Silicon Etching during the HFCVD Diamond Growth

Abstract

The silicon etching that occurs during the CVD diamond growth has been investigated as a function of the methane content in the gas phase by SEM and AFM in the tapping mode on pristine Si(111) surfaces. Size, depth, and angular distributions of the etch pits were recorded. We evidence the strong effect of the carbon content on the etching process. The silicon etching is slightly increased with addition of 0.1−0.25% of methane in the feed gas, and depletes with larger addition of carbon. This etching occurs easily along Si(100) directions. This is explained by the better stability on (100) planes of the precursor SiH2 to remove silane than on (111) planes. A modelization of the process points out the balance between the drop of the atomic hydrogen concentration in the gas phase and the inhibition of hydrogen bulk diffusion into silicon when increasing the methane content and covering the surface with carbon. This explains the occurrence of a maximum of silicon etching. Possible consequences on the diamond nucleation process are then put forward. It is thus expected that the etching of the silicon is generally detrimental as generating low-density silicon surface such as Si(100) where diamond nucleation is inhibited.

In Situ Diagnostics of Methane/Hydrogen Plasma Interactions with Si(100)

“…1 (c). This model would be consistent with initial roughening and hydrogenation of the silicon surface prior to growth of the a-C:H film, as proposed in a previous study of diamond growth [12]. This model is supported by several experimental observations.…”

“…Less is known about the mechanisms and reaction pathways of the plasmasurface interaction Furthermore, there is still debate over the processes occurring during initial stages of a-C:H and diamond deposition. For example, recent hot-wire chemical vapor deposition studies indicate that some etching of silicon occurs during the initial nucleation stage of the deposition, and that this etching affects the deposition rate [12]. In this study, we address the issue of a-C:H film nucleation.…”

Nanostructured sp<SUP>2</SUP>-Carbon Infiltration of Mesoporous Silicon Layers

“…11 The etching was more pronounced for sample PS/C 1_7 (Fig. 2(b)) due to the expected larger concentration of monohydrogen at the sample surface when lower methane contents and higher filament temperatures are employed during HFCVD (Table I).…”

Chemical vapour infiltration of nano‐structured carbon in porous silicon

“…1) showed that the as prepared PS samples were meso-porous with a pore average diameter around 20 nm and with columnar pores developing perpendicularly to the top surface. After the carbon deposition process, all the PS/C samples preserved their columnar pores with dendritic structure, whereas on the top surface the average pore diameters increased up to 40-60 nm, most likely due to Si etching performed by monohydrogen under typical diamond CVD process conditions [7]. Moreover, the SEM analyses indicated that on the surface there were a few diamond micro-crystals and that the diamond nucleation was very low on the PS area and similar to that on the surrounding bare c-Si wafer region.…”