Are IGZO backplanes the answer for the display industry?

Are IGZO backplanes the answer for the display industry?

The display industry is undergoing a fast and fundamental shift

BY DR. KHASHA GHAFFARZADEH

The display industry has been experiencing rapid change. The centre of gravity has shifted away from Japan to Korea. This trend was made abundantly clear recently when Panasonic and Sharp announced that they are expecting a staggering combined loss of $15.2 billion in 2012. In fact, Sharp has already expressed ‘material doubt’ about its survival.

This trend has been in the making during the past decade and the Japanese display giants are set to lose all the profits they accumulated during the past twenty years. There are many reasons for this decline, but chief amongst them has been the inability to bet on the right future technologies for the right markets. The market and technological landscape in the display has been experiencing rapid change, and Korean companies have largely made the right bets and investment decisions.

The Korean giants are now under pressure too, particularly from large-scale investment taking place across China. The rapid pace of change in the market needs and technology landscape are creating opportunities for many new players, and are representing significant risks for incumbent ones. The failure to understand market drivers and technological fits can break the fortunes of incumbents.

This changing market and technological scene not only creates opportunities and risks for display manufactures, but for all those involved in existing and emerging value chains. Many material suppliers, equipment makers and technology providers will stand to benefit, while others will see their market share and revenues dwindle.

Metal oxide thin-film transistors (TFTs) are a key emerging technology in this space. They offer a set of compelling characteristics that make them a good fit in the emerging scene of the display industry. Their set of properties makes a good match for sustaining several underlying market megatrends that are shaping the industry. Indeed, Sharp has already launched 7-in. LCD display tablet based on IGZO backplanes. The intended benefits are high resolution, low power consumptions and of course product differentiation.

Metal-oxide TFTs are however stepping into crowded technological space in which many backplane solutions already exist, including various forms of silicon and organic TFTs. Many are mature, proven and cost-effective solutions, while others offer a different package of characteristics than metal oxides. None however are one-size-fits-all solutions for all market needs and segments.

At the same time however, there are still numerous unresolved technical challenges, including the question of persistent photoconductivity and narrow processing window. Metal oxides are a broad family of materials and the final choice of the best material system and the best corresponding device architecture are not yet settled. The specifics of the manufacturing process and recipes too are in a state of flux. But it is nonetheless clear that they will play a role in future displays.

Major market trends are changing the backplane functional requirements

Several major trends have been driving technological innovation in the display industry since its early days. These trends include image quality, screen size, portability and form factor. While these trends still remain strong undercurrents, new drivers are being introduced that will play a more prominent role in shaping the future of the industry.

These new drivers will open up new frontiers, both on the technology and the market side. Indeed, they enable displays to both expand their existing markets and to diversify into new spaces. They will also fragment the market, at least initially. These major drivers that are set to change the display landscape include product differentiation, flexibility, 3D, transparency, system-on-panel, power savings, interconnectivity and screen size, and new front plane technologies.

Fig. 1: How major trends have driven technology innovation in the display industry at different eras. (Source: IDTechEx, www.IDTechEx.com/oxide)

Critically, these new trends can only be sustained so long as the underlying technology can deliver the required performance demands. This is critical because the new functional needs will stretch many existing solutions beyond their performance limits, suggesting that alternative solutions will be required. One vital piece of technology that largely sets the limits of display industry is the backplane technology. The backplane is responsible for turning the individual pixels ON and OFF. It is composed of thin-film transistors, which act as the switches.

The over-arching trends in the industry are also changing the backplane requirements on several fronts. Product differentiation is resulting in multiplicity of lighting/display technologies, with each demanding a different power output and refresh rate from the backplane. For example, OLED is being increasingly adopted as a means of differentiating products. This in turn is changing the power out and spatial uniformity requirements that the backplane technology must satisfy.

Flexible displays are being developed to offer robustness in the short term, while in the long term they will aim at resolving the conflict between two diverging mega trends by making large-sized and portable devices possible. This push towards flexibility is opening up room for a new value chain consisting of new material systems. This is because many existing solutions are failing the flexibility tests, including many existing backplane solutions.

3D and ultra-high-resolution displays mandate higher refresh rates, stretching the switching speed requirements past the capability limits of today’s dominant technologies, such as amorphous silicon (aSi) TFTs. System-on-panel thinking is requiring ever more processing power to be integrated onto the panel, and therefore the backplane.

Making sense of this changing, fragmented space

This new report by IDTechEx, Metal Oxide TFT Backplanes for Displays 2013-2018: Analysis, Trends, Markets, analyzes major drivers that are shaping the display industry. The major trends examined in detail include product differentiation, size and scaling, power savings, prolonged lifetime, 3D, mechanical flexibility, rimless designs, etc. It analyses how these market drivers create market fragmentation and market opportunities.

The report will then assess how these trends create new functional needs on the technology side. It provides an in-depth review of existing and emerging thin-film transistor solutions and critically assesses the pros and cons of each. The technologies covered include various forms of silicon thin-film transistors (amorphous, nanostructure and polycrystalline), organic semiconductors, various nanostructured semiconductors and metal oxides.

Fig. 2: Radar chart showing the technological suitability of different backplane technologies for sustaining megatrends in the OLED display industry. (Source: IDTechEx, www.IDTechEx.com/oxide)

In terms of metal oxides, it assesses the different material systems available (IGZO, HIZO, IZO, ZNO, TZO, ZnO, etc) and critically assesses the merits of each. In doing so, it outlines and discusses the leading research frontiers in metal oxides science and engineering, including stability and persistent photoconductivity, processing window, p-doping, etc. The report also discusses various requirements of dielectrics for backplane solutions, and explores the material options for use as dielectrics on wide-bandgap metal-oxide semiconductors.

The report links material properties of all thin-film transistor technologies to device figures-of-merit, including mobility, sub-threshold voltage, threshold voltage, stability, contact resistance, etc. These figures-of-merit are then connected to attributes of backplanes and thereby to the emerging functional needs of the display industry as a whole. In other words, material and device properties are linked to future market needs.

OLED displays will be a critical market driver

We map out how the fragmented market for display backplane technologies will look by linking the mega trends with micro level technological details. In our assessment, we also provide a detailed outline of activities in the OLED display segment, which will be a key market driver for metal oxide TFTs. Here, we include:

• A detailed picture of the emerging value chain
• An analysis of announced production capacity
• Number of units sold by OLED display manufacturer
• Which backplane technologies are used by which manufacturers
• A detailed timeline of global venture/partnerships activities in the OLED space
• Product development time cycle for oxide semiconductors

More information on the report and sample pages are available online here: www.IDTechEx.com/oxide ■