20 µm Micro‐LEDs Mass Transfer via Laser‐Induced In Situ Nanoparticles Resonance Enhancement

Abstract

Ultrafast laser is expected as a promising strategy for micro‐LEDs (µ‐LEDs) transfer due to its inherent property of suppressing thermal effects. However, its ultrahigh peak power and the unclear transfer mechanism make its transfer quality and efficiency unsatisfactory. Here, the study reports the high‐precision mass transfer of 20 µm fine‐pitch µ‐LEDs via in situ nanoparticles (NPs) resonance enhancement in burst mode ultraviolet picosecond laser irradiation. This technique suppresses the thermal melting effect and rapid cooling behavior of plasma by temporal modulation of the burst mode, generating NPs‐induced resonance enhancement that accurately and controllable drives a single unit up to tens of thousands of µ‐LEDs. The transfer of large µ‐LED arrays with more than 180 000 chips is also demonstrated, showing a transfer yield close to 99.9%, a transfer speed of 700 pcs s−1, and a transfer error of <±1.2 µm. The transferred µ‐LEDs perform excellent optoelectronic properties and enable reliable device operation regardless of complex strain environments, providing a reliable strategy for preparing broader classes of 3D integrated photonics devices.

Shape-deformable Micro-LEDs for advanced displays and healthcare

“…Thickness reduction by substrate removal can impart certain flexibility to Micro-LEDs. Two major strategies have been developed to take off the growth substrate: laser lift-off (LLO) [6,35,36] and epitaxial lift-off (ELO) [37][38][39][40][41][42][43] . LLO exploits the laser energy absorption at the LED layer/substrate interface, which leads to the release of Micro-LEDs from the substrate due to the high-temperature induced material decomposition at the interface [35] [Figure 1A].…”

“…Schematics for the substrate removal methods, including (A) laser lift-off, (B) chemical lift-off, and (C) mechanical lift-off [35] ; Representative transfer methods for Micro-LED integration on curvilinear substrates reported recently, including (D) ballon-shaped stamp transfer [60] , (E) roller transfer [11] , and (F) photosensitive tape-assisted transfer [17] ; Typical mechanical structure designs for improved stretchability of Micro-LED devices, including (G) island-bridge design [61] , (H) buckling structures [16] , and (I) Kirigami structures [9] . Figure 1A-C reproduced under the terms of the CC-BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0) [35] ; Figure 1D adapted with permission from ref. [60] .…”

“…System-scale flexibility can be partially enhanced by micro-assembling Micro-LEDs onto soft substrates [35,[54][55][56] . With shrinking the Micro-LED size and thickness into the micro-scale regime, fast and accurate manipulation of Micro-LEDs in a reliable manner becomes a critical challenge.…”

“…Strategies toward the fabrication of deformable Micro-LEDs, including substrate removal (A-C), micro-assembly (D-F), and mechanical design (E-I). Schematics for the substrate removal methods, including (A) laser lift-off, (B) chemical lift-off, and (C) mechanical lift-off[35] ; Representative transfer methods for Micro-LED integration on curvilinear substrates reported recently, including (D) ballon-shaped stamp transfer…”