Finding a differentiated design for smartphones is not easy, but display is an important factor, and smart phone providers believe it is the key to getting the user's voice so if there is one The new display technology, which can bring significant differences in screen size, resolution, brightness and power consumption, may thus subvert the entire market.
Is MicroLED really there?
Apple's newly released iPhone X is the first iPhone to feature an OLED display - but more than its rivals Samsung and LG have launched their OLED handsets later, though Apple does not look like Samsung Like LG has its own display technology.
So, if Apple is also developing its own display technology - not only does it have all the advantages of an OLED, but even superior ... like MicroLED? Although Apple has been silent about it, the company has actually accumulated The impressive MicoLED patented product portfolio, with some speculating that it is developing the technology at its fab in Silicon Valley, purchased from Maxim in 2015. But Apple is not the only industry giant dedicated to MicroLED.
MicroLED displays consist of individual pixel-arrayed miniature LED arrays that use traditional GaN LED technology to support higher brightness, high dynamic range and wide color gamut than fast OLEDs for fast update rates , Wide viewing angle and lower power consumption. Proponents of MicroLEDs claim that their overall brightness is 30x higher than OLEDs while providing higher lumen efficiency per watt.
For a long time, whether or not Apple switched to MicroLED has been a heated talk between Apple watchers and monitor technologists, for example, long before the Apple Watch Series 3 was released, it was widely rumored that the smartwatch would be powered by a MicroLED.
However, according to Eric Virey, a veteran market and technology analyst at Yole Développement, MicroLEDs may not appear in the wearable devices market, such as Apple Watch, until at least 2019. However, Virey believes the electronics industry should pay more attention to this technology now, Because the appearance of MicroLED will not only change the appearance of the mobile device, it may also cause the display market to reshuffle the rankings.
Google joins the competition
Currently active in the field of MicroLED layout of key patents, manufacturing technology and expertise in the contest, not including in Asia, traditional consumer display manufacturers; on the contrary, are some, such as Google, Apple and Huawei and other heavyweight manufacturers Continue to invest heavily in MicroLED.
Google recently made its entry into MicroLED by investing in the Swedish maker Glo, a site in Sweden reporting that Glo was $ 15 million by direct licensing of Google and also giving Google a stake of about 13% or more of Glo. The news was not much reported, but Google's investment in Glo reflects the industry's growing interest in this emerging display technology that enables virtual reality glasses, mobile phones and tablets.
Leading the way for MicroLED to emerge is Apple's acquisition of Luxvue in 2014 - a startup that develops low-power MicroLED displays for consumer electronics applications. Apple's investment in Luxvue has caused the market to start rumored and speculating that Apple will push MicroLED .
Facebook's Oculus Rift VR business also acquired a year ago a startup called InfiniLED, which was set free in 2011 from the Tyndall National Institute in Ireland.
Earlier this year, Foxconn revealed its interest in MicroLED, which has partnered with its subsidiary Sharp to acquire an approximately 31.82% stake in eLux, a company that specializes in developing MicroLEDs for VR and augmented reality (AR) devices Technology startups.
A series of activities that have spawned numerous investments and acquisitions around MicroLED startups reflect the never-ending pursuit of a new generation of display technology in the technology industry.
The entire supply chain is facing challenges
Virey said: 'We have seen a proof-of-concept Prototype MicroLED display technology has been put in place, and now is still not enough cost and yield - but this is the key to MicroLED to achieve mass production.' 'Furthermore, he added, MicroLED's challenge exists throughout the supply chain.
Process challenges
In theory, making a MicroLED should be just like making a LED chip, but a typical LED manufacturing device is not suitable for this task, mainly because the MicroLED chip is much smaller than a typical LED chip, which means that in order to make a MicroLED, the LED chip fab needs In addition, a new manufacturing facility with 'cleaner and cleanroom' and 'higher resolution lithography' will be built.
Virey believes that semiconductor foundries would be better suited, for example, to overcome the first hurdle of creating MicroLEDs, 'If Apple and TSMC work together it should be even more helpful.'
Energy efficiency challenge
Producing LED wafers often results in some minor 'sidewall' damage, typically about 1-2 μs on 250 x 250 micron LED wafers, but Virey explains that the number of LED chips required to make a MicroLED is as small as Sidewall defects of 5x5us, 2us have been sufficient to cause damaging effects, leaving the usable area to be extremely small, accounting for only about 4% of the total wafer size.
To address this issue of energy efficiency, the MicroLED industry must take a "two-pronged approach." Virey notes that this may involve the design and manufacturing of new wafers, for example, Glo is working on nanowires, independent of CEA-Leti Aledia, a French start-up, focuses on the development of similar micron-wire technology.
Assembly challenge
In addition to making miniature LED chips, Virey said another bigger issue is the MicroLED-related assembly challenge - 'How to transfer these miniature chips to the back of the monitor?' Porting each LED to a 6-inch MicroLED display, It takes about 4 days, Virey said, in fact, a dozen companies are currently trying to solve this 'wafer-transfer technology' problem, and one of the ways to solve this problem is Vivey's 'monolithic approach.'
The monolithic approach allows MicroLEDs to grow directly on the wafer with the final display pitch, but this monolithic approach is extremely beneficial for microdisplays with high pixel density (> 2000 PPI pixels per inch for example) but does not Universal solution for MicroLEDs.
Why? Because the LED wafer size is limited to 4x6 inches.If the display spacing is too large, most of the precious wafer area will be wasted.Virey said: 'Imagine the surface of the wafer placed 100um pitch 5um MicroLED, you But wasted 99.75% of the wafer surface!
For large displays needed for mobile devices, TVs and displays, most MicroLED display manufacturers use the 'pick and place' approach of placing tiny LED chips on the back of the display.
Defect management and maintenance strategies
Virey said that what the industry needs most is a defect management and repair strategy among the various issues related to the manufacture of MicroLED displays, after all, when most high-end displays ensure zero defects, MicroLED displays will struggle to compete with PPM defect rates.
Assuming a yield of 99.5% for MicroLEDs (combined with epitaxy and wafer fabrication), and a 99% yield for both grafts and interconnects, the combined result for the two is a combined defect rate of 2000 ppm for MicroLEDs, which is certainly not good enough Is triggering large-scale research in the industry and actively seeking ways to develop MicroLED tests.
Who will win?
Virey pointed out that the pursuit of MicorLED patents is not just an Apple company, Google and Facebook are also actively involved in this technology.In addition, there are many research institutions, display manufacturers, LED manufacturers, semiconductor companies and startups, etc. , Too many 'wise men' are actively involved.
Among the participating vendors, Virey observed that Apple now has the broadest portfolio of MicroLEDs available after acquiring Luxvue, and LG and Huawei are also strong competitors.
Sony is also an early developer of MicroLED technology, a company that has been innovating in MicroLED since 2008 and has shown the 55-inch Full HD MicroLED television prototype at CES in 2012. However, Virey said that since Sony The focus of development after that time seemed to have shifted to the industrial / commercial market for large-screen displays.
It remains to be seen who will win the field in the future, but Yole sees Smartwatch as the earliest targeted MicroLED application.On the other hand, Virey also stressed that MicroLED 'will not completely replace OLED and LCD, but eventually such as Niche applications such as wearable devices, ARs, MRs and heads-up displays are in a strong position. '
Compile: Susan Hong