Diffusion of oxygen and silicon in silicon: Silicon monoxide model
- PDF / 114,134 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 48 Downloads / 253 Views
The diffusion of oxygen in silicon was modeled to result from the diffusion of dissolved silicon monoxide. The SiO molecule dissolved in the largest space in the diamond lattice of silicon, oriented in a 〈111〉 direction, with the oxygen lightly bonded to a network silicon atom. This configuration is consistent with infrared spectra, dichroism of infrared spectral lines, and internal friction of oxygen in silicon. The anomalous rapid diffusion of oxygen below 700 °C could result from the diffusion of molecular water or oxygen in silicon, but more evidence is needed to test these possibilities. Diffusion and exchange of silicon tracer in SiO with lattice silicon can possibly explain tracer diffusion of silicon in silicon.
I. INTRODUCTION
Silicon is one of the purest commercial materials; low concentrations of impurities that influence electronic properties in silicon are essential. However, in silicon for integrated circuits grown in a silica crucible there are usually about 1018 oxygen atoms/cm3 [2(10)−5 atom fraction, 10 ppm]. Electrically active oxygen and complexes and precipitation of oxygen can influence the electrical properties of silicon, so oxygen solubility and diffusion are processes of great practical importance. Experiments on the diffusivity and solubility of oxygen in silicon have been summarized by Mikkelsen.1 The diffusion coefficient fits on a single line on a log D versus 1/T plot, where D is the diffusion coefficient and T the absolute temperature, at temperatures from 350 to 1250 °C. An activation energy of 244 kJ/mol (2.53 eV) and a pre-exponential factor of 0.13 cm2/s are found. There is excellent agreement between different investigators and low- and high-temperature data, and the diffusion coefficients are independent of oxygen concentration, wafer orientation, dopant concentrations, and state of oxidation of the ambient atmospheres. Higher diffusion coefficients of oxygen in silicon at temperatures from 400 to 700 °C than given by these results have been reported in several studies.2–5 The solubility measurements of oxygen in silicon show more scatter than the diffusivity measurements; Mikkelsen1 estimated the best fit to be an enthalpy of 146 kJ/mol (1.52 eV) and a preexponential factor of 9(10)22 oxygen atoms/cm3.
a)
e-mail: [email protected] J. Mater. Res., Vol. 16, No. 1, Jan 2001
http://journals.cambridge.org
Downloaded: 26 Mar 2015
Oxygen containing silicon has a strong infrared absorption band at about 1106 cm−1 (9.0-m wavelength), and a less-intense band at 515 cm−1 (19-m wavelength).7 From isotopic shifts Hrostowski and Kaiser concluded that the 1106-cm−1 band results from a single Si–O vibration.7 Kaiser, Keck, and Lange proposed a model for oxygen in silicon in which an oxygen atom breaks a silicon–oxygen bond, and is bonded to the two silicon atoms from the broken bond.8 The resulting silicon–oxygen–silicon bond is not linear and is bent away from the original bond, forming a silicon–oxygen– silicon angle of about 100°. The 1106-cm−1 band is assigned to 3, the antisymmetr
Data Loading...
