in Light Report:
Sector Looking for Alternative Solutions to Spur Adoption of General Lighting
By Paula Doe, SEMI
With the HB-LED sector counting on affordable general lighting to drive its future growth, device makers look at the potential for alternative substrates, innovative packaging and statistical process control.
General Lighting Increasingly Becomes the Driver in a Flattening Market
The packaged LED device market will see modest 1.8 percent CAGR over the next five years, to rise from $13.7 billion to some $15 billion by 2017, according to Strategies Unlimited. With demand for other applications maturing, most of this growth will need to come from general lighting. Use of LEDs for the still small market of general lighting roughly doubled in 2012, to reach $3.1 billion, barely edging out displays to become the largest application for the first time, noted Strategies Unlimited director of LED market research Ella Shum. Sales for almost all other applications, however, are trending down, as both overcapacity and improving manufacturing push down prices, and applications across the board from headlights to TVs used significantly fewer, brighter devices. Strategies Unlimited counts in its total all devices >30lm/W, and as industry technology improves, that means that a large number of off-spec but reasonable quality components go into things like Christmas lights and light tubes and strips now get counted as part of the mid- and high-brightness LED lighting market, explained Vrinda Bhandarkar, SU’s director of LED lighting research.
Lm/W & Klm/$
Though the overall market may be flat, most of the leading suppliers are seeing healthy growth. Shum noted that many of the top 10 component suppliers saw double digit increases in sales, led by Toyoda Gosei at 37 percent, thanks to post-tsunami demand for energy savings in Japan, and Lumens at 32 percent, thanks to growth of its packaging for Samsung. Philips Lumileds and Samsung saw 21-22 percent growth, followed by Sharp, Seoul Semiconductor and Cree at 14-18 percent. Everlight and LG Innotek, however, saw 1 percent declines. Several of these big players were squeezed for capacity, and expanded by acquisitions or partnerships, with Nichia allying with Citizen, LG with Showa Denko, and Epistar acquiring Huga Optotech, while the giant Chinese shipping company San-an bought a chip maker in Taiwan and hired a crowd of engineers from others.
This growth comes as prices have continued to plunge towards what’s needed to drive mass adoption of general solid state lighting. Average price per light output dropped another 45 percent in 2012, to $3.45/klm, according to Strategies Unlimited. Some leaders have pushed device efficiencies up and manufacturing costs down to do markedly better, with Nichia reporting $2/klm with its low-cost plastic QFN package and Cree optimizing all parts of the device and packaging to introduce a commercial 200lm/W device.
Equipment spending will likely decline another ~10 percent this year, to some $1.7 billion, according to SEMI’s Opto/LED Fab Forecast. Equipment investment dropped ~30 percent last year to $1.9 billion after the 2011 boom fueled by aggressive Chinese government subsidies, reported SEMI CMO Tom Morrow. But that excess capacity in China is starting to get utilized. Chinese LED fab utilization has recovered from its 39 percent low in 2011 back up to 61 percent as of 3Q12.
China LED Fab Utilization
While general lighting will drive much of future LED growth, Osram Opto Semiconductor LED VP and GM Wolfgang Lex pointed out that 50 percent of LEDs will still continue to be sold into applications other than lighting and displays — and it’s those other applications with high-value products with specific demands of their own that are actually driving much of the technology development. “It’s these niches that are paying for the R&D to develop the technology, not solid state lighting,” he noted.
“The winners will be those with the best lumens per wafer, the rights to the IP, and the money to develop the technology,” said Cree SVP Norbert Hiller, noting that displays would consolidate around the few big players, but the less mature lighting market still had room for new ideas from a lot of different companies, known and unknown.
Bringing Down Costs: A Look at GaN-on-GaN, GaN-on-Si, and 6-in. Sapphire Substrates
University of California Santa Barbara professor Shuji Nakamura argued that GaN-on-aN LEDs, currently being manufactured by Soraa, which he co-founded, could possibly increase lumen output by as much as tenfold, while reducing the cost per lumen, as the expensive GaN substrates remain a relatively small portion of total cost. GaN substrates mean no lattice or thermal mismatch and drastically fewer dislocations, for easy current spreading and little droop even at high current density. “Ammonothermal technology [for GaN growth] will decrease cost in the near future,” argued Nakamura. Soraa is working on an ARPA-E project to grow GaN crystals with a steel reactor lined with insulating ceramic for the high heat and high-pressure growth chamber, instead of the usual costly and hard-to-scale-up nickel super alloys.
German epi wafer supplier AZZURRO, meanwhile, is supplying 150mm-200mm GaN on silicon wafer templates, with the buffer layers grown, ready for LED makers to largely use their existing epi processes to grow the active layers on top. The company has announced that Epistar has successfully migrated its LED structures to the 150mm templates. AZZURRO co-founder and EVP of business development Alexander Loesing suggests that LED makers now using 2-inch wafers could potentially move to larger substrates with limited capital investment by using the templates, doing the epi in house with existing tools, then using a CMOS foundry to do the rest of the processing. “We don’t believe people will add 200mm lines, but will use a foundry. We are working on deals with foundries for the whole process,” he said. The company grows its buffer layers on thick silicon wafers with its proprietary and patented strain management to control the bow. After LED makers grow their LED structures on the templates, they remove the silicon with standard low-cost removal processes, for wafers with the 50µm bow required for silicon lines. Loesing reported 445.2nm emission with a standard deviation (std) of 2.53nm across the wafer. The company is also marketing GaN-on-Si epiwafers to power semiconductor makers.
China’s Lattice Power reported it is currently running some 10,000-15,000 2-inch GaN-on-Si wafers per month, with typical performance of 130-140lm/W for 45mil chips for some 50 customers to prove the process. It’s developing a 6-inch wafer version, where uniformity remains a bit less, with standard deviation of ~3nm instead of the 1nm on 2-inch, but CTO Hanmin Zhao estimates that the company will get 6-inch uniformity to a similar 1nm std by 3Q this year. He figures the cost per 1mm chip will be about 30 percent less on silicon than on than sapphire, using a vertical chip design. The 2-inch vertical silicon devices are getting about 5 percent higher light output and 5 percent lower yields (70-80 percent) than the lateral sapphire alternative, but about the same as the vertical sapphire version.
But the best bet for cost reduction may still be six-inch sapphires, especially now that there is industry progress on standards for the wafers, cassettes, loadports and software needed to adopt the existing silicon-centric production equipment to efficient commercial volume production of the thicker and more bowed sapphire wafers, noted SEMI’s Morrow.
“We believe when the market improves many will go to 4-6 inch sapphire, as prices of 6-inch wafers come down, and as 6-inch offers about 9X more efficient processing with its 9X more chips per wafer, since cost drives everything,” says Rubicon CEO Raja Parvez. “Besides scaling, it also brings the ability to use excess semiconductor equipment for post epi processing for better uniformity and yield.” He figures only about 15 percent of the industry uses 6-inch so far, 30-40 percent 4-inch, and about 50 percent still on 2-inch, and not much change occurred in the last very challenging 18 months, as LED makers had plenty of capacity and no desire to invest in new equipment in the downturn. But as the industry recovers demand for higher quality and specifications will drive users to flatter, cleaner, thinner, and larger wafers, he suggests, noting that older generation wafers will no longer be good enough as the market gets more sophisticated. “Standards will develop,” he notes. “At the end of the day, this will help to further decrease costs.”
While sapphire wafer prices have fallen sharply recently, the technology developed for the LED industry is now drawing considerable interest for durable, scratch-resistant camera lens covers for cameras and smart phones, or even for smart phone cover plates, which could compete with LEDs for sapphire supply and potentially boost wafer prices.
Wafer makers are also looking to add value, by offering patterned sapphire surfaces (PSS) for light extraction, which has typically been done by LED makers in house as part of their device design. Rubicon is developing PSS in house for 6-inch wafers.
Rethinking LED Packaging
Bridgelux has taken an innovative approach of packaging its newest family (Vero™) of LEDs with a standard- footprint, multilayer plastic substrate with connectors, for “plug and play” connectivity and easy integration of more features for smart lighting in the future, argues Jim Miller, chief Sales and Marketing officer . The line includes multiple color quality options with overlapping performance capabilities to cover a wide range of different applications in one form factor to simplify the supply chain. The chip-on-board platform offers thermally isolated solder pads, or an onboard connector port for snap-in solder-free connections, for easy installation and field upgrades. The standardized packaging is manufactured at a semiconductor OSAT with automated processes which Bridgelux believes provides competitive advantage. The substrate and packaging technology have been designed so smart lighting features like light or occupancy sensors or other chips can be readily integrated on to the same product platform.
Improving Yields with Statistical Process Control
Software and metrology suppliers noted progress in improving LED yields by tracking parameters in line, and automating the analysis of what needs fixing when. Suppliers argued for the need to monitor real-time variables like temperature, reflectance and curvature in the epi process, and patterns in electrical and optical wafer maps, and for analysis of how these measures relate to final yield, and for alarm points for when things are out of spec and need adjustment. “The LED sector’s pain point is that although it can see defects on inspection at various process points, isolating defects to point of origin and establishing root cause still remains a challenge,” says Steven Chen, KLA-Tencor process control technologist. By correlating epi defects to yield, KLA found that while total defect counts did not correlate with yield, higher densities of critical defects of interest did have significant impact. “The inspection equipment’s defect detection sensitivity and classification capabilities need to be matched with yield management software that ties all the data together,” he notes. He estimated that identifying the killer defects and applying inline controls by linking inspection results with defect analysis solutions could potentially save a user $1 million per year by catching problems earlier.
Rudolph Technologies’ Matthew Chriss, LED process control engineer, noted that if fabs connected MES systems to their many MOCVD chambers they could stop going through log books looking for the commonalities among low yielding chambers, and get automated readouts of excursions to locate the tools, pockets, processes, or settings causing problems before things get too far out of spec. “The automated systems may reduce the operators needed for a small reduction in personnel costs, but I believe the much bigger value is in the consistent process control,” says Chriss. Laytec’s CTO Kolja Haberland also reported yield improvements from its system to monitor real-time temperature, reflectance and curvature in the MOCVD tool and report when a reading moves enough out of spec to impact yield.
For more information on SEMI, please visit www.semi.org. Visit www.semi.org/Store/MarketInformation/OptoLEDFabForecast for information on the SEMI Opto/LED Fab Forecast. For information on SEMI’s involvement with HB-LEDs, visit www.semi.org/led.
Also visit the SEMICON China 2013 (March 19-21) website (www.semiconchina.org) to learn more about the LED Manufacturing Pavilion and the LED China 2013 Conference. For information on LED programs at SEMICON West 2013 (July 9-11), visit www.semiconwest.org.
March 5, 2013