Analysis of impact ionization on RF power LDMOS reliability under RF life test in radar system

Abstract

This paper focuses on correlation between the electrical parameter shifts and the failure phenomena that appeared after pulsed RF life tests applied to RF power LDMOS transistor (Radio Frequency Laterally Diffused-Metal–Oxide–Semiconductor). The results of the test bench (radar circuit) are measured in real time. The failure rate is more significant at low temperatures after the aging life test. The electrical performances are shifted, notably, IGS, VTH, GM, RDSON, CRSS, gain, and S-parameter S21. A 3D physical simulation (SILVACO-TCAD) is used to highlight the phenomena linked to the characteristic's degradation. The impact ionization induces physical degradations in the study of transistors, which are manifested by a variation in their electrical performance. It showed that the located failure zone is due to the device's shifted characteristics, which are deeply correlated with the structure area. The goal of the paper is to prove the failure mechanism through the characteristics evaluation origin, that is started by the carrier generation, because of the impact ionization phenomenon. The demonstration is based on the physical simulations are conducted at RF power NLDMOS. The outcomes show that the mechanism is due to the augmented carrier injection into the advanced silicon dioxide layer (SiO2) or/and in the Si/SiO2 interface state. The consistency between the physical simulations and experimental results emphasizes the theoretical analysis performed in this work.