Influence of metal capping thin film transistor with different Si concentration in ZnSnO

Abstract

An amorphous metal-oxide semiconductor is emerging as a representative next-generation semiconductor material due to its high electric field mobility, excellent uniformity, and high transmittance in the visible region. The a-SZTO material shows high performance despite its In-free composition. In addition, Si acts as an excellent oxygen vacancy inhibitor to control its electrical properties and stability. Since Si has high binding energy with oxygen, the concentration of oxygen vacancies decreases as the composition of Si increases. As the Si composition increased due to the reduced oxygen vacancies, the mobility, which is an electrical characteristic, decreased from 27.90 cm2/Vs to 17.37 cm2/Vs, and the on current decreased from 7.0 x 10-4 A to 3.9 x 10-4 A, respectively. Amorphous metal-oxide limits improving its electrical properties due to oxygen vacancies by doping. According to the Si concentrations, a metal capping structure was applied to the a-SZTO thin-film transistor. In the metal capping structure, an additional metal rod is inserted between the source and drain electrodes which helps to improve the device characteristics with simple processing techniques. A systematic change was observed in the device by varying the length of the metal capping. The mobility from conventional to MC structures (40 & mu;m) is improved from 27.90 to 86.25 cm2/Vs and 17.36 to 52.91 cm2/Vs for 0 and 1 wt% of Si concentrations, respectively. As for the stability characteristics for NBTS (Negative Bias Thermal Stress), it was confirmed that as the Si concentrations increased, the threshold voltage (Vth) shift decreased from 0.85 V to 0.71 V, and the stability characteristics improved. It has been confirmed that the stability characteristics of these unique channel characteristics (with different Si concentrations) are maintained even when MC TFT is applied. When an inverter logic circuit was manufactured, an excellent voltage gain of 7.47 was obtained using MC.