| In the fabrication of active-matrix liquid crystal display (AM-LCD) and active-matrix organic light-emitting diode (AM-OLED), the amorphous silicon thin-film transistor (a-Si:H TFT) technology forms the backbone of the driving electronics for the large-size displays. Transistors for such application need to have high electrical performance and stability, as well as a high production output. In this dissertation we present an advanced multi-layer amorphous silicon thin-film transistor structure with a tailored channel region for the flat-panel display application. This specially tailored channel allows the rapid deposition of the TFT's gate insulator and active material without significantly altering its electrical performance and characteristics. We first investigate the nominal film geometry that maximizes the production throughput of the transistor. We fabricate transistors with the conventional structure, and they show a field-effect mobility of 0.95 cm2 V-1 s-1, threshold voltage of 1.18 V, and subthreshold swing of 0.46 V/dec. We are able to produce multi-layer a-Si:H TFTs that show a field-effect mobility of 0.93 cm2 V-1 s -1, threshold voltage of 1.07 V, and subthreshold swing of 0.51 V/dec. However, our proposed TFT structure has a 40% shorter deposition time, which provides it with a competitive edge due to its higher throughput.;In order to further improve the applicability of our a-Si:H TFTs, we present a novel, recess contact TFT aimed to reduce the off-current level. We are able to produce TFTs with an off-current level below 10-14 A. Compared to a conventional TFT, this low off-current TFT has a comparable electrical performance in the on-regime of operation, but approximately one order of magnitude lower off-current.;Finally, we tested the electrical stability of the multi-layer a-Si:H TFTs with the tailored channel. This transistor has similar threshold voltage shift as the conventional transistors, even though the gate insulator is deposited at a high rate. Under 10,000 s of constant current bias (5.5 muA) at an elevated temperature (353 K), our TFT (W/L=24/6) has a threshold voltage of less than 4 V. |
