Anomalous Gate Current Hump after Dynamic Negative Bias Stress and Negative-Bias Temperature-Instability in p-MOSFETs with HfxZr1−xO2 and HfO2/Metal Gate Stacks

Abstract

In this study, the authors investigated an anomalous gate current hump after dynamic negative bias stress (NBS) and negative-bias temperature-instability (NBTI) in HfxZr1−xO2 and HfO2/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 Ehigh-k ɛhigh-k = Q + Esio2ɛsio2. 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 JTunneling ≪ JFrenkel-Poole.