Philips Lumileds mass-producing LEDs on 150-mm wafers
As LED manufacturers seek to increase capacity and yield and reduce cost, moving to larger-diameter wafers is seen as a key enabling step. While many LED manufacturers continue to use 2-inch wafers as the starting point for device fabrication, an increasing number already use 3- and 4-inch wafers. The next step is to transfer production to 150 mm (approx. 6-inch) wafers.
Philips Lumileds recently claimed that it is "the first power-LED manufacturer in mass production on 150 mm wafers." The company says it is now producing "millions of GaN-based LEDs weekly" on the larger substrates. Lumileds operates wafer fabs in San Jose, California, and Singapore.
“The addition of 150-mm manufacturing capacity to our existing capability leverages our epitaxy and wafer-fabrication technology excellence and gives Lumileds the capacity to produce billions of Luxeon LEDs annually,” said Matthijs Glastra, Executive VP of Worldwide Operations for Philips Lumileds.
Lumileds says it will continue its current wafer production while ramping production of its 150-mm capacity to meet increasing demand for high-quality, high-performance LEDs from the lighting, automotive, and consumer electronics segments.
“We expect that the pace of LED adoption will require all other manufacturers to follow our lead and adopt similar strategies," said Glastra. "Their challenge will be to achieve the high yields and quality levels that we have already demonstrated.”
Each 150-mm wafer has approximately four times the surface area of a 3-inch wafer, and nine times the area of a 2-inch wafer, and more than double the area of a 4-inch wafer. Geometrically, because of the need to fit square or rectangular LED chips onto a circular wafer, some material is lost around the edges of each wafer.
The move to larger wafers is more advantageous for larger chip sizes...but only if devices can be produced with the same performance and quality. Critical process steps include the uniformity and reproducibility of epitaxy (deposition of the LED material layers) across the large-diameter substrates.
Lumileds also points out that manufacturing on 150-mm wafers can offer further advantages for capacity expansion. The addition of new epitaxy systems running 150-mm wafers represents a lower capital expenditure to achieve the same capacity expansion compared with adding more systems that run with smaller wafers. “Some of the newer entrants to LED manufacturing require many more reactors to match our volume capacity,” said Glastra.
Other LED makers
Of course, Lumileds is far from being the only company to have worked with 150-mm wafers. Sapphire wafer supplier Rubicon Technology is currently delivering on a $71-million order for 6-inch wafers from an Asian company, believed to be LG Innotek. Rubicon says that its customer has been in mass production for several months using 6-inch material, although the LEDs are likely to be mid-power devices for LCD backlighting applications (in contrast with the higher-power Luxeon LEDs for lighting applications). Rubicon has several other LED customers for 6-inch sapphire, although none are in volume production yet.
Meanwhile, Cree announced in September that it is building a new 150-mm LED wafer production facility in Research Triangle Park, NC. The new production line is scheduled to be installed over the next several quarters with a target of having the first products qualified on this line by June 2011.
