Quantum dots breathe new life into traditional LCD TV market.
The flat panel display (FPD) industry is undergoing a renaissance, with suppliers rolling out a dizzying array of new, high-resolution technologies for mobile devices, computers and TVs.
But despite being in the eye of the innovation storm, FPD equipment makers remain cautious—and for good reason. There are a slew of new LCD fabs being built today, mostly in China. This, in turn, is prompting fears of an LCD capacity glut in the near term.
LCD vendors from China, Korea and Taiwan all are building new fabs in China, although Chinese vendors are the most ambitious players in the arena. For example, China’s BOE Technology Group is building the world’s largest LCD fab in Hefei, China, at a cost of about $6.4 billion. Slated for completion in 2017 or 2018, BOE’s Gen 10.5 fab will produce high-resolution TV displays at sizes up to 65 inches.
In addition, Chinese LCD makers are ramping up several fabs based on low-temperature polycrystalline silicon (LTPS) technology, which is used to make smartphone displays.
China is not only driving a large percentage of LCD equipment spending today, but Chinese consumers are also the early adopters for TVs based on the latest displays. For example, Chinese consumers are among the first in line to buy 4K TVs. These ultra-high definition (UHD) TVs, have four times the resolution of today’s mainstream, high-definition LCD TVs.
What’s more, China is also the early adopter for LCD TVs based on a separate and emerging technology called quantum dots. Basically, quantum dots are inorganic semiconductor nano-crystals that can boost the color gamut in an LCD TV.
In addition, curved TVs, flexible displays, OLED TVs and other technologies are also in the FPD mix. “Five or 10 years ago we took the basic LCD technology and scaled it up to larger and larger substrates. That was the LCD story in a nutshell before the iPhone. Now, the technology is going in a number of directions,” said Max McDaniel, director and chief marketing officer for the Display Business Group at Applied Materials, one of the world’s largest FPD equipment makers.
But there are a number of challenges in terms of making next-generation displays. For example, an LCD TV consists of a number of pixels, which determine the resolution. Each pixel has a thin-film transistor (TFT) ranging from 2- to 1.5-micron geometries.
To make displays, TFT arrays are processed using deposition, etch, lithography and other steps, which are similar to semiconductor fabrication. TFT arrays are typically based on amorphous silicon (a-Si).
The TFT LCD process itself takes place on an entire, and giant, sheet of glass or substrate. LCD glass substrates could go as large as 2,880 x 3,130mm, or 9.5- x 10-feet, which is roughly the size of a garage door.
“The processes don’t sound as hard as they are in semiconductors,” Applied’s McDaniel said. “But because you are doing them on such a large area, they are difficult. In displays, that’s our challenge.”
Watching the cycles
Another challenge is to deal with the topsy-turvy FPD cycles. After years of steady growth, the FPD market hit the wall in 2012. At that time, FPD equipment spending reached $3.3 billion, a 72% drop from 2011, according to Charles Annis, an analyst at IHS.
“Since then, it has recovered on an annual basis,” Annis said. “The big shift in investment has been away from the historical leaders in this industry, Japan, Korea and Taiwan, and towards China. Several Chinese companies have invested a lot in the last few years, particularly BOE. The Chinese have been able to finance these fab expansions through joint ventures with various local governments. They have given them a wide variety of incentives, and in many cases, they are joint venture partners.”
In total, revenue for FPD equipment is expected to reach $9.1 billion in 2015, up 22% from 2014, he said. FPD equipment spending will be split nearly evenly between LCD TV and LTPS smartphone fabs in 2015, he said.
Going forward, the overall FPD market is a mixed bag. “FPD equipment spending in 2016 is currently forecast to be flat or slightly down,” Annis said.
“The long-term prognosis for the investment in total displays is relatively flat,” Applied’s McDaniel said. “It’s still an exciting industry. The demand is still growing, but on an area basis it’s growing at the same rate per year.”
Making bigger TVs
LCDs, meanwhile, are built in giant fabs. Today’s mainstream LCD TV fabs are based on Gen 8 or 8.5 technology. The term “Gen” or generation denotes the glass size. Gen 8.5 fabs produce panels at sizes of 2,200 x 2,500mm. “Gen 8 substrates are essentially designed for 55-inch TVs. You can put six 55-inch TVs efficiently on a Gen 8.5 substrate,” McDaniel said.
In 2008, Sharp built the world’s first and only Gen 10 LCD fab. Then, earlier this year, BOE announced a Gen 10.5 fab, which will produce 43- and 65-inch displays.
Other LCD makers also have Gen 10.5 fabs on the drawing board. Gen 10.5 fabs are ideal for making 60-inch or larger LCD TVs. “There will be more (Gen 10.5 fabs) than just BOE, but no one has officially announced them yet,” McDaniel said. “The real determining factor is how many of these greater than 60-inch TVs will be in demand.”
Making 60-inch and larger displays presents a number of challenges in the fab. “The biggest challenge for panel makers moving to Gen 10-type fabs is preparing the supply chain, because the plate size is so large,” according to one official from Nikon’s FPD Lithography Business Unit.
On top of that, there are more than 300 process steps to make a large-screen LCD in a fab. Basically, the entire panel undergoes the following steps in order—thin-film deposition; lithography; etch; and strip.
“For deposition, particle control, defect control and uniformity are critical. And they are all getting harder as you go to these new display types,” Applied’s McDaniel said. “And if you go to smaller pixel sizes, some of these defects that were not killer defects for HD become killer defects for your 4K TV.”
Regarding the TVs themselves, 4K TVs are gaining steam, especially in China. With resolutions of 3,840 x 2,160, 4K TVs are still relatively expensive, but the prices are tumbling almost on a daily basis.
Like 4K TVs, quantum dot TVs also are taking off in China. Basically, the quantum dots themselves come in two forms—a film or a tube. A quantum dot film or tube can be integrated into any LCD TV, whether it’s a 1080p or a 4K set. “Quantum dots give you a wider color gamut,” said Jennifer Colegrove, chief executive of Touch Display Research. “But the TVs based on quantum dots come at a higher price.”
Still, quantum-dot TVs are hot. They are breathing new life into the traditional LCD TV market. And quantum-dot TVs, in part, are pushing out demand for long-awaited OLED TVs.
In fact, most, if not all, TV makers are jumping on the quantum dot bandwagon. The technology received a huge boost earlier this year, when Samsung rolled out the first in a family of so-called SUHD TVs, based on quantum dots. Samsung licensed the quantum dot technology from Nanosys. Basically, Samsung’s SUHD TVs have 4K resolutions and a wide color gamut.
Based on the principals of quantum mechanics, quantum dots are roughly spherical in shape. “Quantum dots are inorganic semiconductor nano-crystals that emit light at a prescribed wavelength. This means that they can be tuned to any color or divisible spectrum. They can maintain this spectrally pure emission,” said John Ho, product marketing manager for QD Vision, a supplier of quantum dot technology.
Quantum dots solve a problem with today’s LCD TVs, which involves the LED-based backlight part of the set. “Traditionally, people use white LEDs, which are actually blue LEDs with gallium nitride and a yellow phosphor or a YAG phosphor. The problem with that is the phosphor is spectrally broad,” Ho said. “What you get coming out of the backlight is white light that’s going through the glass panel. But the white light isn’t very pure. The filter, which consists of a red, green and blue dye, is supposed to cut out sections of the spectrum to make a blue, green and red channel. But in fact, most color filters don’t do a great job. There’s a lot of leakage between the blue, green and red channels.”
To solve the problem, the LED can be manipulated using quantum dots. “What we do is take the GaN LEDs. Instead of putting the yellow phosphor on top, we remove that phosphor and put a tube in front of those LEDs on the edge. We fill that tube with a combination of red and green quantum dots,” he said. “What happens is the blue light will get emitted from the LEDs. Before it goes into that guide-light plate, it will hit this tube. The red and green quantum dots in that tube will absorb that high energy blue light and it will re-admit it with nearly 100% efficiency.”
One drawback is that the dots are made of binary compounds such as cadmium. Many nations have voiced their concerns over the use of cadmium in quantum dots due to environmental issues. In response, some TV makers are using cadmium-free dots. “This is still not as efficient as a cadmium-type quantum dot,” said Colegrove of Touch Display Research.
Another display technology, organic light-emitting diodes (OLEDs), is having mixed success. “OLED is seeing market success for smartphones, but not for TVs,” Applied’s McDaniel said. “OLED TVs aren’t dead, but its emergence is going to be slower than people think. Long term, OLED is the Holy Grail. You can get rid of the backlight of an LCD. That’s why OLED makes more sense. Ten years from now, I expect OLED displays to dominate.”
Today, though, the OLED manufacturing flow is complex. “The manufacturing, yield and materials challenges are big barriers,” he said. “You can’t do traditional lithography on these sensitive OLEDs. The patterning is done by evaporating the OLED materials through a fine metal mask. Then you have to overlay that.”
In any case, what’s next for TVs? There is still a crying need for more 4K TV content. Curved and flexible displays may gain appeal. And down the road, 8K TVs may take off. “We’ve heard BOE is trying to commercialize 8K,” said Colegrove of Touch Display Research, “but there is no 8K market right now.”