Characterization and exposure measurement for indium oxide nanofibers generated as byproducts in the LED manufacturing environment

ABSTRACT

This article aimed to elucidate the physicochemical characteristics and exposure concentration of powder and airborne particles as byproducts generated from indium tin oxide thin film process by an electron beam evaporation method during maintenance in light-emitting diode manufacturing environment.

The chemical composition, size, shape, and crystal structure of powder and airborne particles as byproducts were investigated using a scanning electron microscope equipped with energy dispersive spectrometer, and an X-ray diffractometer. The number and mass concentration measurements of airborne particles were performed by using an optical particle counter of direct-reading aerosol monitor and an inductively coupled plasma-mass spectrometry after sampling, respectively.

The airborne particles are composed of oxygen and indium. On the other hand, the powder byproducts consist mostly of oxygen and indium, but tin was found as a minor component. The shapes of the airborne and powder byproducts were fiber type. The length and diameter of fibrous particles were approximately 500–2,000 nm and 30–50 nm, respectively. The powder byproducts indicated indium oxide nanofibers with a rhombohedral structure. On the other hand, the indium oxide used as a source material in the preparation of ITO target showed spherical morphology with a body-centered cubic structure, and it was the same as that of the pure crystalline indium oxide powder. During maintenance, the number concentrations ranged from 350–75,693 particles/ft³, and arithmetic mean±standard deviation and geometric mean±geometric standard deviation were 11,624±15,547 and 4,846±4.12 particles/ft³, respectively. Meanwhile, under the same conditions, the airborne mass concentrations of the indium based on respirable particle size (3.5 µm cut-point 50%) were 0.09–0.19 µg/m³.

Physicochemical characteristics of nanoparticle can affect toxicity so the fact that shape and crystal structure have changed is important. Thus, nanoparticle occupational toxicology greatly needs observations like this.

KEYWORDS:

• Electron beam evaporation
• indium oxide nanofibers
• indium tin oxide
• LED industry
• process byproduct

Acknowledgments

The authors are grateful to the Device Analysis Group of Yield Enhancement Team for supporting SEM-EDS analysis. The authors would like to thank the Environment Safety & Health Group of LED Business for supporting the collection of powder and airborne samples during maintenance of the ITO process equipment.