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Excimer laser is used for back channel etched (BCE) a-Si TFT fabrication for the first time. KrF laser could easily and successfully lift-off ITO on photo-resist comparing to traditional chemical lift-off process. Besides, this maskless laser lift-off technology could save much process time from mask alignment step. The mechanism of laser assisted ITO lift-off (LAIL) technology was carefully studied in this paper. With suitable laser fluence energy, ITO could be precisely patterned as designed. Very wide range of laser fluence energy was obtained in our LAIL technology. TFT device fabricated by LAIL technology exhibits the same electrical characteristics performance as traditional non-lift-off one.

A barrierless Cu gate was proposed to fabricate the TFT-LCD. The wholly Cu-based gate is achieved by applying a Cu-alloy film to improve the poor adhesion of Cu to the glass substrate. The taper angle of Cu/Cu-alloy gate can be easily controlled by using the new Cu etchant. We have developed 1.8" panels with the barrierless Cu gate. Without capping any additional Cu barrier, the TFT characteristics and the reliability of the Cu gate TFT were the same as the one with the conventional metal gate such as Al and its alloys.

Abstract— In recent years, reducing the number of TFT‐manufacturing steps has become an unavoidable technology development stream for all TFT‐LCD makers for the purpose of cost reduction. In this paper, an advanced photomask‐process‐reduction technique, a three‐mask TFT process, by chemical lift‐off which is inherent of the conventional four‐mask TFT fabrication process, is proposed. The major feature of this three‐mask technique is the combining of the passivation‐layer and pixel‐electrode formation within one photolithography process. A new halftone mask (HTM) design has been applied to the photolithography process. With this new HTM design, a small SiNx island bridge was formed, located at the TFT source contact‐edge border. And it provided an ITO pixel electrical conducting path and avoided the undercut issue where ITO breaks from the gate insulator (GI). In order to enhance the chemical lift‐off efficiency, different process and structure designs were also implemented and introduced. Furthermore, a new laser lift‐off technology was adopted to improve the ability of ITO lift‐off. By using this new laser lift‐off technology, unnecessary ITO film could be easily lift‐off before photoresist stripping. Finally, the first HTM lift‐off panel was successfully demonstrated by using our new three‐mask TFT design scheme.

Reducing TFT manufacturing steps in recent years has become an unavoidable technology trend for many TFT‐ LCD makers in order of cost reduction purpose. Here, we proposed a new mask reduction process (3‐masks TFT) by chemical lift‐off which based on conventional 4‐masks TFT fabrication process. The major spirit of 3‐masks technique combines passivation layer and pixel electrode formed in one photolithography process with HTM (Half tone mask). with this new HTM design, a small SiNx island cross TFT source contact edge border could be created to provide a pixel electrode conducting path away from electrical signal opening. In order to enhance to lift‐off ability, new optional extra lift‐off enhancement designs could be adopted to improve chemical lift‐off efficiency. Through the development of process and design of TFTs using 3‐masks HTM lift‐off scheme, one first 1.8″ HTM lift‐off panel was demonstrated which exhibits same performance of conventional fabricated one.