Delivered by Publishing Technology to: Purdue University Libraries IP: 61.154.159.25 On: Thu, 11 Feb 2016 08:44:25 Copyright: American Scientific Publishers Copyright © 2014 American Scientific Publishers All rights reserved Printed in the United States of America Article Journal of Nanoscience and Nanotechnology Vol. 14, 7954–7960, 2014 www.aspbs.com/jnn Initial Surface Reaction of Di-Isopropylaminosilane on a Fully Hydroxyl-Terminated Si (001) Surface Jin-Hoon Yang, Seung-Bin Baek, and Yeong-Cheol Kim ∗ School of Energy, Materials, and Chemical Engineering, Korea University of Technology and Education, Cheonan, Chungnam 330-708, Republic of Korea We studied the interaction of di-isopropylaminosilane (SiH 3 N(C 3 H 7  2 , DIPAS) molecules with a fully hydroxyl-terminated Si (001) surface for SiO 2 thin-film growth by using density functional theory. The amino group consisting of DIPAS was chosen in order to obtain a high adsorption energy because its lone-pair electrons in the N atom would help in the adsorption of DIPAS. The absolute value of the adsorption energy (0.67 eV) of DIPAS was higher than its reaction energy barrier of 0.38 eV. Thus, DIPAS could react with the surface without desorption. The reaction between DIPAS and the surface produced a silyl group (–SiH 3 ) as a primary product and di-isopropylamine (NH(C 3 H 7  2 , DIPA) as a by-product. A second DIPAS, which was adsorbed near the pre-adsorbed DIPAS or –SiH 3 with DIPA, required higher reaction energy barriers of 3.91 or 1.92 eV, respectively, because of its interaction with the first DIPAS or DIPA. However, when the second DIPAS was adsorbed near –SiH 3 without DIPA, a low reaction energy barrier of 0.42 eV was required, indicating a negligible effect of –SiH 3 on the second DIPAS reaction. Therefore, to obtain a highly dense Si layer, DIPA must desorb from the surface. DIPA requires a relatively high desorption energy of 0.40 eV because the lone-pair electrons in the N atom of DIPA also enhance its adsorption on the surface. The high desorption energy could reduce the process window of atomic layer deposition. Keywords: Atomic Layer Deposition, Di-Isopropylaminosilane, Initial Surface Reaction, Molecule Interaction, Density Functional Theory. 1. INTRODUCTION In recent years, SiO 2 has received renewed attention as a gate spacer and gap-fill oxide in shallow trench isolation. 1 2 However, due to the miniaturization and inte- gration of semiconductor circuits, the thin SiO 2 films fab- ricated by conventional deposition processes have many problems when they are used for the above applications: unexpected dopant diffusion at high temperatures, diffi- cult film thickness controllability, and poor film quality. 3 4 Atomic layer deposition (ALD) is an alternative chemi- cal vapor deposition-like method, and it has recently come to the fore among semiconductor fabrication processes. Thanks to its self-limiting and sequential surface reactions, ALD film formation controls the film thickness layer-by- layer on an atomic scale. Moreover, the films formed by ALD provide excellent uniformity and step coverage over the entire surface. 5 6 Various silicon precursors, as ALD sources for the deposition of SiO 2 films, have been ∗ Author to whom correspondence should be addressed. investigated in the quest to obtain high-quality films at low operation temperatures. Among these silicon precursors, organoaminosilane pre- cursors have received a great deal of attention because of their catalyst-free reactions and noncorrosive by-product characteristics. 7 8 Due to the lone-pair electrons of the N atoms in the precursors, the precursors could be strongly attracted to the hydroxyl (-OH)-terminated Si surface. The resulting high adsorption energy could weaken the bond strengths between the atoms of the precursors, result- ing in the decrease of the reaction energy barriers between the precursors and the surface. 9 The by-products contain- ing the N atom, however, would be hard to desorb due to the strong attraction with the surface. Therefore, for the optimization of the ALD precursors, it would be necessary to study the effect of the N atoms in the precursors on adsorption and desorption. Lim et al. experimentally investigated the SiO 2 film using tetrakis-dimethylaminosilane (Si[N(CH 3  2  4 , TeDMAS). 10 The film deposited below 250  C showed a low dielectric constant and a leakage current. Won 7954 J. Nanosci. Nanotechnol. 2014, Vol. 14, No. 10 1533-4880/2014/14/7954/007 doi:10.1166/jnn.2014.9474