2088 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 50, NO. 10, OCTOBER 2003 Formation of Hafnium–Aluminum–Oxide Gate Dielectric Using Single Cocktail Liquid Source in MOCVD Process Moon Sig Joo, Byung Jin Cho, Senior Member, IEEE, Chia Ching Yeo, Daniel Siu Hung Chan, Senior Member, IEEE, Sung Jin Whoang, Shajan Mathew, Lakshmi Kanta Bera, N. Balasubramanian, and Dim-Lee Kwong Abstract—We demonstrate that a high quality metal organic chemical vapor deposition (MOCVD) HfAl x O y (hereafter HfAlO) dielectric film can successfully be deposited with a wide range of composition controllability between HfO and Al O in HfAlO using a single cocktail liquid source HfAl(MMP) (OiPr) . A com- position ratio between 45 to 90% of HfO in HfAlO is achieved by controlling deposition process parameters. The effect of the com- position ratio between HfO and Al O on the electrical proper- ties of the film is also investigated. The HfAlO film with 90% HfO (10% Al O ), which has minimum sacrifice of K value (around 19), shows a great improvement in thermal stability and significant reduction of interfacial layer growth during subsequent thermal processes, leading to the reduction in leakage current by around 2 orders of magnitude compared to pure HfO film. The HfAlO film also shows good compatibility with TaN metal gate electrode under high temperature annealing process. Index Terms—Hafnium aluminate, hafnium oxide, high-K, MOCVD, thermal stability. I. INTRODUCTION T HIN hafnium–oxide film (HfO ) has been extensively studied in recent years as a strong candidate for the next generation gate dielectric material because of its reasonably high dielectric constant value, potential compatibility with polysilicon gate process and relatively low amount of fixed charge at the interface [1]–[4]. However, the HfO film has shown a poor thermal stability which results in the increase of leakage current after subsequent thermal processes. The film is easily crystallized at a temperature as low as 400 C [5], forming grain boundaries which serve as leakage current paths and diffusion path of impurities such as oxidant [6]. Therefore, high temperature processing causes the increase of the leakage current of HfO as well as the increment of equivalent oxide thickness (EOT) due to the additional growth of interfacial Manuscript received March 26, 2003; revised May 30, 2003. This work was supported by the Singapore A STAR Research Grant EMT/TP/00/001.2 and National University of Singapore Research Grant R263-000-182-112. The re- view of this paper was arranged by Editor J. Vasi. M. S. Joo, B. J. Cho, C. C. Yeo, and D. S. H. Chan are with Silicon Nano De- vice Laboratory, Department of Electrical and Computer Engineering, National University of Singapore, Singapore 119260 (e-mail: elebjcho@nus.edu.sg). S. J. Whoang is with Jusung Engineering Co., Ltd., Kyunggi-Do 464-892, Korea. S. Mathew, L. K. Bera, and N. Balasubramanian are with the Institute of Mi- croelectronics, Singapore 117685. D.-L. Kwong is with the Department of Electrical and Computer Engineering, The University of Texas, Austin, TX 78752 USA. Digital Object Identifier 10.1109/TED.2003.816920 layer. This can pose a serious limitation to further scaling of HfO into the regime of EOT of 10 Å and below. Recently, sev- eral research groups [5],[7],[8] have reported that incorporation of Al into HfO film helps to improve the thermal stability of HfO film. In addition, the acceptably high dielectric constant value and the band offset values of HfAl x O y (hereafter HfAlO) alloy makes the film one of the most promising candidates for high-K gate dielectric application. Until now, HfAlO has been formed by using two separate metal precursors such as HfCl and Al(CH ) with H O as oxygen source in Atomic Layer Deposition (ALD) [7]–[9], or by using two sputtering targets of Hf and Al in jet vapor deposition (JVD) [5] or PVD [10]. In this paper, we demonstrate the successful deposition of high quality HfAlO film with a wide range of composition ratio controllability between HfO and Al O in HfAlO using a single cocktail liquid source in a metal organic chemical vapor deposition (MOCVD) system, which is the most suitable technique for mass production in terms of process simplicity and reproducibility. In addition, we also evaluate the effect of the composition ratio on the electrical properties of HfAlO. II. EXPERIMENTS MOCVD HfAlO films were deposited using a multi-chamber cluster tool, so that all the processes including surface nitri- dation (SN), HfAlO deposition, and post deposition annealing (PDA) were carried out without breaking the vacuum. Surface nitridation (SN) were preformed at 700 C for 1 min in an NH ambient. HfAlO films were then deposited at 350 C 600 C using a single cocktail source, HfAl(MMP) (OiPr) . Since the precursor which is a liquid at room temperature has extremely low vapor pressure of about 6.4 10 torr, a liquid delivery system (LDS) was adopted for the delivery of the precursor into the chamber. This precursor is first introduced into a vaporizer chamber by a push gas (argon) and its flow rate is controlled by liquid mass flow controller (LMFC). Another gas line of argon, called argon carrier gas, is used to vaporize the liquid precursor in the vaporizer chamber and carries the vaporized precursor into the process chamber. After deposition of high-K dielectric, post-deposition anneal (PDA) was performed at 700 C for 1 min in a N ambient. TaN was deposited for gate electrode using reactive sputtering. For comparison, pure HfO samples were also prepared by MOCVD at 400 C using Hf(OC(CH ) ) precursor contained in a bubbler system, which can be bubbled and delivered by 0018-9383/03$17.00 © 2003 IEEE