To stay ahead of the competition, a major U.S. glass-coating company wanted to increase yield without sacrificing quality. They had ideas about how to improve their coating tool, but needed the large assembly to be designed and built quickly. Their search for a development partner led them to Sputtering Components Inc. (SCI).
SCI is a high-volume manufacturer of rotary cathodes and components for the physical vapor deposition (PVD) industry. Based in Owatonna, Minnesota, the company produces tools used for sputtering — the process by which ultra thin layers of material are deposited onto a substrate. Applications for PVD thin films range from microelectronics and optical assemblies to food packaging and window tinting.
SCI had previously developed product designs for the glass-coating company, proving that they had the technical expertise to bring concepts to reality. However, this project would be especially challenging.
Traditionally, sheets of glass are coated on one side, racked, and then coated on the other. The glass-coating company wanted to potentially double its output. But as traditional coating assemblies are about the size of a football field, adding another assembly would mean doubling the size of the facility — an expensive proposition that would take months or even years to implement. So the company asked SCI to develop a new assembly that could coat both sides of a glass sheet simultaneously.
Double-Sided Coating Tool
Designing a two-sided coating assembly is not as easy as stacking one coating tool on top of another. Hardware must be carefully evaluated for strength and endurance. Factors such as movement, friction, water channels, increased temperature, high voltages and a high vacuum environments must be considered. In addition, the various properties of metals, plastics and other components must also be evaluated, as glass coating assemblies contain at least 20 different materials.
Aluminum, for instance, is a vacuum-compatible metal that is durable, inexpensive, lightweight and easy to machine. The metal is commonly used as a protective layer to prevent target materials from depositing on undesirable surfaces, such as chamber walls and floors. But as thermal management is an issue, aluminum cannot be used near the hot plasma source of the assembly, nor can it be used near the water sources that could cause corrosion.
Plastics are another material typically used in coating tools for bushings, spacers, flexible gaskets and insulation. For the new coating assembly, SCI had to do a thorough evaluation of each plastic's specific properties and choose among the many available types, including PEEK, Ultem, Teflon, Nylon, Viton, Rubber, Delrin and G10.
SCI began development of a "double-decker" glass coating assembly in 2006. Four months later, it was ready for trial in production. Coating both sides of a sheet of glass in one pass as it moves down the conveyor not only doubles production capacity, but also reduces yield loss, as the glass sheets need only be handled once. The two-sided coating assembly is the only one of its kind in the U.S. and has been operating in production mode off and on for nearly two years with few modifications and no failures. This development partnership with SCI saves time and money for the glass-coating company. In addition, as the company plans to install the two-sided coater in other facilities, it will significantly reduce its future investment in capital equipment.
Enhanced Mag Assembly
The same year that the double-sided coating assembly was installed, the glass-coating company asked SCI for design and manufacturing support on another project. In the thin-film coating process, a sputtering target is placed in a vacuum chamber and bombarded with ions. This causes a phenomenon that results in atoms being ejected from the face of the sputtering target. The substrate is within approximately 100mm of the sputtering target and the atoms molecularly bond to the substrate. The glass-coating company wanted an enhanced magnetic assembly that would improve the coverage and uniformity of the thin-film layer on the substrate, while allowing for higher utilization of target materials.
SCI had started brainstorming ways to improve the sputtering process with a more robust magnetic assembly as early as 2002. However, before this assembly could be constructed, some innovations would have to be made to the design as materials used in traditional magnetic assemblies could not be used in the newly developed mechanism because of motion and wear.
While cathode, main bearing, and seal housings are often made of stainless steel due to the metal's sturdiness, low maintenance, low expansion rate and resistance to corrosion, for this more robust assembly, SCI's design engineers recognized that stainless steel might have filing issues. Instead, they decided to use a special plastic with the ideal level of slickness and strength. Non-corrosive brass, an alloy of copper and zinc, was used in fittings, ported plates and the water circuit.
Once the enhanced mechanical assembly was installed, the glass-coating company was able to increase the throughput of its process without sacrificing quality. The company has realized a savings of at least ten percent per target. With the average target costing anywhere from six to ten thousand dollars, and the annual cost of target materials running in the millions of dollars, the savings are very significant.
SCI's 17,000 square foot manufacturing facility houses advanced machining equipment dedicated solely to high-volume manufacturing of cathodes and components for the physical vapor deposition (PVD) industry. But it is the manufacturer's dedication to innovation and willingness to empower its engineers with strategic decision-making ability that enables SCI to rapidly turn innovative ideas into practical equipment. Even though SCI is significantly smaller than its glass-coating customer, SCI's assertive problem-solving attitude and in-depth knowledge of the materials used to design and construct a PVD assembly landed it a cooperative technological development partnership that is now in its fifth year.
X}Contact: Sputtering Components, Inc., 375 Alexander Drive, Owatonna, MN 55060 507-455-9140 fax: 507-455-9148 Web: http://www.sputteringcomponents.com