Micro-LEDs, a Manufacturability Perspective

Abstract

Compared with conventional display technologies, liquid crystal display (LCD), and organic light emitting diode (OLED), micro-LED displays possess potential advantages such as high contrast, fast response, and relatively wide color gamut, low power consumption, and long lifetime. Therefore, micro-LED displays are deemed as a promising technology that could replace LCD and OLED at least in some applications. While the prospects are bright, there are still some technological challenges that have not yet been fully resolved in order to realize the high volume commercialization, which include efficient and reliable assembly of individual LED dies into addressable arrays, full-color schemes, defect and yield management, repair technology and cost control. In this article, we review the recent technological developments of micro-LEDs from various aspects.

A Scalable and Low Stress Post-CMOS Processing Technique for Implantable Microsensors

“…We anticipate that the proposed post-processing method based on PDMS planarization will offer new opportunities in the development of any miniaturized devices incorporating the materials or structures that are incompatible with a front-end chip fabrication process. Besides our current demonstrations having metal or polymer-metal composite electrodes on foundry-fabricated silicon CMOS chips, sub-mm photovoltaic cells or light-emitting diodes (LEDs) can be handled with the PDMS-assisted technique to attach micropatterned metal or dielectric probes to them in the large-scale batch process, as in the state of the art microLED displays [ 42 ]. The proposed method may play a key role in the future semiconductor industry, where the introduction of unconventional materials and structures in conventional IC chips may open up a new opportunity in emerging applications, such as a large network of microscale biomedical implants and environmental sensors.…”

Micro-light-emitting diodes with quantum dots in display technology

“…Mass transfer is a powerful solution to realise large-scale µ-LED displays because of the ability to transfer over 10,000 µ-LEDs at one time at high speed and low cost. Several approaches have been evaluated to massively assemble µ-LEDs including elastomer stamping [58][59][60][61][62] , electrostatic transfer 63,64 , electromagnetic transfer 65,66 , laser-assisted transfer [67][68][69][70] and fluid self-assembly ( Fig. 6) [71][72][73] .…”

“…The realisation of QD-based µ-LED full-colour displays mainly relies on RGB chips prepared by QD colour conversion methods 70 . In 2015, for the first time, Han et al 86 developed aerosol jet printing to spray RGB QDs on the surface of a UV µ-LED array to achieve a full-colour µ-LED display.…”

“…However, the production cost of displays would be dramatically increased. Alternatively, individual pixel repair methods have been proposed to rescue dead pixels, such as laser welding, UV irradiation repair, selective rescue techniques, and redundant circuit design 70 . However, these approaches are also costly and not applicable for displays fabricated by monolithic integration.…”

P‐1: Development of High‐yield Laser Lift‐off Process for Micro LED Display

“…Those demo displays show the possibility of Micro LED commercialization. But there are still many problems for the fabrication of Micro LED panels including epitaxy and chip processing, assembly technologies (mass transfer and monolithic fabrication method), mass testing/repair and driving scheme 3 . Mass transfer is regarded as a bottleneck technology due to the huge quantities of micro-LEDs and high yield requirement adopted by the flat panel makers.…”