Low-temperature conductance measurements of surface states in HfO2-Si structures with different gate materials

• 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. C-V and G-omega 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/omega vs. ln(omega) 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 x 10(11) cm(-2)eV(-1) for Al and up to (3.5-5.5) x 10(12)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 x 10(-17)cm(2) at 200 K for Al-HfO2-Si structure.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Nanoteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Nano-technology (hsv//eng)

Nyckelord

high-k dielectrics

gate stack

interface state density

G/omega measurements

Publikations- och innehållstyp

ref (ämneskategori)

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