Hydrogen-plasma-enhanced oxygen precipitation in silicon

Czochralski-grown silicon crystals with different carbon concentrations hav e been heat-treated in mu -wave hydrogen plasma in the temperature range 50 0-700 degreesC. For comparison, control samples have been treated in a furn ace in a nitrogen ambient. Infrared (IR) absorption measurements show that the loss of oxygen atoms from solution due to the formation of SiO2 precipi tates is strongly enhanced by the H-plasma treatment in both carbon-lean an d carbon-rich Si crystals. The loss of oxygen is accompanied by the loss of substitutional carbon atoms from solution in the C-rich samples. The frequ encies and shapes of the IR absorption bands associated with the precipitat es are different in C-rich and C-lean crystals, indicating the formation of different types of precipitate particle. The former bands (C rich) are sim ilar following heat treatments in a H-plasma or in N-2 gas. It is inferred that a fast diffusing species penetrates into Si crystals during the H-plas ma treatment, leading to a catalytic enhancement of oxygen diffusion that i n turn leads to enhanced precipitation. Possible mechanisms for the enhance d oxygen diffusion and precipitation are discussed briefly.