With advances in both materials and process technologies, thin-film deposition is keeping pace with a rapidly changing marketplace.
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Designed for the deposition of amorphous or microcrystalline photovoltaic absorption layers, Oerlikon Solar's KAI PECVD chamber forms a central part of the ThinFab production line. Photo: Oerlikon
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In 2008, a run on the world’s banks sent the global economy into a tailspin that was halted only with government intervention. Markets plummeted, and demand in most manufacturing sectors sunk to record lows.
Understandably, the multi-billion dollar semiconductor industry took a big hit as the market for computers dried up. This had ripple effects on the industy that supplies the expertise, materials, and know-how to create the perfect 300 mm wafer: thin films.
As a manufacturing equipment industry, thin-film deposition materials and equipment are tied to the fortunes of the global economy. As a broad sector, however, thin films are in demand for a variety of industries including semiconductors, energy, cutting and metal forming tools, packaging, and medical devices. The deposition industry recognizes that, as the economy improves, it can focus less on driving down prices and more on research and development. That focus is expected to accelerate as companies strive to create new opportunities in a recovering marketplace.
Deposition vendors prepare for a turnaround
A March 2011 Global Market Analysts, Inc. report says the thin-film deposition equipment market is expected to reach nearly $17 billion by 2015. Thin-film raw materials account for $10 billion or more.
Thin-film deposition technology is a broad industrial segment that is typically divided into physical vapor deposition (PVD) and chemical vapor deposition (CVD). PVD typically describes methods to deposit thin films by the condensation of a vaporized form of the material onto a surface. It can involve the use of electron beams, plasma, cathodes, low-pressure, pulsed lasers, or sputtering to achieve the desired mechanical layering. CVD, on the other hand, binds materials to substrates through a chemical rather than mechanical process. As a result, CVD can take many forms, including low-pressure CVD, plasma-enhanced CVD, high-density plasma CVD, and atomic layer deposition. Electrochemical plating is another common deposition process. Typical materials used for deposition include tungsten, titanium nitride, aluminum, silicon nitride, silicon dioxide, dielectrics, and a variety of oxides.
Manufacturers of full-scale deposition systems have to be flexible enough to investigate or supply equipment for multiple methods, including both CVD and PVD.
SVT Associates Inc., Eden Prairie, Minn., designs and manufactures ultra-high vacuum thin-film deposition systems and components. Their standard products include a line of molecular beam epitaxy systems (MBE), pulsed laser deposition (PLD), atomic layer deposition (ALD), PVD, and thin film photovoltaic (PV) deposition methods.
The company is especially known for its MBE technology. "We have particular expertise in oxides, nitrides, and antimonides," says Curt VanderBroek, sales engineer at SVT Associates. "Our emphasis has been on R&D, but we have extended our product offering into production deposition tools for the thin film photovoltaics and specialty RF and optoelectronic devices industries."
These industries require precisely controlled deposition, an area that favors beam-assisted and laser-assisted techniques. SVT Associates provides these solutions, but in a way that is attractive to process developers. The SMART line of deposition tools features a table-top chamber that can serve as a platform for multiple deposition techniques including thermal evaporation sources, electron beam evaporation, and sputter deposition. It has an ultra-high vacuum (UHV) configuration to deliver the high-purity environment needed to handle sensitive materials.
"As researchers investigate thinner and more precisely controlled layers, the need to reduce contamination drives the requirement for a controlled UHV environment. SVT has recognized this need and has incorporated UHV capabilities into all of its product lines," says VanderBroek.
Semicore Equipment Inc. of Livermore, Calif., specializes in PVD processes for a wide range of applications: solar, biomedical, semiconductor, optical, structural, and even decorative products. This includes sputtering, electron beam, and thermal evaporation solutions.
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Earlier this year, Oxford Instruments engineers coated 450 mm silicon wafers with silicon oxide. It was a world's first for PECVD, and was accomplished using the company's new PlasmaPro NGP 1000 PECVD system. Photo: Oxford Instruments
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"PVD today is used in a wide range of products from the most sophisticated optical lens to car wheels," says Christopher Malocsay, vice president of Semicore.
Semicore’s most significant contribution to the R&D market is the TriAxis, a versatile research and development PVD coating system that is designed to handle future hardware and orientation changes.
Another PVD-oriented company, Angstrom Engineering, Ontario, Canada, sells about half of its equipment to researchers in corporate laboratories, such as HP and DuPont, and about half to universities. The company offers turnkey solutions that are not intended for high production.
"Our niche is in organic electronics. That's where we've really grown our customer base. We grew up as a company in a phase when the semiconductor industry was starting to struggle and brand-new applications like OLEDs (organic LEDs) were just starting to come out," says Andrew Campbell, sales and marketing manager, Angstrom Engineering.
As the company has grown, so has the market for new materials like organics in deposition products. OLEDs have grown far more slowly than other sectors like coatings and PV, but these materials are gaining traction as interest in CIGS solar cells builds and OLED screen technology finds its way into consumer products like mobile phones and television screens.
"Resistive thermal deposition is the most common procedure for depositing an organic polymer. It’s the cheapest and very controllable. That's what you’re looking for, a controlled rate to a controlled thickness," says Campbell.
Angstrom's instruments provide a high level materialization. For many of the newest deposition processes that use exotic or expensive materials, such indium, this is a significant benefit. One recent tool developed for a research group boasted a high level of efficiency.
"They get nearly 100% of their material landing on a sample. It’s very much like a printing process," says Campbell. The main limitation of this type of deposition process, he says, is temperature. "We can get the material to go exactly where we want, but can only do this in ranges, for example, of 500ºC or less. We can do this process for a lot of active materials, but we just can’t print gold lines."
Boundaries shift in two main deposition camps
Scientifically, PVD and CVD have well-defined roles. PVD tends to be employed when uniform surfaces are crucial and bonding strength is paramount. CVD is often used when exotic materials are being used, or when high-temperatures are required.
However, some companies try to shake up this order. Alchimer S.A., Massy, France, has commercialized a wet chemistry CVD technology for next-generation semiconductor deposition.
According to CEO Steve Lerner, the method is designed to allow the construction 3D interconnect through-silicon vias (TSVs), which he says is going to "be the biggest game-change in the industry in decades."
The advantages of 3D TSVs are readily apparent; by routing an electrical connection passing completely through a silicon wafer or die, the density of vias increases. This potentially allows circuits to be stacked, circumventing the problem with a lack of real estate in 2D circuit boards.
Making them, however, hasn't been easy. Though the semiconductor industry is pursuing this technology, 3D TSVs are still considered to be in the development stage. This is partly because conventional lithographic processes are unable to cope with the very small and high-aspect ratio features that TSVs require.
Unlike conventional lithographic techniques, which tend toward the use of PVD technologies mixed with CVD methods, Alchimer's TSV process relies on a wet chemistry CVD method. The films are grown from the surface in 2D and 3D structures. The chemical composition of the deposited material is determined by the precursors, and the bonding that takes place is reliant on the chemical reactions that occur.
The fundamental attributes of this type of process, says Lerner, can be summed up as unformity (whether any point on a surface is going to be developed in a uniform manner) and conformality—(whether the surface will offer consistent characteristics throughout). The goal of Alchimer's technology is to achieve both uniformity and conformality along high-aspect ratio surfaces, which are typically created by etching (deep reaction-ion etching, for example).
"By growing the film out from the surface," says Lerner, "we can coat even scalloped surfaces because the adhesion is achieved through the chemical bonds themselves."
The company believes that adoption of their CVD technologies can produce similar performance at 60% less cost than PVD. Their current technology platforms include Electrografting, which builds nanometer-scale thickness films from 2 to 500 nm at aspect ratios up to 20 to 1; and Chemicalgrafting, an electroless CVD process sequence that enables the growth of highly adherent, low-resistivity copper-diffusion barrier films on insulating surfaces.
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SVT Associates' SMART NanoTool PVD system combines several deposition methods in a single system.
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Vacuum companies get behind thin-film R&D effort
Digging deeper into the heart of the materials industry reveals that vacuum companies are heavily invested in the success of thin-film deposition technology. Without UHV, deposition processes as we know them would not exist. As a result, many of the leading vacuum suppliers are major R&D forces in the materials industry. This includes companies like Ulvac, Methuen, Mass., a supplier of production systems, instrumentation, pumps, and vacuum components used in the semiconductor, flat panel display, magnetic media, and industrial manufacturing markets.
Deposition is second-nature to Ulvac, which is well-known for its stand-alone pumps, but also has made a name for itself developing deposition processes.
"We’ve done many projects in the past where we’ve deposited thin films on various substrates," says David Mount, manager, marketing & business development at Ulvac, such as diamond-like carbon coatings for Gillette razor blades or cards for Bank of America.
On the R&D side, the company is tackling more technical areas. Ulvac recently partnered with Exatec LLC to help develop their polycarbonate part coating, a glazing that improves wear and toughness. The process may allow polycarbonate to replace glass in automobiles, helping automakers lighten their vehicles and meet future EPA regulations.
"We are adept at taking new technologies and transitioning them to industry," says Mount. "We also manufacture industrial equipment for solar, and we can do flexible substrates," for CIGS cells.
"We see that as one of the largest-growing segments of PV, and the market statistics bear that out," he adds.
Ulvac's involvement in the solar industry spans more than 30 years. They currently manufacture a tandem-junction solar panel, which features a second PECVD process to create a crystalline layer for better efficiency.
"We try to develop processes in which the customer doesn't have to replace the whole line and equipment," adds Mount.
In addition, Ulvac is working with a number of companies on cadmium-indium-gallium-selenide (CIGS) technologies. With Dow Chemical, they are developing a flexible substrate to hold CIGS cells for installation on roofing shingles. Other CIGS developments are taking place with Solyndra, MeoSolé, and SolarPower.
Ulvac isn’t the only company investing in solar. Since 2006, the global PV market has grown nearly 600%, totaling more than 12 GW of combined capacity worldwide.
The growth has of course attracted the interest of vacuum products and deposition equipment vendors, which have stepped up their R&D efforts in developing machinery to handle this growth. The interest is evident across the industry. According to VanderBroek, one of SVT Associates’ most significant technologies is a large-scale CIGS evaporation source, which is a crucial component of a CIGS production line.
Despite the impact of the recession on demand for PV panel products, the feedstock costs of crystalline silicon fell so sharply that overall processing and manufacturing costs also dropped, allowing manufacturers to continue their growth.
Oerlikon, which includes the Oerlikon Leybold vacuum products company, is heavily involved in industrial thin-film equipment for many applications, from textiles to semiconductors. The photovoltaics division, Oerlikon Solar, Trübbach, Switzerland, is one of the leading suppliers of production lines for thin-film silicon modules, having delivered 450 MW of production capacity to 12 customers since 2006.
Oerlikon Solar's level of involvement in PV has been rapid in the last decade, having moved from its first delivery of R&D equipment to Schott Solar, to presenting its own proprietary Micromorph tandem module in 2007. Though feedstock costs were a large contributor to improved efficiency in PV in recent years, companies like Oerlikon Solar are counting on new technology to provide even further gains. According to Michael Buscher, CEO of Oerlikon, the company recently achieved a world record in the module production cost, hitting as little as 0.5 Euro per Watt peak, a reduction of more than 50% from average production costs in 2008. This was made possible with the combination of Micromorph technology and the launch of the company’s CVD-based ThinFab line.
Future of thin film remains in flux
The growth of the thin-film deposition market should mirror that of the manufacturing sector as a whole, but it's also a key driver behind many manufacturing sectors.
In this light, the tug-of-war between various deposition methods isn't as important as continuous practical development. For example, PVD is seeing a renewed interest as the disadvantages of using hazardous or expensive chemicals mount in some applications. The pursuit of green solutions may drive some users back to PVD in more regulated countries.
"PVD is replacing plating due to reduced chemical usages. The clean energy market will require even more thin-film deposition going forward. Many new areas of coating opportunities are discovered every day," says Malocsay.
Competition between methods is especially strong in the solar energy and semiconductor markets. An alternative to dry PVD deposition methods is offered by Alchimer’s wet chemistry process, but will it catch on in the semiconductor industry?
"There are two different camps [on CVD vs PVD]. Some say running costs over time is higher for wet chemistry," says Ryoshin Imai, senior director, systems sales and marketing at Ulvac. Ultimately, Ulvac is looking beyond conventional product lines and toward roll-to-roll deposition for semiconductors and solar cells. The future is probably, Imai says, a hybrid approach to manufacturing.
Published in R & D magazine: Vol. 53, No. 2, April,
2011.
