New observations on complex RTN in scaled high-κ/metal-gate MOSFETs — The role of defect coupling under DC/AC condition

The coupling effect between multi-traps in complex RTN is experimentally studied in scaled high-κ/metal-gate MOSFETs for the first time. By using extended STR method, the narrow “test window” of complex RTN is successfully expanded to full VG swing. Evident defect coupling can be observed in both RTN amplitude and time constants. Interesting nonmonotonic bias-dependence of defect coupling is found, which is due to two competitive mechanisms of Coulomb repulsion and channel percolation conduction. The decreased defect coupling is observed with increasing AC frequency. Based on the new observations on complex RTN, its impacts on the circuit stability are also evaluated, which show an underestimation of the transient performance if not considering defect coupling. The results are helpful for future robust circuit design against RTN.