a-SiGe:H and a-SiGec:H black-matrix films for Liquid Crystal Displays

Abstract

A study was made of sputtered hydrogenated-amorphous (a-)SiGe:H and a-SiGeC:H thin films, which were successfully applied to on thin film transistor (TFT) arrays as an inorganic black-matrix (BM) of liquid crystal displays (LCDs). The sheet resistance of a-SiGeC:H films is generally higher than that of an a-SiGe:H film with the same deposition conditions and the resistance can be varied widely by changing the hydrogen concentration of the film. The deposition and annealing temperatures, and the carbon concentration can also control the sheet resistance by up to about two orders of magnitude. It was found that the activation energy is higher for high sheet resistance films. The deposition conditions were optimized and the thin-film characteristics were studied by FT-IR, electron spin resonance (ESR), Rutherford back scattering (RBS), and forward recoil elastic scattering (FRES). For a crosstalk-free LCD with high contrast ratio (about 150), it was found that the sheet resistance of the BM needs to be more than 1015 ω/□ with an optical density (OD) of more than 2.3.