A study of Al 2 O 3 :C films on Si(100) grown by low pressure MOCVD
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N9.2.1/T7.2.1
A study of Al2O3:C films on Si(100) grown by low pressure MOCVD M. P. Singh1, C. S. Thakur2, N. Bhat2, and S. A. Shivashankar1 Materials Research Centre, 2Electrical Communication Engineering, Indian Institute of Science Bangalore-560 012, India
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ABSTRACT We report the characterization of carbonaceous aluminium oxide, Al2O3:C, films grown on Si(100) by metalorganic chemical vapor deposition. The focus is on the study of the effects of carbon on the dielectric properties of aluminium oxide in a qualitative manner. The carbon present in the aluminium oxide film derives from aluminium acetylacetonate used as the source of aluminium. As-grown films comprise nanometer-sized grains of alumina (~ 20-50 nm) in an amorphous carbonaceous matrix, as examined by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The films are shiny; they are smooth as observed by scanning electron microscopy (SEM). An attempt has been made to explore the defects (viz., oxide charge density) in the aluminium oxide films using room temperature high frequency capacitance – voltage (C-V) and current–voltage (I-V) measurements. The hysteresis and stretch-out in the high frequency C-V plots is indicative of charge trapping. The role of heteroatoms, as characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy, in the transport of charge in Al2O3:C films is discussed. INTRODUCTION The continued scaling down of SiO2-based complementary metal-oxide-semiconductor (CMOS) devices leads to the serious problem of gate leakage (tunneling) current, prompting the search for alternative gate dielectrics [1]. Many materials, such as Al2O3, HfO2, Ta2O5 etc., are currently under consideration as the alternative gate dielectric in the coming generations of CMOS devices [1,2]. Aluminium oxide, Al2O3, is a promising candidate, because its dielectric constant is twice as high a high as that of SiO2, while the band gap is comparable [1]. Therefore, the growth and characterization of thin film of aluminium oxide on Si(100) is much of current interest [2-6]. Metalorganic chemical vapour deposition (MOCVD) is an attractive process for the fabrication of thin film and coatings of dielectric(s) because it works at relatively low growth temperatures, and provides conformal coverage of high aspect ratio features. But MOCVD may lead to the incorporation of heteroatoms, namely C and H into the film [3,4]. Choosing the appropriate precursors and CVD conditions, the composition and structure of the film-and hence its properties -can be tailored. Several attempts have been made to study the effects of CVD growth conditions and post-growth annealing on aluminium oxide films on the crystal structure, crystallinity, microstructure, defects, and interface, reactivity with Si, and on their optical and transport properties [4,5]. The effect of nitrogen on the transport properties of Al2O3 has been studied by oxidizing AlN thin films in a controlled ambient [7]. However, there are few reports addressing
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