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Equipment and Materials ♦ news digest


looking forward to the task of leading Aixtron as a leading provider of semiconductor technology production solutions along the way towards industrial mass production.”


He adds, “We have the opportunity to address some of the current social megatrends such as energy efficiency and intelligent networking, which are dominated by LEDs, OLEDs and power electronics. There is substantial growth potential for Aixtron in all of these areas.”


Hyland comments, “I am very pleased that I had the opportunity to participate in Aixtron’s route to becoming a globally acknowledged leading technology company. I am pleased to be able to hand over the CEO role to Mr. Goetzeler at this time. Mr. Goetzeler can build on a solid foundation, and he has both the leadership qualities and experience to take Aixtron successfully onto the next level.“


Kim Schindelhauer, the chairman of the Supervisory Board of Aixtron SE, expressed his gratitude to Hyland for his contributions to the company and says, “Mr. Hyland has successfully managed the Company during his tenure through many ups and downs in the semiconductor industry. For this, we would like to express our great appreciation. We are delighted to have found someone like Mr. Goetzeler, a versatile manager with extensive knowledge in the high-tech market and international experience. Mr. Hyland will actively support Mr. Goetzeler in taking up his office and ensure a smooth transition.”


Laytec upgrades in-situ GaN


LED monitoring system The firm’s latest UV pyrometer incorporates real-time UV emissivity correction for enhanced accuracy of gallium nitride surface temperature during the growth of complex LED structures


In an ideal world, LED manufacturers would know the emission wavelength of the final device during MOCVD growth.


Today, according to the Solid State Lighting road map, the wavelength variation across a wafer should be less than 1 nm. This means a less than 1 K (10C) variation of the GaN surface temperature during InGaN MQW growth.


LayTec’s Pyro 400 is widely used for enabling fab-wide GaN surface temperature uniformity in many LED manufacturers production lines.


Meanwhile, more complex LED structures and tighter cost reduction targets need even more advanced in-situ metrology. Figure 1, below, shows such an example; ternary InGaN and AlGaN layers cause emissivity changes that lead to 0.7 K error of the UV pyrometry reading.


Figure 1: Effect of changing emissivity to UV pyrometer temperature reading: up to 0.7 K errors show up without emissivity correction during growth of a GaN/AlGaN-GaN-SL/ InGaNMQW/ GaN structure


LayTec‘s answer to this challenge is the Pyro 400 Gen 2. Along with in-situ UV pyrometry the new generation tool includes real-time UV emissivity correction for enhanced accuracy of GaN surface temperature during growth of more complex LED structures.


A further challenge to reliable GaN temperature control in HB- LED production is the view-port coating.


Figure 2 shows its effect just before maintenance; the UV transmission of the view-port is significantly reduced and an uncorrected UV pyrometer would give a -10 K temperature artefact. Pyro 400 Gen 2 solves this problem,too. Laytec claims the tool automatically senses and corrects these coatings and enables a long-lasting 24/7 accuracy in HB-LED emission wavelength.


Figure 2: GaN MOCVD view-port before (red) and after maintenance (blue): the transmission at the 400nm detection wavelength of a UV pyrometer is suffering from the window coating (red). The resulting -10K artifact is avoided by Pyro 400 Gen2


Last, but not least, an assisting infrared pyrometer has been integrated into Pyro 400 Gen 2 for simultaneous monitoring of wafer pocket temperature throughout the full LED growth run.


March 2013 www.compoundsemiconductor.net 131


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