We're happy to interview Coherent, as part of our series of interviews with MicroLED Industry Association members. Coherent is one of the world's leading laser innovators and manufacturers, providing systems and components for the production of OLED and microLED displays.
Q: Can you introduce your company and technology?
Oliver Haupt, Director, Marketing, Display Vertical, Coherent Corp: For over 50 years, we have been providing high-performing, reliable photonics-based solutions that have become the enabling tool in many applications. Today, Coherent Corp. is one of the world’s leading photonics innovators and manufacturers.
Displays are getting larger and more interactive in our homes and cars. State-of-the-art displays are slim, bendable, and high-resolution, with a wide color gamut. Future displays will range in size from tiny ones for AR/VR applications, to more than 100-inch in diagonal for very large wall TVs.
For decades, we have partnered with display companies worldwide, including many customers in the microLED field. As a leader in laser-based display equipment, we deliver laser solutions that drive innovations in display manufacturing and performance, especially for mobile devices. Lasers are critical tools for processing the tiny features of microLEDs.
Q: Can you say why you joined the MicroLED Industry Association and what it is you hope to achieve?
MicroLED displays and process technologies are still in an early stage of the overall product life cycle, with a huge growth potential. It’s valuable to have a platform to exchange knowledge, be informed about what other companies are working on, and have a coordinated way to collaborate on topics related to MicroLEDs. The events and invited talks from companies outside the MIA are a big benefit as well and revitalize the consortium.
Q: What are your biggest challenge and success to date in the microLED industry?
Starting with the success, it’s already possible to produce RGB microLED displays for very small and very large screens today with laser processing. Companies are using our equipment to lift the microLEDs from the epiwafer, transfer them to the final backplane, and if necessary, repair (remove/refill) individual dies.
The challenge is that there are many different approaches to produce microLED displays, and therefore different requirements, sizes, and processes are requested by our customers. From our perspective, the only way to make microLED displays competitive is to match the costs of other display technologies (e.g., OLEDs). The more microLEDs that can be produced on a single wafer the lower the costs can be. Smaller microLEDs require more sophisticated and precise processing equipment. Lasers have demonstrated their capability to be faster and more precise than other technologies.
Q: Can you detail your latest prototype/demonstration?
As mentioned earlier, we are engaged with many companies working on microLED displays and manufacturing technologies. The good news for us is that for some process steps, the only option is to use a laser. MicroLEDs based on GaN are mainly produced on sapphire wafers. A look to the physics gives us a perfect window for short-UV laser light. UV lasers are already producing OLED displays on large panels, a perfect match and base for the next display technology. We have been providing high-power UV laser sources and optics for industrial 24/7 manufacturing for decades. We are experts in beam shaping, so whatever beam geometry is the best for microLED processing, we can offer solutions. In our latest publications, we report that we can process microLEDs down to 5 µm, which is what customers have on their roadmaps, but most are not there today. That’s why we call our laser-based approach “future-proof.”
We offer line beam systems including UV lasers to process 6- to 8-inch wafers as well as mass transfer systems that offer superior throughput compared with alternative technologies.
Display makers have often asked us to provide a solution that they can use in their R&D departments to evaluate the process chains and determine single process steps. In response, Coherent offers a turnkey solution called UVtransfer. This multifunctional tool provides laser lift-off, mass transfer, and repair in one box. The tool demonstrates the capability of laser-based microLED processing and is designed for R&D and pilot production.
Additionally, Coherent offers another type of lasers for laser-assisted bonding (LAB). Once the microLEDs are transferred to the driving backplane, they must be bonded. In the past, this was done by heating up the entire display in a reflow oven. Now, we can use laser light to bond the microLEDs to the backplane. Advantages include defined temperature profiles to reduce bonding stress, selectivity, and large-area laser beam shaping to achieve industrial-scale throughput. We offer laser sources and beam shaping optics for LAB.
Q: How do you see microLEDs changing the display industry in the next 5-10 years?
MicroLED discussions have been around for a while -- we saw the first real samples in 2015 in our application labs. Today, in 2023, there are reports that the tech giants are going to offer the first products using microLED displays within the next two years. It’s well known that microLEDs have several advantages compared with other display technologies, but those will only materialize when the displays are price-competitive.
The OLED industry is well established and nowadays is active mainly in Korea and China. The move to epiwafer-based pixels that need to be placed individually on a driving backplane opens up opportunities to a broader industry. A lot of activities are seen in Taiwan now, where the semiconductor industry is well established. That said, the microLED display industry could be different in a couple of years from what we see now in OLED. More differentiated companies and providers are going to take some share of the forecasted strong and growing microLED market. Coherent is well prepared for the next display technology and will be a reliable partner in the future. As a global laser solutions provider, Coherent’s team is organized worldwide, and the local contacts are happy to support you.