Fabrication of suspended amorphous indium-gallium-zinc oxide thin-film transistors using bulk micromachining techniques

In this article, we propose a novel application of amorphous indium-gallium-zinc oxide (a-InGaZnO) thin films to micro electromechanical systems (MEMS). For this purpose, we investigated the residual stress in the a-InGaZnO thin films deposited by magnetron sputtering. The films with various residual stresses were characterized using atomic force microscopy, scanning electron microscopy, and X-ray diffraction. We found that the residual stress strongly depended on the sputtering gas pressure. In addition, we discovered a relationship between the residual stress and the microstructure in a-InGaZnO thin films. To gain more insight into the a-InGaZnO thin films with various residual stresses, we fabricated a-InGaZnO thin-film transistors (TFTs), and measured their transfer characteristics. We also fabricated a-InGaZnO TFTs on self-supported membranes, combining the typical TFT fabrication process and bulk micromachining techniques, for the application of a-InGaZnO to MEMS devices. (C) 2014 The Japan Society of Applied Physics