Flexible, Heterogeneously Integrated µLED Displays in Elastomeric Substrates using Fan-Out Wafer-Level Packaging (FOWLP)

Speaker: Goutham Ezhilarasu
Affiliation: Ph.D. Candidate

Also Via Zoom:   https://ucla.zoom.us/j/96498596268?pwdYzVYWXJFQ3pBQ1UyUHJGWnRoMlQ5dz09

Abstract:   In recent years there has been a growing demand to develop next generation flexible displays that can achieve higher brightness, dynamic range and contrast ratios compared to LCDs or OLEDs. This demand has been driven by new application spaces such as wearable Augmented Reality (AR), conformable vehicular Head UP Displays (HUDs), and emerging medical fields such as Optogenetics where implanted high brightness displays are used to stimulate biological cells such as neurons. The only display technology that can meet these requirements is flexible microLED displays. microLEDs are light emitting devices made from compound semiconductor materials like GaN or InP that have demonstrated unparalleled brightness (>10⁶ cd/m²), color quality, response times (in ns range) and lifetime (>100,000 hours). The task of fabricating flexible microLED displays has however proven to be difficult. Inorganic microLEDs cannot be fabricated directly on flexible organic substrates due to the high processing temperatures involved and lattice matching considerations. Instead, they are fabricated on a growth substrate, released from it, and then assembled onto a target flexible substrate using a massively parallel transfer process, simply called mass transfer. Flexible microLED display technology has however not picked up due to: (1) complex and expensive mass transfer processes that suffer from yield issues & (2) primitive flexible electronic integration approaches that use coarse interconnects and are not well suited to the heterogeneous integration of micron sized LEDs. To overcome these challenges, we have developed a novel microLED mass transfer process based on thermoplastic adhesive (HD3007) bonding that is much simpler to implement, low cost and can potentially attain much high yields (> 99%) and panel-level scalability. We also use a novel Fan-Out Wafer-Level Packaging (FOWLP) technology called FlexTrate^TM to heterogeneously integrate 50 X 100µm² blue InGaN/GaN microLEDs with Si CMOS display driver ICs at < 40µm interconnect pitch to demonstrate a high density, functional, high resolution (> 150PPI) flexible microLED display. Detailed analytic and experimental studies of the various process steps, especially the Laser Lift-Off (LLO) process that is used to release GaN microLEDs from the growth substrate, is conducted in this thesis.

Biography: Goutham Ezhilarasu received the B.Eng. degree in electrical and electronics engineering from the College of Engineering, Guindy, India, in 2014, and the M.S. degree in electrical engineering from the University of California, Los Angeles in 2016. He is currently pursuing the Ph.D. degree with the Center for Heterogeneous Integration and Performance Scaling Group, University of California, Los Angeles, CA, USA. His current research interests include Fan-Out Wafer-Level Packaging (FOWLP) for flexible electronics, panel-level assembly processes and 3D integration.

For more information, contact Prof. Subramanian Iyer (s.s.iyer@ucla.edu)

Date/Time:
Date(s) - Jul 20, 2021
10:00 am - 12:00 pm

Location:
EE-IV Shannon Room #54-134
420 Westwood Plaza - 5th Flr., Los Angeles CA 90095