Controlling In‐Ga‐Zn‐O Thin‐Film Resistance by Vacuum Rapid Thermal Annealing and Application to Transparent Electrode

This study reveals that an amorphous indium gallium zinc oxide film shows a large resistance change under vacuum rapid thermal annealing, whereas a zinc tin oxide film shows little resistance change under the same treatment. Based on these findings, the applicability of amorphous indium gallium zinc oxide thin films to a transparent source/drain electrode in zinc tin oxide thin‐film transistors is investigated. The optical transmittance of the amorphous indium gallium zinc oxide and amorphous zinc tin oxide films in the visible region is greater than 85%. Furthermore, a zinc tin oxide thin‐film transistor with an amorphous indium gallium zinc oxide source/drain electrode exhibits superior operation characteristics than devices with indium tin oxide source/drain electrodes, such as a lower threshold swing (from 369.96 to 315.45 mV dec−1), higher mobility (from 28.47 to 36.187 cm2 V−1s−1), and higher on/off current ratio (from 1.25 × 107 to 3.56 × 107). In addition, in positive and negative bias temperature stress tests, the zinc tin oxide thin‐film transistor with an amorphous indium gallium zinc oxide source/drain electrode shows almost equal stability compared to the zinc tin oxide thin‐film transistor with an indium tin oxide source/drain electrode. This study reveals that a‐IGZO film shows a large resistance change under vacuum RTA, whereas an a‐ZTO film shows only little resistance change under the same treatment. Based on these findings, the authors apply as a‐IGZO thin‐films to a transparent source/drain electrode in a‐ZTO thin‐film transistors. The electrical characteristics are evaluated in comparison with ITO S/D a‐ZTO TFTs.