iLED iLED December 2012 : 12

DECEMBER 2012 ISSUE N°6 COMP ANY INSIGHT Chemical cooperation is material gain for LEDs Dow Electronic Materials is now tailoring photoresist and polishing products for GaN, and ramping phosphor production, according to Nate Brese, Global Marketing Director for growth technologies within the company. S Nate Brese, Global Marketing Director, Dow Electronic Materials ometimes a supplier is prepared to listen and make exactly the product you need. At other times, you have to make do with what’s already available. Until recently the LED industry was usually in the second situation, explains Nate Brese, Global Marketing Director for growth technologies within Dow Electronic Materials. Previously, silicon semiconductors had been the main bene fi ciary of customer intimacy with the Midland, Michigan, headquartered chemical giant. But now LEDs are mature enough that it has set up a business unit dedicated to its service, including developing and customising materials speci fi cally for them. Dow is both re fi ning its established products and adding new ones, such as phosphor compounds, to fi t with the ongoing shift in the industry’s needs, Brese explains. “Initially it was about technology, increasing lm/W,” he said. “Now we’re in the lm/$ phase, improving yields, throughput, and utilisation of assets. Our efforts are helping them to drive down the cost. The price drops that I’ve seen for LEDs are astounding and part of that is overcapacity. There’s an awful lot of excess capacity on the epi side that developed in the last couple of years. People are basically saying ‘I have these assets, I need to use them and maximize my return on capital’. So people are trying to utilise their assets wisely and that almost automatically requires looking at materials and process ef fi ciency to make sure there’s no waste in the process or utilisation.” For example, UV-reactive photoresist suitable for typical LED feature sizes tended to rely on technology more than a decade old, which doesn’t provide adequate dry-etch performance or process speed. Rather than compromise, manufacturers can now call on products that Dow is speci fi cally optimising, Brese underlined. “We are able to screen all of our technologies, take a master batch with very low cost infrastructure and customise for the LED industry,” he said. “How quickly can you expose, how quickly can you develop, how quickly can you strip? Those are minor improvements, but every little bit counts. People are fi nding more value in less waste, speed, and ef fi ciency.” Another set of materials used in routine operations, polishing pads and slurries, can also play a surprisingly important role in improving manufacturing uniformity. “Binning of different colour and power devices has a lot to do with the quality of the starting wafer, and therefore ultimately with the polishing chemistry and process,” Brese said. “How those are utilised is really quite different from a 2-inch to a 6-inch wafer. We’ve been doing engineering studies with customers to fi gure out what slurry fl ows and downward forces should look like to get the smoothness across the wafer that they need.” In May 2012, Dow Electronic Materials added phosphors to its portfolio by acquiring Princeton, New Jersey, based Lightscape Materials Inc., a spin-off of research company SRI International. Lightscape had developed high performance carbidonitride materials that convert blue GaN LED emission to red, green and other colors, offering the industry new choices. “They had something unique, but didn’t have the capital to expand and produce at levels that customers required,” Brese explained. “As part of Dow they can accelerate their new product development as well as ensure high quality and suf fi cient capacity for high volume manufacturing.” Combining yellow yttrium aluminium garnet (YAG) phosphors with blue-emitting chips was the original way to make white light. However, their use is limited by patents, while this method creates a ‘colder’ white light than many people desire. “To warm up the light they’ve been evolving to multi-phosphor systems including reds and alternatives to YAG,” Brese said. “Our carbidonitride reds and oxycarbidonitride greens “The price drops that I’ve seen for LEDs are astounding and part of that is overcapacity”, says Nate Brese. Shining in different facets: For the LED industry, Dow provides epitaxial precursors, photoresists, polishing slurries and pads, and metals for producing electrical contacts. (Courtesy of Dow Electronic Materials) 12 i LED

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