Electronic Resource
[S.l.]
:
American Institute of Physics (AIP)
Journal of Applied Physics
68 (1990), S. 5155-5161
ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The change in the chemical surface state of polished Si wafers [p-type, (100) oriented] during storage in air at room temperature was investigated for storage times up to half a year. Measurements were performed by x-ray Photoelectron Spectroscopy (XPS) and High Resolution Electron Energy Loss Spectroscopy (HREELS). Immediately after the HF treatment (1 min 5% HF, 2 min water rinse) vibrational spectroscopy (HREELS) shows a predominant coverage of the surface with hydride groups (80%–90% of a ML), which can be inferred from the presence of the stretching (2100 cm−1), scissor (900 cm−1) and bending (640 cm−1) vibrations in the spectra. A slight additional coverage with oxygen is proved by XPS and originates from Si-OH groups (3670 cm−1) and oxygen-related hydrocarbon groups (XPS). These Si-OH groups result from an exchange reaction of Si-F with water during the two-minute water rinse. The development of an oxygen coverage during subsequent storage in air occurs extremely slowly and shows a logarithmic behavior. A monolayer coverage of oxygen (7×1014/cm2) is reached after approximately 7 days of storage in air. HREELS spectra exhibit the concurrent development of the asymmetric Si-O-Si vibration, which indicates that oxygen penetrates the lattice and breaks Si—Si bonds. During this period the Si-O-Si frequency shifts from about 1060 to 1100 cm−1.The penetration of backbonds of Si—H gets evident by broadening of the Si-H stretching vibration and finally by a shift to higher wavenumbers. Chemically shifted components of the Si 2p line (partially oxidized Si) are present with the SiO2−x component (chemical shift (approximately-greater-than)3.4 eV) becoming dominant after roughly a week. Further oxidation proceeds essentially by an increase of the SiO2 peak in combination with a steeper slope of the logarithmic growth curve. The SiO2 thickness after half a year is about 8 A(ring). The frequency of the Si-O-Si vibration shifts up to 1120 cm−1, which can be related to a growing angle of the Si-O-Si bridge. Si—H groups are still present, the final peak position is about 2220 cm−1. The measurements show an extended induction period until the monolayer range of oxide coverage is attained. We ascribe this to the passivation of the surface by hydrogen and to a HF treatment according to Very-Large-Scale-Integration standards.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.347056
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