Development of plasma enhanced chemical vapor deposition (PECVD) gate dielectrics for TFT applications

Abstract

This study investigated a variety of electrically insulating materials for potential use as a gate dielectric in thin-film transistor applications. The materials that were investigated include silicon dioxide and oxynitride films deposited using PECVD and LPCVD techniques. Silicon source materials included tetraethylorthosilicate (TEOS) and silane (SiH4). Oxygen sources included diatomic oxygen (O2) and nitrous oxide (N2O). The optical, electrical, and material properties of the dielectrics were analyzed using Variable Angle Spectroscopic Ellipsometry (VASE), Fourier Transform Infrared Spectroscopy (FTIR), Capacitance-Voltage (C-V) analysis and current-voltage (I-V) analysis. Transistors were also fabricated at low temperatures with different gate dielectrics to investigate the impact on device performance. While a deposited gate dielectric is intrinsically inferior to a thermally grown SiO2 layer, an objective of this study was to create a high quality gate dielectric with low levels of bulk and interface charge (Qit & Qot~1x1010 cm2); this was achieved