Properties of Atomic Layer Deposited HfO₂Films on Ge Substrates Depending on Process Temperatures

Abstract

The effect of deposition temperature and post deposition annealing (PDA) on the electrical properties of HfO2 films grown on a Ge substrate by atomic layer deposition (ALD) was investigated. The HfO2 films deposited at 280 degrees C (280 degrees C-HfO2) showed a large capacitance-voltage (C-V) hysteresis, but it was significantly reduced at 200 degrees C (200 degrees C-HfO2). Further reduction of deposition temperature to 160 degrees C resulted in the abrupt increase of C-V hysteresis. The reduction of C-V hysteresis was originated from the smaller degree of intermixing between the HfO2 and Ge substrate with decreasing temperature, while the increase of C-V hysteresis comes from the low density of films grown at low temperatures. The C-V hysteresis characteristics were also strongly influenced by PDA temperatures. PDA temperatures higher than 550 degrees C induced a large C-V hysteresis regardless of deposition temperature. Interestingly, after the PDA process, the HfO2 grown at 200 degrees C is crystallized to the tetragonal phase, while the HfO2 grown at 280 degrees C is crystallized to the monoclinic phase. These different crystalline phases result in a lower equivalent oxide thickness in the 200 degrees C-HfO2 compared to the 280 degrees C-HfO2 (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.014204jes] All rights reserved.