We investigated the copper grain size dependence on the interconnect line height using the EBSD (Electron Back Scattering Diffraction) pattern method. In our grain size measurements, we excluded the twin boundaries because of its small contribution to the electron scattering. Our experiments showed that the average grain size of a 70 nm-high line was about 24% smaller than for a 190 nm-high line.

We estimated the grain boundary scattering components by the Fuchs-Sondheimer (FS) and the Mayadas-Shatzkes (MS) models including the line height dependence of the grain size parameter (d). In order to evaluate precisely the influence of height dependence of grain size in the FS and MS models, we also determined the surface scattering coefficient of the Ta/Cu and SiC/Cu interfaces by an independent experiment.

From this, we found that grain boundary scattering components became approximately 32% larger for the 70 nm-wide line when the line height dependence of the grain size was taken into consideration.

Substrate surface roughness effects on Ag film texture were investigated using pole figure analysis. X-ray diffraction results confirmed that Ag thin films on smooth SiO2 substrates had strong {111} texture when compared with Ag films on PEN. It was noted that the difference of strain energy density (δEε) in Ag film on PEN (0.039 MPa) was almost 5 times greater than that on SiO2 (0.0084 MPa). The comparison between surface and strain energies revealed that the {111} texture of Ag thin film on SiO2 was explained by minimization of the surface energy and the weaker {111} texture of Ag on PEN was a result of reduced diffusion length of Ag adatoms on the rough PEN surface.

In this paper, we highlight a new method to obtain smoother silver (Ag) film characterized by much smaller average RMS surface roughness of ∼0.7nm, peak-to-valley separation of ∼4nm and grain-size distribution ~15nm as compared to conventionally obtainable Ag film characterized by RMS surface roughness of ∼10nm, peak-to-valley separation of ∼20nm and grain-size distribution of ∼100nm. Thin Ag films of ∼15nm (optically thin) were deposited on double-polished borosilicate glass and silicon (100) substrates with 2nm Germanium (Ge) intermediate layers. An optically thick Ag film of 60nm was also prepared with 2nm Ge. The Germanium thicknesses were also varied and similar surface morphology improvements are observable on all the samples. The AFM image analysis shows that having the evaporated Ge intermediate layer drastically changes the Ag surface morphology, namely, the surface roughness, peak-to-valley and grain size distribution. Our smooth Ag results are very promising for applications in molecular electronics interconnect, optical metamaterials, plasmonic superlens and nanophotonics.

Small amounts of copper were added to enhance the adhesion and minimize agglomeration of Ag thin films on SiO2 substrates. Comparison of texture profiles between Ag and Ag(Cu) thin films showed that Cu additions enhanced (111) texture in Ag thin films. For the case of Ag film, (111) texture was enhanced mainly by recrystallization of amorphous regions during annealing. In addition to the recrystallization, (111) texture enhancement in Ag(Cu) film attributes to the dissociation of grains with other crystallographic orientations.

A novel method for studying the penetration of wet chemicals into caulked and uncaulked porous dielectrics was developed, and the barrier properties of parylene X were evaluated. Rutherford backscattering spectrometry (RBS) was used to study the penetration of chlorine-tagged organics, 3-chloro-1-propanol and a %5 HCl solution. After one minute of exposure time, eight times more 3-chloro-1-propanol diffused through uncaulked porous dielectric compared to caulked porous dielectric. Penetration from the side of the samples was found to be insignificant.

The down-scaling of CMOS interconnects increases dielectric reliability challenges. Porous ULK materials used in advanced interconnects may suffer from charge trapping and detrimental aging during bias-thermal stress experiments. We demonstrate that a threshold between charging and aging domains may occur for an injected electrical energy of 0.1 MJ/cm3. Electron injection in the dielectric induces hydrogen radical formation first. For more damaging current stressing, in-situ Auger experiments demonstrate that the degradation is mostly due to the modification around carbon bonds.

Development of photoresist stripper with copper compatibility is challenging as conventional corrosion inhibitors do not protect the metal as expected. Copper corrosion inhibition mechanism of newly developed photoresist stripper is proposed that significantly reduces copper corrosion with small amount of corrosion inhibitor.

As the size of integrated circuit elements decreases, the properties of carbon nanotubes (CNTs) become increasingly attractive for interconnect applications. To be used by industry, full characterization of the electronic properties of CNT aggregates is essential.

Dielectrophoresis from CNTs suspended in liquid has been demonstrated as a simple route to bundles of aligned parallel nanotubes. We describe a method by which circuits including such bundles may be fabricated, and provide some high-frequency measurements of their electrical properties. The contributions of the contacts can be separated from those of the bundle itself.

Fatigue in damascene copper line has been investigated by using alternating currents to generate cyclic temperatures and stresses/strains. Interconnects using beyond 65 nm node design rules and materials have been studied. We demonstrate that cyclic thermal strains lead to Cu or Cu/Co-based cap surface modification and open circuits in Cu lines during the application of an alternating electrical current. We underline that the narrower the copper lines are, the more reliable they are and the major role of the cap layer to improve the Cu lines reliability. Moreover, a statistical approach is presented in this paper in order to discuss about the thermal fatigue associated distribution model (exponential, lognormal and Weibull distributions). At present, the lognormal distribution seems to be the most appropriate one.

During an O2 plasma ashing process, carbon depletion and subsequent moisture uptake caused increase of keff and the leakage current in an organosilicate (OSG) low-k dielectric. For dielectric restoration, additional CH4 plasma treatment on the O2 plasma ashed OSG low-k dielectric was investigated using angle resolved x-ray photoelectron spectroscopy (ARXPS), XPS depth profiling, x-ray reflectivity (XRR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and contact angle goniometer. After CH4 plasma treatment on the O2 plasma ashed OSG, the surface carbon concentration and surface hydrophobicity were partially recovered. A dense surface layer containing C=C bonds was found to have formed on the top of the damaged OSG. The C-V hysteresis and the leakage current were reduced as a result of the CH4 plasma treatment. XPS depth profiling revealed that the recovery effect was limited to the surface region.

Channeling cracks in low-k dielectrics have been observed to be a key reliability issue for advanced interconnects. The constraint effect of surrounding materials including stacked buffer layers has been studied. This paper analyzes the effect of interfacial delamination on the fracture condition of brittle thin films on elastic substrates. It is found that stable delamination along with the growth of a channel crack is possible only for a specific range of elastic mismatch and interface toughness. An effective energy release rate is defined to account for the influence of interfacial delamination on both the driving force and the fracture resistance, which can be significantly higher than the case assuming no delamination.

Triruthenium dodecarbonyl and trimethylphosphine or triphenylphosphine, and cis-ruthenium(II)dihydridotetrakis-(trimethylphophine) were used in flowing hydrogen or argon at 575 K to explore the effect of changing the percentage of P on the amorphous character of the films and on the electrical properties of the films. First-principles density-functional calculations are presented that reveal the interaction of Ru with P, and that predict the amorphous structure should be most stable above 20 at.% P and 10 at.% B. The films contained a carbon impurity that depended on the delivery gas and the alkylphoshphine source; film resistivity was highly dependent on the carbon impurity level. The microstructure changed with the percentage P; amorphous films formed provided the percentage of P exceeded 15 at.%. Film resistivity was most sensitive to the carbon impurity and also changed with microstructure. A 15 nm thick, amorphous film containing ∼15 at.% P had a resistivity of 210 μohm-cm.

Wafer level chip size packages (WL-CSP) have been successfully fabricated for bulk acoustic wave (BAW) filters. WL-CSP has been completed at the wafer level prior to dicing. Two silicon wafers are used as a die and a lid for chip size packaging. Both device and lid wafers have the same expansion coefficient and the package is strong enough to withstand the thermal stress. The package has a hermetic seal with copper-tin intermetallic bonding. The bonded wafers are then thinned by grinding. Via holes are formed by reactive ion etching (RIE) and filled by copper electroplating. The package has solder bumps on each terminal, ready for flip-chip assembly. We have succeeded to produce CSP-BAW filters with a hermetically sealed cavity, which is 840 micrometers squared and 280 micrometers in height including solder bumps.

Thin ruthenium films were deposited using chemical vapor deposition from the single-source precursor tricarbonyl(1,3-cyclohexadiene)Ru(0) onto silicon, silicon dioxide and c-plane sapphire substrates in the absence of a carrier gas by thermolysis. Growth rate, resistivity, purity, crystallinity and microstructure were determined. Tricarbonyl(1,3-cyclohexadiene)Ru(0) gave metallic ruthenium films with near bulk resistivities (11-21μΩ-cm), high growth rates (up to 20 nm/min), and nearly featureless microstructures. Nucleation was rapid on all substrates tested. These results suggest that tricarbonyl(1,3-cyclohexadiene)Ru(0) is an excellent, practical precursor to use for practical applications that require depositing thin ruthenium films.

Pinhole densities of electroless cobalt alloy films on copper substrate are characterized using optical and electrochemical methods. The impact of pits or pinholes on deposit film barrier property is discussed. The improved film barrier property is shown by reduction of pits formation through deposition process optimization.

Thermally stable, amorphous HfO2 thin films deposited using atomic layer deposition have been studied as a diffusion barrier between Cu and the Si substrate. 4 nm thick as-deposited HfO2 films deposited on Si are characterized with X-ray photoelectron spectroscopy. Cu/HfO2/<Si> samples are annealed at different temperatures, starting from 500 °C, in the presence of N2 atmosphere for 5 min and characterized using sheet resistance, X-ray diffraction and scanning electron microscopy. Ultrathin HfO2 films are found to be effective diffusion barrier between Cu and Si with a high failure temperature of about 750 °C.

In this paper, a novel nano-scale conductive film which combines the advantages of both traditional anisotropic conductive adhesives/films (ACAs/ACFs) and nonconductive adhesives/films (NCAs/NCFs) is introduced and developed for next generation high performance ultra-fine pitch packaging applications. This novel interconnect film possesses the properties of electrical conduction along the z-direction with relatively low bonding pressure (ACF-like) and the ultra-fine pitch (< 100 nm) capability (NCF-like). Unlike typical ACF which requires 1–5 vol% of conductive fillers, the novel nano-scale conductive film only needs less than 0.1 vol% conductive fillers to achieve good electrical conductance in the z direction. The nano-scale conductive film also allows a lower bonding pressure than NCF to achieve a much lower joint resistance (over two orders of magnitude lower than typical ACF joints) and higher current carrying capability. With low temperature sintering of nano-silver fillers, the joint resistance of the nano-scale conductive film could be as low as 10−5 Ohm, even lower than the NCF and lead-free solder joints. The reliability of the nano-scale conductive film after high temperature and humidity test (85°C/85%RH) was also improved compared to the NCF joints. As such, a high performance, fine pitch conductive film was developed.

High-resolution Computed Tomography (CT) widely expands the spectrum of detectable internal micro-structures. The new nanotom CT system allows the analysis of samples with the exceptional voxel-resolution of less than 0.5 microns per volume pixel (voxel). Thus internal detail related to a variation in material, density or porosity can be visualised and precisely measured. This opens a new dimension of 3D-microanalysis and will partially substitute traditional destructive methods in industrial quality control and research.

The nanotom® is the first 180 kV nanoCT system world-wide which is tailored specifically to the highest-resolution applications in material science, micro electronics, geology and biology. Therefore it is particularly suitable for nanoCT-examinations of material samples of any type like synthetic materials, ceramics, composite materials, mineral and organic samples.

Several results of high-resolution nanoCT demonstrate the capability to analyse the 3D-microstructure of materials with only minimal sample preparation. For instance, it is possible to image different metal phases in solder joints, the texture of fibres in composites or the volume and distribution of voids in castings.

The volume data set is visualised by slices or compiled in a three-dimensional view which can be displayed in various ways. By means of volume visualisation software, the three-dimensional structure of the reconstructed volume can be easily analysed for pores, cracks, and materials density and distribution with the highest magnification and image quality available.

By granting the user the ability to navigate the internal structure of an object slice-by-slice with highest resolution in a non-destructive manner, the nanotom creates new possibilities for analysis which have so far been unreachable.

Excimer-laser-induced rapid lateral solidification was used to produce large grain microstructures in copper and silver thin films. These were multilayer thin film structures consisting of sputter deposited copper and silver thin films encapsulated by silica (SiO2/metal/SiO2/Si substrate). In this process, a single excimer laser pulse and projection imaging optics were used to melt a 60 micron wide line in the metal film. The resolidification of the melted lines is found to occur laterally in the plane of the film, resulting in grains greater than 20 um in length and 1 um wide. Electron diffraction analysis allowed identification of a strong <001> texture in the growth direction along the major axis of the elongated grains as well as similar texture parallel to the film surface. Various dislocation and faulted defect structures are identified and examined in the context of the rapid solidification and potential application to interconnects.

This work investigated the viability of tungsten-titanium barrier layers for silver metallization. Reactive sputtered W-Ti was deposited on a Si wafer followed by an Ag thin film over layer. These samples were then annealed in vacuum at temperatures up to 700 °C. Characterization of these samples included using x-ray diffractometry, Rutherford backscattering spectrometry, scanning transmission microscopy, secondary ion mass spectroscopy, transmission electron microscopy, and four point probe analysis. The results indicated that the metal/diffusion barrier stack was stable up to 600 °C. Silicon started moving into the tungsten-titanium film at temperatures above 600 °C. Movement of Si resulted in local Si voiding. These results showed the promise of W-Ti as an effective barrier layer for silver metallization for process temperatures below 600 °C.