Optical reduction lithography is an established technique for producing waveguide combiners used in AR glasses. This approach leverages the well-developed infrastructure of the semiconductor supply chain, offering mature, reliable tools capable of supporting high-volume production.

Nevertheless, a waveguide combiner is a fundamentally different product than a semiconductor chip. It has its own unique set of requirements raising the valid question of how a lithography tool designed for chip manufacturing can address these.

This masterclass will explore the requirements involved and assess how lithography tools measure up to them. We’ll illustrate that some commonly mentioned industry challenges are either nonexistent or can be effectively addressed, although certain factors still require attention from waveguide combiner designers. As is true with any advanced technology, the best results come from jointly refining both product design and manufacturing methods, starting with a solid understanding of the relevant production processes.

This class will discuss the latest technology used in Optical See Through (OST) hardware and optics. MicroLED, LCOS, and Laser Beam Scanning displays; Diffractive Waveguides, Geometric Waveguides, and other combiner optics; as well as dimming technologies.

The advantages and disadvantages of the various approaches will be presented. There will also be some discussion about the issues with bringing the various technologies to market.

Micro-LED technology is widely regarded as a key enabler for next-generation displays and emerging photonic applications; however, its large-scale commercialization remains constrained by the complexity, cost, and yield limitations of transfer, bonding, and repair processes. In this masterclass, I present SITRAB (Simultaneous Transfer and Bonding), a laser-based technology developed by ETRI that fundamentally addresses these challenges by integrating micro-LED transfer and bonding into a single process step.

SITRAB is based on a Laser-Assisted/Compression Bonding process combined with a proprietary material that has already been commercialized. The technology eliminates multiple conventional process steps, reduces thermal stress, and enables high-throughput, high-yield assembly. Importantly, SITRAB is not limited to laboratory demonstrations; both the material and the associated equipment have been deployed at OSAT companies, allowing the micro-LED supply chain to transition from R&D to manufacturing readiness.

In addition, ETRI has developed a complete laser-based micro-LED transfer platform, encompassing first-, second-, and third-stage transfer technologies. Using this platform, we demonstrate full-color micro-LED displays fabricated with approximately 20 µm × 30 µm devices, as well as a 4,000 PPI monochrome micro-LED display targeting AR/VR applications.

This masterclass will focus on the practical implementation of SITRAB, lessons learned from commercialization, and its implications for scalable micro-LED manufacturing across advanced packaging, display, and photonic integration ecosystems.

Why is it so difficult to ramp-up volume manufacturing of microLED microdisplay with decent yield and cost?

Tight pitch integration of compound semiconductor with advanced node CMOS like in microLED displays requires a full wafer level monolithic approach. Dedicated microLED display fabs are hereby an unlikely solution since older generation fabs used for compound semiconductor (e.g. 4”-6”) do not have the capability and precision while Si-CMOS fabs (e.g. 200mm/300mm) require a very large CAPEX that during the slow AR market ramp up would be under-utilized for several years. Process and tool compatibility to existing CMOS foundries is therefore a must.
At pitches below 5um, the CMOS bonding is at the center and cannot be considered as an afterthought of a great LED process. In this presentation we discuss different option for CMOS integration, color generation and how they influence cost effective volume manufacturing.