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Low-temperature conductance measurements of surface states in HfO2–Si structures with different gate materials
Authors:Y Gomeniuk  A Nazarov  Ya Vovk  Yi Lu  O Buiu  S Hall  JK Efavi  MC Lemme
Affiliation:aInstitute of Semiconductor Physics, NASU, 41, pr. Nauky, 03028 Kiev, Ukraine;bDepartment of Electrical Engineering and Electronics, Brownlow Hill, University of Liverpool, Liverpool L69 3GJ, UK;cAdvanced Microelectronic Center Aachen (AMICA), AMO GmbH, Huyskensweg 25, 52074 Aachen, Germany
Abstract:Metal-oxide-semiconductor capacitors based on HfO2 gate stack with different metal and metal compound gates (Al, TiN, NiSi and NiAlN) are compared to study the effect of the gate electrode material on the trap density at the insulator–semiconductor interface.CV and Gω measurements were made in the frequency range from 1 kHz to 1 MHz in the temperature range 180–300 K. From the maximum of the plot G/ω vs. ln(ω) the density of interface states was calculated, and from its position on the frequency axis the trap cross-section was found. Reducing temperature makes it possible to decrease leakage current through the dielectric and to investigate the states located closer to the band edge.The structures under study were shown to contain significant interface trap densities located near the valence band edge (around 2×1011 cm−2eV−1 for Al and up to (3.5–5.5)×1012 cm−2 eV−1 for other gate materials). The peak in the surface state distribution is situated at 0.18 eV above the valence band edge for Al electrode. The capture cross-section is 5.8×10−17 cm2 at 200 K for Al–HfO2–Si structure.
Keywords:High-k dielectrics  Gate stack  Interface state density  G/ω  measurements
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