Analysis and Characterization of Polycrystalline Silicon Thin-Film Transistors

Polycrystalline silicon thin-film transistors (Poly-TFTs) are getting more and more attractive for future, active-matrix, flat-panel displays (AMFPDs) and, more generally, for large-area electronic products. This is due to the relatively-large carrier mobility in polycrystalline silicon, which typically exceeds the amorphous-silicon mobility by two orders of magnitude and makes this material suitable for applications requiring a fair degree of speed or, for a given speed, the ability to drive large capacitive loads. In order to successfully design analog and digital circuitry based on TFTs, however, a clear understanding of their static and dynamic behaviour is required. In this paper, we address the issue of quantitatively modelling TFTs under static and dynamic conditions; we thus simulate their transfer and output characteristics at different temperatures using our device analysis tool (HFIELDS) which has been suitably enhanced to account for the most important physical effects occurring in TFTs. So doing, we determine a set of consistent parameter values by which very good agreement with experimental data at various temperatures is observed. Next, we simulate the switching behaviour of a saturated-load Poly-TFT inverter, and assess the suitability of TFT-based logic circuits to carry out the matrix-addressing function.