Polycrystalline silicon thin-film transistor technology for flexible large-area electronics

The burgeoning number of mobile consumer electronics has created a demand for lightweight, low-cost, portable displays. The development of a polycrystalline-silicon (polysilicon) thin-film transistor (TFT) technology compatible with plastic substrates will enable displays and large-area electronics that are low power, rugged and flexible. Significant challenges exist in the development of a polysilicon TFT fabrication process that is compatible with plastic substrates, since plastic has a much lower thermal budget than glass substrates. In general, superior polysilicon TFT performance is achieved with higher temperature fabrication processes because the quality of the polysilicon and gate-dielectric films are very sensitive to process temperature. In this work, an ultra-low-temperature process for fabricating high-quality self-aligned polysilicon TFTs on flexible plastic substrates is described. All fabrication steps are performed at or below 100 degreesC. Polysilicon is formed by crystallizing sputtered amorphous Si (a-Si) films using a XeCl excimer laser (lambda =308 mn) with a pulse duration of similar to 35ns. Gate oxide deposition is formed using high-density plasma (HDP) CVD, and metal films are deposited by sputtering.