Thermal decomposition of tetraethoxysilane (TEOS) on Si(111)-(7×7)

Abstract

We report results of a combined scanning tunneling microscopy and X-ray photoelectron spectroscopy study on the thermal decomposition of tetraethoxysilane (TEOS), a precursor for SiO 2 formation by chemical vapor deposition, on Si(111)-(7 × 7). Annealing after predominantly dissociative adsorption at room temperature, where triethoxysiloxane and ethyl groups are the main adsorbate species, leads to further decomposition with various products evolving, including diethoxysiloxane and further ethyl groups. This goes along with structural changes on the (7 × 7) reconstructed surface. A characteristic new structural element, with a maximum on interstitial sites, is interpreted as the very beginning of surface oxide formation.Over the last few years chemical vapor deposition (CVD) of SiO 2 has emerged as an attractive alternative for producing ultrathin dielectric layers on silicon at relatively low temperatures. One of the most frequently used precursors for this purpose is tetraethoxysilane (TEOS) [1-3]. Because of the complexity of the processes involved in oxide formation via TEOS CVD a microscopic understanding of these steps is essential for a quality improvement of the resulting insulating layers. First studies aiming at the microscopic understanding of TEOS decomposition and oxide growth involving high resolution electron energy loss spectroscopy (HREELS) [4,5], thermal desorption spectroscopy (TDS) [4,5], and X-ray photoelectron spectroscopy (XPS) [5,6], yielded information on the dissociation mechanisms and the oxide composition on Si(100)-(2 × 1). For a detailed understanding, however, locally resolved structural information on the distribution of the various decomposition products and their thermal evolution is essential, in particular for the first stages of TEOS decomposition, since the structure of the interface between the silicon substrate and the growing oxide is likely to critically influence the growth and hence the properties of the final oxide. First scanning tunneling microscopy (STM) and XPS results on the adsorption process of TEOS on Si(111)-(7 × 7) at room temperature have been published recently [7]. In that study it was found that TEOS dissociates mainly into triethoxysiloxane and ethyl groups in a highly site selective reaction, with the former species adsorbing on adatoms and the latter on rest atoms/corner hole atoms. In this work we focus on the thermal decomposition of these adsorbates upon annealing. We will concentrate on microscopic structural changes induced and on the Si(111)-(7 × 7) substrate surface. To this end we mainly evaluate STM topography images obtained after TEOS exposure and various annealing steps, supplemented by XPS results. We will restrict ourselves to the more clear case of rather low TEOS coverages, resulting from exposures of less than or equal 1 L. ExperimentalThe STM and XPS experiments were performed in two different ultra-high vacuum (UHV) systems, equipped with a pocket-size STM and a Fisons CLAM 2 XPS system, respectively, and standard equipment for surfa...

Rapid and alternative fabrication method for microfluidic paper based analytical devices

“…Tri and diethoxysiloxanes and a Si-O-Si network were formed during the reaction. Thus, the hydrophobization of the filter paper was established through the interaction with the hydroxyl groups of cellulose [37][38][39].…”

Evaluation of CVD‐Deposited SiO2 as a Sintering Aid for Cubic Boron Nitride Consolidated with Alumina by Spark Plasma Sintering

“…It has been reported that thermal decomposition of TEOS, i.e., by scission of the residual O-C bonds and reorientation of the Si-O bonds with the remaining Si = O fragments, represents the very beginning of SiO 2 phase formation. 21 In this study, the supply rate of TEOS or the SiO 2 content would essentially affect the structure.…”

The synthesis of twinned silicon carbide nanowires by a catalyst-free pyrolytic deposition technique

“…where the TEOS monomer implemented a nonlinear polymerization and formed a three-dimensional structure due to its tetrafunctional structure. The structure of the original materials would basically determine the final structure and amorphous nature of nanowires [8,14,21].…”