Article

Journal of Electronic Materials

, Volume 25, Issue 12, pp 1806-1817

First online:

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

  • Je-Hsiung LanAffiliated withCenter for Display Technology and Manufacturing, University of Michigan
  • , Jerzy KanickiAffiliated withCenter for Display Technology and Manufacturing, University of Michigan
  • , Anthony CatalanoAffiliated withNational Renewal Energy Laboratory
  • , James KeaneAffiliated withNational Renewal Energy Laboratory
  • , Willem den BoerAffiliated withOptical Imaging Systems Inc.
  • , Tieer GuAffiliated withOptical Imaging Systems Inc.

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Abstract

The patterning characteristics of the indium tin oxide (ITO) thin films having different microstructures were investigated. Several etching solutions (HC1, HBr, and their mixtures with HNO3) 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 HNO3 to the HC1 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.

Keywords

Al-doped zinc oxide etching, films hydrogen containing plasma indium tin oxide