Effect of Oxidizer on Chemical Vapor Deposited Hafnium Oxide-Based Nanostructures and the Engineering of their Interface
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Effect of Oxidizer on Chemical Vapor Deposited Hafnium Oxide-Based Nanostructures and the Engineering of their Interfaces with Si(100) Manish K. Singh1, Rajesh Katamreddy1, and Christos G. Takoudis1,2 1 Department of Chemical Engineering, University of Illinois at Chicago, 810 S Clinton St, Chicago, IL, 60607 2 Department of Bioengineering, University of Illinois at Chicago, 851 S Morgan St, Chicago, IL, 60607 ABSTRACT Thin films of hafnium oxide were deposited on silicon substrates using tetrakisdiethylamino hafnium as precursor. Two different oxidizers: (a) ozone/oxygen mixture, and (b) dry oxygen were used for comparative study of the effect of different oxidizers on the deposited films. The deposition using dry oxygen was carried out in a cold-wall rapid thermal processing metalorganic chemical vapor deposition (MOCVD) reactor, whereas ozone/oxygen mixture was used in a cold-wall atomic layer deposition (ALD) reactor. Annealing studies were carried out at 600 and 800 ∞C in high-purity argon at atmospheric pressure. X-ray photoelectron spectroscopy (XPS) analyses of as-deposited and annealed films were performed to study the HfO2/Si interface. The films deposited using these two different oxidizers appeared to be of comparable quality. Silicon oxide formation at the interface occurred after annealing at 600 ∞C and it increased upon further annealing at 800 ∞C. INTRODUCTION The silicon based complementary metal oxide semiconductor field effect transistor is the most important component in modern electronic devices. To meet the need for faster electronics and smaller devices, transistors have been continuously miniaturized over the past several decades. This scaling has allowed for increasingly more transistors to fit on a single chip. But this scaling has led to the silicon dioxide layer reaching a limit below which the leakage current has become too large. A possible way identified to continue miniaturization is to replace the currently used silicon dioxide layer with a suitable gate dielectric material having a higher dielectric constant (κ) [1]. The new dielectric material has to meet several criteria most important of which are: (i) it should form a good interface with silicon, and (ii) it should be thermodynamically and kinetically stable during post deposition processing at temperatures up to 1000 ∞C. In contrast to silicon oxide, which can be thermally grown, the high κ material has to be deposited. Quality of deposited films depends on the method of deposition. Industrially, metal organic chemical vapor deposition (MOCVD) and its modified version atomic layer deposition (ALD) are the two most widely used techniques for high-κ film deposition. Choice of oxidizer for these techniques strongly influences the quality of deposited films and their interfaces with Si.
Hafnium oxide (κ ~ 25) is currently one of the promising high-κ replacements. Several precursors have been studied including halide, alkoxide, and amide-based ones [2-5]. In this study, thin films of hafnium oxide are deposited using
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