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TaCy has been reported to have the appropriate work function for negative metal-oxide semiconductor metal in high-k metal-oxide field-effect transistors. As device size continues to shrink, a conformal deposition for metal gate electrodes is needed. In this work, we report on the development and characterization of a novel TaCy process by atomic layer deposition (ALD). Detailed physical properties of TaCy films are studied using ellipsometry, a four-point probe, Rutherford backscattering spectrometry (RBS), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD). RBS and XPS analysis indicate that TaCy films are near-stoichiometric, nitrogen free, and have low oxygen impurities. Powder XRD spectra showed that ALD films have a cubic microstructure. XPS carbon bonding studies revealed that little or no glassy carbon is present in the bulk of the film. Excellent electrical properties are obtained using ALD TaCy as a metal gate electrode. Well-behaved capacitance-voltage characteristics with ALD HfO2 gate dielectrics are demonstrated for TaCy thicknesses of 50, 100, and 250 Å. A low fixed charge (∼2–4×10-11 cm-2) is observed for all ALD HfO2/ALD TaCy devices. Increasing the thickness of ALD TaCy results in a decrease in work function (4.77 to 4.54 eV) and lower threshold voltages. [ABSTRACT FROM AUTHOR]

We report on the thermal decomposition of uncapped, ultrathin HfO[SUB2] films grown by chemical vapor deposition on SiO[SUB2]/Si(100) substrates. Medium energy ion scattering, x-ray photoelectron spectroscopy, scanning electron microscopy and atomic force microscopy were used to examine the films after they had been annealed in vacuum to 900-1050°C. Film decomposition is a strong function of the HfO[SUB2] overlayer thickness at a given temperature, but the underlying SiO[SUB2] layer thickness does not significantly affect the thermal stability of the HfO[SUB2] film. Oxygen diffusion in the system was monitored by [SUP16]O/[SUP18]O isotopic labeling methods. Direct evidence of silicide formation is observed upon decomposition. [ABSTRACT FROM AUTHOR]

We report the effects of annealing on the morphology and crystallization kinetics for the high-κ gate dielectric replacement candidate hafnium oxide (HfO[sub 2]). HfO[sub 2] films were grown by atomic layer deposition (ALD) on thermal and chemical SiO[sub 2] underlayers. High-sensitivity x-ray diffractometry shows that the as-deposited ALD HfO[sub 2] films on thermal oxide are polycrystalline, containing both monoclinic and either tetragonal or orthorhombic phases with an average grain size of ∼8.0 nm. Transmission electron microscopy shows a columnar grain structure. The monoclinic phase predominates as the annealing temperature and time increase, with the grain size reaching ∼11.0 nm after annealing at 900°C for 24 h. The crystallized fraction of the film has a strong dependence on annealing temperature but not annealing time, indicating thermally activated grain growth. As-deposited ALD HfO[sub 2] films on chemical oxide underlayers are amorphous, but show strong signatures of ordering at a subnanometer level in Z-contrast scanning transmission electron microscopy and fluctuation electron microscopy. These films show the same crystallization kinetics as the films on thermal oxide upon annealing. [ABSTRACT FROM AUTHOR]

A study was undertaken to determine the efficacy of various underlayers for the nucleation and growth of atomic layer deposited HfO[sub 2] films. These were compared to films grown on hydrogen terminated Si. The use of a chemical oxide underlayer results in almost no barrier to film nucleation, enables linear and predictable growth at constant film density, and the most two-dimensionally continuous HfO[sub 2] films. The ease of nucleation is due to the large concentration of OH groups in the hydrous, chemical oxide. HfO[sub 2] grows on chemical oxide at a coverage rate of about 14% of a monolayer per cycle, and films are about 90% of the theoretical density of crystalline HfO[sub 2]. Growth on hydrogen terminated Si is characterized by a large barrier to nucleation and growth, resulting in three-dimensional, rough, and nonlinear growth. Thermal oxide/oxynitride underlayers result in a small nucleation barrier, and nonlinear growth at low HfO[sub 2] coverages. The use of chemical oxide underlayers clearly results in the best HfO[sub 2] layers. Further, the potential to minimize the chemical oxide thickness provides an important research opportunity for high-κ gate dielectric scaling below 1.0 nm effective oxide thickness. [ABSTRACT FROM AUTHOR]

Many materials systems are currently under consideration as potential replacements for SiO[sub 2] as the gate dielectric material for sub-0.1 μm complementary metal-oxide-semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward successful integration into the expected processing conditions for future CMOS technologies, especially due to their tendency to form at interfaces with Si (e.g. silicates). These pseudobinary systems also thereby enable the use of other high-κ materials by serving as an interfacial high-κ layer. While work is ongoing, much research is still required, as it is clear that any material which is to replace SiO[sub 2] as the gate dielectric faces a formidable challenge. The requirements for process integration compatibility are remarkably demanding, and any serious candidates will emerge only through continued, intensive investigation. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Deals with a study that investigated hafnium and zirconium silicate gate dielectric films with metal contents. Results of transmission electron microscopy and x-ray photoelectron spectroscopy; Physical characterization; Electrical characterization.

A comparison of the kinetics of titanium dioxide deposition between titanium nitrate (TN) and titanium isopropoxide (TTIP) over a large range of temperature revealed substantial variances in the reaction rate-limited regime. This is attributed to the differences in the surface lifetime of the two precursors, its diffusion length as well as its selectivity. The results also provide an explanation for the observed decrease in titanium dioxide grain size with increased temperature.