Room-temperature oxidation of silicon catalyzed by Cu3Si

Abstract

We demonstrate remarkably rapid oxidation of (100) silicon at room temperature catalyzed by the presence of Cu3Si. Thermal oxidation of Si is normally carried out at temperatures above 700 °C. Oxidation of many metal silicides occurs more rapidly than that of Si, but under controlled conditions results in a surface layer of SiO2. In contrast, the oxidation process described here produces a thick layer of SiO2 underneath the copper-rich surface layer. The SiO2 layer grows spontaneously to over 1 μm in thickness in several weeks in air at room temperature. Analysis by Rutherford backscattering, Auger electron spectroscopy, cross-sectional transmission electron microscopy, and scanning electron microscopy reveals the presence of Cu3Si at the buried SiO2/Si interface, epitaxially related to the underlying Si substrate. Catalytic action by this silicide phase appears responsible for the unusual oxidation process.

Surface Protrusions of Chemical Vapor Deposited TiN Films Caused by Cu Contamination of Silicon Substrates

“…Therefore, high diffusivity of Si, O, as well as Cu, are important for maintaining the catalytic reaction. These results are quite different from the model of Harper et al, 6) where only the diffusivity of Cu and O are believed to be important for the catalytic reaction. They also observed a copper-rich layer near the sample surface as well as at the SiO 2 /Si interface.…”

“…It is believed that copper is the dominant diffusing species in the formation of copper silicide. 5,6) A comparison of the diffusivities (D 0 ) and activation energies (E) also supports this conclusion. At 1073 K, for the diffusion of Cu in Si, Samsonov 12) gives D 0 = 4 × 10 −2 cm 2 /s and E = 96.3 kJ/mole, while at the same temperature the values corresponding to the diffusion of Si in Cu are D 0 = 3.7 × 10 −2 cm 2 /s and E = 167.47 kJ/mole.…”

“…Cu 3 Si formation at Cu/Si interfaces has been studied by several authors over a wide range of temperature. [5][6][7][8][9][10][11] But little has been reported about the formation of CuSi. Cu 3 Si can form at temperatures as low as 473 K at the interface between a copper film and a single-crystal Si substrate, because Cu dif- L 607 fuses interstitially in Si.…”

Reaction of nanometer-sized Cu particles with a SiO2 substrate

“…13,14,16 Roomtemperature oxidation of Si is catalyzed by Cu 3 Si and a thick amorphous SiO 2 layer grows spontaneously beneath the Curich layer. 17,18 So the ease of regeneration of the annealed Cu/SiO 2 samples as described above can be understood from the oxidation behavior of a silicide and is another piece of evidence for the presence of Cu silicide after annealing in UHV.…”

“…Strongly bonded Cu may catalyze the Si-O bond breaking, since Cu also catalyzes the reverse reactions of Si-O formation. 13,14,[16][17][18] Metal evaporation as applied by others 9,21 may result in a weaker metal-support interaction 4 and, therefore, not result in a reaction between Cu and SiO 2 during UHV annealing. We note that also impurities on the sample surface or constituents of the residual gas may help to reduce SiO 2 .…”