Effect of High Film Stress of Mo Source and Drain Electrodes on Electrical Characteristics of Al Doped InZnSnO TFTs

We report how the intrinsic film stress of Mo source and drain (S/D) electrodes affects the electrical properties of Al doped InZnSnO thin-film transistors (TFTs). By controlling the Ar pressure during the sputtering process, Mo films with different film stresses (1948.2 MPa and 168.8 MPa) were formed. Two kinds of TFTs were fabricated applying these films as S/D electrodes. The TFTs made with the high-stress S/D showed linear mobility (
$\mu _{\text {lin}}$
) of 29.44 cm
₂
/Vs and hysteresis of 3.39 V while the TFTs with the low-stress S/D showed
$\mu _{\text {lin}}$
of 35.25 cm
₂
/Vs and hysteresis of 1.97 V. Under positive bias temperature stress (1 MV/cm, 60°C, 3600 s),
$\text{V}_{\text {on}}$
was 4.48 V and 7.28 V for the TFTs with the low-stress S/D and high-stress S/D, respectively. X-ray photoelectron spectroscopy and finite element (FE) simulation results revealed that oxygen deficient sites in the active layer generated by the film stress of the Mo S/D induced degradation of the device characteristics.