The reactions of boron trichloride (BCl3) and hydrazine (N2H4) with hydrogen- and halogen-terminated Si(100) surfaces were studied in order to understand the interaction of these molecules with the different terminated surfaces for designing wet chemistry-based silicon surface monolayer doping processes using carbon- and oxygen-free precursors. The reactions reported utilized hydrogen and chlorine-terminated surfaces prepared by wet chemistry and Br-terminated Si(100) prepared in ultra-high vacuum. The modification was followed primarily by X-ray photoelectron spectroscopy (XPS). Within the reaction conditions investigated, boron trichloride reacts preferentially with the Cl-terminated surface compared to H-terminated surface. The direct Si-B direct bond is formed on the Cl-Si(100) as confirmed by XPS. At 70°C, the reaction loses its selectivity and both surfaces form B-containing surface species. However, on H-terminated silicon, the boron is attached through Si-O-B rather than through Si-B bond. In addition, the reactions of hydrazine with H-terminated Si(100) and halogen-terminated Si(100) in a liquid phase were performed in order to compare the reactivity of these surfaces. The results of this reaction show that hydrazine reacts with all these surfaces forming the Si-N direct bond observed in the Si 2p region at 102.7 eV and does not show significant selectivity. Density functional theory calculations were used to supplement the experimental findings, propose the possible major surface species resulting from these reactions, and analyze the reasons for similarities and differences of surface reactivities of differently terminated Si(100) surfaces. This work provides fundamental understanding of boron and nitrogen incorporation into silicon surface using carbon- and oxygen-free compounds that can be used for further functionalization or as a means of selective doping.

Reaction of BCl3 and N2H4 with hydrogen and halogen-terminated Si(100) surfaces

ACS Spring Meeting 2021

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