Real-time spectroellipsometric characterization of nucleation, islanding, and coalescence behavior of boron films grown by soft x-ray excited chemical vapor deposition

Abstract

Real-time spectroscopic ellipsometry was applied to the in situ monitoring of soft x-ray excited chemical vapor deposition of boron films on a Si(001) substrate. While B2H6 molecules cannot reactively stick to a Si clean surface below 400 °C, the decomposition of the precursor molecule through electronic excitation enables boron atoms to secure themselves on the surface. After the incubation period had ended, boron islands began to grow at isolated nucleation centers, exhibiting the Volmer–Weber-type growth. The activation energy for creating the nucleation centers was 2.9 kcal/mol, which presumably corresponded to the clustering of deposited boron atoms. The following growth stage was scaled with an activation energy of 10.3 kcal/mol. The thermally activated process corresponded to the networking of surface-terminating hydrides while releasing H2. As further growth continued, boron islands coalesced, which eventually became two-dimensional boron film. The amorphous boron films could be transformed into a crystallite phase through postannealing at 1000 °C and they were characterized in terms of their optical properties.

Study of the phase nature of boron- and nitrogen-containing films by optical and photoelectron spectroscopy

“…The sample exhibits refractive index n = 1.71 at 632 nm and n = 1.69 at 1500 nm, which reasonably agrees with the reported values for BN. [57][58][59] For pure-B, a B-spline fit to a combined dataset of in situ (18 frames) and ex situ (18 frames) SE from eight deposition runs revealed an absorption spectrum comparable to that in the literature, [60][61][62][63][64][65][66][67][68] which can be modeled by a Tauc Lorentz (Eq. S4 35 ) oscillator.…”