Formation of ultra-shallow junction by BF{sub}2{sup}+ implantation and spike annealing

摘要

Ultra shallow p-type junction was formed by low energy BF{sub}2{sup}+ implantation and optimizing rapid thermal annealing (RTA). RTA at various soak time and temperatures in pure N{sub}2 atmosphere. Especially, the spike annealing was defined as a fraction of a second soak time at the peak temperature. The dependence of junction depth and sheet resistance on ramp-up rate were investigated for rates of 23 °C/s and 38 °C/s. The samples implanted BF{sub}2{sup}+ at energy of 2 keV with doses of 6×10{sup}14 cm{sup}-2 and 1×10{sup}15 cm{sup}-2 were annealed. The peak carrier concentration was calculated from sheet resistance and SIMS profile. The carrier concentration depends on the implant dose strongly; the carrier concentration of 1×10{sup}15 cm{sup}-2 is higher than one of 6×10{sup}14 cm{sup}-2. In the case of 6×10{sup}14 cm{sup}-2 lower thermal budget by decreasing the soak time or increasing the ramp-up rate results in shallower junction depth monotonously. It is observed that junction depth is deeper and peak carrier concentration decreases by decreasing thermal budget with extremely high ramp-up rate of spike annealing at dose of 1×10{sup}15 cm{sup}-2. It is concluded that moderate ramp up rates of spike annealing for low energy and high dose BF{sub}2{sup}+ implant, e.g. 2 keV, 1×10{sup}15 cm{sup}-2, can achieve the shallowest junction and lowest sheet resistance.