INFLUENCE OF NITROGEN ION IMPLANTATION ON THE ELECTROPHYSICAL PROPERTIES OF THE GATE DIELECTRIC OF POWER MOSFETs
Power MOS-transistors with vertical structure are investigated. Additionally, in some devices, ion implantation of nitrogen with energies of 20 and 40 keV was carried out in a dose range of 1 ⋅ 1013-5 ⋅ 1014 cm-2 through a sacrificial oxide 20 nm thick. For one group of wafers, rapid thermal annealing was first carried out, then oxide removal (forward order), for the other group - in the opposite sequence (reverse order). It was found that with the additional doping of nitrogen ions in doses of 1 ⋅ 1013-5 ⋅ 1 013 cm-2 with energy of 20 keV, an increasing of gate dielectric charge to breakdown for both types of annealing is observed. The maximum effect occurred for the samples at a dose of nitrogen ions of 1 ⋅ 1013 cm-2 with the forward heat treatment order. This is due to the interaction of nitrogen atoms with dangling bonds of the Si - SiO2 interface during annealing, as a result of which strong chemical bonds are formed that prevent charge accumulation on the surface of the Si - SiO2 interface. It is assumed that the main contribution to the gate leakage current is made by the tunneling of charge carriers through traps.