Integrating microLEDs with advanced CMOS

Bonding 300 mm GaN-on-silicon LED wafers to CMOS backplanes of the same size offers the best approach for producing displays that have a microLED pitch of just a few microns.

BY Soeren Steudel FROM MICLEDI Microdisplays

For the last five years or so microLED manufacturing has been a very hot topic within the display industry. It’s been high on the agenda at leading display events, such as Display Week, with the focus on flat panel manufacturing of various displays, ranging in size from smart watches to mobile phones and TVs. For this technology, efforts at scaling manufacture are thwarted by challenges associated with mass transfer of the microLED, as well as the repair of defective die.

A new set of issues are faced when considering microLEDs for microdisplay applications, like augmented-reality (AR) glasses. One approach to making a microLED-based display module for that type of application involves uniting microLEDs and CMOS backplane ASICs, which control and drive the microLEDs. This approach eliminates issues associated with mass transfer, but comes up against a different set of obstacles. Consider the primary application on the horizon for this technology, AR glasses: there’s a need for a brightness exceeding 1 Mnits, pixel pitches below 3 mm, a resolution of up to 2K and beyond, ultra-low power consumption and acceptable cost, all in a light-weight module.

As of today, none of these specifications are being met by existing microdisplay manufacturing methods. But progress is underway. The chipmaker JBD of Shanghai, China, has introduced several impressive prototypes and is delivering modest volumes. However, high-volume manufacturing is elusive. Meanwhile, our company, MICLEDI Microdisplays of Leuven, Belgium, is making good strides on addressing issues that limit the brightness and resolution of microLED displays. To this end, we are developing an approach that’s needed to deliver high-volume, low-cost manufacturing. Read on to discover the details of the challenges we face and our compelling solutions.