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Physical properties and electrical characteristics of H2O-based and O3-based HfO2 ?lms deposited by ALD Jibin Fan ? , Hongxia Liu, Qianwei Kuang, Bo Gao, Fei Ma, Yue Hao School of Microelectronics, Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, Xidian University, Xi'

an 710071, China a r t i c l e i n f o Article history: Received

16 September

2011 Received in revised form

14 January

2012 Accepted

17 January

2012 Available online

21 February

2012 a b s t r a c t Ozone (O3) and H2O are used as the oxidant to deposit hafnium oxide (HfO2) thin ?lms on p-type Si (100) wafers by atomic layer deposition (ALD).

The physical properties and electrical characteristics of HfO2 ?lms change greatly for different oxidants and deposition temperature. Compared with O3 as the oxidant, HfO2 ?lms grown with H2O as the oxidant are more consistent in composition and growth rate. The O3- based HfO2 ?lms have lower C impurity and higher concentration N impurity than the H2O-based HfO2 ?lms. The impact of the annealing process on the electrical properties and stability of HfO2 ?lms are also investigated. A width step is observed in the O3-based HfO2 CCV curves, which disappears after annealing process. It is because the unstable HfCOCN and HfCN bonds in O3-based HfO2 ?lms are re-bonded with the non-HfO2 oxygen after annealing process, and the binding energy of N1s shifts. ?

2012 Elsevier Ltd. All rights reserved. 1. Introduction To meet future static power dissipation constraints, Hf-based high-j dielectrics in combination with the metal gate electrodes are currently being implemented for transistor production into sub-30 nm CMOS technology nodes [1,2]. Among them, the haf- nium oxide has been extensively studied as a potential alternative to silicon dioxide. H2O and tetrakis (ethylmethylamino) hafnium (TEMAH) are used as the oxidant and the hafnium precursor, respectively [3,4]. However, one of the disadvantages of H2O-based ALD is the high concentration hydroxyl groups in the ?lms, which degrades the dielectric interface during the post-deposition anneal- ing process. Meanwhile, the purge time is needed suf?ciently due to H2O tends to physisorb on the surface strongly, especially at low temperature [5,6]. To solve this problem, O3 is used as one of the most promising alternative oxidants in ALD process, due to its strong oxidization and high volatility [7]. However, the mechanism of O3-based ALD HfO2 has not been understood completely because its by-products cannot be accurately determined. In this work, the HfO2 ?lms are deposited using different oxi- dants at different deposition temperature. TEMAH is used as the hafnium precursor, H2O and O3 are used as the different oxidants, respectively. The HfO2 ?lms are annealed with thermal treatments in nitrogen atmosphere. The impurities and composition of the ?lms are analyzed by X-ray photoelectron spectrometer (XPS). The ?at-band voltage and the hysteresis of the layers are analyzed by the mercury-probe CCV testing system. 2. Experiments The wafers are obtained after RCA cleaning and

30 s dip in diluted HF solution to remove the native oxide, which followed by

60 s rinse in deionized water. Liquid TEMAH is used as the haf- nium precursor. The container of Hf precursor is heated to

95 °C, corresponding to the vapor pressure of 10C15 hPa. When H2O is used as the oxidant, the container is set at the room temperature, corresponding to a vapor pressure of

7 hPa. The ozone generator uses the ultra pure O2 (99.995%) to obtain O3, the concentration is