Pulsed laser induced annealing and spin-on-doping in silicon wafers

Pulsed laser induced annealing of amorphous silicon wafer, and spin-on-doping have been performed using an excimer laser (λ=308 nm). Structural and electrical characterization were carried out by Hall effect measurement, spreading resistance profiling, channeled Rutherford Backscattering (RBS/c), and Raman spectroscopy. It was found that the damage in amorphous lapel generated by implantation was effectively removed by the irradiation of laser pulses. Pulsed laser irradiation introduces negligible structural damage in the crystalline wafer. In the spin-on-doping of boron in silicon, the sheet resistance decreases with laser fluences up to a threshold value. After this threshold, the sheet resistance attains a minimum value. The optimal “Box-like” profile we have produced in this work has a surface carrier concentration of 0.9×10¹⁸ cm^-3 and with a junction depth of 0.37 μm, under a laser fluence of 1.5 J cm^-2 /25 pulses. The junction depth of the doping profile was also found to be closed to the melt-depth. It is believed that the migration of boron atoms into the silicon wafer has been completed when the surface was in liquid phase