Properties of c-axis-aligned crystalline indium–gallium–zinc oxide field-effect transistors fabricated through a tapered-trench gate process

Abstract

To achieve both low power consumption and high-speed operation, we fabricated c-axis-aligned crystalline indium–gallium–zinc oxide (CAAC-IGZO) field-effect transistors (FETs) with In-rich IGZO and common IGZO ( in atomic ratio) active layers through a simple process using trench gates, and evaluated their characteristics. The results confirm that 60-nm-node IGZO FETs fabricated through a 450 °C process show an extremely low off-state current below the detection limit (at most 2 × 10−16 A) even at a measurement temperature of 150 °C. The results also reveal that the FETs with the In-rich IGZO active layer show a higher on-state current than those with the common IGZO active layer and have excellent frequency characteristics with a cutoff frequency and a maximum oscillation frequency of up to 20 and 6 GHz, respectively. Thus, we demonstrated that CAAC-IGZO FETs with trench gates are promising for achieving both low power consumption and high-speed operation.