Nonmelt laser annealing of 5-KeV and 1-KeV boron-implanted silicon

Nonmelt laser annealing has been investigated for the formation of ultrashallow, heavily doped regions. With the correct lasing and implant conditions, the process can be used to form ultrashallow, heavily doped junctions in boron-implanted silicon. Laser energy in the nonmelt regime has been supplied to the silicon surface at a ramp rate greater than 10 ¹⁰°C/s. This rapid ramp rate will help decrease dopant diffusion while supplying enough energy to the surface to produce dopant activation. High-dose, nonamorphizing boron implants at a dose of 10¹⁵ ions/cm² and energies of 5 KeV and 1 KeV are annealed with a 308-nm excimer laser. Subsequent rapid thermal anneals are used to study the effect of laser annealing as a pretreatment. SIMS, sheet resistance and mobility data have been measured for all annealing and implant conditions. For the 5-KeV implants, the 308-nm nonmelt laser preanneal results in increased diffusion. However, for the 1-KeV implant processed with ten laser pulses, the SIMS profile shows that no measurable diffusion has occurred, yet a sheet resistance of 420 Ω/sq was produced