Published by MIT
Thursday, March 22, 2012
TVs and Tablets to Get the "Retina Display" Treatment
Gadget manufacturers are adopting a manufacturing technique that will significantly increase resolution in coming months.
A manufacturing technique being adopted by companies that make gadgets for some of the biggest names in consumer tech will help them significantly improve the resolution of TV and tablet displays later this year.
Applied Materials, which makes electronics manufacturing equipment, has introduced machines that make it feasible to use an advanced approach for making displays—previously limited to R&D—at a large scale. This will enable consumer electronics companies to put screens with much higher resolution into many gadgets, Applied Materials says.
Sharper display resolution has become a popular feature with gadget buyers, and both Apple's iPhone 4 and the latest version of the iPad come with a very-high-resolution "retina display." Some competitors of Apple have launched phones with similarly high resolution displays, but no other tablets are available that can match the latest iPad's sharpness. Apple's competitors are eager to catch up. An engineer at Microsoft posted an article online this week about efforts to ready Windows 8, the next version of the company's flagship operating system, for tablets with very-high-resolution displays.
Applied Materials's new machines perform plasma-enhanced chemical vapor deposition (PECVD), a process that deposits thin films of material onto surfaces. The machinery makes it possible to produce displays that use a different material for the display's backplane—the layer of transistors that sits behind the display and controls its pixels. That material, known as indium gallium zinc oxide, or IGZO, makes it easier and cheaper to build displays with extra-dense pixels, like the one Apple installed in the latest iPad. Making displays with this kind of resolution larger than seven inches diagonally would be impossible without using IGZO, Applied Materials claims.
"I would expect to see products this year," says Doug Hayden, senior director of global product management at Applied Materials's displays division, AKT. "It will probably be tablets followed by TVs, but it will be close." In TVs, the new material will mean both higher resolution and faster refresh rates.
Although Applied Materials announced the new production equipment just this week, five customers have already installed the new machines and are using them to produce displays, says Hayden. He wouldn't name those customers, but Applied Materials is known to supply display-making equipment to Samsung, Sharp, and LG, and Sharp and Samsung are believed to supply Apple with displays for its iPad tablet.
LCD televisions and monitors, as well as mobile devices, all have displays that rely on a backplane of many thin film transistors (TFTs), each of which turns one pixel on or off. That TFT layer is typically made using a layer of amorphous silicon, so called because its atoms are not arranged in a neat crystal. However, amorphous silicon doesn't have the right electrical properties for controlling very large, or very-high-resolution, displays, says Hayden.
Electrons can't travel fast enough in amorphous silicon to drive very high refresh rates in large TVs, he says, and that same limitation is a problem for the smaller TFTs needed to build very pixel-dense high-resolution displays. Although the new iPad does use amorphous silicon, some reports suggest that the device gets significantly hotter than previous models because it pushes a low-efficiency backplane to its limit. Hayden says the best way to make similarly dense displays at this size is to switch to a different backplane material and that making displays with a pixel density matching that of the new iPad, but in larger sizes, requires using IGZO. "Amorphous silicon is a limitation," he says.
One alternative to amorphous silicon, called partially crystallized silicon, or LTPS, is already used in the iPhone 4S and other smart phones, but LTPS is about twice as expensive to use in a backplane as amorphous silicon. IGZO is only a third more expensive, says Hayden--low enough to enable a flood of TVs and tablets with significantly improved displays. IGZO could even become almost as cheap to use as amorphous silicon, as Applied Materials and its customers ramp up production, Hayden says.
Charles Annis, an analyst with DisplaySearch who tracks display manufacturing technology, says that before the year is out, Apple may be making iPads using IGZO displays. "We believe IGZO-based LCDs from Sharp are currently being evaluated by Apple, and they have a good chance of being adopted this year," he says.
That would make the iPad one of the first gadgets to use the new design. "Although several companies are close to commercializing IGZO-based displays, they are not quite there yet," says Annis. He says that Applied Materials's new equipment should help change that, and that IGZO will also likely help establish the next upgrade to TV picture quality, known as "ultra definition," which has four times the resolution of 1,080-pixel HD images.
However, Annis notes, the new equipment introduced by Applied Materials can't perform every step in the process of making a display backplane using IGZO. The machines make building up the layers of the material needed easier, but they cannot be used to pattern the actual transistors of a backplane. Methods exist for making those transistors, says Annis, but they could stand to improve.
Looking further ahead, Applied Materials's Hayden says that making it easier to use IGZO should also make flexible displays more practical to manufacture. The process takes place at room temperature, which is compatible with the plastic needed to make a bendy display. Amorphous silicon and other technologies in use today involve temperatures of several hundred degrees.
Copyright Technology Review 2013.