Reverse Current of Plasma Doped p+/n Ultra-Shallow Junction

Abstract

Rapid scaling in silicon CMOS devices has forced the junction depth requirement needed for S/D extensions of MOSFET to be as shallow as 10 nm in the next 45 nm technology node [1]. For this reason, the plasma doping method is considered to be promising compared to the conventional ion implantation, since it has significant advantages such as very high throughput and more compact in system hardware [2]-[6]. Formation of ultra-shallow p-type junction using boron is considerably difficult due to low energy requirement on doping and rapid diffusion of boron during thermal annealing that can increase junction depth. Very short time annealing such as flash lamp annealing (FLA) or spike rapid thermal annealing (RTA) is required to form such shallow junctions [7]-[ 10]. Fig. 1 is a plot of the R,-Xj relationship using the combination of the plasma doping and dopant activation process by FLA or spike RTA, which shows a successful formation of ultra-shallow junction [11][ 12]. However, the study on the leakage current across the ultra-shallow junction has been relatively limited. Since the impurity profile, the condition of amorphization, and the defect formation in the silicon wafers doped by the plasma doping are different from those by the conventional ion implantation, the characteristics ofthe residual defects after the activation annealing, to which the electrical characteristics of the junction is sensitive, might be different between the two.