Session: Advances in Mass Spectrometry:

Organosilicon compounds are commonly used as precursors in chemical vapor deposition (CVD) of SiC film. The gas phase pyrolysis studies of organosilicon precursors are useful for understanding SiC film productions. As potential precursors, thermal decomposition of allyltrichlorosilane and allyltrimethylsilane at temperatures up to 1340 K were studied using flash pyrolysis coupled with molecular beam sampling and vacuum ultraviolet single-photon ionization time-of-flight mass spectrometry (VUV-SPI-TOFMS). The initial reaction of allyltrichlorosilane was homolysis of the Si-C bond, producing SiCl₃ and C₃H₅ radicals. The SiCl₃ radical then underwent sequential Cl losses to form :SiCl₂, SiCl and Si. The C₃H₅ radical also underwent secondary reactions, producing a series of C₃H_x species (m/z = 39-42), consistent with previous studies. In the pyrolysis of allyltrimethylsilane, molecular elimination reaction forming Me₂Si=CH₂ + C₃H₆ and Si-C bond ruptures producing Me₃Si + C₃H₅ and Me₂SiCH₂CH=CH₂ + CH₃ were identified as the main initiation decomposition steps. HSiMe₃ was also identified as one of the initiation reaction products. The observed secondary reactions of Me₂Si=CH₂ and Me₃Si were consistent with previous studies. Possible thermal decomposition mechanism of the Me₂SiCH₂CH=CH₂ product was also proposed.

Yi Tian

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