White Paper | Technology | Dec 15, 2011

Independent Study Demonstrating that Pink Sapphire Produces Highest Transmission Colorless Epi-Wafers

GT Advanced Technologies Inc. announced the release of a case study that details the findings of a series of blind material studies conducted to evaluate the impact of sapphire color on the LED manufacturing process. The studies demonstrated that all sapphire, regardless of source, exhibits color at the core level, that the pink hue of GT Advanced Sapphire Furnace (ASF™) material is not indicative of impurities, and that pink ASF sapphire does not have an adverse affect on the LED manufacturing process nor does it require extra steps or incremental costs to remove the pink hue. In addition, it was demonstrated that GT ASF pink sapphire material makes the lowest absorption, highest transmission epi-wafers of the samples examined.

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 has been supplying sapphire to the LED industry for over 12 years. These studies further validate the positive observations that we have long heard from our materials customers on the superior quality and performance of ASF-grown sapphire material, despite its pink hue,” said Cheryl Diuguid, VP and GM Sapphire Material and Equipment. “The findings of the recent case study confirm what we have known for a long time; namely, that GT’s ASF tool produces sapphire material that is of the highest quality and that exhibits the metrics that matter most to LED manufacturers. These include low to no levels of critical defects such as bubbles, good performance on key LED wafering parameters such as surface roughness (Ra), total thickness variation (TTV), warp and bow and ultimately high wafer yields.”

The new study is part of a larger comprehensive material characterization project initiated by GT to examine the effects of sapphire material properties on the entire manufacturing processes in the HB LED value chain. The company will present the findings of the color case study at the GG LED Conference, December 9-10, in Shenzhen, China.

The case study paper is available in the resource section of the company’s web site or can be downloaded here.
The company has also released a Frequently Asked Questions document on the metrics that matter in assessing sapphire material quality. The FAQ is also available at www.gtat.com/resources-casestudies.htm.

“GT has been supplying sapphire to the LED industry for over 12 years. These studies further validate the positive observations that we have long heard from our materials customers on the superior quality and performance of ASF-grown sapphire material, despite its pink hue”

About GT Advanced Technologies Inc:
GT Advanced Technologies, Inc. is a global provider of polysilicon production technology, and sapphire and silicon crystalline growth systems and materials for the solar, LED and other specialty markets. The company's products and services allow its customers to optimize their manufacturing environments and lower their cost of ownership. For additional information about GT Advanced Technologies, please visit www.gtat.com.