Advantest Talks Semi

The Future of Display Technology: Micro LED Revolution

• Keith Schaub Vice president of Technology and Strategy at Advantest,Kotaro Hasegawa (Applied Research & Venture Team Lab leader in Japan) • Season 2 • Episode 7

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In this episode of Advantest Talks Semi, we dive into the world of Micro LED technology, a cutting-edge display innovation set to transform the way we interact with digital content. 

Join host Keith and expert Kotaro Hasegawa from Advantest (Applied Research & Venture Team Lab leader in Japan) as they discuss the evolution of display technology, the advantages of Micro LED over LCD and OLED, and its potential applications in AR, VR, and beyond. They also explore the challenges faced by Micro LED in manufacturing, cost, and testing, as well as the breakthrough approaches that could accelerate its adoption in the market. 

Don't miss this fascinating conversation on the future of display technology!

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Keith:  

The latest innovation that will be the focus of today’s podcast is micro-LED (light-emitting diode), a new display technology that is poised to completely change how we interact with digital content.  

The evolution of display technology has been rapid and transformative. 

In the early 2000s, LCD (Liquid Crystal Display) emerged, and quickly became the dominant display technology, providing bright, sharp images and low power consumption.  

A decade later, it was followed by OLED (Organic Light Emitting Diode), which brought deeper blacks, and improved contrast ratios, making images appear even more lifelike. OLED also enabled new applications like the new curved screens that are popular with gamers. In this year, in 2023, it is expected that more than 50% of all smartphones sold will ship with OLED displays. That’s up from 30% in 2019.  

But, there is something even newer, which, if you haven’t seen it, you soon will. 

Hello and welcome to Advantest Talks Semi. I’m your host Keith Schaub, Vice President of Technology and Strategy at Advantest.   

Micro LED, despite being relatively new, is already being hailed as the future of display technology,  

Micro LED displays, like all semiconductors, require testing to ensure their performance and quality. However, in addition to electrical testing, display technology must also undergo special optical testing. Therein lies the growing challenge. Micro LEDs are less than 100 microns in size, allowing for incredibly high pixel densities, but that means the testing just got a lot harder and a lot more costly.   

To take us through this exciting Micro LED display journey, we are joined by Advantest’s own Kotaro Hasegawa, (Applied Research & Venture Team Lab leader in Japan), an expert in display technology working on next-generation innovations that help to enable these new markets. Hello Kotaro, and welcome to Advantest Talks Semi. 

Kotaro: 

Hi Keith. Thanks for having me.  

Keith: 

So, Kotaro, you’ve been following this display technology for quite some time with Advantest. Let’s first talk about the underlying technology. Can you give us a brief overview of LCD and OLED technology? What are the main differences and benefits? 

Kotaro: 

Keith, as you said, LCD and OLED are two of the most popular display technologies in use today.  

While both produce high-quality images and video, they differ in several key ways that make each technology unique. 

An interesting example is their use in smartphones.  

LCD displays have been the go-to technology for smartphones for many years.  

However, in recent years, OLED displays have become popular, thanks to their ability to produce more lifelike images.  

The current display technologies are limited in their physical size., it’s difficult to go beyond 70 inches with either LCD or OLED. 

Keith: 

OK, so tell us about this new micro-LED technology. What are some of the cool new features? 

Kotaro: 

Micro LED is the next evolutionary step for display technology.  

It is cutting-edge and poised to reshape the world of digital displays.  

Unlike traditional LCD or OLED, micro-LEDs use tiny LEDs that are less than 100 microns in size, which is about the size of a human hair.  

They can all be individually controlled, provide a sharp image down to the smallest detail.  

They are also faster, and brighter, and they consume much less power, which is a key environmental benefit. And, because of how they are manufactured, they can be used for new applications like transparency. 

Moreover, micro led based technology displays could be used tiling scheme to build over 100-inch displays by tiling small display units for luxury and signage purpose TVs. 

Keith: 

Kotaro, that is interesting. You mention transparency, which I think is pretty interesting. That sounds very intriguing. What sort of new applications would use transparency? 

Kotaro: 

Imagine AR (Augmented Reality) applications where you need to overlay important digital information on top of your real-world view.  

When people hear AR, most people think about gaming, but there are many new and evolving applications outside of gaming. For example: Retail displays.  

Imagine if all the windows used transparent micro-LEDs.  

This would give a new meaning to the term ‘Window shopping’, or if the entire side of a building is architected with micro-LED.  

Because of how they are manufactured, you can tile them together to create extremely large signs or industrial AR displays for manufacturing and assembly. 

This would provide operators with real-time information about production processes or machine status. A car mechanic is a good example.  

Imagine the mechanic wearing the AR glasses can be guided and assisted, live with important information overlaid.  

You could suddenly upskill workers for a variety of industries. 

Or, for the medical field: Enabling doctors and nurses to see digital information could be used for training and for actual surgeries. 

Keith: 

Kotaro, that is pretty interesting. Me, personally, I have a VR headset, but mostly I use it for games, because it is still too big and bulky to wear for any length of time. 

Kotaro: 

Exactly. Imagine if it is 10 times lighter and lasts 10 times longer. That will change things a lot.  

Keith: 

Wow, 10x improvement, that sounds significant! How does it do that?  

Kotaro: 

That’s one of the more exciting promises of micro-LEDs.  

Studies have shown them to consume 90% less power than OLEDs in high-brightness displays.  

They use GaN , which is just a more stable and energy-efficient material. 

Their much better power efficiency makes them ideal for any type of application, especially wireless applications such as AR and VR. 

Keith: 

Kotaro, where are we with these micro-LEDs in the market? And what’s the outlook?  

Kotaro: 

Micro LED is still in the early stages and not yet widely available for commercial applications.  

However, this is all about to change.  

According to a recent market report, the global micro-LED display market is projected to grow from the current 0.1 billion US dollars to over 20 billion US dollars by 2026.  

That’s a compound annual growth rate of 89%. 

The growth is being mainly driven by the demand for high-resolution and power-efficient displays for all types of applications like we’ve been discussing here: smartphones, wearables, automotive and AR/VR.  

This new technology is poised to disrupt the industry and is expected to become a major player in the display market.  

Keith: 

That is a pretty substantial growth. What sort of new challenges are facing this new tec since it is so new.  

Kotaro:  

The 2 key challenges right now are manufacturing and cost, and they go together.  

Micro LEDs are very small, like we said, the size of a human hair.  

This makes them challenging to fabricate and assemble in high volumes with the required quality. Because of their small size, they require high-precision manufacturing to ensure uniformity and high quality across the display.  

It’s all technically do-able, it just takes time to set up the manufacturing lines with the new higher precision equipment and processes.  

And this goes to the cost challenge. Currently, micro-LEDs are more expensive to produce than LCD or OLED.  

Part of this is due to the manufacturing challenges, but part of it is the material cost is higher. 

But, as the new manufacturing advancements come on-line, the economies of scale will kick-in and those costs will start to come down, which in turn will open it up for the mass consumer applications.  

Keith: 

That makes sense. So basically, we are looking at a new technology that is just coming online. So, it’s a little bit expensive right now, and there are a lot of new tools and processes to be put in place. Sounds like that is the situation.   

Kotaro: 

Exactly. It’s not a question of ‘if’, it’s a question of ‘when’.  

Keith: 

I also imagine that there are new test challenges that we are working on as well. What are some of those?  

Kotaro:  

With these smaller sizes and higher packed densities, the quality requirements are increasing.  

When we look at these new displays, there are millions of LEDs. If even one of the LEDs has an issue, the human eye notices it. It means there is a lot of testing required for mass production.  

It’s a similar cost challenge that leading-edge processors have.  

New processors shrink, so you get more transistors in the same given area. In this case, we get more LEDs in the given area. The test cost will go up unless you do something differently.    

Keith: 

OK, so we’ve got a cost challenge. What about the actual testing of the micro-LEDs? How are they tested?  

Kotaro: 

There are two key testing aspects for testing display technology which is: 

Electrical testing and optical testing. 

For electrical testing, we are measuring the diode characteristics and looking at things like voltages, currents, and power consumption.   

One of Advantest’s greatest strengths is with HVM (High Volume Manufacturing) and massive parallel testing, which the industry uses ATE (Automatic Test Equipment) for that.  

But we also need to measure the optics themselves, so now we are talking about things like brightness and wavelengths. Think about, if, you are buying a new TV. You look at the picture and decide if it’s good or not. It’s the same idea.  

Keith: 

The optics, obviously, are challenging. How do we test the optics? 

Kotaro: 

Currently there are two typical optical test methods. 

  1. Photoluminescence test: This is a method of measuring the trend of physical properties of the emission layer as an optical response. It is a good approach to see the relative optical behavior, but it cannot detect electrical defects. 
  2. Electroluminescence test: Force current and measure optical output by using a spectrometer. It is closer to real world use case, but it’s slow. 

 

As an example, the brightness levels are critically important and are key parameters that must be tested.  

Keith: 

Ok, so how is that actually done?  

Kotaro: 

We do that at wafer test. There are two typical ways to test brightness level in HVM. 

The most popular method uses an integrating sphere with spectroradiometer.  

There is also a 2D approach using CCD cameras.  

Neither method works well for micro-LEDs because it either gets too costly or there isn’t enough accuracy. 

It’s a difficult, challenging problem, but one that Advantest has been working on for quite some time. The solution needs to meet all the technical requirements, but just as importantly, to fit within the cost envelope.  

Keith: 

Sounds like, pardon the pun, there might be some light at the end of the tunnel?  

Kotaro: 

Yes, we think we’ve come up with a new breakthrough approach that uses an embedded test cell approach. The breakthrough was coming up with a way that leverages parallel testing for both the electrical and optical testing.  

This embedded approach solves both the technical hurdles and the cost challenges, and we feel this could really help to accelerate the adoption of micro-LEDs in the market.   

Keith:  

That sounds intriguing. Is there anything more you can say about it?  

Kotaro: 

What I can tell you at this phase is that it is a completely new parallel approach that tests both the electrical and the optical in a single touch down. We looked at the older approaches, but it was not meeting our needs because of technology and cost limitations.  

Early pilots have been successful, and we have started working with prober vendors to integrate this at the test cell level, which will provide another efficiency boost.  

Keith: 

Great! It seems like this is going to be exciting to see how the micro-LED market develops in the coming months. And it’ll be interesting to see the new applications. Maybe some new transparency, maybe some larger displays; we’ll see at CES in 2024. 

Keith:  

Well, Kotaro-san, thank you so much for joining us today and sharing your insights on the emerging micro-LED market.  

Kotaro: 

Thanks, Keith, for having me. It was a pleasure.  

Keith: 

That does it for another episode of Advantest Talks Semi. Be sure to subscribe to this podcast to stay up to date on the latest technological innovations in the semiconductor industry. If you would like additional information on the latest with micro-LED testing, please contact Advantest.  

See you next time.