Low-energy Ar plasma enhanced decomposition of SiH4 and B2H6 enables B-doped Si epitaxial film formation on Si(100) without substrate heating. For the concentration of B atoms and carriers in the B-doped Si films, depth profiles were investigated. At a fixed partial pressure and microwave power for the deposition, increasing tendency of the concentrations from interface to surface and the lower electrical activation ratio of the B atom for the higher B concentration were clarified. The activation ratio was typically below 1% in the higher B concentration region above 1020 cm−3, while it was as high as above 5% up to 100% in the lower B concentration region below 1019 cm−3. By reducing deposition rate in the fixed Ar plasma condition, the activation ratio in the higher B concentration region was apparently improved. Moreover, effect of post Ar plasma irradiation without substrate heating after about 1.2 nm-thick film deposition was examined for the films with the B concentration of 8 × 1019 cm−3 and initial carrier concentration of 2 × 1019 cm−3. By the post Ar plasma irradiation, 200% enhancement in the activation ratio was successfully observed and the carrier concentration reaches as high as 6 × 1019 cm−3. By increasing the post plasma irradiation time, the activation ratio tended initially to increase and then to degrade. This indicates that Ar plasma irradiation possibly induces incorporation of B atoms at substitutional sites even in nanometer-order deep region beneath surface, while deactivation of the B atoms also proceeds gradually and overtakes the activation finally. These results of plasma-enhanced activation process without substrate heating is expected to be utilized for smart fabrication of semiconductor devices with high carrier concentration and abrupt junction interfaces.
- Electrical activation
- Epitaxial growth
- In-situ doping
- Plasma chemical vapor deposition