Nanostructural characterization of thin-film transistors using a combination of scanning force microscopy and transmission electron microscopy

The nanostructure and morphology of MoTa films deposited on glass substrates as gate metals are studied by combined scanning force microscopy and plan-view transmission electron microscopy (TEM). Hydrogenated amorphous silicon bottom-gate thin-film transistors (TFTs) are used to investigate whether the deposition of each subsequent layer of metal or dielectric is a conformal process. The improvement in the electron mobility of TFTs is discussed in relation to the surface roughness of the bottom-gate metal. The conformability of the nanometer-scale multilayered structure of the TFTs is confirmed by means of cross-sectional TEM. The electron mobility of the TFTs increase with a decrease in the surface roughness of the bottom-gate metal. The improvement in the TFT performance indicates that the smooth surface of the bottom-gate metal is the key factor. (C) 1996 American Vacuum Society.