Gate dielectric breakdown induced microstructural damages in MOSFETs

Numerous failure mechanisms associated with hard breakdowns (HBD) in ultrathin gate oxides were physically studied by high resolution TEM. Migration of silicide from silicided gate and source/drain regions, abnormal growth of dielectric-breakdown-induce-Si epitaxy (DBIE), poly-Si gate melt-down and recrystallization, severe damage in Si substrate and total epitaxy of poly-Si gate and Si substrate of the entire transistor are among the common microstructural damages observed in MOSFETs after hard breakdowns in gate oxides (Gox) were observed electrically. The type of catastrophic failures and its degree of damage are found to be strongly dependent on the allowable current density and total resistance of the breakdown path during the breakdown transient. The physical analysis data from TEM analysis allow us to establish the sequence of the physical damages associated with the Gox HBD in transistors. The proposed model is able to predict the next possible microstructural damage induced by HBD.