Electrical characteristics of 8-/spl Aring/ EOT HfO/sub 2//TaN low thermal-budget n-channel FETs with solid-phase epitaxially regrown junctions

Abstract

The authors demonstrate high-performing n-channel transistors with a HfO₂/TaN gate stack and a low thermal-budget process using solid-phase epitaxial regrowth of the source and drain junctions. The thinnest devices have an equivalent oxide thickness (EOT) of 8 Aring, a leakage current of 1.5 A/cm² at V_G=1 V, a peak mobility of 190 cm²/Vmiddots, and a drive-current of 815 muA/mum at an off-state current of 0.1 muA/mum for V_DD=1.2 V. Identical gate stacks processed with a 1000-degC spike anneal have a higher peak mobility at 275 cm²/Vmiddots, but a 5-Aring higher EOT and a reduced drive current at 610 muA/mum. The observed performance improvement for the low thermal-budget devices is shown to be mostly related to the lower EOT. The time-to-breakdown measurements indicate a maximum operating voltage of 1.6 V (1.2 V at 125 degC) for a ten-year lifetime, whereas positive-bias temperature-instability measurements indicate a sufficient lifetime for operating voltages below 0.75 V