Liq. crystal display with capacitive-resistive coupling element - uses electrode of tantalum and dielectric of tantalum-pent-oxide between indium-tin oxide electrode contacting liq. crystal

摘要

The switching elements, used for active control of image elements in liq-crystal displays, consist of a base electrode, dielectric and counter electrode. The mfg process consists of the following steps: forming a pattern in a Ta-layer (12) deposited on a transparent substrate (10) by etching, pref forming a tapering edge, anodic oxidn of the Ta-layer to form the dielectric layer Ta-pentoxide, first annealing in vacuum, pref for 1 hr at a temp of at least 150 deg C, sputtering of the counter electrode (18), pref In-Sn-oxide, second anneal in oxygen ambient, pref in air for about 1 hr at 250-380 deg C, forming the overlap of the 2 electrodes by defining a photo resist pattern using irradiation of the resist layer, pref udner a sharp angle, through the transparent substrate, etching the counter electrode pattern. Also claimed is the use of a second dielectric layer, pref transparent, pref of Si-oxide, -nitride or -oxynitride, deposited after the first anneal. USE/ADVANTAGE - The process results in a capacitive layer with a defined voltage-current characteristic which can be adjusted by modification of the second anneal. This characteristic is symmetrical wrt polarity and contains a low conductivity region with a width dependent on the second anneal temp. The steepness of the current characteristic above this voltage depend son the dielectric thickness. The process allows these parameters to be adjusted independently and can be easily integrated with the liquid crystal mfg process.