"Cost reductions and increased yields throughout the LED value chain are critical to accelerating the growth of the LED industry," said Cheryl Diuguid, GT's vice president and general manager of its sapphire equipment and materials business. "Our sapphire summit brings together leaders from across the LED value chain to examine the key metrics that matter most in achieving this goal."
GT today also released its latest sapphire material characterization case study that examined the critical properties and quality indicators of sapphire material - the "Metrics that Matter" - that have the greatest impact on yields and costs in manufacturing HB-LEDs.
"The results of our newly released HB LED manufacturing case study reinforce the important role that high quality sapphire plays in driving cost reductions and improving yields throughout the LED manufacturing value chain. The body of evidence collected from our series of case studies published over the past year overwhelmingly confirms that our ASF(TM) sapphire growth system produces some of the highest quality sapphire in the industry and results from our ASF equipment customers confirm the findings of the case studies. Sapphire material grown in their new production facilities using GT's ASF systems is already being qualified for LED production and achieving the initial targets for high yielding boules. We are very pleased with the early successes our ASF customers have achieved."
For the latest study, 240 epi-ready wafers were selected from 24 individual two-inch sapphire core samples, all of which had been graded as "LED-grade" sapphire cores by their respective makers. The cores were selected from material grown using different sapphire crystal growth methods, including GT's ASF(TM) furnace, the Kyropoulos method, and another method commonly referred to as a "HEM-like" growth method. The findings in the case study conclude that:
• ASF-grown LED grade material has the highest yield of all samples; 96.6%, whereas the baseline wafers had 96.1% and the next closest competitor had a yield of 94.1%;
• ASF sapphire wafers have a statistically significant higher brightness advantage on average across the functional wavelength for the HB-LED category of 450-460nm; and
• ASF-grown material has the tightest IV performance (wavelength vs. brightness) distribution, indicating that HB-LEDs made on ASF-grown sapphire has more consistency and tighter binning around the color-to- brightness distribution;
Background:
In January 2011, GT initiated an extensive sapphire material qualification project to determine the sapphire material "metrics that matter" in the manufacturing processes of HB LED devices. The sapphire characterization study was designed to evaluate the effects of sapphire material on yields in LED manufacturing and to objectively evaluate properties and differences between different sapphire growth techniques.
All studies were conducted using blind samples of GT ASF sapphire material as well as LED grade sapphire from other sources. The case study results were obtained from an independently conducted Glow Discharge Mass Spectroscopy (GDMS) analysis as well as a High Brightness (HB) LED device fabrication study performed using Photo-thermal Common-path Interferometry (PCI) analysis.
GT will present the findings of the HB LED case study at the Metrics that Matter Sapphire Summit, May 9-10, in Shanghai, China. The recent HB LED case study, along with the other case studies from GT's sapphire material characterization project
