Trap Reduction through O-3 Post-Deposition Treatment of Y2O3 Thin Films Grown by Atomic Layer Deposition on Ge Substrates

Abstract

For Ge-based metal-oxide-semiconductor field-effect transistor application, high-k Y2O3 thin films are deposited on Ge single-crystal substrate using atomic layer deposition. The primary drawbacks of a metal-oxide-semiconductor capacitor with pristine Y2O3 are large hysteresis and high leakage current. Through forming gas annealing (FGA), the leakage current can be reduced by approximately three orders of magnitude, along with the reduction of interface trap density. However, there is still a large hysteresis in the capacitance-voltage curves. O-3 post-deposition annealing (OPA) is used to solve the problem. The formation of the YGeOx interfacial layer through OPA and the reduction of the defect level of the Y2O3 thin film effectively decrease the hysteresis, which also decreases the leakage current. Additionally, the hysteresis is 690 mV when only FGA is performed. However, it is further reduced to 260 mV through OPA. Moreover, the remote oxygen scavenging effect using TiN/Pt electrodes prevents an unintentional increase in equivalent oxide thickness (EOT). The 4.7 nm thick Y2O3 film results in an EOT of 1.77 nm and leakage current density of 2.1 x 10(-7) A cm(-2) (at flat band voltage-1 V) after the OPA.