Material and Electrical Characterization of HfO 2 Films for MIM Capacitors Application
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Material and Electrical Characterization of HfO2 Films for MIM Capacitors Application Hang Hu, Chunxiang Zhu*, Y. F. Lu, Y. H. Wu, T. Liew, M. F. Li, B.J. Cho, W. K. Choi, and N. Yakovlev1 Silicon Nano Device Lab, Department of Electrical and Computer Engineering National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260 Phone: 65-6874 8930 Fax: 65-6779 1103 E-mail: [email protected] 1 Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602 ABSTRACT Thin films of HfO2 high-κ dielectric have been prepared by pulsed-laser deposition (PLD) at various deposition conditions. X-ray diffraction (XRD), atomic force microscopy (AFM), and secondary ion mass spectroscopy (SIMS) were used to characterize the deposited films. Experimental results show that substrate temperature has little effect on the stoichiometry, while deposition pressure plays an important role in determining the ratio of Hf and O. The electrical properties of HfO2 Metal-Insulator-Metal (MIM) capacitors were investigated at various deposition temperatures. It is shown that the HfO2 (56 nm) MIM capacitor fabricated at 200 oC shows an overall high performance, such as a high capacitance density of ~3.0 fF/µm2, a low leakage current of 2x10-9 A/cm2 at 3 V, etc. All these indicate that the HfO2 MIM capacitors are very suitable for use in Si analog circuit applications. INTRODUCTION Recently, Metal-Insulator-Metal (MIM) capacitors in silicon analog circuit applications have attracted great attention due to their high conductive electrodes and low parasitic capacitance [1-2]. SiO2 and Si3N4 are dielectrics that are commonly used in conventional MIM capacitors [3-4]. Though they can provide good voltage linearity properties and low temperature coefficients, their capacitance density will be limited due to low dielectric constants. Therefore, to adopt high-κ dielectric materials seems to be an alternative way to provide good electrical performances, and increase the circuit density as well. Among various high-κ dielectric candidates, HfO2 has been researched as a promising material in gate dielectric of MOSFETs with great interest [5]. Therefore, it seems that HfO2 will be a very promising candidate for the MIM capacitor application. For successful integration of MIM capacitors, extremely reliable and high quality HfO2 thin films are desired. Pulsed-laser deposition (PLD) is increasingly being used to prepare a wide variety of materials in thin film form, since PLD has been established as a simple, reliable and fast technique that offers great experimental versatility [6]. More importantly, the PLD technique is well known for the quality of the layers grown at relatively lower substrate temperatures, which is suitable for MIM capacitor integrated into back-end of line (BEOL) process where a low thermal budget (≤ 400 oC) is needed. In this paper, HfO2 thin films were fabricated and investigated using PLD at various deposition conditions. The effects of deposition conditions on the physical properties of the asdepo
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