Sequential Clustering Reactions of SiD sub 3 sup + and SiH sub 3 sup + with SiH sub 4: Another Case of Arrested Growth of Hydrogenated Silicon Particles.

Formation of hydrogenated silicon duct in silane plasmas poses one of the biggest quality control problems in the subminiaturization of silicon devices. Circumstantial evidence suggests that this dust begins as small ions of silane which grow incrementally be reactions with silane. Our current study focusses on the the sequential clustering reactions of SiH sub 3 sup +, the most abundant initial ion in silane plasmas. Rates and products of clustering reactions of SiD sub 3 sup + with SiD sub 4 and SiH sub 3 sup + with SiH sub 4 are measured in the ion cell of a Fourier transform mass spectrometer. Clustering occurs either by addition of SiD sub 2 SiH sub 2 accompanied by loss by D sub 2 or H sub 2, or by the formation and stabilization of the bimolecular adducts. All of the clustering reactions are highly inefficient and lead to bottleneck structures at small silicon sizes. Ab initio electronic structure calculations of the reaction pathways have been performed by Raghavachari.