Hot-carrier degradation for deep-submicron N-MOSFETS introduced by backend processing

Severe hot-carrier-induced device lifetime degradation has been observed on deep submicron N-MOSFETs after they are processed through the backend for multi-layermetal interconnect. Our experimental data show that the hot-carrier lifetime degradation is dependent on (1): H₂ annealing/sintering time; (2): choice of inter-metal-dielectric process, i.e., Spin-On-Glass (SOG) or High-Density-Plasma Chemical-Vapor-Deposition (HDP-CVD) process; and (3): choice of pre-metal-dielectric process, i.e., BPSG (Borophosphosilicate glass) or BPTEOS/O₃ (Borophosphosilicate-Tetra-Ethoxy-Silane and Ozone oxide) deposition. The device hot-carrier lifetime can degrade more than 50% due to prolonged H₂ sintering time, and it could easily degrade by an order of magnitude when HDP-CVD oxide, instead of SOG, is used for inter-metal dielectric deposition. The gate oxide always remains of excellent quality through the entire backend processing, which indicate that the degradation is not caused by plasma damage to the gate oxide but by hydrogen-related defects at the Si-SiO₂ interface instead.