

Demand for silicon carbide (SiC) is expected to increase substantially in the coming years, especially to be used in the semiconductors needed in several sectors, including electric vehicles (EVs), power supplies and renewable energy.

For the past 60 years, silicon has been, and continues to be, the most widely used material in power electronics, but silicon carbide, which has traditionally been used in abrasives and refractories, offers higher temperature resistance, reduced power consumption and can withstand higher voltages than silicon alone, and market insiders see it as a key substitute for the chip industry.

"The advantage of SiC in power electronics is that it has a larger band gap than silicon, which allows it to work with higher voltages and temperatures," Malte Köhler, engineer at the Faculty of Electrical Engineering & Information Technology at RWTH Aachen University in Germany, told Metal Market Magazine.

SiC has a number of applications, including onboard battery chargers, high-voltage onboard power converters, solar inverters, energy storage systems and EV powertrains. Rising demand for this material in various industries has sparked global interest, resulting in increased investment by manufacturers, governments and research institutes in its applications.

Global compound semiconductor material manufacturer II-VI Inc announced in April that it had expanded its SiC wafer finishing manufacturing footprint in China. The company is also looking to expand its US production base.

"We are planning to substantially increase our global production capacity for SiC boules and substrates in the US over the next five to 10 years, to address the accelerating power electronics market, including for electric vehicles and clean energy applications," executive vice president at II-VI’s new ventures and wide-bandgap electronics technologies business unit, Sohail Khan, said.

In the US, President Joe Biden announced on April 22 that the country was committed to achieving a 50-52% reduction in net greenhouse gas emissions from 2005 levels by 2030. This will require a rapid expansion of renewable energy, including wind and solar, and will therefore increase the need for advanced, wide-bandgap power electronics.

In the UK, the government has set a new target to cut the country’s greenhouse gas emissions by 78% by 2035 compared with 1990 levels, and has backed that pledge with funding for the technology. In March, Swansea University was awarded state funding of £4.8 million ($6.65 million) to develop equipment to manufacture SiC semiconductor devices. "This new pilot line will manufacture new innovations in SiC semiconductor chips for use in the next generation of power electronic systems that will be more efficient, lighter and play a crucial role in helping the UK to meet its carbon reduction targets," associate professor at Swansea University’s College of Engineering Mike Jennings said.

Lower costs and charging times
The automotive sector has seen significant growth in electrification, especially in hybrid vehicle charging technology, and SiC has the potential to increase EV driving ranges through improved system efficiency as well as being well suited to high-voltage applications.
In the insights pages (Silicon carbide’s meteoric rise) on its website, Goldman Sachs has estimated that SiC could slash the cost of manufacturing and maintaining an electric vehicle by up to $2,000 and cut charging times in half.

Automakers such as Tesla were among the first to use this technology in traction inverters, while the Renault-Nissan-Mitsubishi Alliance signed a deal with STMicroelectronics to be its supplier of SiC power electronics for advanced on-board chargers in its EVs, such as the infiniti QX model. The devices are scheduled to enter volume production in 2021.

"Silicon carbide is switching gears: industrial still holds the biggest share, but about half the incremental revenue [is] contributed by automotive," German semiconductor manufacturer Infineon said.

Despite the coronavirus pandemic, global pure EV sales are estimated to have grown by 32% in 2020, and sales will rise by 43% year on year in 2021, head of Fastmarkets battery raw materials research William Adams said. In 2020, more than 3.2 million EVs were sold.

The main challenge for implementation, however, is that manufacturing costs are higher than for some more widely used materials – especially upfront costs, since mass production requires a robust infrastructure and manufacturing capacity. "We haven’t seen that many companies using SiC because the [initial] cost is expensive," national accounts manager at Mitsubishi Electric Power Products, Anthony Pinkey said in a recent webinar. "But we are starting to see prices coming down as it [becomes] more widely used. It is a disruptive technology [and] in a few years’ we will see silicon carbide even in our mobiles and other devices," he added.

Powering up solar cells
The advantage of the larger band gap of SiC can be exploited in solar cells, sources said, and some projects in this field are already progressing.

"In solar cells, you want to convert sunlight into electrical energy using an absorber material (semiconductor) [and] 95% of today’s solar cells use silicon as the absorber material," Köhler said. "To reach high voltages with solar cells, the surfaces of the silicon need to be passivated, which means that open atomic bonds at the silicon surface need to be covered and bonded, for example by using extra layers on top and below the silicon."

"For the front side, this extra layer must fulfil three basic requirements to reach a high efficiency," he said. "It needs to be transparent, so that the sunlight reaches the silicon absorber and is not absorbed beforehand; it needs to passivate the silicon surface to reach a high voltage; and it needs to be conductive."

Köhler noted that nano-crystalline SiC fulfils all three of these requirements. The efficiency has been discussed in a paper by Köhler and an international team ('A silicon carbide-based highly transparent passivating contact for crystalline silicon solar cells approaching efficiencies of 24%’) published in Nature Energy. "This topic is [attracting] a lot of interest, which could lead to more [stakeholders] looking into the technology and [more] manufacturers picking it up," he said.

Refractory-grade silicon carbide prices move up

Silicon carbide, refractory grade 95% SiC min, ddp Europe, €/tonne  

 

Silicon carbide, FEPA 8-220 black about 99% SiC acid wash, ddp Europe, €/tonne

Prices for refractory-grade silicon carbide moved up on short availability and increased demand while abrasive-grade material prices remained steady on Tuesday May 4. But both grades have the potential to rise if demand continues to be diverted from China to Europe to avoid shipping disruptions, sources said.

Fastmarkets’ price assessment for silicon carbide, refractory grade 95% SiC min, ddp Europe was €1,050-1,150 ($1,261-1,381) per tonne on May 4, widening up from €1,050-1,125 per tonne a month earlier – the second consecutive month the price has increased. "The price range has widened, and some people are asking for higher prices for spot material; the final price depends on the urgency and the needs of the consumers," a consumer in Europe said.

Similarly, Fastmarkets assessed the price of silicon carbide, refractory grade 98% SiC min, ddp Europe at €1,150-1,300 (1,381-1,561), up from €1,150-1,200 the previous month. "Demand is strong… we are seeing new customers coming to us," a European trader said.

A significant proportion of refractory-grade silicon carbide is used in steelmaking and, over the past few months, infrastructure and construction project activity has recovered, especially in Asia, leading to strong demand for steel products. At the same time, a surge in construction activity is expected in the United States after the $2-billion infrastructure stimulus program was announced by US President Joe Biden on March 31. And even if it takes time to materialise in terms of physical demand, just the announcement has improved sentiment.

But it is not only demand that has been supporting prices. Market participants continue to report difficulties in shipping material from China because of the container shortage that has sent freight rates for both bulk vessels and container ships to record highs.
In fact, the main immediate legacy of March's Suez Canal obstruction has been worsening congestion at several global ports following the major disruption to vessel scheduling. The delays to shipping times have also exacerbated shortages in container availability around the globe.

"Earlier in the year, shipping disruptions were starting to ease with more space available in the vessels, and I thought we were seeing the light at the end of the tunnel," a silicon carbide trader said. "But things have worsened over the past two weeks."

China is the world’s leading producer of silicon carbide, with a production capacity of 400,000 tonnes in 2019, according to data released by the US Geological Survey (USGS). But because of the limited availability of prompt-delivery material from China, sources in Europe have reported that trade is being diverted to other countries, with manufacturers in Central and Eastern Europe reporting extra inquiries.

"Consumers and even producers [that usually rely on China] are also asking for material," a European trader said. "We buy our product from Ukraine at the moment and we do not depend on China so we are well covered for the time being."

Abrasive SiC prices continue to rise
Prices for abrasive silicon carbide grades remained also increased, amid good activity and the shipping disruption, with market participants also citing shortages of raw materials from China.

Fastmarkets’ price assessment for silicon carbide, FEPA 8-220 black, about 99% SiC, acid wash, ddp Europe, was €1,350-1,400 ($1,621-1,681) per tonne on April 27, stable month on month.

The automotive industry is a key steel-consuming sector where a good share of silicon carbide material is used. Demand from the downstream automotive and manufacturing sectors have so far kept prices steady. "Sales of passenger cars in the EU rocketed by 87.30% year-on-year in March 2021, the European Automotive Manufacturers Association (ACEA) said on Friday April 16".

Some consumers were said to be waiting for freight costs to move down before making any new orders. A European buyer of refractory-grade silicon carbide said he had not purchased any material in April due to the high freight costs. "We can wait to import from China and we have some stock, but I am not sure how long [that will last]. We are looking to buy in Europe if the [shipping] congestion persists, but there is not that much material available in Europe either," he added.