Gate dielectric-breakdown-induced microstructural damage in MOSFETs

Numerous failure mechanisms associated with hard breakdowns (HBD) in ultrathin gate oxides were physically studied with high-resolution transmission electron microscope (TEM). Migration of silicide from silicided gate and source/drain regions, abnormal growth of dielectric-breakdown-induced epitaxy (DBIE), poly-Si gate meltdown 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 metal-oxide-semiconductor field-effect transistors (MOSFETs) after HBDs in gate oxides (Gox) were observed electrically. The type of catastrophic failures and its degree of damage were 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 damage associated with the Gox HBD in narrow transistors. The proposed model is able to predict the next possible microstructural damage induced by HBD. Such knowledge will allow failure analysts to be able to retro-predict the current and power consumption in a field EOS/ESD failure based on the physical analysis and propose a knowledgeable guess on the potential root cause of the failures.