Metal oxides

A new technology for processing metal oxide films

In order to push the boundaries for new high-end LCD and OLED type displays new semiconductor technologies are needed. Current solutions like amorphous silicon (a-Si) and low temperature polysilicon (LTPS) are limited in performance and size, respectively.
Metal oxides are currently one of the most promising materials to master these challenges as they offer several major advantages:
  • For high-resolution panels a mobility of >10 cm2/Vs is required. Only metal oxides can offer these values on substrates > Gen 6 and offer therefore universal applicability of the semiconductor.
  • Compared to silicon-based TFTs, metal oxides show an excellent performance in turn-off current, which results in two advantages: First, the low off-current means lower power consumption and offers longer operating times for mobile devices, in particular. Second, the low current leakage shortens the driving time and therefore decreases the influence of the TFTs on touch sensors. This facilitates the integration of touch screens and displays.
  • TFTs built with metal oxide semiconductors are smaller compared to a-Si which results in a high aperture ratio. Therefore the backlight intensity can be reduced which means again a lower power consumption.
  • Metal oxide TFTs have a proven potential for use in low-temperature processes needed to realize flexible displays. Regarding the high-end and novel application, it can be expected that metal oxide TFTs will be the most popular high-end display technology in the near future.
For many years Evonik has been focusing on metal oxide semiconductors in order to optimize and adapt them to the customers’ needs and conditions. Evonik has developed a coating technique to apply metal oxide material on substrates, which compares favourably with the well-established sputtering or chemical vapour deposition (CVD) technology (see section Coating). This results in iXsenic being the most effective solution in terms of price-performance ratio.

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