Thermal pyrolysis investigation of self-assembled molecular monolayer for defect-free doping in silicon

A thermal pyrolysis method, prior to a conventional rapid thermal annealing (RTA) treatment, was developed for octadecylphoshponic acid (ODPA)-modified Si samples. The thermal pyrolysis could break P-C linkage at 500 degrees C and release carbon impurities from silicon surfaces, because of its weak bonding energy (similar to 260 kJ/mol) in ODPA molecules. The results show that large amounts ( > 60%) of C impurities are successfully eliminated. Hall effect measurements suggest that the electrical activation rate of P dopants rises up to 56.7% from 3.8%, while all C-related defects at 133 meV below the conduction band are excluded. The calculated ionization rate of P dopants is approximately 83%. The resultant similar to 17%, assigned to C-i-P-s defects, could be further minimized by extending RTA time. Therefore, it is promising to manufacture defect-free doped Si materials by the thermal pyrolysis, together with RTA treatments.