A novel methodology using a combination of ion scattering, x-ray reflectivity (SXR), and small angle neutron scattering was used to characterize the structure and properties of a hydrogen silsesquioxane (HSQ) based porous low-k dielectric films after varying process conditions. The dielectric constant and the remaining Si-H fraction (degree of cure) of the samples were varied from 1.5 to 2.2 and from 30 % to 52 %, respectively, by controlling the mass ratio of the solvent and the HSQ resin in the initial solutions and the wet ammonia treatment time. We determined the density depth profile, average mass density, wall density, porosity, average pore size, average wall thickness, pore connectivity and atomic composition. The chemical bond structures were also measured using Fourier transform infrared (FTIR) spectroscopy. The density profile of each porous low-k film was uniform and only two layers were required to fit the experimental SXR data. Higher dielectric constant films show significantly higher wall densities and lower porosities and pore sizes. The measured increases in the wall density with lower Si-H fractions are consistent with the FTIR results.

We report a study on the properties of Ionized Metal Plasma (IMP) Ta, Ta(N) and multi-layer Ta/Ta(N) based on a comparative evaluation of their performance as diffusion barriers in Cu based metallization schemes. The film structures used in this study are: IMP Cu(2000Å)/IMP Ta(250Å)/Si; IMP Cu(2000Å)/IMP Ta(N)(250Å)/Si; and IMP Cu(2000Å)/IMP multi-layer Ta/Ta(N)(250Å)/Si. The samples were annealed in N2 ambient at 500 °C, 550°C, 600°C and 650°C, respectively, for 30 minutes. The failure behavior and film properties of different barriers were investigated using MetaPULSE, Film stress measurement (FSM), Four-point probe (FPP), X-ray diffractometry (XRD), Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM). It has been observed clearly from the sheet resistance measurements that failures of Ta(N) and Ta barriers occurred at 550°C and 600°C respectively, whereas the multi-layer Ta/Ta(N) could still survive from the annealing up to 650°C. Evidence showing the formation of Cu3Si in the failed film stacks was found from XRD spectra. Based on our studies, it can be concluded that microstructures of the barriers has the major effects on preventing Cu from diffusing through them to react with Si and this makes the multi-layer Ta/Ta(N), in overall, superior to the other two Ta and Ta(N) barriers.

We have successively developed a new x-ray scattering technique for a non-destructive determination of pore-size distributions in porous low-κ thin films formed on thick substrates. The pore size distribution in a film is derived from x-ray diffuse scattering data, which are measured using offset θ/2θ scans to avoid strong specular reflections from the film surface and its substrate. Γ-distribution mode for the pores in the film is used in the calculation. The average diameter and the dispersion parameter of the Γ-distribution function are varied and refined by computer so that the calculated scattering pattern best matches to the experimental pattern. The technique has been used to analyze porous methyl silsesquioxane (MSQ) films. The pore size distributions determined by the x-ray scattering technique agree with that of the commonly used gas adsorption technique. The x-ray technique has been also used successfully determine small pores less than one nanometer in diameter, which is well below the lowest limit of the gas adsorption technique.

Scaling requirements of the semiconductor industry demand interlayer dielectric materials with low dielectric constants, chemical compatibility with Cu, thermal and mechanical stability, and the capability of integration into planned device structures. We have developed a novel low-k silica gel processing technique capable of both bulk and spin-on film architectures. Derived from fluorinated silica, this gel exhibits very low dielectric constants (1.18 in bulk and 2.1 in thin film measured using AC impedance methods). Structural determination from FTIR illustrates a fluorinated silica structure with shortened Si-O bonds, however, the fluorine is lost after annealing at elevated temperatures. Microstructural analysis by TEM indicate a highly unusual morphology with highly linked features and pore sizes in the 30nm range, coinciding with nitrogen adsorption results. Mechanical properties of the thin films, as studied by nanoindentation methods, shows that the films have extraordinarily high elastic moduli (12GPa) and hardness (1GPa).

Copper interconnect metallizations in next generation integrated circuits will require thin diffusion barrier layers (<20 nm) between the Cu and low-k dielectric which may also function as seed layers for subsequent material depositions. One possible structure entails a multicomponent diffusion barrier with a lower resistivity component, such as W on WNx. In this study, sputtered WNx/W bilayer thin films were investigated as diffusion barriers between Si and Cu. The total thickness of the WNx/W bilayer was fixed at 20 nm while the WNx thickness was varied from 0 to 20 nm. After deposition of the barrier films, a 100 nm thick Cu film was sputtered over the top of the á-W and amorphous WNx bilayer. The as-deposited WNx/W film stress was found to be strongly dependent on the relative amount of WNx and W present and the addition of a Cu overlayer was found to mitigate the stress levels. The WNx/W barriers remained stable after 650°C anneals and exhibited phase transformations to W2N. Microstructural characterization using transmission electron microscopy and x-ray diffraction and chemical analysis by x-ray photoelectron spectroscopy of the films were used to identify the as-deposited and transformed phases.

The effects of Al underlayer between Ti and TiN on the electromigration (EM) lifetime of Al stack film were compared by the package-level and conventional wafer-level EM tests. The higher EM resistance of the Al stacks prepared with Ti underlayer can be best explained by their better Al (111) texture and grain size distribution than those with TiN underlayer. The surface roughness of the underlayer is related to the grain size distribution and surface roughness of Al film.

The density depth profile and chemical bond structure of hydrogen silsesquioxane (HSQ) thin films treated with an N2 plasma with varying power and exposure time were measured using specular x-ray reflectivity (SXR) and Fourier transform infrared (FTIR) spectroscopy. The SXR data indicate that the density profile of an untreated HSQ film is not uniform and four layers with different electron densities were required to fit the SXR data. For HSQ films treated with either increasing plasma power or plasma exposure time, the film roughness increased and a densified layer was observed at the film/air interface. The thickness of the densified layer increased with both plasma power and plasma exposure time. As a result, up to seven distinct layers were used to model the experimental SXR data from plasma treated films. The FTIR data show that the plasma transforms the Si-H bonds in the HSQ film into Si-O bonds leaving more oxygen atoms around a Si atom. These data are also consistent with the densification observed in the SXR measurements. In general, the HSQ film is more sensitive to increasing plasma power than to increasing plasma exposure time.

Carbon-containing silicon oxide (SiOC) is regarded as a potential low dielectric constant (low-κ) material for an interlayer dielectric (ILD) in next generation interconnection. In this study, we present the fundamental film properties and integration process compatibility of the low-κ SiOC film deposited by using bistrimethylsilylmethane (BTMSM) precursor. As more carbon was incorporated into film, both film density and dielectric constant decreased. The lowest κ-value, which we have obtained in this study, was 2.3 and the hardness of SiOC film was 1.1GPa as well as showing the thermal stability up to 500°C. In case of using conventional gases, organic components in SiOC film restricted etch rate. However, O2 addition could make it possible to obtaine a reasonable etch rate. The post-treatment of SiOC film in hydrogen plasma improved the resistance to O2 plasma in ashing process. The compatibility of SiOC film to the CMP process was also examined.

Application to aluminum deposition using ion-plating method is described. This method has several superior features for generating highly (111) orientation. The origin of this orientation and surface roughness are discussed in connection with a kinetic energy of the ions. The film properties thus made were compared with those of a conventional sputtered film. The higher (111) oriented film showed high resistance against hillock formation even after annealing at high temperatures. An effect of a plasma cleaning of substrate surface was confirmed to be quite helpful for promotion of (111) preferred orientation.

We have characterized the electromigration performance of copper damascene interconnects using moderately and highly accelerated lifetime tests respectively at package and wafer level. Two metallizations have been studied: Chemical Vapor Deposition (CVD) copper deposited on CVD TiN (Process A) and electroplated (ECD) copper deposited on CVD TiN using 90 nm of CVD copper as a seed-layer (Process B). All metallizations were passivated with SiO2. Two line widths have been characterized: 0.6μm and 4μm.

For wide lines, we obtained similar activation energies (Ea) for both metallizations (0.63 for process A and 0.65 eV for process B). For narrow lines, the Ea value is 0.8eV for CVD copper whereas it is higher than 1eV for ECD copper. For wide lines of both metallizations, failure analysis performed with a Scanning Electron Microscope (SEM) gave clear evidences that microstructural gradients have a strong impact on voids and extrusions formation (i.e. that grain boundaries are an active diffusion path in spite of low Ea values). For narrow lines, diffusion at the upper interface is believed to be the main diffusion path.

From the reliability point of view, the extrapolated lifetimes of the metallization including ECD copper are much higher (1 to 2 orders of magnitude depending on the line width) than for CVD copper.

The electromigration performance of copper damascene interconnects has been studied with respect to hillock formation and is compared to void formation failure mode. The metal lines consisted of Chemical Vapor Deposition (CVD) copper deposited on CVD TiN and capped with SiN. SiO2 was used for copper lines insulation and final passivation. Two line widths (0.5 and 3µm) have been characterized. It is shown that higher activation energy values are obtained for void formation failure mode, respectively Ea = 0.86 eV for wide lines (poly-grain microstructure) and Ea =1.04 eV for narrow lines (quasi-bamboo microstructure) than for extrusion failure mode. Failure analysis performed with a Scanning Electron Microscope (SEM) showed that grain boundaries are active diffusion paths in polycrystalline copper lines whereas interface diffusion is believed to be the main diffusion path in narrow lines. Extrusions are shown to occur at the upper interface of copper damascene lines and to extend laterally as a consequence of cracks in dielectric layers and are thus responsible for short circuit between adjacent lines. Implications on extrapolated lifetimes at operating conditions are discussed.

Density/porosity and stiffness are the most critical parameters determining properties of porous films, however they are difficult to measure. Here we report characterization of density/porosity and Young's modulus values of a range of nanoporous silica aerogel films via dispersion of laser-generated wideband surface acoustic waves. Results are compared to dielectric constant, Rutherford Backscattering Spectrometry (RBS), Ellipsometric Porosimetry (EP) and Nanoindentation (NI). RBS density correlates well to SAW. EP and NI also show a correlation, however the absolute values do not match. Low Young's modulus values show that the film stiffness is drastically reduced with increasing porosity. The technique is rapid, nondestructive and relatively inexpensive, and yields absolute values of nanoporous aerogel elastic properties which are useful for process control and are difficult to access with other techniques.

Copper penetration in thermal oxide was investigated using MOS capacitors by annealing at 450 °C and bias-temperature stress at 250 °C. Copper induces minority carrier generation lifetime decay and oxide leakage current increase. Degradation is enhanced by capacitor biasing, which confirms the role of Cu+ ions. The current-voltage characteristics are consistent with Poole-Frenkel model, showing that electron transport proceeds through traps created in the oxide bulk by copper. When a negative bias is applied, copper traps are removed from oxide near SiO2-Si interface and the leakage current is cancelled but the generation lifetime remains nil, copper contamination of silicon surface being not removed.

None of these effects are observed when the copper gate is separated from oxide by a 10 nm TiN layer, proving that this material is an efficient barrier against copper diffusion at 450°C.

A new process was developed for deposition of the tungsten nitride at moderate substrate temperatures (350-400 °C). The tungsten source bis (tert-butylamido)bis(tertbutylimido) tungsten, (tBuNH)2(tBuN)2W, reacts with ammonia in a low-pressure CVD reactor. Growth rates ranged from about 0.6 to 4.1 nm per minute. The stoichiometry of the films varied from WN1.2O1.7 to WN1.6o0.25, depending mainly on deposition temperature. The films are amorphous by X-ray diffraction, and smooth by scanning electron microscopy. Step coverage is nearly 100% in vias with an aspect ratio of 6:1 for films deposited at 400 °C or lower. Barriers 45 nm thick resist diffusion of copper up to temperatures of 600 °C. Adhesion is strong to all substrates tested, including silicon, silicon dioxide, soda-lime glass, glassy carbon, aluminum and stainless steel. This new halogen-free process avoids halogen contamination of films and corrosion of equipment. Uniformity of thickness and stoichiometry are readily achieved. This process is a promising method for forming copper diffusion barriers in future generations of microelectronics.

In this work we present investigations of the nucleation and growth of evaporated copper on several low-k polymers. The evolving interfaces were characterized using transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results were compared between the PMDA/ODA polyimide, Teflon AF 1601 and Silk®. A diffusion coefficient for copper atoms in Silk® determined by low energy ion-beam depth profiling in conjunction with XPS is reported.

In these studies a comprehensive picture of void shape evolution dynamics and its strong dependence on the initial configuration has been thoroughly investigated by utilizing hypocycloid algebra to generate four different shapes of main interest. Our mathematical model on the isotropic diffusion and mass accumulation on void surfaces, under the action of applied electrostatic potential and capillary effects, follows a novel irreversible but discrete thermodynamic formalism of interphases and surfaces.

As a result during the intragranual motion, in addition to the crescent-like slit formation, very rich and also unusual void morphological variations such as fragmentations into the daughter voids or inner island generation have been observed under the severe (normalized) electron wind intensities or very long exposure times. In these numerical experiments, the Euler's method of finite differences with an automatic time step self-adjustment has been utilized in combination with a rather powerful and fast indirect boundary element method (IBEM) for the solution of the Laplace equation.

Atomic Layer Deposition (ALD) is an emerging ultra-thin film deposition technique for advanced microelectronics applications. Enabling features of ALD are precise control over film thickness, excellent conformality and relative insensitivity to wafer size. Additionally, ALD allows interface and film engineering that can be utilized to maximize device performance within the minimum feature size requirements. This paper reports on the compositional, structural and electrical properties of engineered Ti-Ta-N composite films grown by ALD at 360°C. For a wide range of composition these Ti-Ta-N films exhibit resistivity from 500 to 2000 μω-cm, high density, and 100 % step coverage. Additionally, the ability to control texture by changing film composition is established. Based on experimental results, an approach to grow Composite Engineered Barriers by ALD (CEBA) is described that could provide a solution to the challenging barrier requirements.