Hafnium oxide (HfO 2 ) is one of the most promising high-k materials to replace SiO 2 as a gate dielectric. Here we report material and electrical characterization of atomic layer deposition ͑ALD͒ hafnium oxide and the correlations between the results. The HfO 2 films were deposited at 200, 300, or 370°C and annealed in a nitrogen ambient at 550, 800, and 900°C. Results indicate that deposition temperature controls both the material and the electrical properties. Materials and electrical properties of films deposited at 200°C are most affected by annealing conditions compared to films deposited at higher temperatures. These films are amorphous as deposited and become polycrystalline after 800°C anneals. Voids are observed after a 900°C anneal for the 200°C deposited films. The 200°C deposited films have charge trapping and high leakage current following anneals at 900°C. The 300°C deposited films have lower chlorine content and remain void-free following high-temperature anneals. These films show a thickness-dependent crystal structure. Annealing the films reduces leakage current by four orders of magnitude. Finally, films deposited at 370°C have the highest density, contain the least amount of impurities, and contain more of the monoclinic phase of HfO 2 than those deposited at 300 and 200°C. The best electrical performance was obtained for films deposited at 370°C.

We demonstrate the synthesis of large-area graphene on Co, a complementary metal-oxide-semiconductor (CMOS)-compatible metal, using acetylene (C(2)H(2)) as a precursor in a chemical vapor deposition (CVD)-based method. Cobalt films were deposited on SiO(2)/Si, and the influence of Co film thickness on monolayer graphene growth was studied, based on the solubility of C in Co. The surface area coverage of monolayer graphene was observed to increase with decreasing Co film thickness. A thorough Raman spectroscopic analysis reveals that graphene films, grown on an optimized Co film thickness, are principally composed of monolayer graphene. Transport properties of monolayer graphene films were investigated by fabrication of back-gated graphene field-effect transistors (GFETs), which exhibited high hole and electron mobility of ∼1600 cm(2)/V s and ∼1000 cm(2)/V s, respectively, and a low trap density of ∼1.2 × 10(11) cm(-2).

HfO 2 films deposited via tetrakis diethylamido hafnium ͑TDEAH͒ precursor using MOCVD ͑metal organic chemical vapor deposition͒ are presented. TDEAH is a promising precursor candidate for the deposition of high permittivity gate dielectrics. We report the impact of process and annealing conditions on the physical and electrical properties of the film. Deposition and annealing temperatures influence the microstructure, density, and impurity levels of TDEAH HfO 2 films. Spectroscopic ellipsometry shows that film microstructure manifests itself in the optical properties of the film, particularly in the presence of a band edge related feature at 5.8 eV. An impurity analysis using Auger electron spectroscopy, secondary ion mass spectroscopy, and Raman spectroscopy, indicates that carbon impurities from the precursor exist as clusters within the HfO 2 dielectric. The impact of deposition temperature and annealing temperature on the capacitance vs. voltage and current density vs. voltage characteristics of platinum gated capacitors is studied. Correlation of physical film properties with the capacitance and leakage behavior of the TDEAH HfO 2 films indicates that impurities, in the form of carbon clusters, and low HfO 2 film density are detrimental to the electrical performance of the gate dielectric.As the smallest feature size on a microprocessor approaches 50 nm, the primary dielectric layer in the field effect transistor, referred to as the gate dielectric or gate oxide, will thin to below 15 Å. Around this thickness, electrical leakage current through the dielectric becomes excessive and is expected to cause problems due to either high power dissipation or circuit reliability. 1 One solution to this problem is to replace SiO 2 dielectrics with higher permittivity dielectrics. A higher permittivity dielectric can be thicker and still achieve the same capacitance as a thinner SiO 2 dielectric. The starting point for identifying possible replacements for SiO 2 dielectrics is to evaluate their thermal stability in direct contact with silicon. Reactions between the high permittivity dielectric and the silicon substrate or electrode are undesirable. Extensive thermodynamic calculations have been performed by Hubbard and Schlom, 2 identifying numerous binary and ternary oxides that are candidate materials. Some of the binary oxides that are leading contenders for replacing SiO 2 include: ZrO 2 , HfO 2 , Y 2 O 3 , and Al 2 O 3 . In addition, there are numerous ternary ͑or mixed͒ oxides that have also been predicted, or experimentally determined, to be stable in contact with silicon.In general, the class IIIB and IVB oxides tend to be the most thermodynamically stable oxides for potential use in integrated circuit manufacturing. Doping the IIIB and IVB oxides with Al 2 O 3 or SiO 2 increases the crystallization temperature. Such amorphous dielectrics are desirable because grain boundaries enhance diffusion of dopants from the electrode to the substrate and possibly contribute to electrical leakage. On the other hand, doping...

In this article, we report film properties of HfO2 and La2O3 gate dielectrics grown on Si(100) substrate using atomic layer deposition (ALD) with various surfaces modified before film growth. The precursors used for HfO2 and La2O3 films are hafnium tetrachloride (HfCl4), lanthanum tris[bis(trimethylsilyl)amide] (C18H54N3LaSi6) and water. Pre-deposition treatments examined for HfO2 dielectric films include (1) surface nitridation using NH3, N2O, or NO, (2) substrate annealing in an oxidizing or reducing ambient, and (3) surface fluorination. These results were compared to those obtained using established approaches of growing HfO2 on an OH terminated surface produced chemically. Linear film growth was observed for the HfO2 with all pre-deposition treatments. Time-of-flight-secondary ion mass spectrometry (TOF-SIMS) and transmission electron microscopy (TEM) analysis indicated that all pre-treatments result in good film coverage with no interaction between HfO2 and silicon at the silicon substrate. The as deposited ALD HfO2 film is mainly amorphous, continuous, and relatively smooth on all pretreated Si surface. The thickness of a thin interfacial layer varies depending on the particular pre-treatments. Similar studies were also conducted for the growth of ALD La2O3. In this case, a significant interaction between La2O3 and silicon substrate was observed on films grown directly on chemical oxide. A rough interface between La2O3 and the silicon substrate is clearly seen in XTEM results. This interaction is more significant when the film is deposited at higher temperature. The XTEM images showed that the ALD La2O3 films are mostly amorphous. Results show that independent of surface pre-treatments, interactions between La2O3 and the silicon substrate occur for the deposition conditions explored here. Electrical characterization using evaporated platinum electrodes and mercury probe of the high-k film stacks have been carried out to determine the impact of the pre-treatments on the electrical properties of the films. Results indicated that ALD HfO2 films have higher dielectric constant, lower leakage and better flatband voltage stability during post deposition annealing compared to ALD La2O3 films. These results indicate that ALD HfO2 is a more promising candidate than ALD La2O3 due to superior thermal stability in contact with silicon.

The impact of 8-to45-at.% Ti on physical and electrical characteristics of atomic-layer-deposited and annealed hafnium dioxide was studied using vacuum-ultraviolet spectroscopic ellipsometry, secondary ion mass spectroscopy, transmission electron microscopy, atomic force microscopy, x-ray diffraction, Rutherford backscattering spectroscopy, x-ray photoelectron spectroscopy, and x-ray reflectometry. The role of Ti addition on the electrical performance is investigated using molybdenum (Mo)-gated capacitors. The film density decreases with increasing Ti addition. Ti addition stabilizes the amorphous phase of HfO2, resulting in amorphous films as deposited. After a high-temperature annealing, the films transition from an amorphous to a polycrystalline phase. Orthorhombic Hf–Ti–O peaks are detected in polycrystalline films containing 33-at.% or higher Ti content. As Ti content is decreased, monoclinic HfO2 becomes the predominant microstructure. No TiSi is formed at the dielectric/Si interface, indicating films with good thermal stability. The band gap of Hf–Ti–O was found to be lower than that of HfO2. Well-behaved capacitance-voltage and leakage current density-voltage characteristics were obtained for Hf–Ti–O. However, an increased leakage current density was observed with Ti addition. The data from capacitance-voltage stressing indicate a smaller flatband voltage (Vfb) shift in the HfO2 films with low Ti content when compared with the HfO2 films. This indicates less charge trapping with a small amount of Ti addition.