Ultra shallow junction (USJ) formation using plasma assisted doping on 3D devices structures

Abstract

Advanced inductively coupled plasma techniques and surface treatments have been used to demonstrate 5nm conformal shallow junctions at low energy with no silicon structure damage. N-type PH3 plasma assisted doping was characterized by dopant diffusion and electrical activation with increasing wafer temperature. Plasma assisted doping at high wafer temperature showed no structure damage even at a high incident energy condition with a bias power applied to the wafer, while a shallow junction of less than 7nm of Xj formation was achieved with low incident energy condition without bias power. Adding a silicon surface modification step when using the decoupled plasma condition prior to PH3 doping was found to enhance the dopant level and lower Rs dramatically. Various annealing techniques were compared to understand the impact to dopant activation and levels to form shallow junctions of less than 7nm.