Low-temperature amorphous boron nitride on Si0.7Ge0.3(001), Cu, and HOPG from sequential exposures of N2H4 and BCl3

Abstract

Low-temperature sequential exposures of N2H4 and BCl3 have been performed on Si0.3Ge0.7(001), Cu, and HOPG surfaces at 350 °C. A novel BN ALD process has been achieved on Si0.3Ge0.7(001) with 60 cycles of BN ALD producing a uniform, pinhole-free thin film with low contamination, as characterized with XPS and AFM. On Cu and Si0.3Ge0.7(001), XPS spectra indicated a near stoichiometric BN film. While AFM imaging indicated the deposition on Cu yielded nanometer-scale etching, conformal deposition was observed on Si0.3Ge0.7(001). The BN ALD also nucleated on inert HOPG via step edges. In situ STM imaging showed that cyclic exposures at 350 °C were able to decorate step edges with features ∼2 nm tall and ∼200 nm wide, indicating the propensity for BN to grow in the planar direction. The N2H4 and BCl3 ALD allows for the deposition of low oxygen, low carbon films, but to avoid etching, the growth should be nucleated by N2H4, since exposure to BCl3 can result in the formation of volatile Cl-containing surface species on many substrates. Therefore, the formation of a stable surface nitride prior to BCl3 exposure is necessary to prevent formation and desorption of volatile species from the substrate.