Thin and continuous CVD Cu seed layer was successfully deposited on Ru under-layer by Cu oxide deposition and reduction method at 100°C with novel chemistry. Cu oxide was formed with Cu(hface)TMVS and H2O2 at 100°C, and this film was reduced with formic acid at 100°C. Deposited Cu oxide films were Cu2O that was confirmed by XRD and XPS. The morphology of oxide films showed smooth and continuous on Ru and Ta substrate. The reduced Cu film on Ru maintained good surface morphology, and no impurity was detected not only in the Cu film but also the interface between Cu and Ru. However, that on Ta had poor morphology by agglomeration of Cu film during reduction due to poor Cu wettability on oxidized Ta that was oxidized during oxide deposition. The readiness of reduction is very important merit of using Ru under-layer for this oxide deposition and reduction process. The oxide deposition and reduction method on Ru under-layer can be a promising candidate for thin and continuous seed layer deposition method.

As silicon-based microelectronic devices continue to aggressively scale down in size, traditional BEOL dielectric materials have become obsolete due to their relatively high dielectric constant. Organosilicate glass (OSG) materials have emerged as the predominant choice for intermetal dielectrics in advancing technology nodes. A potential failure mechanism for this class of low-k dielectric films during the manufacturing process is catastrophic fracture due to channel cracking. To improve the mechanical strength and stability of these silicon-based materials, the use of post-deposition curing processes is under evaluation. In this work, the effects of UV curing on the properties of OSG films were characterized. After UV curing, film hardness and elastic modulus are improved, with no change in the residual film stress. The average film density increases linearly as a function of UV exposure time. Channel crack propagation velocities decrease with UV exposure. The improvements in the mechanical properties of OSG films are believed to correlate with the increasing Si-O-Si bond population. Comparisons between post-deposition UV and Electron Beam curing processes are provided.

This work shows that the addition of dielectric levels in interconnect stacks increases significantly the CMP-induced peeling. The fracture energies, measured by 4-point bending technique, are less sensitive to the level number increase, even if they are slightly degraded. This leads to the conclusion that delamination during polishing depends highly on the stack elastic properties and there is no simple correlation between stack adhesion and peeling during CMP. In this work, mechanical damages generated during CMP in the dielectric stack before peeling were also investigated. It was shown that, if no peeling appears, CMP have no effect on stack reliability. This indicates that negligible “fatigue” effect takes place during CMP.

This paper describes the influence of microstructure, or more specifically grain orientation and grain size, on the in-line monitoring of copper interconnect properties during (self)-anneal using surface acoustic wave spectroscopy (SAWS). In electroplated Cu after (self)-anneal the SAWS frequency is lower for samples annealed at higher temperature because of the lower porosity induced elasticity. In sputtered Cu, the SAWS frequency shows a clear correlation with grain size, which is induced by a strong re-orientation of the copper film from the as-deposited (111) texture (E=190 GPa) to a strongly (100) textured super grain structure (E=78GPa).

Spin-on pure-silica-zeolite MFI films consist of zeolite nanocrystals embedded in a compacted silica matrix of zeolite primary nanoparticles. They appear to be promising as a low-k material due to their good mechanical properties and high microporosity, parallel to their intrinsic low k-value. Results are promising but the implementation of this material is still far away. To contribute to the implementation we present a study on the final film properties depending on the zeolite MFI nanocrystal size. Different techniques are used for the characterization: Dynamic Light Scattering, X-ray diffraction, Scanning Electron Microscopy, Nitrogen adsorption, EllipsoPorosimetry using toluene and NanoIndentation. The results show a clear dependence of the film properties on the nanocrystal size. Clearly, smaller nanocrystals provide better homogeneity, smaller pore size and higher mechanical properties. However, due to the hydrophilicity of the silica matrix lower k-values are only obtained for larger zeolite nanocrystals which provide with higher crystallinity in the films.

A recently developed bidirectional thermal expansion measurement (BTEM) method was applied to different types of low-k films to substantiate the reliability of the Poisson's ratio found with this technique and thereby to corroborate its practical utility. In this work, the Poisson's ratio was determined by obtaining the temperature gradient of the biaxial thermal stress from substrate curvature measurements, the temperature gradient of the whole thermal expansion strain along the film thickness from x-ray reflectivity (XRR) measurements, and reduced modulus of the film from nanoindentation measurements. For silicon oxide-based SiOC film having a thickness of 382.5 nm, the Poisson's ratio, Young's modulus and thermal extension coefficient (TEC) were determined to be Vf = 0.26, αf =21 ppm/K and Ef =9,7 GPa. These data are close to the levels of metals and polymers rather than the levels of fused silicon oxide, which is characterized by Vf = 0.17 and Er = 69.6 GPa. The alkyl component in the silicon oxide-based framework is thought to act as an agent in reducing the modulus and elevating the Poisson's ratio in SiOC low-k materials. In the case of an organic polymer SiLK film with a thickness of 501.5 nm, the Poisson's ratio, Young's modulus and TEC were determined to be Vf = 0.39, αf =74 ppm/K and Er =3.1 GPa, which are in the typical range of V= 0.34~0.47 with E =1.0~10 GPa for polymer materials. From the viewpoint of the relationship between the Poisson's ratio and Young's modulus as classified by different material types, the Poisson's ratios found for the silicon oxide-based SiOC and organic SiLK films are reasonable values, thereby confirming that BTEM is a reliable and effective method for evaluating the Poisson's ratio of thin films.

During the manufacturing process of the BEOL the low-k brittle ILD dielectrics are exposed to wet environments. These environments could and do affect the films fracture toughness, the so called critical film thickness, above which spontaneous cracking occurs. Nanoindentation combined with AFM imaging methods allow to study these phenomena.

Very few porous low-k dielectric materials meet the basic requirements for integration into the back end of the line (BEOL) metallization. According to the International Technology Roadmap for Semiconductors, 2005, candidates for the 45 nm node need a k<2.2 and a minimum adhesion strength of 5 J/m2. Recently, a low-k dielectric material was developed, called nano-clustered silica (NCS). It is a spin-on glass with k<2.3. NCS is constitutively porous, with a micro- and mesopore size of ~2.8 nm. The first reported adhesion strength of this material was 10+ J/m2. We investigated the nature of the adhesive strength of NCS by critical and sub-critical fracture and Fourier Transform IR Spectroscopy (FTIR). The four-point bend technique and a mixed-mode double cantilever beam technique were employed. The sub-critical crack growth studies were performed in humid environments and ambient temperatures. Different post-treatments were used on NCS to achieve different molecular structure, as measured with FTIR. A correlation between molecular structure and critical adhesion energy was found. Atomistic parameters were calculated from the sub-critical crack growth data. A dependency of fracture behavior on post-treatment and, therefore, structure was observed.

The degradation of SiOC(H) low-k films upon plasma treatments has been investigated. Three generations of SiOC(H) low-k dielectrics (k=3.0, k=2.6 and k=2.3) were used. The low-k materials have been exposed to N2O, NH3, O2, H2, He, Ar and N2 based plasmas, representing the most commonly-used plasmas during interconnect integration. For all plasma-treated samples, an increase in k-value and decrease in breakdown voltage was observed. These observations could be attributed to chemical degradation, in particular to carbon depletion and OH-bond formation. The latter leads to moisture adsorption, which was confirmed by contact angle measurements and FTIR spectra. The N2O plasma treatment was found to be the most aggressive for all low-k dielectrics studied. It drastically increases the k-value and the leakage current and results in complete carbon removal on the top-surface. This effect is most pronounced on the most porous material. On the other hand, an in-situ helium plasma shortly after low-k deposition enhances the resistance to chemical degradation upon exposure to other plasmas, even for the most aggressive ones. For the argon and reactive pre-clean plasmas, only small compositional changes were observed. In conclusion, it can be said that not only the plasma treatments have to be tuned in accordance with the low k integration requirements, but also attention has to be paid to limit moisture absorption during integration.

Porosity introduction in a-SiOCH matrix is a main research field in microelectronic. Two techniques are used to deposit these dielectric thin films: spin-on or Plasma Enhanced Chemical Vapor Deposition (PECVD). In this work, different porous a-SiOCH thin films (k close to 2.2 – 2.3) are studied. Several synthesis ways are used to deposit these a-SiOCH layers: by porogen approach, self assembling or nanoclustering techniques for spin-on, and using a porogen approach for PECVD. Impact of deposition process and curing on material crosslinking are investigated. The skeleton structure is correlated to the elastic properties whatever the deposition technique used. Finally, porosity and pore interconnectivity are studied and the results show that barrier diffusion is less pronounced in case of small pores size such as those obtained by PECVD.

To improve the speed of integrated circuits it is highly important to minimize the electrical resistivity of their interconnects. However, as the dimensions of the interconnects approach the mean free path of the electrons, a substantial rise in resistivity occurs due to additional electron scatterings from grain boundaries and interfaces. To investigate the role of interfaces, in-situ resistivity measurements were preformed for thin copper films on which different materials were deposited. The resistivity was monitored before and after the deposition, enabling to observe the changes as a new top interface was created. Among the materials tested, tantalum resulted in the highest resistivity increase. This fact is of special importance since this material and its nitride serve today as the common diffusion barrier for copper metallization. Titanium resulted in a smaller resistivity increase, but still higher than that of a free copper surface in vacuum. The developed approach enables to test the influence of different diffusion barriers on copper resistivity. With the continuously shrinking dimensions of copper interconnects, this factor will have an increasing importance in future technology nodes.

Ultra-thin platinum (Pt) films grown by atomic layer deposition (ALD) have been investigated as an alternative to conventional physical vapor deposited (PVD) Cu as seed layer for copper (Cu) electroplating. The wetting angles between the electrolyte and both Pt and Cu seed layers were analyzed using sessile-drop contact-angle analysis prior to plating. Both constant current and pulse reverse current (PRC) were applied to electroplate Cu on both types of blanket seed layers. Scanning electron microscope (SEM) revealed that Cu nucleation density on ALD Pt is lower than on its PVD Cu counterpart, after 30 seconds plating using PRC. Nevertheless, Cu nuclei were observed after only 1.0 minute plating on ALD Pt surfaces, and continuous Cu films were achieved at longer plating times. To fill trench structures coated with ALD Pt/TaN, PRC was applied using the same organic-additive-free electrolyte. Initial results suggest that these seed layers were adequate for ECD fill of trenches with 200 nm feature size and aspect ratio 7:1. The composition and microstructure of the Cu films were analyzed by Auger electron spectroscopy (AES), X-ray diffraction (XRD), and cross-sectional transmission electron microscopy (TEM). Thermal stability of the Cu/Pt system was examined by annealing in forming gas at 450°C for 1 hour and subsequent analysis by XRD and TEM.

This paper describes film characterization of Ultra Low-k (ULK) dielectrics modified by UV curing with different wavelength bands. We have demonstrated UV hardening of ULK-SiOC (k=2.65) with two types of UV bulbs (UV-X and UV-Y) and the UV modifications of ULK-SiOC film properties are characterized by using FT-IR spectroscopy, 29Si Solid-state NMR spectroscopy and Raman spectroscopy. FT-IR and NMR analyses reveal that UV-Y curing is preferable for UV curing modification of ULK-SiOC. UV-Y curing increases Q mode peak in NMR, resulting in the enhanced Si-O crosslinking, while UV-X curing increases TH mode and TOR mode peaks. Spin lattice relaxation time T1 for 29Si is decreased with UV curing. This result indicates that UV curing enhances molecular motion in Si-O network. Raman analysis shows that UV curing increases amorphous carbon groups, which corresponds to the enhanced molecular motion in Si-O network.

For the study of dielectric failures by Cu migration, TDDB (time dependent dielectric breakdown) and 1-D FDM simulation was carried out. We tested TDDB using a simple MIS structure with no barrier Cu electrode. From our TDDB results, the TTF's in the acceleration condition and the characteristic parameter of TDDB were obtained. In the simulation parts, 1-D FDM simulation was accomplished considering space charge effect due to Cu ions.

The objective of TDDB is to predict of TTF (time to failure) in the service condition form the results of an accelerating condition. The characteristic of TTF's follows E model in the accelerating condition, in the service condition, the deviation from E model was observed. This different characteristic of TTF can be explained by the mechanism of Cu migration enhanced by an applied E field. Our simulation and TDDB results reveal that the deviation from E model does not mean the change of failure mechanism, but it shows the characteristics of Cu migration.

The electrical and mechanical properties of low-k dielectric materials have received a great deal of attention in recent years; however, measurements of thermal properties such as the coefficient of thermal expansion remain minimal. This absence of data is due in part to the limited number of experimental techniques capable of measuring this parameter. Even when data does exist, it has generally not been collected on samples of a thickness relevant to current and future integrated processes. We present a procedure for using x-ray reflectivity to measure the coefficient of thermal expansion of sub-micron dielectric thin films. In particular, we elucidate the thin film mechanics required to extract this parameter for a supported film as opposed to a free-standing film. Results of measurements for a series of plasma-enhanced chemical vapor deposited and spin-on low-k dielectric thin films will be provided and compared.

Nanoindentation is the most convenient local technique for measuring elastic modulus, hardness, and fracture toughness of dielectric thin films. This approach is applied to bulk silicon and dielectric thin films (porous and non-porous) on silicon substrate. Reproducible stable cracks are generated from the edges of a cube corner indentor. The validity of theoretical model of use to estimate the toughness from cracks length has been checked on these reference cases. To calculate the toughness of thin film on Si substrate, we first established the loading range in which the cracks only affect the thin film without substrate damage. Several corrective terms have been introduced to the classical toughness estimation formula to take into account the proximity of the film/substrate interface and the residual stress pre-existing in the film. This approach is discussed by comparing experimental results obtained including these improvements to literature results.

We demonstrate the efficacy of Photoemission Electron Microscopy (PEEM) as a tool to detect metal diffusion processes at nanoscale spatial resolution in real time. For a sample comprising a nominally 1 nm physical vapor-deposited (PVD) Ru thin film covering a thick Cu substrate, we have observed the appearance of bright features on a dark background as the temperature is monotonically increased and irradiated with photons from a Hg arc lamp. These bright features are the result of a lower work function due to Cu diffusion through the Ru film.

The barrier metal properties of Plasma Enhanced ALD (PEALD) TaN deposited on low-k dielectric film (SiCOH) with a k value of 3.0 at a deposition temperature of 300°C by using pentakis (ethylmethylamino) tantalum (PEMAT) and various plasma gases was investigated. The film resistivity of TaN is about 1000 μΩ.cm under the plasma power of 200 W and the frequency of 400 KHz, respectively. The resistivity was significantly reduced by approximately 360 μΩ.cm for the optimized condition of 300 W and 13.56 MHz. In addition, good uniformity was obtained by applying two-step plasma treatment process. The film thickness per cycl of the TaN using two-step plasma was decreased from 1.0 Å to 0.65 Å by reducing a base pressure, indicating the increase of the film density. The PEALD TaN with almost 100% coverage in this paper's dual damascene structure has a contact resistance of about 1.6 Ω /chain at via size of 0.19um.

We study new deposition chemistry in Cu-SCFD (supercritical fluid deposition), especially effect of acetone is investigated as reducing agent and additives into H2 reducing Cu-SCFD. Acetone reduction yields Cu film deposition onto Ru coated Si substrate, because Ru has catalytic effect to generate reducing agent from acetone. When acetone is added into H2 reducing chemistry, the solubility of precursor is enhanced approximately 50 %, which is so-called “entrainer effect”. Ethanol can enhance the deposition of Cu in H2 reduction chemistry, which is a solvent effect. Two effects of entrainer effect by acetone and solvent effect by ethanol works independently, without interfering each other.

Slurries used for copper CMP have a rich chemistry, which may change during the course of polishing due to consumption and decomposition of molecular species. Various aspects, such as small layer thickness (<50 μm), continuous flow of the slurry, and dynamics of the film removal process pose great challenge to the monitoring of slurry components between the pad and the wafer. The slurry constituents such as oxidants and corrosion inhibitors have unique signatures that can be detected using spectroscopic techniques. In this paper, work carried out to explore the use of Raman spectroscopy to detect and quantitate chemical species such as hydroxylamine, benzotriazole and hydrogen peroxide in-situ will be presented. More detailed study pertaining to the protonation of hydroxylamine with respect to the pH will also be presented. An abrasion cell integrated with a Raman spectrometer was used to make the measurements.