4.6 Article

Negative Capacitance in HfO2 Gate Stack Structures With and Without Metal Interlayer

期刊

IEEE TRANSACTIONS ON ELECTRON DEVICES
卷 69, 期 5, 页码 2680-2685

出版社

IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/TED.2022.3157579

关键词

Logic gates; Metals; Capacitance; Voltage measurement; Hysteresis; Electrodes; Semiconductor device measurement; Ferroelectric materials; gate stack; hafnium oxide; negative capacitance (NC); NC-FET

资金

  1. European Union's H2020 Research and Innovation Program [780302]
  2. European Research Council (ERC) [ERC-2015AdG-695459]
  3. Swiss National Science Foundation (SNSF) [200021_169339]
  4. Swiss National Science Foundation (SNF) [200021_169339] Funding Source: Swiss National Science Foundation (SNF)

向作者/读者索取更多资源

In this work, the authors experimentally explore and compare FET gate stacks with and without an inner metal plane, demonstrating that the absence of the inner metal plane stabilizes the negative capacitance regime, leading to hysteresis-free performance.
In this work, we experimentally explore and compare FET gate stacks with and without an inner metal plane between a linear dielectric (SiO2) and a ferroelectric layer (Si-doped HfO2) operating in the negative capacitance (NC) regime. The use of nanosecond-range pulses enables us to observe hysteresis-free NC and reconstruct the S-shaped polarization-voltage curves. The devices with the inner metal plate show a higher equivalent NC value, which offers the potential for a higher differential amplification in a NC-FET. However, such a NC region is observed over a smaller range of electric field and polarization, which leads to hysteresis. Moreover, the presence of a metal layer in between the ferroelectric and the insulator favors domain formation resulting in destabilization of the NC effect. For the gate structure where the ferroelectric and the insulator are in contact, the S-shaped polarization-voltage curve shows a better agreement with Landau-Ginzburg-Devonshire formalism for the monodomain state. The uniform polarization closely mimicking the monodomain state is possible due to the polarization imprint occurring due to the structural asymmetry. By nanometer resolution polarization mapping via off-resonance piezoelectric force microscopy (PFM), we corroborate the presence of imprint, which can intrinsically stabilize one ferroelectric state. Overall, the article provides an experimental demonstration that the absence of the inner metal plane in the gate structures stabilizes the NC regime favorable for hysteresis-free NC-FET.

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