TECHNOLOGICAL, STRUCTURAL AND MORPHOLOGICAL ASPECTS OF SCREEN-PRINTED ITO USED IN ITO SI TYPE-STRUCTURE

ITO thin films (In2O3(Sn)) have been prepared by a screen-printing technique (SPT). Deposits obtained from a paste (ESL #3050) on a Pyrex substrate are fired in air at approximately 600-degrees-C. Layers thus realized are found to be polycrystalline. Their crystalline structure has been identified by comparing their x-ray diagram with that of pure In2O3 (ASTM). Then the crystalline texture of the films is studied as a function of fabrication parameters. X-ray diffraction pattern analysis shows that dopant tin atoms can exist outside the In2O3 matrix in an Sn3O4 minority phase. Surface transmission electron microscopy (TEM) of ITO grown on a silicon substrate shows that screen-printed ITO is granular and porous. The average grain size measured from surface TEM Micrographs is about 120 angstrom. Cross section TEM observations of the ITO/Si structure confirm that screen-printed ITO is granular and porous. Growth of an expected SiO2 interfacial layer has been pointed out. It was found that the SiO2 interfacial thickness is due to firing temperature and ITO porosities which facilitate oxygen diffusion.