MicroLED Metrology: Challenges and Solutions

The upcoming μLED display technology promises high contrast, fast response time, wide color gamut, low power consumption, and long lifetime. However, the technology is not only challenging for mass transfer of the µLEDs from wafer to display, but also for massive parallelization of optical quality control at different manufacturing steps. Additionally, metrological challenges arise from µLEDs` small size, narrow spectral bandwidth and substantial manufacturing tolerances of the emission peak wavelength and bandwidth. For speed and resolution, a high-resolution camera is the preferred testing option, because display pixels or individual µLEDs on a wafer or display can be measured parallel in a single shot. For absolute color, however, spectroradiometry is the most accurate method. Consequently, we combined the two techniques in the LumiTop measuring system. For highest µLED measurement accuracy, we introduce a live calibration, optimized for every single image taken, enabling high quality true color µLED-displays.