Carbon diffusion through SiO2 from a hydrogenated amorphous carbon layer and accumulation at the SiO2/Si interface

Carbon diffusion in a SiO2/Si system was investigated. The source was provided by chemical vapor deposition of a hydrogenated amorphous carbon layer onto the oxide at low temperature. From layers with low oxygen content no carbon outdiffusion was detected up to 1190 degreesC. If the O content was high, the diffusion would start suddenly at 1140 degreesC, and carbon accumulation would be found on the Si side of the SiO2/Si interface in the form of SiC precipitates. These results ate interpreted by assuming oxygen-assisted dissociation of carbon atoms from the carbon layer in form of CO molecules, fast CO diffusion through SiO2 and an exothermic reaction of CO with Si. No carbon segregation was found in SiO2, Consequences of carbon island formation during SiC oxidation are pointed out.