Studies on the Surface Reactions of Substituted Disilanes with Silica Surface
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1066-A05-07
Studies on the Surface Reactions of Substituted Disilanes with Silica Surface Tom Blomberg1, Raija Matero1, Suvi Haukka1, and Andrew Root2 1 R&D, ASM Microchemistry Ltd., Väinö Auerin katu 12 A, Helsinki, 00560, Finland 2 MagSol, Tuhkanummenkuja 2, Helsinki, 00970, Finland ABSTRACT Both CVD and ALD deposition techniques benefit from a detailed understanding of the reaction mechanisms of the precursor molecules with the surface. In this paper, the reactions of hexakis ethylaminodisilane (AHEAD™), hexamethoxydisilane and hexamethyldisilane were studied on high surface area silica granules at 200-375 °C. Silica was heat treated at 200-820 °C to control the number of surface Si-OH groups. The samples were characterized by FTIR and solid state NMR spectroscopy. After the chemisorption of the precursors with silica, Si-H bonds, not originally present in the molecules, were identified for AHEAD and hexamethoxydisilane, but not for hexamethyldisilane. It is suggested that with AHEAD and hexamethoxydisilane, cleavage of the Si-Si bond takes place during the chemisorption with Si-OH sites. Since no reaction for hexamethyldisilane at the studied temperatures was observed, a prerequisite for the reaction with Si-OH groups seems to be the presence of electronegative O or N atoms in the ligands. In the paper, possible reaction mechanisms with the various surface species are discussed. INTRODUCTION In the semiconductor industry, SiO2 is typically deposited by CVD at elevated temperatures. For instance from silane and oxygen between 300 and 500 °C, from dichlorosilane and N2O around 900 °C, and from TEOS (Si(OC2H5)4) and O2 between 650 and 750 °C. The requests for lower thermal budgets in the device processing flows call for new silicon precursors and deposition methods that work at lower temperatures. ALD is one of the most promising advanced deposition methods that can provide good quality films with excellent step coverage in deep vias and trenches. In CVD the growth is based on the continuous introduction and decomposition of the precursors to the growing surface, while in ALD the precursors are pulsed alternately to the surface and the growth relies on the chemisorption or reaction of the precursors with the reactive sites. For instance Al(CH3)3 reacts with Al-OH groups forming Al-O-Al(CH)2 surface species and CH4 gas. Thus the ligands stay intact until the ligand removal agent is introduced. Both CVD and ALD deposition techniques benefit from a detailed understanding of the reaction mechanisms of the precursor molecules with the surface. For ALD in particular, it is important to know whether the precursor is able to chemisorb and how it actually chemisorbs, in other words, which type of reactive sites it uses. In the growth of SiO2 the possible reactive sites are Si-OH or Si-O-Si groups. In this paper the reactivity and reaction mechanisms of three different disilanes, namely hexakis ethylaminodisilane (AHEAD™), hexamethoxydisilane and hexamethyldisilane were studied on high surface area silica granules at 200-37
