Metal Oxides Compound The Problem
July 11, 2012, FlexTech Alliance, San Francisco—David Barnes from Bizwitz talked about the various technologies and the challenges associated with them as new materials and use patterns come into being. At the same time, he cautioned that very little is actually new.
Displays depend on the characteristics of the front plane and the drive electronics. Some of the technology choices have been around for a long time. II-VI compound semiconductors has been in development for over 80 years, long before germanium and silicon transistors existed. Papers on thin-film transistors were published before World War II.
One outcome of this long-term research is that low-temperature polysilicon may become the gallium arsenide of flat-panel displays. As the industry moves beyond devices and starts looking at circuits, current research is now addressing some of the complications and the design issues associated with the new metal oxide TFTs. One paper at the Society for information display this year looked at compensating for threshold voltage changes, and designing around depletion mode complications.
As a result of all this work, we’re now seeing metal oxides move into production. The primary material seems to be IGZO (or alternatively GIZO for gallium indium zinc oxide) in a C-axis aligned crystalline (CaaC) structure. After channel deposition, the material is annealed at temperatures between 50 and 300° C. The difficulty is in reducing hydrogen and oxygen defects. A lot of functions are possible with these types of transistors.
The changes in TFT manufacturing can lead to reduced costs and competition. A negative to slope on the supply — demand curve affords increase profits for the manufacturers even with decreasing prices. New companies coming into the business will increase rivalry and decreased profits.
Technology substitutions are easily implemented from existing processes. TV will go from 20 to 80 percent MOTFT in the next four years. All this sounds very quick, but will often take up to 10 years to get there. The changing cost structures allow manufacturers to trade off market share and profitability, but long-term these choices are not sustainable.
Despite prognostications that OLED will be everywhere, LCD will still be viable for a long time. The more likely victims of these process changes will be e-ink and plasma. The technology must be optimized to serve specific markets, and no single technology is best for all possible display configurations.
The best outcome for the industry will be technology specialization and consolidation. A manufacturer could carve out a differentiated space and dominate that market. The ability to distribute capacity versus everyone piling in will depend upon differentiable capabilities. A manufacturer might be able to dominate a single segment for two or three years, because that is the incubation time for new products. If there is no unique technology there cannot be real differentiation, and a need lead will be quickly lost.
