NBTI and PBTI are studied in IL/HK/MG gate stacks having EOT down to ∼ 6Å and fabricated using low T RTP based thermal IL and a novel IL/HK integration. At equivalent EOT, proposed stacks provide improved NBTI and similar PBTI when compared to conventional Chem-Ox IL based HKMG stacks. EOT scaling achieved by RTP thermal IL scaling shows lower rate of increase in NBTI and PBTI when compared to Chem-Ox IL scavenged stacks. Impact of Nitrogen and role of post HK nitridation are studied. Physical mechanism of improved BTI in proposed stacks is discussed in detail.
DC and AC NBTI in deep EOT scaled HKMG p-MOSFETs with different IL (scaled to sub 2Å) are measured by UF-MSM method with 10μs delay. A model with interface trap generation (ΔV IT-IL ) at Si/IL interface, hole trapping (ΔV HT ) in IL bulk and trap generation (ΔV IT-HK ) linked to H passivated Oxygen vacancy (Ov-H) defects in IL/HK interfacial transition layer has been proposed. The existence of Ov defects and their energy levels are verified using DFT simulation. The model can successfully predict V T shift (ΔV T ) during and after DC stress, dependence on pulse duty cycle (PDC) and frequency (f) for AC stress, and gate insulator process dependence with consistent set of parameters. Impact of EOT scaling on DC and AC NBTI is studied, and end-of-life degradation has been estimated.
Ultrafast DC and AC negative bias temperature instability (NBTI) measurements are done in high-k metal gate p-MOSFETs having deeply scaled interlayer. Time evolution of degradation during and after DC and AC stress at different duty cycle and frequency are characterized. Impact of last pulse cycle duration (half or full) and pulse low bias on AC stress are studied. Equivalence of measured data from large and small area devices are shown. Experimental results are qualitatively explained using known NBTI physical mechanism.Index Terms-AC duty cycle, AC frequency, AC stress, DC stress, high-k metal gate (HKMG), negative bias temperature instability (NBTI), recovery, ultrafast measurements (UFMs).
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