Degradation of pMOSFETs due to hot electron induced punchthrough

Abstract

This paper proposes a method which can separate the parasitic effect from the drain current I-d vs. gate voltage V-g curves of MOSFETs, then uses this method to analyze degradation of experimental pMOSFETs due to hot-electron-induced punchthrough (HEIP). An I-d vs. V-g curve of the parasitic MOSFET formed by a shallow trench isolation (STI) is obtained by extrapolating the line of Id vs. channel width W at each V-g to W = 0 pm. The I-d vs. V-g curves of the parasitic MOSFET indicate that HEIP caused electron trapping at the interface between SiN and the sidewall oxide of STI, but the curves of the main MOSFET indicate that HEIP caused negative oxide charges and positive interface traps in the channel region. These charges and traps decreased the threshold voltage V-th of the parasitic MOSFET but increased V-th of the main MOSFET. These two opposite behaviors of V-th, resulted in little HEIP-induced shift of V-th at W = 2.5 mu m. vertical bar Vd vertical bar to secure ten-year HEIP lifetime of 10% shift of V-th was <= 2.2 V at W = 03 mu m, <= 3.5 V at W = 1.0 mu m, and <= 3.6 V at W = 10 mu m; these changes indicate that degradation of parasitic MOSFET influences the HEIP lifetime of narrow pMOSFET significantly. (C) 2016 Elsevier Ltd. All rights reserved.