THE PROCESS LIMITATION FOR FORMING TI SILICIDED SHALLOW JUNCTION BY BF(2)+ IMPLANTATION INTO THIN POLYCRYSTALLINE SI FILMS AND SUBSEQUENT TI SILICIDATION

Excellent shallow p+n junctions have been formed by implanting BF2+ ions into thin polycrystalline Si films and subsequent annealing; these junctions which show a leakage of 1 nA/cm2 and a junction depth of about 0.05 mum. An anomalous boron diffusion occurs when subsequent silicidation is carried out. Silicidation using 300-angstrom Ti just slightly affected the junction profile. However, the junction is considerably deepened for 600-angstrom Ti silicidation, yielding a resulting depth of about 0.11 mum. The large boron redistribution is attributed to the point defects induced by silicidation. Hence, proper silicide thickness should be chosen to retain the junction profile as well as to reduce the parasitic source/drain resistance.