Low temperature polycrystalline silicon integrated analogue and digital display drivers

The active-matrix OLED (AMOLED) technology has emerged as the most promising candidate for the next generation of largearea highresolution flat panel displays. And, to date, excimerlaserannealed low temperature polysilicon (LTPS) is the primary thin film transistor (TFT) technology for the realization of AMOLED display backplanes. Still, for LTPS TFT AMOLED displays to establish themselves against the ubiquitous liquid crystal displays, superior image quality and affordable costs must be achieved. The picture requirements demanded by high-quality display applications can be achieved by overcoming the spatial nonuniformities of LTPS TFT electrical characteristics, which affect the uniformity of OLED driving currents on the backplane. Fabrication costs can be greatly reduced through the monolithic integration of row and column drivers on the backplane, allowing to spare the peripheral chips and leading to higher production yields. Further manufacturing cost reductions can be achieved by employing singlechannel (either NMOS or PMOS) LTPS TFT processes, which require a reduced number of fabrication process steps compared to the complementary (CMOS) approach. In the present work advanced single-channel LTPS TFT devices and electronic circuits for the realization of high-performance AMOLED backplanes and integrated digital and analogue peripheral drivers are investigated. Reliable parameter extraction processes, accurate device simulation models and layout guidelines for reducing transistor nonidealities and nonuniformities are determined. A novel threeTFTs (3T) pixel circuit, enabling the external compensation driving method for high resolution displays, is successfully implemented in a 4.4 inch qVGA PMOS LTPS TFT AMOLED display demonstrator, upon the design of a reliable cell layout and the determination of the optimum driving conditions. A novel twophase ratioed dynamic NMOS LTPS TFT shift register with a dual bootstrap output stage, conceived for addressing the two independent switching TFTs in the 3T pixel circuit, is integrated in a 4.4 inch qVGA NMOS LTPS TFT AMOLED display demonstrator. Reliable row driver operation has been achieved through the implementation of widechannel sliced TFT structures, which greatly reduce the selfheating degradation effects. The electrical behaviour of a novel NMOS singlechannel outputoffsetcompensated operational amplifier (op amp) is simulated. For the accurate implementation of basic analogue building blocks, integrated ITO thin film resistors (TFRs) and longchannel sliced TFT pairs are developed.