Constant mobility of TFT with dendritic crystallized silicon in wide temperature range and ring oscillator characteristics

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Abstract
An evaluation of the basic thin-film transistor (TFT) characteristics of polysilicon and annealed silicon films over the temperature range between 90 and 370 K is discussed. The electron mobility of solid-phase crystallized film made from an Si/sup +/-implanted disordered phase is most constant in this range, due to the improved dendritic grain boundary. Because of the almost constant mobility and threshold voltage, the temperature dependence of the n- and p-channel FET drain currents is quite small. As a result, the propagation delay time of a 19-stage ring oscillator is almost constant in a wide temperature range at about 7 ns per stage. This solid-phase-grown polysilicon TFT is expected to operate with good temperature stability in monolithic large-area LSIs such as LCDs, contact-type line sensors, etc., and has a potential for other applications.<>