Thermal decomposition behavior of the HfO 2 / SiO 2 / Si system J. Appl. Phys. 94, 928 (2003); 10.1063/1.1578525 Interfacial properties of ZrO 2 on silicon J. Appl. Phys. 93, 5945 (2003); 10.1063/1.1563844Yttrium silicate formation on silicon: Effect of silicon preoxidation and nitridation on interface reaction kineticsThe interfacial chemistry of the high-k dielectric HfO 2 has been investigated on nitrided and un-nitrided Si͑100͒ using x-ray photoelectron spectroscopy ͑XPS͒ and secondary ion mass spectroscopy ͑SIMS͒. The samples are prepared by sputter depositing Hf metal and subsequently oxidizing it. A 600°C densification anneal is critical to completing Hf oxidation. These spectroscopic data complement electrical testing of metal oxide semiconductor capacitors fabricated with ϳ50 Å HfO 2 on nitrided and un-nitrided Si͑100͒. Capacitors with interfacial nitride show reduced leakage current by a factor of 100 at a Ϫ1 V bias. Concurrently, interfacial nitride increased capacitance 12% at saturation. XPS shows that an interfacial layer composed of nonstoichiometric hafnium silicate (HfSi x O y ), forms at both the HfO 2 /Si and HfO 2 /SiN x interfaces. Differences in the Si 2p and O 1s XP spectra suggest more silicate forms at the un-nitrided interface. HfO 2 films on un-nitrided Si show more O 1s and Si 2p photoemission intensity characteristic of HfSi x O y . SIMS depth profiles through the buried interface are consistent with interfacial silicate formation, as shown by a HfSiO ϩ ion signal, that is sandwiched between HfO 2 and SiN x . SiN x is suggested to minimize interfacial HfSi x O y formation by limiting the amount of Si available to interact with the HfO 2 layer.

We demonstrate the electrical properties of metal-oxide-semiconductor capacitors on molecular beam epitaxial GaAs in situ passivated with ultrathin amorphous Si (a-Si) layer and with ex situ deposited HfO2 gate oxide and TaN metal gate. Minimum thickness of the Si interface passivation layer of 1.5 nm is needed to prevent the Fermi level pinning and provide good capacitance-voltage characteristics with equivalent oxide thickness of 2.1 nm and leakage current of ⩽1.0mA∕cm2. Transmission electron microscopy analysis showed that the Si layer was oxidized up to 1.4 nm during ex situ processing while the interface between the GaAs and a-Si remained atomically sharp without any sign of interfacial reaction.

We report the electrical properties of a high dielectric constant (high-k) material, ZrO2, deposited directly on SiGe, without the use of a Si buffer layer or a passivation barrier. ZrO2 thin films of equivalent oxide thickness (EOT) down to 16.5 Å were deposited on strained SiGe layers by reactive sputtering. Results indicate that ZrO2 films on SiGe have good interfacial properties and low leakage currents. Sintering in forming gas at 350 °C for 1 h could further improve the film quality. Although threshold voltage stability and dielectric dispersion become a concern for thick ZrO2 films, thin ZrO2 films of EOT less than 20 Å exhibit excellent electrical properties making them a good candidate for SiGe applications.

Electrical and physical characteristics of the atomic layer deposited beryllium oxide (BeO) grown on the Si and GaAs substrates were evaluated as a barrier/passivation layer in the III-V devices. Compared to Al2O3, BeO exhibits lower interface defect density and hysteresis, and smaller frequency dispersion and leakage current density at the same effective oxide thickness, as well as an excellent self-cleaning effect. These dielectric characteristics combined with its advantageous intrinsic properties, such as high thermal stability, large energy band-gap(10.6 eV), effective diffusion barrier, and low intrinsic structural defects, make BeO an excellent candidate for the interfacial passivation layer applications in the channel III-V devices.

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