ALUMINUM-BASED GATE STRUCTURE FOR ACTIVE-MATRIX LIQUID-CRYSTAL DISPLAYS

This paper describes the development of an Al-based thin-film gate str ucture for use in large, high-resolution active-matrix liquid crystal displays (AMLCDs). Aluminum films are suitable for forming the data li nes of such displays, but they are not suitable for forming the gate l ines because of the hillock-induced shorts that can occur to overlying metal lines during the heating necessary for insulator deposition. Al loying with yttrium, gadolinium, and neodymium was examined with the a im of reducing hillock and whisker formation during such heating. Alth ough Al films alloyed with 2 at.% of those metals exhibited low hilloc k densities (10-100 mm(-2)), the densities were not low enough for the fabrication of SXGA (1280 x 1024 pixels) panels. After investigation of several means to further reduce the formation of hillocks and whisk ers, the most effective approach was found to be anodization of the Al -alloy gate lines, suitably patterned for anodization, followed by pho toresist application and laser-cutting steps. Illustratively, by use o f an anodized AI-Nd (2 at.%) thin-film gate structure, the short-circu it defect rate and contact defect rate for an 11.3-in.-diagonal experi mental SVGA (800 x 600 pixels) display could be effectively reduced to zero.