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In-situ IR Absorption Study of Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Luis Fabián Peña, Eric C Mattson, Charith E Nanayakkara, Kolade A. Oyekan, Anupama Mallikarjunan, Haripin Chandra, Manchao Xiao, Xinjian Lei, Ronald M Pearlstein, Agnes Derecskei-Kovacs, and Yves J. Chabal Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.7b03522 • Publication Date (Web): 30 Jan 2018 Downloaded from http://pubs.acs.org on February 5, 2018
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Langmuir
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In-situ IR Absorption Study of Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride
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Luis Fabián Peña†, Eric C. Mattson†, Charith E. Nanayakkara†, Kolade A. Oyekan†, Anupama Mallikarjunan‡, Haripin Chandra‡, Manchao Xiao‡, Xinjian Lei‡, Ronald M. Pearlstein‡, Agnes Derecskei-Kovacs||, Yves J. Chabal†*
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Abstract
Department of Materials Science & Engineering, The University of Texas at Dallas, Richardson, Texas 75080, United Sates ‡ Versum Materials, Inc., 1969 Palomar Oaks Way, Carlsbad CA 92011 || Versum Materials, Inc., 7201 Hamilton Blvd., Allentown PA 18195
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Despite the success of plasma enhanced atomic layer deposition (PEALD) to deposit
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quality silicon nitride films, a fundamental understanding of the growth mechanism has been
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difficult to obtain due to a lack of in-situ characterization to probe the surface reactions non-
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invasively and the complexity of reactions induced/enhanced by the plasma. These challenges
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have hindered the direct observation of intermediate species formed during reactions. We address
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this challenge by examining the interaction of Ar plasma using atomically flat, monohydride-
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terminated Si(111) as a well-defined model surface and focusing on the initial PEALD with
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aminosilanes. In-situ IR and XPS spectroscopy reveals that an Ar plasma induces desorption of H
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atoms from H-Si(111) surfaces, leaving Si dangling bonds, and that the reaction of di-sec-
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butylaminosilane (DSBAS) with Ar plasma-treated surfaces requires the presence of both active
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sites (Si dangling bonds) and Si-H; there is no reaction on fully H-terminated or activated
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surfaces. In contrast, high-quality HF-etched Si3N4 surfaces readily react with DSBAS, resulting
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in the formation of O-SiH3. However, the presence of back-bonded oxygen in O-SiH3 inhibits H
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desorption by Ar or N2 plasmas, presumably due to stabilization of H against ion-induced
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desorption. Consequently, there is no reaction of adsorbed aminosilanes even after extensive Ar
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or N2 plasma treatments; a thermal process is necessary to partially remove H, thereby promoting
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the formation of active sites. These observations are consistent with a mechanism requiring the
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presence of both under-coordinated nitrogen and/or dangling bonds and unreacted surface
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hydrogen. Because active sites are involved, the PEALD process is found to be sensitive to the
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duration of the plasma exposure treatment and the purge time during which passivation of these
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sites can occur.
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Introduction
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Silicon nitride (Si3N4) thin films are important for applications in microelectronics such as
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dielectric layers in complementary metal oxide semiconductor (CMOS) devices,1-8 gate spacers,4,
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9-15
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temperatures (
