We have investigated the use of low-temperature (320 °C) molecular-beam epitaxy (MBE) to form highly conductive, p+, ultra-shallow layers in Si. Although the as-grown B-doped Si is electrically active, in a practical application the doped layers may be exposed to high temperature during post-growth device processing. To minimize the B diffusion, we investigated the use of SiGe diffusion barrier layers. In this work we demonstrate there is less B redistribution with the SiGe diffusion barriers. The use of SiGe diffusion barriers may prove to be critical in the activation of B implants for the formation of ultra-shallow junctions.

We have investigated physical and electrical properties of Al2O3, HfO2, and their alloy films deposited on 300mm Si wafers by Atomic Layer Deposition (ALD). It is found that Al2O3 films are not crystallized even after the heat treatment of 1050°C, while HfO2 films are already crystallized even after a-Si deposition (530°C). The crystallization temperature can be higher by adding Al2O3 to HfO2. It is confirmed by in-plane XRD and plane views of TEM that HfAlOx films with lower Hf content (Hf/(Hf+Al) <30%) are amorphous without phase separation after annealing at 1050°C and 5sec. The dependences of equivalent oxide thicknesses (EOT) on the physical thicknesses of Al2O3, HfAlOx (Hf/(Hf+Al)∼22%), and HfO2 films in poly-silicon gate capacitors indicate that those dielectric constants k are ∼9, 14, and 23, respectively. The gate dielectric with EOT of 1.5nm and the leakage current density Jg of 3mA/cm2 can be fabricated with 2nm-thick HfAlOx (22%) film.

First-principles calculations are performed for high-K gate dielectric materials using model bulk and interface systems. Detailed electronic structures and atomic configurations are investigated for transition metal (Hf and Zr) oxide, metal doped silicate bulk system and a model Si-silicate interface system. Pseudo polymorphs of metal oxides are investigated to elucidate the underlying driving mechanisms in microscopic configurations of metal oxides and silicates in amorphous structures. We studied energetics and electronic structure of metal oxide pseudo morph with varying oxygen coordination. Dielectric constants of metal oxide and silicate materials are also investigated using the density functional perturbation theory method implemented in the ABINIT code. Electronic and dielectric properties of silica interface layers between high-κ dielectric and Si substrate are investigated leading to a confirmation that 1 nm is the physical limit of gate oxide thickness. Furthermore silica interface layer is found to have small dielectric constant of 3.4∼3.9.

We report on metal-organic chemical vapor deposition (MOCVD) of ultrathin zirconium dioxide on (100) silicon. Special emphasis is put on the evolution of surface topography and the impact of processing parameters on the chemical composition of the films. Electrical characterization by means of MOS structures has been performed to assess the interface quality and the dielectric properties of the layers. Interface trap density is observed to be around 5.1011 cm-2.eV-1 at midgap for (100)-oriented substrates. Leakage currents in the ultrathin regime are significantly reduced compared to equivalent SiO2-layers. Trap density and leakage current are strongly sensitive to annealing in different atmospheres. However, electrical characteristics are shown to be positively affected rather by annealing in slightly reducing than in oxidizing atmospheres. All temperatures throughout the gate insulator formation process do not need to exceed 650°C, and thus allow to keep the thermal budget low.

The effects of several rare earth oxide on the capacitance-voltage (C-V) characteristics and the SiO2 interlayer growth of ZrO2 based gate dielectrics were examined. The width of the hysteresis window of La2O3 stabilized ZrO2 (LaSZ) gate dielectric was only 0.2V, on the other hands, that of Sc2O3 stabilized ZrO2 (ScSZ) gate dielectric was 1.4V HRTEM analysis indicated that the growth of SiO2 interlayer of RSZ (R=Sm,Nd,La) gate dielectric was about 1nm, which was less than half of the ScSZ one. These results indicate the advantage of the ZrO2 gate dielectric doped with rare earth oxide composed of larger ionic radius cation.

A fast screening technique is used to study the ALD HfO2 growth behavior on different types of starting surfaces (H-passivated, chemical oxide, thermal oxide). The amount of Hf deposited at the early stages of the ALD process is measured by means of RBS. The HfO2 film quality on different starting surfaces is examined with ToFSIMS. The results suggest an island growth mechanism on a H-terminated starting surface: nucleation, development of separated nuclei and flattening. It is shown that ALD growth starts faster if –OH groups are present on the surface. A remote H2 plasma surface pre-treatment at room temperature is also studied. The influence of the plasma exposure time and number of water pulses prior to HfO2 deposition was examined. The H2 plasma surface pre-treatment can be considered as a promising candidate for sub 1 nm EOT performance.

Thin films of samarium oxide, Sm2O3, have been grown on Si(100) and fused quartz by low-pressure MOCVD using an adducted β-diketonate precursor developed in house. It is found that the nature of the film grown is strongly dependent on substrate temperature. As examined by X-ray diffraction, the films of Sm2O3 grown at lower temperatures (∼550°C) on fused quartz are cubic and display a random grain orientation, while they become highly oriented in the (111) direction as the growth temperature is increased (to 625°C). On Si(100), highly oriented films of cubic Sm2O3 are obtained at a substrate temperature of 625°C. When the growth temperature is raised, the phase changes to monoclinic. The morphology of the films grown on both quartz and Si(100) substrates has been studied by scanning electron microscopy and atomic force microscopy. The growth of strongly oriented Sm2O3 on the disordered surface of fused quartz may be interpreted as being driven by the minimization of surface energy.

Targeting very thin equivalent oxides (<1 nm) requires the deposition of (very) thin dielectrica onto silicon surfaces with minimal interfacial oxide. Typically, high-k dielectric layers are deposited using ALD or MOCVD with, at present, a prime emphasis on Hf-based high-k dielectrics, either as pure HfO2, as silicate or mixed with Al2O3. In some cases nitrogen is added to improve the high-temperature stability. Depending on the deposition conditions ALD as well as MOCVD show serious deficiencies in terms of film closure and material density for ultra thin (<3 nm) films. Various surface preparation methods and deposition conditions are used to improve the film quality. Detailed studies on the film growth and its evolution requires the use of many analytical methods such as Rutherford Backscattering Spectrometry, Low Energy Ion Scattering, Time-of-flight SIMS, (spectroscopic) ellipsometry and X-ray photoelectron spectroscopy. When trying to correlate the results in terms of film thickness, apparent discrepancies can be observed which relate to non-homogeneous growth and reduced material density.

TaN has become a very promising diffusion barrier material for Cu interconnections, due to the high thermal stability requirement and thickness limitation for next generation ULSI devices. TaN has a variety of phases and Cu diffusion characteristics vary with different phases and microstructures. We have investigated the diffusivity of copper in single-crystal (NaCl-structured) and polycrystalline TaN thin films grown by pulsed laser deposition. The polycrystalline TaN films were grown directly on Si(100), while the single crystal films were grown with TiN buffer layers. Both of poly and single-crystal films with Cu overlayers were annealed at 500 °C, 600 °C, 650 °C, and 700 °C in vacuum to study the copper diffusion characteristics. The diffusion of copper into TaN was studied using STEM-Z contrast, where the contrast is proportional to Z (atomic number), and TEM. The diffusion distances are found to be about 5nm at 650°C for 30 min annealing. The diffusivity of Cu into single crystal TaN follows the relation D = (160±9.5)exp[-(3.27 ±0.1)eV/kBT]cm2s-1 in the temperature range of 600°C to 700°C. We observe that Cu diffusion in polycrystalline TaN thin films is nonuniform with enhanced diffusivities along the grain boundary.

We propose a new process for forming ultra-thin metal oxide films called vapor-liquid hybrid deposition (VALID). This process consists of two steps: i) adsorption of a metal-organic or metal-halide precursor from the gas phase, and ii) liquid-phase hydrolysis of the adsorbed precursors. Al2O3 films were grown using Al(CH3)3 and water. Growth rate was 0.18 nm per cycle at room temperature. The interface layer thickness was less than 1 nm after post-deposition annealing in vacuum at 750°C. C-V and I-V characteristics of Au/Al2O3/Si capacitors fabricated using VALID were well-behaved suggesting that this concept is a viable approach to form device-quality dielectrics.

In the present work, we report the deposition of zirconia thin films on Si(100) at various substrate temperatures by low-pressure metalorganic chemical vapor deposition (MOCVD). Three different zirconium complexes, viz., tetrakis(2,4-pentadionato)zirconium(IV), [Zr(pd)4], tetrakis(2,2,6,6-tetramethyl-3,5-heptadionato)zirconium(IV), [Zr(thd)4], and tetrakis(t-butyl-3-oxo-butanoato)zirconium(IV), [Zr(tbob)4] are used as precursors. The relationship between the molecular structures of the precursors and their thermal properties, as examined by TG/DTA is presented. The films deposited using these precursors have distinctly different morphology, though all of them are of the cubic phase. The films grown from Zr(thd)4 are well crystallized, showing faceted growth at 575°C, whereas the films grown from Zr(pd)4 and Zr(tbob)4 are not well crystallized, and display cracks. These differences in the observed microstructure may be attributed to the different chemical decomposition pathways of the precursors during the film growth, which influence the nucleation and the growth processes. This is also evidenced by the different kinetics of growth from these three precursors under otherwise identical CVD conditions. The details of thin film deposition, and film microstructure analysis by XRD and SEM is presented. The dielectric behavior of the films deposited from different precursors, as studied by C-V measurements, are compared.

This paper discusses metal organic chemical vapor deposited (MOCVD) HfO2 layers using tetrakis(diethylamido)hafnium (TDEAH) as precursor. We have studied the influence of the starting surface and deposition temperature on the growth kinetics and physical properties of the HfO2 layers. Important characteristics such as crystalline state, density, and organic contamination in the layers were found to be dependent on these parameters.

Typical for this deposition process is the formation of an interfacial layer underneath the high-k layer. Its composition and thickness, affecting scaling of the equivalent oxide thickness, are shown to be closely related to the HfO2 process parameters mentioned above.

Finally, we will show electrical results for HfO2/polySi gate stacks indicating the effect for deposition temperature.

Silicon germanium pMOSFETs with channel lengths down to 0.4m have been fabricated on limited area silicon germanium virtual substrates. The devices have a 5nm thick Si0.3Ge0.7 active layer grown by MBE on top of relaxed Si0.7Ge0.3 virtual substrate. Virtual substrates were grown on top of 10μm square silicon pillars defined by etching trenches around their perimeter into the original silicon substrate. This limits the area of the growth zone, which in turn promotes the relaxation of the virtual substrate. Electrical measurements on 2μm long channel devices show that the maximum mobility in the strained SiGe devices is 211cm2V-1cm-1, compared to 104cm2V-1cm-1 for silicon reference devices. This increase in hole mobility increases the current drive of 0.4m devices measured at Vgt=-2V, Vds=-2.5V from 154μA/m to 192μA/μm.

Yttria stabilized zirconia (YSZ) and zirconia (ZrO2) thin films without and with Nb-doping were prepared on Si substrate by rf-magnetron sputtering. Undoped YSZ and ZrO2 thin films had (001) orientation, and the orientation was unchanged by the Nb-doping. For both undoped YSZ and ZrO2 thin films, around 2.0 V ion-drift type hysteresis was clearly observed in capacitance-voltage (C-V) characteristics. Nb-doping into YSZ brought about the increase of lattice parameter up to 20 mol% of Nb, which suggests that Nb was incorporated into YSZ lattice up to 20 mol%. By the Nb-doping, the hysteresis in C-V characteristics for YSZ thin film was considerable decreased to around 0.1 V. Drastic suppression of the hysteresis in C-V characteristics was observed for Nb-doped ZrO2 thin film. In this case, the hysteresis was completely disappeared. These facts suggest that oxygen vacancies in YSZ and ZrO2 thin films would be suppressed or disappeared by Nb-doping. This means that Nb is a excellent dopant for both YSZ and ZrO2 to suppress the ion-drift type hysteresis.

We have studied the kinetics of NiSi agglomeration and NiSi2 phase formation during heating of NiSi on Si, using simultaneous in situ measurements of resistance, light scattering and x-ray diffraction. NiSi is a desirable contact to Si because of its low resistivity, limited Si consumption and low formation temperature. However, the formation of the higher resistivity phase NiSi2 must be avoided for device applications. Ni thin films 5 to 30 nm thick were deposited on substrates of poly-Si and silicon-on-insulator (SOI) and were studied using heating rates from 0.3 to 27 °C/s. At low heating rates and for the thinnest films studied, NiSi agglomeration precedes NiSi2 nucleation by as much as 350°C. The agglomeration temperature decreases with decreasing film thickness and linewidth. Once the film is agglomerated, the formation of NiSi2 is delayed to higher temperature by its low nucleation site density and decreased contact area. We conclude that agglomeration is the primary failure mechanism limiting the morphological stability of NiSi as a contact material to Si devices.

We report the characterization of carbonaceous aluminium oxide, Al2O3:C, films grown on Si(100) by metalorganic chemical vapor deposition. The focus is on the study of the effects of carbon on the dielectric properties of aluminium oxide in a qualitative manner. The carbon present in the aluminium oxide film derives from aluminium acetylacetonate used as the source of aluminium. As-grown films comprise nanometer-sized grains of alumina (∼ 20–50 nm) in an amorphous carbonaceous matrix, as examined by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The films are shiny; they are smooth as observed by scanning electron microscopy (SEM). An attempt has been made to explore the defects (viz., oxide charge density) in the aluminium oxide films using room temperature high frequency capacitance – voltage (C-V) and current–voltage (I-V) measurements. The hysteresis and stretch-out in the high frequency C-V plots is indicative of charge trapping. The role of heteroatoms, as characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy, in the transport of charge in Al2O3:C films is discussed.