Low Temperature Polysilicon Thin Film Transistors in Advanced Display Technologies

Abstract

Abstract : In this final project report, we detail the work completed in developing a polysilicon thin film transistor (TFT) technology that was successfully applied in fabricating a working VGA Active Matrix Organic Light Emitting Diode (AMOLED) display prototype. Using the high throughput, low cost method of Rapid Thermal Processing (RTP), we achieved glass compatible crystallization temperatures of polysilicon. We identify that RTP results in superior TFT performance uniformity, which is critical for fabrication of AMOLEDs. We successfully developed and integrated novel microelectronic processes and techniques while fabricating AMOLED displays, culminating in the demonstration of a VGA AMOLED prototype display operated at a brightness of 101 nits. Using our high throughput, low cost process polysilicon TFT technology, we fabricated display driver circuits, including low temperature shift registers that run at clock frequencies as high as 20 MHz. Finally, several processing issues that were investigated in order to improve the performance of AMOLED displays are described. This includes work on low temperature silicides for TFTs, a novel hillock-free aluminum metallization, and the ability of this aluminum metallization to form ohmic contacts to indium tin oxide.