Fun In The Sun

THE SEMICONDUCTOR and photovoltaic industries converged, literally and figuratively, in San Francisco last month.

The literal convergence was the cohabitation of the Semicon West and Intersolar North America trade shows in the city's Moscone Center convention hall. The more figurative convergence was evident in the pervasive effort by companies that sell chemicals and gases to the semiconductor industry to also supply the photovoltaic industry.

Chemical companies aren't pursuing the solar market because of any trouble among their computer chip customers. Global computer chip sales increased a respectable, although below average, 3.2% in 2007 to $256 billion, according to the Semiconductor Industry Association. Likewise, Semiconductor Equipment & Materials International, the sponsor of Semicon West, estimates that sales of materials that go into computer chips grew by 16.1% last year to $25.2 billion.

But growth in the photovoltaic industry these days is phenomenal. The consulting firm Solarbuzz reports that world photovoltaic installations last year amounted to 2,826 MW of electricity-generating capacity, up 62% compared with 2006 and valued at $17.2 billion. More than two-thirds of the installations were in Germany and Spain, where tax incentives favor solar panel installation.

Air Products & Chemicals, a major supplier of materials to the semiconductor industry, was one of several chemical companies at Semicon that were also emphasizing their solar offerings.

Corning F. Painter, the firm's vice president for global electronics, said much of the solar growth is coming from thin-film photovoltaic panels, which are less expensive to manufacture than traditional polysilicon-based panels and thus have lowered the barrier to entry into the photovoltaic energy business. Indeed, Solarbuzz says installation of thin-film systems more than doubled last year and now account for some 12% of solar installations around the world.

Companies such as Applied Materials, traditionally a supplier of semiconductor-making equipment, are selling virtually complete thin-film solar panel manufacturing systems. The process, according to Painter, requires a supply of industrial gases including silane, nitrogen trifluoride, argon, hydrogen, helium, and nitrogen. "The volumes can be quite large," he said.

At the Intersolar show, Applied Materials was showing off a 5.7-m² thin-film photovoltaic panel—the world's largest, the company said—manufactured using its SunFab system. The panel was supplied by Signet Solar, a California-based company that started making the large panels in Mochau, Germany, this summer. Air Products has a contract to supply the German plant with several bulk gases.

Most of the gases required in thin-film panel production are in ample supply, but Christophe Fontaine, group vice president for electronics at Air Liquide, said that's not true of silane, which is used to deposit a thin film of amorphous silicon onto a glass plate. "In the specialty gases area, the number one subject is silane," he said. "There will almost certainly be a gap between supply and demand for the next two to three years."

According to Fontaine, Air Liquide is the only major industrial gas company to manufacture its own silane—the others buy it from third parties. Between its own production and distribution agreements, the firm enjoys a silane market share of more than 38%. In March, the French company announced that it will more than triple capacity at its joint venture silane plant in Japan to 2,000 metric tons per year. Fontaine said the company is looking at projects in other countries.

Industrial gas companies are not the only ones sharpening their focus on the solar market. Last year at Semicon, Mallinckrodt Baker announced new capacity for ALEG-380, a solution that strips unwanted photoresist from silicon wafers during semiconductor manufacturing. This year, the company's news was that it is expanding capacity for a surface preparation product used to make silicon solar cells.

The product, PV-160, treats the thin polysilicon wafer in traditional solar cells. John W. Harris, Mallinckrodt's global marketing manager for photovoltaic materials, explained that implanting phosphorus ions into the wafer to produce junctions creates a layer of phosphorus silicate glass that must be removed. Companies were making do with a hydrogen fluoride bath, but the Energy Research Center of the Netherlands approached Mallinckrodt scientists at the firm's plant in nearby Deventer for help in developing a superior approach.

Mallinckrodt started making the resulting glass removal product at the Dutch facility last September and already plans to double capacity by expanding there and adding output at its Paris, Ky., site. On the market for only nine months, PV-160 has been accepted by 12 photovoltaic-producing companies, Harris said.

In addition to cleaning the glass, PV-160 has an effect on solar-cell efficiency, boosting it by about 0.3%. "That may not sound like a lot, but when you are talking about 14 to 15% overall efficiency, it is significant," Harris said.

For another Semicon exhibitor, the New Jersey-based electronic chemicals maker Voltaix, it has been "back to the future" this year. The company was originally set up to supply thin-film photovoltaic materials to the solar pioneer Electronic Conversion Devices. Voltaix set out on its own in 1986 under the leadership of John P. de Neufville.

The photovoltaic industry was developing so slowly in the 1980s that de Neufville decided to diversify the company into materials for semiconductors and flat-panel displays, he told C&EN. Today, its products include germane (GeH₄), boron trifluoride, silicon tetrafluoride, and trimethylsilane.

Matthew D. Stephens, chief operating officer, said Voltaix' sales have traditionally gone 60% to semiconductor makers and 40% to the photovoltaic industry. But just in the past two months, the firm has seen a "tremendous amount" of photovoltaic activity, he said, driven largely by interest in the Applied Materials system. By next year, he believes, sales will be split 50-50.

FOR EXAMPLE, Voltaix has been selling germane for depositing a silicon-germanium alloy that strains the bonds of semiconductor silicon for faster electron movement. But now germane sales are growing to high-end photovoltaic panel makers that use SiGe to expand the range of the solar spectrum that their panels can absorb. Voltaix just announced a $12.5 million investment by Intel Capital that will help it expand in both markets.

At Honeywell Electronic Materials the ascent of photovoltaics is breathing new life into an old semiconductor product line. Chief Technology Officer Brian J. Daniels said that Honeywell has long sold a line of polymeric dopant materials, called Accuspin, that are "spun onto" silicon wafers. Demand has been on the decline as customers shifted to gas-based doping, Daniels acknowledged, but now polysilicon solar-cell manufacturers are interested in the polymeric dopants as a cheap way to implant elements such as boron, antimony, and phosphorus.

Likewise, Honeywell is transferring its expertise in antireflective coatings to the photovoltaic industry. Chip makers apply the coatings to prevent errant light from blurring the ultrathin circuit lines they create via photolithography. Manufacturers of photovoltaic panels, in contrast, are looking to antireflective coatings to bridge the difference in refractive index between air and the protective glass that covers the photovoltaic silicon. Daniels said judicious use of the coatings can reduce the 4% or more of incoming sunlight that bounces off the glass instead of passing through to be converted into electricity.

Beyond polysilicon and thin-film systems is a third class of solar panel based on the semiconducting material copper indium gallium selenide. This material is the focus of an investment by industrial gas maker Matheson Tri-Gas. According to Kevin J. Finn, general manager for electronic gases, Matheson is building a hydrogen selenide facility in New Johnsonville, Tenn., that will be the world's only plant dedicated solely to the chemical.

Finn says Matheson is also investing in a plant in Asan, South Korea, that will produce mixtures of specialty gases such as germane, trimethylboron, phosphine, and diborane. Already employed in semiconductor manufacturing, such gases are used in photovoltaic panel production to implant efficiency-improving ions.

Terry A. Francis, Matheson's chief technologist for electronics, sees multiple opportunities for crossover between the semiconductor and photovoltaic worlds. "In the photovoltaic industry they are trying to get costs down and efficiency up," he said. "We're looking at how we can help them use our chemicals to do that more effectively."

To survive without government subsidies, Air Products' Painter pointed out, photovoltaic manufacturers will need to reduce their costs to that of making conventional electricity—so-called grid parity. He sees that journey progressing much like the search for a cure for cancer. Despite initial hopes for a magic bullet, the reality has been a series of small steps in the fight against the disease.

In the photovoltaic world, Mallinckrodt's Harris noted, each of those steps forward is an opportunity for suppliers of electronic chemicals and gases. "Everyone's looking for ways to get that extra one-tenth of 1%," he said.