Abstract

The rising demand for high efficiency, resolution, and life-time in display propels extensive research and development of microLED (μLED) through last decade for a large-size display with superior image quality, energy efficient and high-brightness mobile displays, and even high-resolution virtual/augmented-reality devices. The most key technology to mass production, however, is still far behind and hinders the bourgeoning next-generation μLED display. Here, we show ultrafast and wafer-scale alignment of millions of μLED chips by controlling van der Waals (vdW) forces between the μLED chip and interposer. Two surfaces of μLED chip are engineered to have maximal difference in vdW forces, and their dynamics is mediated by dipping-in and drying-out fluidic conditions. Through comprehensive experimental and theoretical analysis, the alignment process is revealed to be single-faced and irreversible. Therefore, 259k μLED chips are aligned with 100％ and transferred with 99.996 ％ yield only within 40 trials, respectively.

Lastly, we demonstrate μLED passive- and active-matrix displays by integrating the interposer with transferred μLED chips into the LTPS TFT panel through wafer bonding process. Our vdW force driven alignment process with unprecedented high-speed and yield can resolve a critical deterrent toward the coming age of μLED displays.