LayTec’s Pyro 400 endorsed by GaN LED manufacturer Lextar
The pyrometer, which operates in the 400nm range, has been specifically designed to measure real surface temperature in gallium nitride based LEDs. The temperature can be correlated to wafer bow and optimised to improve wafer yields
Lextar Electronics, a major Taiwanese LED producer, headquartered in Hsinchu, has qualified LayTec´s GaN surface temperature measurement tool Pyro 400 for its GaN LED production.
Pyro 400 on Aixtron planetary reactor
A niggling problem in today’s GaN based LED production is the inability to measure and control the real wafer temperature during epitaxial growth. The real surface temperature of GaN-based materials is sensitive to changes in carrier gas, rotation speed, and reactor pressure.
To measure the real temperature in III-nitrides, it is not possible to use conventional infrared pyrometry (which is around 950nm). To overcome this problem, Laytec has developed the Pyro 400 ; it measures the exact surface temperature of GaN layers using pyrometry at 400 nm. At this wavelength GaN absorbs and thermally emits light.
Another important factor in LED manufacturing is wafer bow and temperature uniformity; this is critical for III-nitride process yield enhancement. LayTec says its Pyro 400 provides excellent insight into the correlation between the wafer bow and real wafer surface temperature uniformity.
Johnson Wang, the department manager of EPI Engineering/Manufacturing, who was responsible for the Pyro 400 product qualification process, states, "With Pyro 400 we can now better control the later emission wavelength of the LED already during growth. The qualifications tests have proven that the surface temperature of the GaN measured by Pyro 400 at MQW growth can be directly correlated with the later ex-situ PL emission wavelength. This tool is a quantum leap in wafer-to-wafer temperature control in LED Production."
Elisabeth Steimetz, Director, Marketing & Sales at LayTec, adds, “The qualification of Pyro 400 by Lextar is a significant milestone for LayTec. Through collaboration with this important and innovative customer we were able to further improve our product and qualify it for daily LED production application. We could successfully demonstrate that precise surface temperature control gives room for even further LED yield improvement and cost reduction. We are very thankful to Johnson Wang and his team at Lextar Corporation for giving us the opportunity to qualify the product.”