Insights into the Nature of SiH₄−BH₃Complex:  Theoretical Investigation of New Mechanistic Pathways Involving SiH₃^•and BH₄^•Radicals

Abstract

We have investigated a new type of interaction between silane (SiH4) and borane (BH3) using high level ab initio calculations. The SiH4−BH3 complex is found to be extremely stable with the formation of a bridged hydrogen bond between SiH4 and BH3. Hence, it might have a hitherto unknown role in the mechanism of chemical vapor deposition (CVD), which is employed in the fabrication of boron doped silicon semiconductor materials. In an attempt to unravel this role and the underlying reasons responsible for the stability of this complex, we have carried out a detailed analysis based on the structure and molecular orbitals. The results indicate that the binding strength and electronic character of the bridged hydrogen bond in the SiH4−BH3 complex is between those observed in double hydrogen bridged B2H6 and mono-hydrogen bridged anion B2H7 -. In contrast to B2H6 and B2H7 -, it should be noted that the complex is stabilized by direct strong electrostatic interaction between the positively charged Si atom and the negatively charged B atom as well as by monobridged hydrogen bonding. Furthermore, we also note that the SiH4−BH3 complex would dissociate to form SiH3 • and BH4 • radicals. The existence of this complex is also inferred from good agreement between the calculated IR spectra and experimentally observed spectra of thin solid films of boron doped silicon semiconductor materials.

Theoretical Study of the Binding of Silane (SiH4) with Borane (BH3), Diborane (B2H6), and Boron Trichloride (BCl3): The Role of Core–Electron Correlation

“…It has been suggested that electron correlation is important in describing the binding of these complexes and that the Hartree−Fock (HF) method fails to predict the correct structure for the SiH 4 •••BH 3 complex. 6 Usually, core electrons are excluded from the electron correlation calculations because most chemical phenomena involve only the valence electrons. Excluding the core electrons, that is, the frozen core approximation (FC), can save significant computational cost.…”

Structural Characterization of a Boron(III) η2-σ-Silane-Complex

“…13 Nonetheless, structural characterization of unsupported Type II σ-complexes still remains an unmet challenge, despite the fact that they have long been perceived as key intermediates in σ-bond metathesis. 14 Intriguingly, theoretical studies by Kim 15 and Gordon 16 suggested that Lewis acid BH 3 could form Type II σ-complexes with SiH 4 in gas phase in which one of the H−Si bond is substantially activated. Recently Piers successfully isolated a borane-HSiEt 3 adduct with a borole derivative, 1,2,3-tris-(pentafluorophenyl)-4,5,6,7-tertafluoro-1-boraindene.…”

Experimental and theoretical investigation on binary semiconductor clusters of B/Si and Al/Si

“…Many studies have been carried out of precursor compounds used for chemical vapor deposition of boron‐doped silicon. Hu et al 20, 21. studied the reactions of SiH 4 and B 2 H 6 , and the interactions of SiH 4 and BH 3 .…”