High performance, amorphous InGaZnO thin-film transistors with ferroelectric ZrO2 gate insulator by one step annealing

Abstract

Ferroelectric thin film transistors (FE-TFTs) are of increasing interest for next generation memory applications. Post fabrication annealing plays a crucial role to induce ferroelectricity in the gate insulator used for FE-TFT. The one step post fabrication annealing can induce ferroelectric phase in the gate insulator and reduce the defects in the semiconductor channel layer. We report a new technique to induce the ferroelectricity in spray coated ZrO2 with sputtered amorphous InGaZnO (a-IGZO) capping layer by employing one-step annealing. We achieved a large memory window of 1.5 V, high ION/IOFF ratio of 1 × 107, and steep subthreshold swing (SS) of 0.12 V/decade by one step annealing at 550 °C. The low thermal expansion coefficient (≈ 4.31 × 10−6/K) of a-IGZO helps to induce polar orthorhombic phase by providing suitable mechanical stress to the underlying ZrO2 layer. This work provides a new approach to induce ferroelectricity in ZrO2 for high performance ferroelectric thin film transistors.