AVS 50th International Symposium
    Thin Films Monday Sessions
       Session TF-MoM

Paper TF-MoM5
In-situ Infrared Analysis of Atomic Layer Deposition Half-Reactions: Hafnium Diethyl- Amide Adsorption and Dissociation on SiO@sub2@ and HfO@sub2@

Monday, November 3, 2003, 9:40 am, Room 329

Session: Atomic Layer Deposition
Presenter: M.J. Kelly, North Carolina State University
Authors: M.J. Kelly, North Carolina State University
T.D. Abatemarco, North Carolina State University
G.N. Parsons, North Carolina State University
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A critical challenge in ALD is to control bond structure at the initial heterostructure interface. For example, the deposition of metal oxide dielectric materials on silicon results in unwanted substrate oxidation and uncontrolled interface structure. To better understand elementary ALD half reactions, we have built an in-situ attenuated total internal reflection infrared spectrometry system, and used it to observe adsorption, desorption and decomposition of Hf diethlyamide [Hf(N(CH@sub 2@CH@sub 3@)@sub 2@)@sub 4@] (HDA) on oxidized silicon and on deposited HfO@sub 2@ at substrate temperatures from 50 to 300°C. The effect of water exposure on adsorbed HDA was also characterized under some conditions. We find that for adsorption on thin HfO@sub 2@ at 50 and 175°C, the C-H stretching modes indicate adsorption and saturation of the molecular precursor at typical dosing pressures (10-40mTorr), followed by desorption upon pumping, consistent with molecular physisorption at low temperature. At 300°C, minimal CH stretching mode adsorption is observed, consistent with rapid decomposition of the precursor upon adsorption. At intermediate temperatures (250°C), non-self-limiting adsorption and decomposition are observed, and Si-O-H bond formation indicates silicon oxidation. Analyzing the precursor uptake curves as a function of temperature, we find that the rate of adsorption on HfO@sub 2@ is thermally activated with an effective barrier of ~0.1eV, consistent with a reduction in entropy upon adsorption. Results will be discussed in terms of the inter-relation of precursor structure and surface pretreatment on the energetics and kinetics of precursor reaction and substrate oxidation.