New method of Plasma doping with in-situ Helium pre-amorphization

A new method of plasma doping process was developed to achieve the ultra shallow junction with low sheet resistance (Rs) and very steep abruptness. In-situ Helium pre-amorphization (He-PA) was employed in conjunction with plasma doping (PD) of dopant species. The optical absorption rate of the amorphous Si layer and the junction depth (Xj) were predominantly controlled by the He-PA conditions. The increase in the optical absorption of the shallow doped layer enabled the high activation of the dopant species. The feasibility of this new technique to form ultra-shallow p+−n junction was studied by using spike rapid thermal annealing (RTA) and flash lamp annealing (FLA). Excellent results on Rs, Xj, abruptness of profiles and reverse-biased leakage current of p+−n diode were obtained. The thickness control and the uniformity of the amorphous Si layer in the He-PA process were discussed.