Patterning of transparent conducting oxide thin films by wet etching for a-Si:H TFT-LCDs

• Published in: Journal of electronic materials Vol. 25; no. 12; pp. 1806 - 1817
• Main Authors: LAN, J.-H, KANICKI, J, CATALANO, A, KEANE, J, DEN BOER, W, GU, T
• Format: Journal Article
• Language: English
• Published: New York, NY Institute of Electrical and Electronics Engineers 01.12.1996; Springer Nature B.V
• Subjects: ALUMINIUM; Applied sciences; Display; Electronics; ETCHING; Exact sciences and technology; FABRICATION; HYDROGEN; INDIUM; Indium tin oxides; MATERIALS SCIENCE; Materials Science and Semiconductors; MIXTURES; OXIDES; PLASMA; RESIDUES; SOLAR ENERGY; Solar Energy - Photovoltaics; THIN FILMS; TIN OXIDES; ZINC OXIDES; Binary compound; Silicon; Thin film transistor; Zinc Oxides; Aluminium addition; Manufacturing; Chemical etching; Experimental study; Liquid crystals; Display
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/bf02657158

The patterning characteristics of the indium tin oxide (ITO) thin films having different microstructures were investigated. Several etching solutions (HCl, HBr, and their mixtures with HNO^sub 3^) were used in this study. We have found that ITO films containing a larger volume fraction of the amorphous phase show higher etch rates than those containing a larger volume fraction of the crystalline phase. Also, the crystalline ITO films have shown a very good uniformity in patterning, and following the etching no ITO residue (unetched ITO) formation has been observed. In contrast, ITO residues were found after the etching of the films containing both amorphous and crystalline phases. We have also developed a process for the fabrication of the ITO with a tapered edge profile. The taper angle can be controlled by varying the ratio of HNO^sub 3^ to the HCl in the etching solutions. Finally, ITO films have been found to be chemically unstable in a hydrogen containing plasma environment. On the contrary, aluminum doped zinc oxide (AZO) films, having an optical transmittance and electrical resistivity comparable to ITO films, are very stable in the same hydrogen containing plasma environment. In addition, a high etch rate, no etching residue formation, and a uniform etching have been found for the AZO films, which make them suitable for a-Si:H TFT-LCD applications. [PUBLICATION ABSTRACT]