Characterization of stress-controlled a-IGZO thin films and their applications to thin-film transistor and micro-electromechanical system processes

The residual stress in the amorphous indium-gallium-zinc oxide (a-IGZO) thin films deposited by magnetron sputtering is reported. The films with various residual stress are characterized by atomic force microscopy, scanning electron microscopy, and X-ray diffraction. We found that the residual stress strongly depends on sputtering-gas pressure. We also found that there is relationship between residual stress and microstructure of a-IGZO thin films. In order to gain more insight for the a-IGZO thin films with various residual stress, we fabricated a-IGZO thin-film transistors (TFTs), and measured their transfer characteristics. We also fabricated a-IGZO TFTs on self-supported membrane, using micro- electromechanical systems (MEMS) process techniques, for the a-IGZO applications to MEMS devices.