Growth and Physical Properties of MOCVD-Deposited Hafnium Oxide Films and Their Properties on Silicon
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N5.15.1
Growth and Physical Properties of MOCVD-Deposited Hafnium Oxide Films and Their Properties on Silicon S. Van Elshocht°, M. Caymax°, S. De Gendt°, T. Conard°, J. Pétry°, M. Claes°, T. Witters°, C. Zhao°, B. Brijs°, O. Richard°, H. Bender°, W. Vandervorst°, R. Carter°, J. Kluth+, L. Daté*, D. Pique*, and M.M. Heyns° ° Imec v.z.w., Heverlee, Belgium * Applied Materials France, Meylan, France + International Sematech, Austin, Texas, US, assignee at IMEC ABSTRACT This paper discusses metal organic chemical vapor deposited (MOCVD) HfO2 layers using tetrakis(diethylamido)hafnium (TDEAH) as precursor. We have studied the influence of the starting surface and deposition temperature on the growth kinetics and physical properties of the HfO2 layers. Important characteristics such as crystalline state, density, and organic contamination in the layers were found to be dependent on these parameters. Typical for this deposition process is the formation of an interfacial layer underneath the high-k layer. Its composition and thickness, affecting scaling of the equivalent oxide thickness, are shown to be closely related to the HfO2 process parameters mentioned above. Finally, we will show electrical results for HfO2/polySi gate stacks indicating the effect for deposition temperature. INTRODUCTION To ensure increasing device performance, the transistor gate dielectric is aggressively scaled down, rapidly approaching the physical limit of only a few atomic layers resulting in a drastic increase of the gate leakage current density. To allow further scaling, SiO2 will be replaced by materials with a higher k-value (“high-k materials”),[1, 2] where at present the most likely candidates appear to be the Hf-based materials, i.e. HfO2, HfSiOx, HfAlOx,… Besides the most obvious concerns of scaling the dielectric (equivalent oxide thickness and leakage current density), the ideal candidate should comply to a whole range of prerequisites as listed by the ITRS roadmap, including for example thermal stability up to 1000°C 10s, a mobility not lower than 95% of SiO2, etc. complicating the task of finding a suitable replacement. To be able to satisfy these requirements, obviously a high-quality HfO2 will have to be deposited, highquality meaning having a high density, smooth interfaces, an interfacial layer as thin as possible, minimal amount of contamination, and being preferably amorphous, thermally stable, etc…, all of which are important characteristics and more or less dependent on the deposition technique (for example atomic layer deposition (ALD), metal organic chemical vapor deposition (MOCVD), or physical vapor deposition (PVD)) and the precursors used. In addition, besides the deposition technique itself, also the chosen process conditions and surface preparation are of vital importance affecting the quality of the deposited layer.
N5.15.2
In this paper, we will focus on MOCVD-deposition of HfO2 where we have made an analysis of the interfacial layer formation and some bulk HfO2 properties as function of deposition temperature
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