The Preparation And The Influence Of Annealing On The Characterization Of Hafnium-based High K Films

With the dimensions of MOSFETs shrinking, the thickness of the silicon oxide hasbeen scaled down. However, the thickness of the silicon oxide scaling down below1nmwould cause quantum tunneling. In order to avoid the quantum tunneling, high k materialsare realized to replace the traditional SiO₂gate dielectric, which can keep wellperformance of MOSFETs under reliable physical thickness. High k materials haveattracted much attention and the Hf-based materials have been successful used insemiconductor technology. Hf-based materials, which have higher dielectric constant, highcrystallization temperature, good thermal stability and suitable band gap, have attractedmore and more scholars to investigate them.Annealing is essential in MOSFETs process. The structure of the high k films changeduring the annealing process, which would influence the electrical characteristics.Therefore, we investigated the effect of different annealing conditions on thecharacteristics of high k films. The structures of the high k films in relation to theannealing process were examined by XRD, XPS, SEM, AFM, Raman and so on. Besides,the influence of annealing on capacitance, flat band voltage and leakage current of high kfilm has been investigated, which is extract from CV and IV characteristics. Firstly, ultrathin HfO₂films grown by Atomic layer deposition （ALD） were annealed in differenttemperatures and atmospheres. The variation of structure and electrical characteristics ofHfO₂films were investigated. In addition, HfTaO films were deposited by Dual Ion BeamSputtering Deposition （DIBSD） technique, then proceeding with annealing on the filmsafter deposition and analyzing the structure and electrical characteristics.The experimental and analysis results indicated that:（1） HfO₂films grown by ALD have been annealed in different temperatures, and the influence of annealing temperatureon the structure and electrical characteristics of HfO₂films are investigated,（2） after theHfO₂film annealed in nitrogen, which is grown by ALD, there is a little N doped in HfO₂.The films performed better thermal stability and electrical characteristics, which due to theless traps and better densification,（3） the crystallization temperature of HfTaO filmsdeposited by DIBSD is much higher than the pure HfO₂films. Although the capacitancedecreased a little, the oxide traps and the leakage both reduced and the densification offilms enhanced.