Nanolaminated Structural Design of PEALD InAlO TFTs for Optimizing Mobility and Stability

Simultaneous modulation of mobility and stability for InAlO (IAO) thin-film transistor (TFT) is studied through nanolaminated structural design. By optimizing and designing the growth sequence of IAO subcycles using plasma-enhanced atomic layer deposition (PEALD), IAO films with the same total subcycle numbers but different nanolaminated structures were fabricated. The film thickness and Al atomic percentage gradually decrease as the Al2O3layer becomes more centralized, which can be attributed to the etching effect of Al(CH${}_{{3}}\text {)}_{{3}}$on In2O3and the change in the surface adsorption environment of In2O3. Furthermore, as the In2O3layer thickness increases, the fabricated IAO TFTs demonstrate an improved field-effect mobility ($\mu _{\text {FE}}\text {)}$with a negligible change in bias stress stability because relatively dispersed Al2O3layers can effectively mitigate defect generation in IAO films. The optimized device exhibits a decent threshold voltage (${V}_{\text {th}}\text {)}$of −0.46 V, an ideal subthreshold swing (SS) of 64 mV, a high$\mu _{\text {FE}}$of 18.7 cm2/V$\cdot $s, and excellent bias stress stabilities with a${V}_{\text {th}}$shift of −86 and −18 mV after 60-min stress at 3 and −3 V, respectively. This methodology for designing the channel nanolaminated structure addresses the tradeoff between mobility and stability in amorphous oxide semiconductor (AOS) TFTs.