The Evaluation of Interface Quality in HfO₂ Films Probed by Time-Dependent Second-Harmonic Generation

Abstract

Time-dependent second-harmonic generation (TD-SHG) is an emerging sensitive and fast method to qualitatively evaluate the interface quality of the oxide/Si heterostructures, which is closely related to the interfacial electric field. Here, the TD-SHG is used to explore the interface quality of atomic layer deposited HfO₂ films on Si substrates. The critical SHG parameters, such as the initial SHG signal and characteristic time constant, are compared with the fixed charge density ($Q_{ox}$) and the interface state density ($D_{it}$) extracted from the conventional electrical characterization method. It reveals that the initial SHG signal linearly decreases with the increase in $Q_{ox}$, while $D_{it}$ is linearly correlated to the characteristic time constant. It verifies that the TD-SHG is a sensitive and fast method, as well as simple and noncontact, for evaluating the interface quality of oxide/Si heterostructures, which may facilitate the in-line semiconductor test.