LF Noise Analysis for Trap Recovery in Gate Oxides Using Built-In Joule Heater

The importance of the reliability of gate oxide materials is increasing continuously as CMOS technology advancing. Joule heating to induce localized high temperature via a built-in gate heater has recently been introduced as a rapid and efficient method to cure instances of gate oxide damage, including damaged interface traps and bulk traps in the gate oxide. In this paper, spatially distributed deep oxide traps were generated by Fowler-Nordheim (FN) stress, and a recovery process by electrothermal annealing (ETA) using local Joule heat was clearly demonstrated with low-frequency (LF) noise characteristics. The generation and recovery of the oxide traps were quantitatively analyzed with LF noise, and the results showed that the border traps generated by the FN stress were cured by ETA. The recovery process was predominantly affected by the applied gate voltage and the duration. Excessive gate voltage beyond the critical value permanently destroyed the gate oxide. The effect of a forming gas annealing (FGA) process on the gate oxide traps was also analyzed with LF noise and compared with that of ETA. Although electrical Joule heating was applied under a condition of ambient air, not hydrogen-rich atmosphere, the passivation effect was superior to that of a FGA process conducted in diluted H ₂ ambient.