Anomalous Gate Current Hump after Dynamic Negative Bias Stress and Negative-Bias Temperature-Instability in p-MOSFETs with Hf_xZr_(1-x)O_2 and HfO_2/Metal Gate Stacks

摘要

In this study, the authors investigated an anomalous gate current hump after dynamic negative bias stress (NBS) and negative-bias temperature-instability (NBTI) in Hf_xZ_(1-x)O_2 and HfO_2/metal gate p-channel metal-oxide-semiconductor field-effect transistors. This result is attributed to hole trapping in high-k bulk. Measuring gate current under initial through body floating and source/drain floating conditions indicates that holes flow from source/drain to gate. The fitting of the gate current-gate voltage characteristic curve demonstrates that Frenkel-Poole mechanism dominates the conduction under initial. Next, fitting the gate current after dynamic NBS and NBTI indicates Frenkel-Poole then tunneling mechanisms, finally returning to the Frenkel-Poole mechanism. These phenomena can be attributed to hole trapping in high-k bulk and the formula E_(high-k) ε(high-k) = Q + E_(sio2εSiO_2). To further understand the gate current hump, both Zr-undoped and 8 ~ 10% Zr-doped in high-k bulk devices were used for comparisons. These results indicate that initial gate current is also a significant factor in generating the anomalous gate current hump, and all results obey the hump generation condition of J_(Tunneling) J_(Freenkei -Poole) --