Interface reactions during processing of chemical vapor deposited yttrium oxide high-k dielectrics
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Date
2002-11-28
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Abstract
High dielectric constant (high-k) insulators are important for advanced MOS devices to limit gate leakage and increase gate capacitance. Reactions between high-k's and the substrate during deposition or post-deposition processing lead to an increase in the equivalent oxide thickness, and the mechanisms that control the changes need to be well understood. We investigate yttrium-based high-k dielectrics formed by oxygen plasma assisted CVD on Si(100), using two different yttrium diketonate precursors. Characterization techniques include IR, XPS, TEM, EELS, AES, and IV and CV electrical analysis. During deposition and post-deposition anneals a thin Y-O-Si (silicate)/SiO₂ structure due to intermixing of Y, O and Si and substrate oxidation is formed at the interface, between the Y₂O₃ and silicon. The extent of the intermixing depends on substrate surface preparation, process conditions, and annealing conditions. As-deposited Y₂O₃ films show evidence for O-H bond due to water absorption. With in-situ deposited Si capping layers, water pickup is significantly reduced, and interfacial SiO₂ layer after annealing is less than 5 Å. Analysis of reaction mechanisms suggests that Si diffusion is attributed to silicate formation, and water absorption, catalytic dissociation of residual O₂, and O₂ plasma may account for SiO₂ formation.
Nitridation of chemical vapor deposited yttrium oxide using N₂ plasma during deposition and post-deposition treatments is investigated. The use of N₂ instead of O₂ during deposition minimizes the substrate oxidation. Similar activation energies for post-deposition anneals of O₂ and N₂ films indicate substrate oxidation processes are likely the same. Bulk properties including chemical bonding, concentration and distribution of N are also studied for as-deposited and annealed films.
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Interface reaction mechanisms, High-k gate dielectrics, CVD, Yttrium Oxide
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PhD
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Chemical Engineering
