Compensation technology could boost AMOLED yields

Sara Ver-Bruggen - 15 Feb 2010

Canada-based Ignis, which is developing compensation technology for active matrix (AM) OLED displays, is further improving its technology to help display makers improve yields.

Increased yields bring down the expense of display manufacturing, crucial in such a cost-driven industry. Ignis has developed its core technology - to compensate for defects in AMOLED displays fabricated using amorphous and also polysilicon backplane processes - to help manufacturers prepare for volume production of AMOLED displays.

'Driving AMOLEDs is challenging because unlike pixels in liquid crystal displays, pixels in OLED devices are current driven', explains Corbin Church, VP, Ignis. 'So any variation in a thin-film-transistor (TFT) driving circuit's performance affects the OLED display's luminance.'

Over the years, in parallel with AMOLED display commercialisation, companies have developed 'fixes' to correct and compensate for the discrepancies that occur within TFT-AMOLED processes. Large TFT-LCD makers such as AUO and Samsung use compensating circuits, often designed in-house, in addition to the transistor arrays used to drive OLED pixels. Kodak also developed a process based on its OLED work, called Global Mura Compensation, to correct defects in displays.

Ignis, which was set up to commercialise technology originally developed at the University of Waterloo, focuses exclusively on compensation technologies for AMOLED displays from small to larger size dimensions. Its pixel circuit technology also integrates into existing TFT-LCD processes.

 

Mid-size

While Ignis claims its technology is applicable to all LCD panel makers - large and small - because it can integrate with all existing TFT processes, it is the smaller and mid-size players that could benefit most from Ignis's pixel circuit technology. While these companies want to exploit opportunities for AMOLED displays in smart phones and other applications, they do not have the budgets for investing in new backplane lines or financing the extensive R&D needed to develop new backplane technologies better suited to driving AMOLED frontplanes.

One such company is Prime View International, a TFT-LCD producer in Taiwan investing early in emerging display technologies with good long-term growth prospects including AMOLED and e-paper.

Ignis's focus has led it to develop sophisticated technologies such as an algorithm-based system - MaxLife - that can keep the OLED pixels in the display stabilised over time. 'It works like one big feedback loop monitoring the pixels and correcting them over time,' explains Church.

At the upcoming Society for Information Display conference Ignis will discuss advances to its technology, which will enable display manufacturers to refine AMOLED processes, to obtain good yields in volume production.

Yield improvement is a critical strategy for panel manufacturers. In the LCD market for example, a 1% increase in yield can save over $10 million a year.