In recent years, microLEDs technology have received rapid attention for its incredible lifetime, wide color gamut, and high EQE. Therefore, innovations in high throughput and high efficiency fabrication methodologies are actively investigated. Additionally, there are great interest in thinner and higher resolution flexible displays created from such microLED technologies – this calls for fine-pitch and multi-layer wiring structures to increase display resolution and also effectively interconnect microLEDs to its driver and other passive components. In our demonstration of such a high resolution. flexible microLED display, we use a novel mass transfer process to transfer an entire array of GaN UV microLEDs (30 um x 30 um size with 10um spacing) to our flexible substrate using a single mass transfer process then integrate them using fine pitch, two-layer interconnect methodology in a passive matrix driving configuration using current and voltage drivers in addition to other passive components. Our mass transfer process comprises of an initial bonding of GaN microLED dies grown on sapphire directly on a layer of thermal release tape. Then. a single laser lift-off process separates the microLEDs from their sapphire substrate, allowing us to transfer these microLEDs to our flexible substrate by molding an ultra-thin layer of PDMS directly with a second glass handler wafer ( < 50um). We then initially fabricate our two wiring levels and bonding pads using our standard FlexTrate [1] process before flip-chip bonding our drivers and passive components onto the previously created bonding pads to form an a fine pitch monochrome display. In our presentation of this flexible, heterogeneously integrated quantum dot micro-display, we overcome previous multi-level wiring challenges and also limitations on minimum thickness of PDMS by using novel solutions.
.jpg "Henry Sun photo")