Si diffusion

In addition to the configuration, electronic stmcture and thennal stability of point defects, it is essential to know how they diffuse. A variety of mechanisms have been identified. The simplest one involves the diffusion of an impurity tlirough the interstitial sites. For example, copper in Si diffuses by hopping from one tetrahedral interstitial site to the next via a saddle point at the hexagonal interstitial site. 

The effect of low energy (0.4 eV) H+ ion implantation into Si diffused with Ti, V or Cr has also been examined (Singh et al., 1986). The electrically active concentration of a Cr-related level at Ev + 0.30 eV was reduced after hydrogenation, although substantial loss of this level was also... 

Enhanced Al/Si diffusion in KAlSisOg at high pressures the effect of hydrogen. /. Geol. 96, 109-124. 

Instead, the approach taken was to anneal the polycide films at temperatures over 800°C. In this case. Si diffused up to the TasSi3 film in sufficient quantity to convert it to TaSi2. An anneal at 1000°C for 15 minutes in argon produced a resistivity of 48 n l-cm in 2500 A thick TaSi2 layers. 

Sputtered TiW and TiN are already in extensive use as barrier layers against Si diffusion in contacts. It is therefore fortunate that these layers show also good adhesion to CVD-W (i.e. no "new" adhesion material needs to be introduced). Sputtered TiN has some drawback in that, especially with the blanket H2/WF6 chemistry, substantial initiation times (of the order of 10 minutes) can be observed [Rana et al.8, Iwasaki et al.9]. This will be exhibited by apparent lower deposition rates and thickness or uniformity control problems. The reason for the nucleation problem atop TiN is not... 

The oxidation rate in dry oxygen was found to be very similar to that of < 100 > silicon (see figure 9.8). This indicates that during oxidation silicon from the underlying poly-Si diffuses to the surface of the WSix where it becomes available for oxidation. It has been found [Saraswat et al.225] that for practical purposes the dry oxidation rate of CVD-WSix atop of poly-Si can be described by ... 

Schaber, H., Criegem, R.V., Weitzel, I. Analysis of polycrystalline Si diffusion sources by secondary ion mass spectrometry. J. Appl. Phys. 58, 4036-4042 (1985)... 

The formation of SiC is kinetically limited by Si diffusion to the surface through the growing carbide layer (note that Lux and Haubner suggested that it is limited by the C diffusion through the carbide layer) thus, even if there... 

Luoyuan Bay belongs to a sub-tropical region, and is a typical semi-closed bay. Annually P and Si diffusing into overlying waters from the bay sediments are 6.61x10 g P/yr and 4.95x10 g Si/yr, respectively. The average fluxes... 

M. Fukumoto, C. Tachikawame, Y. Matsuzaka, M. Hara, Formation of Si diffusion layer on stainless steels and their high temperature corrosion resistance in molten salt, Corros. Sci. 56 (2012) 105—113. 

Self-diffusion of ions in silica has been measured both experimentally and computationally. Experimentally, Mikkelsen (Mikkelsen Jr. 1984) used SIMS (secondary ion mass spectroscopy) to measure the concentration profiles of labeled O deposited on silica to obtain the diffusion coefficient. Brebec et al (Brebec et al. 1980) used labeled Si and SIMS analysis for determining Si diffusion. Hetherington (Hetherington et al. 1964) used viscosity measurements of commercial silica to determine diffusion constants. Their experimental data are shown in Table 1, along with results from several computational studies. 

The diffusion of Si was studied in <100> GaAs which had been implanted with 40keV 30si+ ions. Profiles were determined by means of secondary-ion mass spectrometry and nuclear resonance broadening techniques. The implanted samples were subjected to annealing in Ar at 650 to 850C. Two independent Si diffusion mechanisms were observed. A concentration-independent diffusion, seen as a broadening of the initial implanted distribution, was very slow and was attributed to Si atoms that diffused interstitially. A concentration-dependent diffusivity with low solubility, was quantitatively explained in terms of the diffusion, via vacancies, of Si atoms on the Ga and As sub-lattices. The concentration-independent diffusion of Si was described by ... 

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