The market for discrete light emitting diodes (LEDs) is growing rapidly. Silicon carbide (SiC) and sapphire (AL203) wafers are used as the substrate materials for white and blue LEDs. Today, European companies, most of them SMEs, account for less than 5 percent of global wafer production. This low figure is due to the high manufacturing costs compared to the main producers in Russia, USA and Japan. The most time-consuming and therefore most expensive machining operations in the manufacture of sapphire wafers are the "lapping" and "polishing" processes. The manufacturing process can be significantly shortened by replacing the lapping process with a grinding process, as this technology is capable of producing much better surface qualities in far less time. The polishing time is also reduced. This will be a decisive step for European wafer manufacturers, enabling them to improve their share of a highly profitable market.
The Fraunhofer IPT is making progress in sapphire wafer manufacture and has concentrated on the development of the rotational grinding process. The institute initiated the EU “ThermoGrind” project that is funded by the European Commission (contract number: 232600) as part of the 7th Framework Programme’s “Research for the benefit of SMEs” program.
Together with the Department of Electrical, Management and Mechanical Engineering (DIEGM) at the University of Udine, Italy, the Fraunhofer IPT is providing its research services to the following companies:
Although the grinding of silicon wafers, the substrate material for red and yellow LEDs, is now state-of-the-art, the technology is unable to cope with the changeability and interdependency of the individual effects when grinding sapphire wafers. This is why the direct detection of in-process parameters within the contact zone between the wafer and the grinding tool is of such relevance for the development of a stable grinding process.
ThermoGrind makes it possible to measure one of the key parameters: grinding temperature. This is based on sapphire’s optical transparency to the infrared radiation initiated in the contact zone. Part of the project therefore involves the development of a new infrared-transparent wafer clamping system (chuck). It then becomes possible to detect the infrared radiation transmitted through the wafer and the clamping system and to directly measure the contact zone temperature. A second project phase involves the development of temperature-based controls for the grinding process with which to achieve the best process stability under industrial conditions.
Research Executive Agency REA
University of Udine
Dept. of Electrical, Management and Mechanical Engineering DIEGM
Prof. Elso Kuljanic
Via delle Scienze, 208
G&N Genauigkeits Maschinenbau Nürnberg GmbH
Atlantic Diamond Ltd.
Mícheál Ó Ceallaigh
Docklands Innovation Park, East Wall Road
9503 GA Stadskanaal
TKF Technische Keramik Frömgen GmbH