Ans
(1)The issue of shallow junction: lower thermal budget, low energy, higher dosage are used.
(2)In PMOS, Boron is too light for sub-micron devices, BF2 are used instead.
(3)S/D implant would cause substrate damage, additional annealing stage is required to reduce junction leakage.(~600C to anneal damage, raise to 850~900C to activate impurity)
(4)Implant uniformity, temperature control, surface charging effects need to be controlled.