Surface Decomposition Kinetics of Organosilane Precursors to Silicon Carbide
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SURFACE DECOMPOSITION KINETICS OF ORGANOSILANE PRECURSORS TO SILICON CARBIDE
BIN HAN', JOHN B. HUDSON' AND LEONARD V. INTERRANTE" "Materials Engineering Department, Rensselaer Polytechnic Institute, Troy, NY 12180 "Chemistry Department, Rensselaer Polytechnic Institute, Troy, NY 12180
ABSTRACT Reactive molecular beam scattering techniques with mass spectrometric detection have been used to characterize the kinetics and mechanism of the decomposition of two 1,3-disilacyclobutane precursors to SiC on the Si(100) surface to yield SiC and gas-phase byproducts. Both compounds adsorb and desorb without dissociation at ambient temperature. Reaction probability increases with increasing surface temperature to a maximum exceeding 0.8 at 1100 K. Both compounds yield large quantities of gas-phase intermediates, while only one produces a significant yield of SiC in the initial collision. In situ and ex situ analysis of the SiC film indicate that it is stoichiometric SiC. A combination of mass spectrometric detection with time of flight analysis of surface reaction products permits formulation of a reaction scheme involving a multistep surface decomposition sequence. INTRODUCTION In previous papers from this laboratory we have described the application of cyclic carbosilanes as single component precursors in the chemical vapor deposition of silicon carbide films. The imtial study [1] involved deposition from 1,3-dimethyl-3methylsilamethylene-1,3-disilacyclobutane onto a silicon surface in a conventional hot wall reactor. Results indicated that stoichiometric SiC films could be grown at temperatures above 1070 K. In a second study [2], growth was carried out in a cold wall reactor configuration, with both the compound used initially and the related compound 1,3dimethyl-1,3-disilacyclobutane. In this case, deposition on a silicon surface at temperatures above 1030 K led to the formation of SiC films. Films grown at the lower end of this temperature range were carbon rich, with ideal stoichiometry being approached at 1150 K. In this study hydrogen, methane, C2H,, hydrocarbons and various methylsilanes were observed as byproducts of the deposition process. The results of these two studies showed significant differences in the behavior of the two compounds studied, in terms of both the temperature required for film formation and the film deposition rate. In an attempt to understand the surface chemistry involved in the precursor decomposition and film formation, we have studied the interaction of these same two compounds with clean silicon surfaces using molecular beam scattering techniques, in which only surface reactions, as opposed to gas-phase reactions, could occur, and in which the primary reaction products produced could be measured directly, without the possibility of secondary gas-phase reactions subsequent to the surface reaction process. The intent of this work is to identify the surface processes that control the deposition rate and film stoichiometry, and hopefully to suggest modifications in precursor chemistry that
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