n‐LDD Ultra‐Shallow Extension Formation Using Cold and Carbon Ion Implantation

The sheet resistivity and junction depths of P implants with and without Ge PAI implants and C co-implants were compared. Phosphorus activates well under RTA+LSA annealing conditions, but junction depths did not reach the 15 nm target. Arsenic junctions achieved the junction depth target but with higher sheet resistance. NMOS junction depth was determined to depend heavily on both channeling and transient enhanced diffusion of phosphorus. Combining Ge and C co-implants reduced junction depths to a much larger degree than either species alone. The substitution of the C7H7 molecule for monomer C or the reduction of implant temperature to as low as -40 degrees C had little effect on the overall sheet resistivity and junction depth. It is possible to eliminate the Ge-PAI for n-LDD if C co-implant energy and dose could be modified. The low implant temperature technique could help the formation of amorphous layer from C co-implant, for which the implant dose and energy need to be tailored in order to reduce junction leakage.