Thermal reaction of polycrystalline SiC with XeF2

Abstract

Studies on the thermal reaction behavior of polycrystalline cubic silicon carbide (SiC) with effusive xenon difluoride (XeF2) have been carried out over the sample temperature (Ts) range from 300to900K using molecular beam quadrupole mass spectrometry combined with a time-of-flight technique and ex situ surface analyses, i.e., x-ray photoelectron spectroscopy (XPS) and scanning Auger microscopy (SAM). Above Ts=700K, the reaction product desorbed from the SiC surface was identified as SiF4. The flux intensity of SiF4 increases monotonically as a function of Ts above 700K. The flux intensity of XeF2 desorbed from the SiC surface decreases above Ts=700K, and at Ts=900K, approximately 10% of the incident XeF2 was found to be consumed by the thermal reaction. No ions at m∕e=31 (CF+), 50 (CF2+), and 69 (CF3+) to be ascribed to carbon fluoride species were detected under the present experimental conditions, and thus C atoms in SiC were found to remain as residue. From the XPS and SAM observations of the SiC samples exposed to XeF2 vapor at 1.8×10−4Torr, we find that fluorination of a native oxide layer formed on the SiC surface takes place at Ts=300K. At Ts=520K, the native oxide layer was partially removed from the surface, and the presence of a reaction layer composed of partially fluorinated C atoms was observed. As Ts is increased above 520K, the reaction layer becomes thicker. Above Ts=700K, a thick reaction layer mainly composed of C atoms is formed, while only the near-surface reaction layer is fluorinated. The fast desorption of SiF4 products reduces the Si concentration in the SiC surface and the residual C atoms having comprised the SiC lattice are left as the reaction layer.

Grafting and Polymer Formation on Silicon from Unsaturated Grignards: II. Aliphatic Precursors

“…This signal is probably typical of the anchoring part. Such a low-energy position of C 1s is very specific and considered as an unambiguous indication of Si−C bonding. − Similar low-energy positions for the C 1s peak are reported on alkyl-terminated silicon surfaces . Therefore, our XPS results demonstrate that Si−C bonds are present at the buried interface.…”

“…At the last stages of layer abrasion corresponding to the unique and specific low-binding-energy C 1s position (Figure , curve c), the Si 2p spectrum can be fitted with only two spin−orbit doublets (Figure a); one centered at 99.3 eV associated with bulk Si and the other one at 99.8−99.9 eV related to the Si/polymer interface (here and below the energies given are those of the 2p 3/2 line maximum). At this ultimate stage of polymer profiling, O and X signals are missing, which is plausibly due to higher sputtering yields for O and X as compared to those for C. The Si 2p contribution associated with a bulk SiC phase would appear at 100.4 eV, − as compared to 99.3 eV for bulk Si. However, for alkyl-terminated Si the chemical shift of Si 2p may be as low as 0.2−0.3 eV .…”

Site-selective local fluorination of graphene induced by focused ion beam irradiation

“…In contrast to CVD graphene on SiO 2 , epitaxial graphene on SiC has better surface quality and thus is suitable for STM imaging. However, SiC can react with injected XeF 2 gas, making the analysis of graphene using XPS more ambiguous, while SiO 2 substrate is more inert to fluorination 17 35 . Thus, CVD graphene was mainly used in fluorination experiment followed by spectroscopic analysis and epitaxial graphene was used for STM imaging.…”

Dry etching of SiC using Ar/F2plasma and XeF2plasma

“…Watanabe et al have reported on the thermal reaction of polycrystalline SiC with XeF 2 vapor. 23,24) However, there are few reports on the XeF 2 plasma etching process for the microfabrication of SiC. Therefore, we also propose a XeF 2 plasma etching process for the microfabrication of SiC.…”