LED Production Yield Improvement Using Advanced In Situ Metrology Systems

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Optoelectronic compound semiconductor (CS) structures such as LEDs are typically grown in a complex multi-step hetero epitaxial process. Hence close supervision of the tight growth conditions is a must in order to manufacture high quality devices. Differently to the silicon semiconductor industry, CS devices are still manufactured on relatively small substrates. In 2009 nearly 70% of the compound semiconductor devices were still produced on 2" sapphire wafers. In-situ metrology provides real time access to pocket and wafer temperature, growth rate of individual layers and morphology information to eventually control the complex multi-layer growth. By 2015 market researchers predict a lager penetration of 4" and 6" sapphire wafer, which increases the device count per wafer and is expected to reduce manufacturing cost. However, on such larger substrates several wafer bow effects become much more critical for the device performance. Hence, advanced in-situ control of wafer curvature optimization will become mandatory to improve and maintain high production quality and yield.