Study of Dopant Redistribution at the Substrate-Source/Drain p-n Junction of Nanoscale MOSFET During Progressive Breakdown

During the evolution of dielectric breakdown (BD) in MOSFETs, the substantial localized temperatures (which could exceed the silicon melting point) in the vicinity of the BD spot may cause dopants at the source/drain (S/D) to be redistributed (IEDM Tech. Dig., p. 717, 2004; IEEE Proc. IPFA, p. 131, 2005). The preliminary study of dopant redistribution based on the diode current-voltage (I-V) characteristics at the substrate-S/D p-n junction of a BD MOSFET was presented by Lim (IEEE Proc. IPFA, p. 131, 2005). The post-BD MOSFET diode current measured in the reverse bias as well as the low-voltage region of the forward bias was found to increase significantly as progressive BD evolves. The simulation results associated with the dopant redistribution are in good agreement with the experimental measurements. This confirms that the dopant redistribution is one of the dominant mechanisms responsible for the change in the post-BD MOSFET diode I-V characteristics. In addition, the dopant redistribution in a large-area long-channel BD MOSFET is found to be a function of BD location. However, the BD location dependence of the dopant redistribution will vanish in a "narrow" short-channel BD MOSFET