Scaled HfAlxOy/SiO2 stacks down to 1.5 nm EOT have been achieved. Although the addition of Al to the HfO2 matrix can be beneficial, it is observed that the benefit of using a Hf-aluminate is compromised if the film has a high Al-content. This is observed in terms of a dielectric constant close to that of pure Al2O3 (∼ 9) and a large amount of negative fixed charge in the film (∼ 1012 cm-2). Using oxygen post deposition anneals we have been able to reduce flatband voltage shifts associated with fixed charge as well as CV hysteresis. In terms of scaling, the benefit of using a high-k material is compromised if a SiO2 layer is also present in the gate stack. Therefore, it is necessary to perform an O2 PDA at moderate temperatures or in low O2 partial pressures in order to control the thickness of the interfacial oxide layer.

The XAFS measurement of the MSQ type low-k dielectrics (LKD™) was conducted to clarify the structure change with and without the EB cure. Furthermore, three different types of other MSQ films, the ladder structure, the random structure and the CVD film, have been investigated as references. We have determined Si-O-Si bond angle and Si-O(Si-C) bond length by fitting the Fourier transformed EXAFS spectra.

The ladder structure and the random structure have Si-O-Si bond angle of 133 and 146, respectively.

Si-O-Si bond angle of LKD™ film is among that of the ladder and the random structure, and the XANES spectrum of LKD™ film displays two broad features, corresponding to the mixture of both structures. In contrast, Si-O-Si angles of the EB cured LKD™ film and the CVD film resemble each other, and the XANES features of both films are almost identical with that of the random structure.

We have confirmed that the EB cure process for LKD™ film makes drastic structure change from the mixture of ladder and random structure to the random network structure.

Ultrashallow doping of silicon wafers with boron was done by implantation of B+ or BF2+. Nickel silicide on them was formed by annealing of thin Ni layer. As it was revealed by secondary ion mass spectrometry, after the growth of NiSi, boron remains in Si just under the silicide layer, but fluorine accumulates in the NiSi layer. This accumulation suppresses agglomeration of the silicide.

A fast way to monitor the quality of high-k dielectric layers is wet etching, either monitored by Open Circuit Potential analysis or by Scanning Electron Microscopy. Defect densities in the order of 1.109 defects/cm2 are observed for as-deposited HfO2 layers. It is assumed that the mechanism for wet chemical defect observation is either due to crystallization and/or due to an oxygen deficient HfO2 layer resulting in Si/SiO up-diffusion upon thermal treatment. However, after appropriate post deposition annealing wet etch defect free layers can be prepared.

New materials with high dielectric constant are currently being explored to replace silicon dioxide as gate dielectric for device scaling below 0.1 μm. With respect to conventional SiO2, these high permittivity dielectrics provide the required equivalent oxide thickness (EOT) without of further reduction of the insulator physical thickness, which is a key issue to limit gate leakage current and to maintain comparable MOSFET operation and reliability. The present paper presents preliminary results on conduction mechanisms in thin epitaxial SrTiO3 films grown by MBE on Si (100). I-V measurements were performed on Al/STO/Si structures at temperatures ranging from 40 K to 290 K. At temperatures lower than 100 K the conduction mechanism of electrons from gate electrode across the oxide barrier neither Schottky emission nor tunneling. For temperatures higher than 100 K Schottky emission occurs and barrier heights were extracted, showing an approximate linearly increase with temperature. In case of Si/STO interface, a Fowler-Nordheim tunneling mechanism was detected at 40 K and at intermediate fields. The extracted barrier heights are: 0.07 eV at Si/STO interface and from 0.26 eV (130 K) to 0.53 eV (290 K) at Al/STO interface.

The alkoxide and alkylamide complexes [Hf(mmp)4] and [Hf(NMe2)4] 2 are both promising precursors for the MOCVD of HfO2. A comparison has shown that [Hf(NMe2)4] 2 deposits oxide at lower temperatures and over a wider temperature range then [Hf(mmp)4].

Two layer co-sputtered Bi over In thin films (40 nm/layer) act as a microfabrication resist with many potential applications. Their physical, chemical and optical characteristics change after laser exposures that produce a rapid thermal anneal in selected areas. Unlike organic photoresists, Bi/In is a bimetallic thermal resist whose sensitivity shows a near wavelength invariance for wavelengths from Near IR to UV. The laser-induced patterns are developed by an etch that selectively removes unexposed areas and retains converted ones. The optical density (OD) of 40 nm thick Bi/In films on quartz substrates, for example, changes from 3.3 OD to 0.37 OD in the annealed area. This has enabled the creation of direct-write photomasks for standard photoresist exposures. In this paper, the composition, morphology, and nanostructure of the resist before and after laser processing were studied in order to determine the mechanism of the laser-induced material conversion. AFM, XRD, and TEM show that the as-deposited films are polycrystalline, continuous, but with a rough, island morphology. Furnace anneals in air above the eutectic temperature (150–250°C, 3 hours) result in the formation of the tetragonal phase BiIn with a small degree of oxidation. The island morphology is maintained but there is evidence of melting and recrystallization. Transparency is much lower than after laser annealing. RBS and NRA depth profile analysis show that Bi/In films exposed to laser annealing in air contain a large fraction of oxygen and suggest that the converted film may be a BiIn0.6O6 /Bi0.3InO6 bilayer.

The formation of Ni germanosilicides during solid-state interaction between Ni and heavily B-doped strained epitaxial Si1-xGex films with x=0.18, 0.32 and 0.37 is studied. No NiSi2 is found in these samples even after annealing at 850 °C, which can be compared to the formation of NiSi2 at 750 °C on Si(100). Resistance and diffraction studies for the Si0.82Ge0.18 sample indicate that NiSi0.82Ge0.18 forms and the NiSi0.82Ge0.18/Si0.82Ge0.18 structure is stable from 400 to 700 °C. For the NiSi1-uGeu formed in all Si1-xGex samples, where u can be different from x, a strong film texturing is observed. When the Ge fraction is increased from 18 at.% to 32–37 at.%, the morphological stability of the film is degraded and a substantial increase in sheet resistance occurs already at 600 °C. The contact resistivity for the NiSi0.8Ge0.2/Si0.8Ge0.2 interface formed at 550 °C is determined as 1.2×10-7 Ωcm2, which satisfies the RS contact resistivity requirement for the 70 nm technology node.

In this work, low temperature (300 – 450°C) plasma nitridation was conducted using N2O and NH3 atmosphere to produce an ultrathin SiOxNy layer. The bonding structure, distribution, and quantity of nitrogen and their effects on the growth kinetic of SiOxNy layers are studied by X-ray photoelectron spectroscopy (XPS). It is found that nitrogen atoms pile at the SiOxNy/Si interface at the very beginning of plasma N2O and NH3 nitridation. Due to the lack of additional Si source and low diffusivity of O or N atoms at low temperature, plasma nitridation will form a self-limited growth of SiOxNy layer. Thermal stability of the interlayer between ultrathin Ta2O5 films on bare Si, plasma N2O nitrided Si, and plasma NH3 nitrided Si is also studied.

Once annealed, high-k metal oxides such as HfO2 and Al2O3 can be extremely difficult to etch by wet chemical methods. Here we describe how ion bombardment at relatively low energy (a few hundred eV) can be used to make exposed regions of annealed HfO2 films etchable in aqueous HF-based solutions. HfO2 layers, 2–5 nm in thickness, were deposited by atomic layer chemical vapor deposition (ALCVD) on Si substrates, annealed at 700 °C, and subjected to selected-area ion bombardment supplied by an oxygen plasma in a reactive ion etching tool. Etch times (as indicated by time to “dewet“) were examined as a function of HfO2 thickness, the power and time of oxygen plasma treatments, post-oxygen-plasma anneals, and wet etch chemistry. Strategies for etching thicker films and additional data provided by electrochemical open circuit potential (OCP) measurements will also be discussed.

A plasma-enhanced chemical vapor deposition-based nitrogen-free dielectric anti-reflective coating was successfully developed for use in 90nm interconnects in conjunction with low κ materials. By choosing N-free precursors, it was possible to eliminate any adverse interactions between the NH2 amine group and the DUV 193nm photoresist that is directly in contact with the anti-reflective coating (ARC), thus eliminating major source of photoresist poisoning-induced footing. N-free dielectric ARC demonstrated a wide tunable range of its optical properties at 193nm in a single wafer PECVD reactor: 1.6<n<1.9 and 0< k<1.1. This range enables cost-effective and in-situ deposition of a dual-layer dielectric ARC on the low λ dielectric layers during the dual damascene process. The dual-layer coating, which consists of a phase-shift layer on an absorbing layer, can keep the substrate reflectivity below 1% across the wafer, minimizing CD swing. N-Free dielectric ARC can be easily integrated with low κ dielectrics. Its adhesion with low κ materials is excellent and it can be etched and chemically and mechanically polished together with low κ dielectrics.

A series of electron microscopy investigations on the microstructure produced by surface-diffusion reactions between Si substrates heated to 700–800°C and Ti-Co, Ti-Ni or Ta-Ni alloys deposited in a nitrogen ambient with and without barrier layers are described. The TEM data show clear phase separation into TaSi2 and NiSi2 for the Ta-Ni film deposited in a high N2 pressure ambient. Deposition at lower N2 pressure led to the formation of a mixed Ni-Ta-Si layer. The phase separation effect was also absent for Ni-Ti films even at high N2 pressure. The presence of barrier layers strongly affected the surface diffusion reactions in the Co-Ti-Si system. Formation of Ti-(O) or CoSix amorphous layers at the Si surface prevented the interdiffusion of Si and Co, such that even pure Co or Co2Si layers could be formed.

Y2O3 thin films were grown directly on Si (001) by MBE and annealed in-situ under UHV at various annealing temperatures. The samples were investigated in-situ by RHEED and ex-situ by HRTEM. A 7 to 15 Å thick non-uniform interfacial amorphous layer is observed in the as-grown sample. After annealing at 490°C under UHV for 30 minutes the amorphous layer is reduced and a sharp Y2O3/Si interface is obtained. At higher annealing temperatures, YSi2 islands start to form at the Y2O3/Si interface. I-V measurements performed on generic MIS structures show that the annealed samples exhibit higher leakage current density than the as-grown sample, due to reduction of the wide band gap interfacial layer. Leakage current densities in annealed samples remain below 1A/cm2, which is acceptable for future high-κ transistor fabrication.

The ability of controlling the growth and interfaces of ultrathin dielectric films on Si and compound semiconductors by ultrahigh vacuum physical vapor deposition has led to comprehensive studies of gate stacks employing the high κ gate oxide Ga2O3(Gd2O3), and the rare earth oxides Gd2O3 and Y2O3. The epitaxy and the interfaces of Gd2O3 on GaAs, GaN, and Si were characterized with atomic precision, and show strong tendency to conform to the underlying substrate, thus providing insight into the fundamental mechanism for low interfacial state density and effective passivation of GaAs and GaN surfaces. These Gd2O3 and Y2O3 gate stacks of abrupt interfaces and controlled microstructures were employed as a model system to elucidate critical issues of materials integration in CMOS scaling.

The reactions of Ni with polycrystalline Si, Si0.82Ge0.18 and Si0.818Ge0.18C0.002 films in two different configurations during rapid thermal processing were studied. For the usually studied planar configuration with 20 nm thick Ni on 130–290 nm thick Si1-x-yGexCy, NiSi1-xGex(C) forms at 450°C on either Si0.82Ge0.18 or Si0.818Ge0.18C0.002, comparable to NiSi formed on Si. However, the agglomeration of NiSi1-xGex(C) on Si0.818Ge0.18C0.002 occurs at 625°C, about 50°C higher than that of NiSi1-xGex on Si0.82Ge0.18. For thin-film lateral diffusion couples, a 200-nm thick Ni film was in contact with 80–130 nm thick Si1-x-yGexCy through 1–10 μm sized contact openings in a 170 nm thick SiO2 isolation. While the Ni3Si phase was formed for both the Si0.82Ge0.18 and Si0.818Ge0.18C0.002 samples, the presence of 0.2 at.% C caused a slightly slower lateral growth.

Nickel silicides were formed on Si (100) substrates and CVD grown Si0.9Ge0.1/Si layers by low thermal budget annealing of evaporated Ni films to evaluate their utility for ultra shallow junctions. The phase formation and microstructure of silicides formed using conventional furnace and rapid thermal annealing were studied by x-ray diffraction, Rutherford backscattering (RBS), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy. RBS simulations and XPS study revealed the formation of a ternary nickel germanosilicide phase for the SiGe alloy. The incorporation of Ge resulted in a higher temperature window for the stability of low-resistive monosilicide phase. Electrical properties of the grown silicides were characterized by four-probe resistivity and contact resistance measurements.

Substantial amount of fixed charge present in most of the alternative gate dielectrics gives rise to large shifts in the flat-band voltage (VFB) and charge trapping and de-trapping causes hysterectic changes on voltage cycling. Both phenomena affect stable and reliable transistor operation. In this paper we have studied for the first time the effect of post-metallization hydrogen annealing on the C-V curve of MOS capacitors employing zirconia, one of the most promising gate dielectric. Samples were annealed in hydrogen ambient for up to 30 minutes at different temperatures ranging from room temperature to 400°C. C-V measurements were done after annealing at each temperature and the hysteresis width was calculated from the C-V curves. A minimum hysteresis width of ∼35 mV was observed on annealing the sample at 200°C confirming the excellent suitability of this dielectric.

Hafnium oxide is a promising dielectric for future microelectronic applications. HfO2 thin films (10–75nm) were deposited on Pt/SiO2/Si and quartz substrates by Pulsed DC magnetron reactive sputtering. Top electrodes of Pt were formed by e-beam evaporation through an aperture mask on the HfO2/Pt/SiO2/Si samples to create MIM capacitors. Various process conditions (Ar/O2 ratio, DC power, and deposition rate) and post-deposition annealing conditions (time and temperature) were investigated. The structure of the HfO2 films was characterized by X-ray diffraction (XRD) and the roughness was measured by a profilometer. The electrical properties were characterized in terms of their relative permittivity (εr(T) and εr(f)), and leakage behavior (I-V and I-t). The electrical measurements were performed over a temperature range from –5 to 200°C. For the best samples, the relative permittivity of HfO2 was found to be ∼27 after anneal and increased by 0.027%/°C with increasing temperature over the measured temperature range. At 25°C, leakage current density was below 10-8 A/cm2 at 1 volt. The optical bandgap was measured to be 5.4eV after anneal.

Using density-functional theory with ultrasoft pseudopotentials, we previously investigated the structural and electronic properties of the low-pressure (cubic, tetragonal, and monoclinic) phases of ZrO2 and HfO2, in order to elucidate phonon modes, Born effective charge tensors, and especially the lattice dielectric response in these phases. We now extend this previous work by carrying out similar calculations on the two high-pressure orthorhombic phases, and by providing density-of-states and band-gap information on all polymorphs. Our results show that the electronic structures and dielectric responses are strongly phase-dependent. In particular, the monoclinic phases of ZrO2 and HfO2 are found to have a strongly anisotropic dielectric tensor and a rather small orientational average () compared to the two other low-pressure phases. Our calculations show that is even smaller in the orthorhombic phases.

There is great need for a mechanistic understanding of growth chemistry during atomic layer deposition (ALD) of films for electronic applications. Since commercial ALD reactors are presently not equipped for in situ spectroscopy, we have constructed a model reactor that enables single-pass transmission infrared spectroscopy to be performed in situ on a layer-by-layer basis. We demonstrate the viability of this approach for the study of aluminum oxide growth on silicon surfaces, motivated by alternative gate oxide applications. Thanks to submonolayer dielectric and adsorbate sensitivity, we can quantify oxide thicknesses and hydroxyl areal densities on thermal and chemical SiO2/Si(100) substrates. Methyl formation and hydroxyl consumption upon initial trimethylaluminum (TMA) reaction can also be followed. We verify that in situ grown Al2O3 films are compatible in structure to films grown in a commercial ALD reactor.