Jusung MOCVD tool heralds sharper displays

25 Nov 2011

Korean equipment developer adapts LED production method to make new 'IGZO' thin-film transistors that may feature in Apple's next iPad.

Jusung Engineering, the Korean supplier of capital equipment for solar cell, LED and semiconductor manufacturing, has released a new tool that allows deposition of high-performance transparent thin-film transistors (TFTs) for next-generation liquid crystal and organic LED displays.

The tool is based on the well-known metal-organic chemical vapor deposition (MOCVD) technique, which is widely used for LED and laser diode manufacturing. Jusung has developed its tool so that it can now produce high-quality films of indium gallium zinc oxide, known as “IGZO”.

IGZO is seen as a replacement technology for amorphous silicon TFTs, because the new material has a much higher electron mobility. That means that much smaller TFTs can be used, and each pixel in a liquid crystal display can transmit more light. As a result, much more energy-efficient LCD screens can be produced – important for extending the battery life of products like tablet PCs and e-readers.

In April 2011, the Japanese electronics giant Sharp said that it had developed the first LCD panels based on IGZO, and announced plans to start mass production before the end of the year. “High energy performance LCD panels will be made possible by downsizing the transistor and by increasing the light transmittance for each pixel,” Sharp explained.

Higher resolutions
Jusung, which claims to be the only supplier of MOCVD-based equipment compatible with the latest (8th) generation of LCD panels, says that the panel makers will also be able to offer screens with higher resolutions, because the IGZO semiconductors offer much faster display refresh speeds.

The Korean firm adds that MOCVD production will allow panel manufacturers to fine-tune the IGZO composition for their individual applications – in much the same way that LED epiwafer manufacturers can alter indium gallium nitride “recipes” to suit specific types of emitter and tweak key attributes such as peak emission wavelength.

While other methods for IGZO production, such as sputtering, are available, Jusung says that these do not allow the same subtle changes in elemental ratios that MOCVD supports. The technology is also said to be compatible with OLED displays, likely to be the fastest-growing segment within the displays market over the next five years.

According to media reports this week quoting Jeffries analyst Peter Misek, Apple is likely to use Sharp’s IGZO technology in next-generation iPads and iPhones, because the new transistors would support an enhanced screen resolution of more than 300 pixels-per-inch – a level typically regarded as equivalent to “print quality” – while offering lower power consumption and extended battery life. The Apple Insider web site has suggested that the technology will debut in the third-generation iPad.

Jusung initially developed its MOCVD tool for production of conventional LEDs, in a challenge to Germany’s Aixtron and US-based Veeco Instruments – the two companies that have long dominated the global market for such tools.