SemiSouth starts battling with silicon chipmakers

This year’s headlines have been dominated by political uprising across the Middle East. While the promise of far greater democracy in this region will be seen as good news by many, these onlookers will not get any pleasure at seeing the cost of black gold shoot past $100 a barrel on the back of greater uncertainty of oil supply.

The rising cost of oil, which is tending to drive up all energy costs, is taking place against a backdrop of increasingly vocal calls to reduce the burning of fossil fuels and ultimately cut carbon dioxide emissions.

Ways to do this, which are achievable on an individual, corporate and national level, are to generate more electricity from renewable sources and to switch to systems that use electricity more efficiently. Oil is still essential for transportation, but extracting this commodity efficiently will also help to cut global energy expenditure.

One company that can help with all these efforts is the Starkville-based SiC electronics pioneer SemiSouth Laboratories, which spun out of Mississippi State University in 2000. This start-up has developed highvoltage diodes and junction field effect transistors (JFETs) that are superior to silicon incumbents in many ways: They switch more efficiently at higher frequencies, which improves DC to AC conversion; they can perform at higher operating temperatures, which reduces the need for cooling; and they are capable of withstanding far higher levels of radiation, enabling them to provide power management in harsh environments.

SemiSouth has a well equipped, 10,000 square foot cleanroom at its headquarters in Starkville, Mississippi

SemiSouth’s European Director of Sales, Dieter Liesabeths, who is based in Munich, Germany, describes the company’s product range as a mix of SiC diodes and JFETs operating at 1200 V and 1700 V. The diodes are available in a range of popular packages covering the 5-60 A range, and customers can also buy normallyon and normally-off JFETs with on-resistances down to 45 mΩ. The revenue generated by these products is not clear, because SemiSouth, like most privately owned companies, does not talk publicly about its sales figures. But Liesabeths did reveal that this year’s income from sales should triple that generated in 2010, and a similar year-on-year percentage gain is expected in 2012.  

Capacity build out To increase its capacity and cater for the expected hike in orders, SemiSouth switched its production from 3-inch to 4-inch wafers this March. In this respect, the company is anything but a trailblazer – many of its rivals upgraded to the larger platform two or three years ago.

SemiSouth has recently switched device manufacture from 3-inch to 4-inch SiC

“We were very conservative,” admits Jeff Casady, SemiSouth’s Chief Technology Officer and Vice President of Business Development. “We wanted to wait to make sure that there were no quality issues [with 4-inch SiC]. Now the quality is very good, and some of our suppliers tell us that 4-inch is even better than 3-inch.”

The company’s capacity expansion is also driven by a $12-15 million investment in a variety of new fab tools. Some money is coming from existing investors, such as Schneider Electric Ventures, Delta Capital Management and Southern Appalachian Fund. However, SemiSouth has also benefited from a significant cash-injection by NASDAQ-listed, California-based firm Power Integrations. This West-coast firm is a manufacturer of chips for ACDC power supplies deployed in computers, mobile phone chargers, consumer electronics and LED lights.

SemiSouth’s fab upgrade includes the installation of an Aixtron AIX 2800G4 WW system that will more than double the company’s epi-capacity. This reactor, which is due to arrive this June, will initially churn out 4-inch wafers. However, it can also accommodate six pieces of 6-inch SiC, a size that SemiSouth plans to adopt in a few years. Transitioning to this larger wafer size should be relatively painless, because the existing line can already accommodate 6-inch material.

To aid the capacity increase, the Starkville start-up is aiming to increase its headcount this year from 80 to 100, with the majority of new hires working in the cleanroom. This 10,000-ft2 facility should be able to churn out enough material to fulfil SemiSouth’s order book until the end of 2013. If sales are still rising, a ‘mirror’ fab could then be built on the same site.

Multiple markets Today the solar inverter represents the biggest market for SemiSouth. Its diodes are already being used in this application and customers are starting to launch products that also incorporate the company’s JFET. For the designers of solar inverters, the attraction of turning to these wide bandgap devices is the opportunity to develop superior architectures.

“If you push the efficiency up, you reduce the heat sink, and if you push the frequency up, you reduce the ‘magnetics’ and capacitors,” explains Casady. “SiC allows you to do both of those things.”

Thanks to these benefits, inverters sporting SemiSouth’s devices have a very low bill of materials, even though the cost of the SiC components in the system is higher than the silicon ones that have been superseded. Lower shipping costs result, which stem from substantial reductions in the weight of the system.

SemiSouth’s products are suitable for other renewable energy markets, such as wind energy. However, that particular application requires modules handling powers of around a megawatt, far more than that associated with the solar inverters, which span the 1-30 kW range.

To go to higher powers requires manufacture of larger die. “We’re working on those products,” says Casady. “You can get to megawatts now if you need to, but it’s very expensive because the die is so large.”

SemiSouth also hopes to make an impact on the hybrid electric vehicle market. In this market, just like solar, one attraction of turning to SiC electronics is that it cuts the weight of the inverter, which in this case converts the DC output from the battery to the AC form that drives the motor. However, here this weight saving is relatively small – instead, the biggest advantage of the wide bandgap semiconductor is that it is capable of operating at far, far higher temperatures.

SiC devices are attractive alternatives to silicon for power conversion in hybrid electric vehicles. By operating at higher temperatures, SiC electronics places far less demand on the cooling system within the car

By running the electronics at 175 °C or more, watercooling demands are slashed, allowing the inverter to hook into the engine’s water-cooling system, rather than needing it own dedicated one. Three major benefits result for the automobile: lower manufacturing costs; higher miles per gallon; and more space under the hood. Despite the strong appeal of SiC electronics for hybrid electric vehicles and SemiSouth’s longstanding interest in this application, silicon still has a stranglehold on this market.

“We have a lot of potential OEMs, people working on research projects,” explains Liesabeths. “But silicon carbide is still a new technology and the car industry is very, very conservative.”

According to Casady, many players in this market are keeping a close eye on how SiC fairs in the solar industry. If it has success there, carmakers will feel more confident of deploying this new technology.

Reaching new highs… SiC transistors and diodes are also attractive alternatives to silicon for satellite power management. “If you can eliminate the heat sink – and if you can run more efficiently and require a smaller power source – you can save a lot in weight,” explains Casady. Reducing weight is critical, because propelling an object from the Earth into space takes so much energy. Once SiC is in orbit, it can offer another big advantage over silicon – tremendous resistance to the high levels of radiation that are found in that environment. Aerospace also offers opportunities for SemiSouth. One way to reduce the weight on the plane is to move landing gear up and down with electric actuators, rather than hydraulics, but this requires 1200 V components handling high powers and operating at high temperatures. SiC excels in all these areas, while delivering high efficiencies.

In addition, this wide bandgap semiconductor is an ideal candidate for lightening and circuit protection on-board aircraft. “Silicon carbide is so robust that it can tolerate abuse where silicon components would just be destroyed,” says Casady. “So there is a lot of interest in using silicon carbide for solid-state circuit breakers.”

… and plunging new depths SemiSouth can also help to improve oil extraction efficiency. “If you talk to the oil companies, it’s getting harder and harder to find oil,” says Casady. “So they want to go deeper and deeper, and that requires higher and higher temperatures”. Searching and extracting oil at such depths is very expensive, and if anything goes wrong, it takes a long time to rectifying. What are needed are systems that can operate reliably at very high temperatures.

“Our die can survive very high temperatures, maybe even up to 500°C,” says Casady. Realizing such hightemperature capability is only possible, however, if die are housed in packages that can also operate in this regime.

To ensure that this is the case, SemiSouth has teamed up with Micross, a US firm with expertise in packaging electronics products for operation in harsh environments.

“It’s a non-exclusive partnership, but one that we are both very excited about,” says Casady. “They have all the military and aerospace quality certification needed to sell into those markets, and it’s the same things that the down-hole market values: A very reliable product operating in an extremely high-temperature environment.”

Audio manufacturers are also interested in SemiSouth’s products. This market is markedly different from the rest, placing very little value on the energy savings that this company’s products can help to realize. Instead, the audio community prizes very high levels of linearity, a characteristic strongly associated with SemiSouth’s JFET.

Audio component manufacturer First Watt has used SemiSouth’s JFETs to make the J2, a stereo amplifier that delivers 25W into an 8 ohm load. The amplifier’s designer, Nelson Pass, selected the SiC JFET for its high linearity: “ Compared with MOSFETs, they exhibit a fraction of the distortion.” According to him, the audio press are impressed with the J2: “There are great reviews in Tone Magazine and 6Moons.com, and Stereo Sound has awarded it ‘best-value’ component.”

Casady admits that interest from the audio community came as a “really pleasant surprise”. According to him, hi-fi manufacturers are using these components to build amplifiers with a sound quality that had never been realized with solid-state electronics. Efforts have been led by First Watt, a firm founded by audio engineer Nelson Pass, who is better known in audio circles for his founding of Pass Labs. Other hi-fi manufacturers, which cannot be named due to confidentiality agreements, are following in his footsteps, and are either evaluating SemiSouth’s transistors or starting to use them for lowvolume production. In addition to the manufacture of SiC diodes and JFETs, SemiSouth is offering epitaxial services. “It’s not a regular thing for us,” admits Casady. “It tends to come as a spot capacity issue, and it seems to be pretty popular.”

SiC rivals The mix of products and services offered by SemiSouth, along with the many markets that the company serves, should give this company a great chance of substantial commercial success over the next few years. But exactly how well it fares may depend on whether it wins the highvolume orders, or loses out to one of its SiC rivals.

Arguably, SemiSouth’s greatest opposition will come from another US SiC specialist, Cree. This company has the advantages of making its own substrates and the opportunity to self-fund extensive SiC development programmes, thanks to its profitable LED business. However, SemiSouth is confident that Cree and other SiC developers will not overshadow it. Liesabeths points out that his company has a significant head start, being the first to launch a SiC transistor. And he says that SemiSouth’s products deliver better energy efficiencies, have lower switching energies and are more cost-effective than those of competitors.

Liesabeths also argues that as a small company, SemiSouth can react faster to market demands: “With big companies, [SiC] is a niche product, not the main focus. We are one hundred percent focussed on this area, while our competitors have other areas that they also have to look at.”

If SemiSouth doesn’t get distracted – and there is no reason why it will – it should be a major player in the SiC market, which is destined for growth throughout this decade.

© 2011 Angel Business Communications. Permission required.