Post deposition anneal effect of $HfO_2$ thin film deposited by atomic layer deposition method

Abstract

In this thesis, Post Deposition Anneal (PDA) effect of HfO2 thin film deposited by Atomic Layer Deposition (ALD) method has been investigated. With optimized PDA conditions (N2, 400℃, 30min), leakage current density is decreased by 67% at VG=-2V and hysteresis is also decreased, maintaining accumulation capacitance value. Furthermore, from the Capacitance-Voltage(C-V) curve, it can be inferred that interface trapped charge density is additionally reduced. In high temperature (N2, 600℃, 30min) PDA, drastic increase of leakage current density was observed. With x-ray diffraction (XRD) result, HfO2 crystallization is a possible cause of increasing leakage current density. It was found that a major phase of crystallized HfO2 at 600℃ is monoclinic. Leakage current mechanism of optimized PDA conditions is also suggested. At low electric field, Schottky emission is dominated and at high electric field, Poole-Frenkel conduction is fitted well. Both cases, extracted dielectric constant are well matched with the one which is calculated by capacitance value.