A NEW PATTERNING PROCESS CONCEPT FOR LARGE-AREA TRANSISTOR-CIRCUIT FABRICATION WITHOUT USING AN OPTICAL MASK ALIGNER

A new concept to produce large thin film transister liquid crystal dis plays (TFT-LCD's) without using an optical mask aligner is proposed wh ich emphasizes patterning technology. Some experimental thin film tran sistors (TFT's) are fabricated according to the concept and operated l ike conventional transistors fabricated by using an optical mask align er. The concept includes improvement of printing technology and develo pment of a double-layer resist method. The latter method employs a pri nted ink pattern and a photoresist. This prevents contamination of thi n films by metal impurities which affect electrical characteristics of the TFT's. A special gravure offset printing technology is proposed, composed of a large thixotropy valued UV ink, and a fine, precision et ched glass intaglio. The experimental TFT's, with a designed minimum g ate length of 10 mu m, have comparable electric characteristics to tho se of conventional poly-Si TFT's.