In a copper-SiO2 dielectric multilevel interconnection scheme a diffusion barrier is needed between the metal and the dielectric to prevent the diffusion of Cu into SiO2 when subjected to thermal treatments and high electric bias. Ultra thin layers (50–100Å) of Al and Ti are being investigated for use as the required diffusion barrier as well as an adhesion promoter between Cu and SiO2 The results of our investigations, using C-V, resistance, and XPS measurements, will be presented and discussed. It will be shown that both Al and Ti reduce the SiO2 surface leading to a metal, oxygen, and Si bonded layer which acts as diffusion barrier under applied electrical bias of 1.5 MV/cm at temperatures as high as 250–300°C. Upper layers of Al and Ti are consumed by reaction with Cu. Such reactions increase the electrical resistivity and corrosion resistance of Cu (especially with Al). The results and the applicability of such barriers in practical cases will be presented and discussed.

A modified form of nanoscratch test, continuous micro-wedge scratch technique was applied to characterize the adhesion strength of 0.2 μm thick, 10 μm width sputtered copper fine lines on 50 μm thick solid PMDA-ODA polyimide films. A 20 μm width wedge-shaped diamond tip was used to mechanically debond Cu fine lines to polyimide substrate. Using a microindenter under control depth testing mode, critical loads for delaminations were obtained. The scratch morphology and the debonded areas were observed by scanning electron microscopy. The scratch test results by conical-shaped tip on plain films are also presented here and are compared to the results by wedge-shaped tip in fine metal lines. Practical work of adhesion of 4.1 J/m2 was calculated by FEM based on bimaterial fracture mechanism

Thermal and electromigration effects on the thicknesses of aluminum oxide at the aluminum-1% silicon/thermal silicon dioxide interface were quantitatively determined by AES. Void sites corresponded with thinner aluminum oxide thicknesses at this interface. Changes in surface topography and grain structure were quantitatively determined for thermally annealed aluminum-1% silicon metallizations by AFM.

Plasma enhanced chemical vapor deposited tungsten nitride (PECVD-W67N33) thin film has been proposed as a diffusion barrier. The resistivity and lattice constant of PECVD-W67N33 are 110-28 μΩ-cm and 4.134 Å, respectively and this film has compressive stress of 2.6 × 1010 dyne/cm2. Thermal stability of PECVD-W67N33 as a diffusion barrier reveals that the interdiffusions between Al or W and Si substrate can be prevented by N interstitial atoms in fcc-W2N grains and grain boundaries.

A novel lower cost wet-processing technique, for producing toughened zirconia ceramics with complex geometries, is presented. It is based mainly on modifications to the particle surface chemistry. The sintered materials produced so far are significantly harder (ca 50%) as well as being tougher (ca 10%) than a commercial CeTZP.

Interfacial cohesion is determined by the cohesive energy of the interface. Knowing the segregation energies of solute in the interface and on the adjoining free surfaces and mobilities of segregant atoms, the change in cohesive energy of the interface due to solute segregation can be evaluated within the framework of the Langmuir-McLean isotherm. A control of the interfacial cohesion is thus achievable by promoting segregation of the desired solute.

The effect of laminate geometry and thermal treatment on the microstructural evolution of interfacial reaction products and thin film stress in Al/SiC microlaminates has been investigated by x-ray diffraction, transmission electron and optical microscopy, and thin film stress measurements. Both stress-temperature and stress-time studies are conducted. Crystalline Si of two dimensional ‘dendritic’ morphology is observed as a solid state reaction product at the Al/SiC interface following an anneal at 400 °C. This interfacial reaction is associated with a sharp change in thin film stress in laminates with very thin AI layers to a highly compressive state during isothermal annealing at 400 °C of as-deposited laminates. The change in film stress state is in agreement with the expected larger molar volume of the likely product phases.

Unsized, type II carbon fibers were treated for 2 to 60 minutes in either an oxygen or nitric oxide gas plasma and were investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). XPS revealed plasma treatments increased both oxygen and nitrogen functionality on the fiber surface. O2 plasma treatments showed a progressive increase of fiber surface oxidation from alcohol to carboxyl species, increasing the total surface oxygen from 3 atomic % to 46% after 60 minutes. N(1s) spectra for these fibers showed a broad peak centered at ca. 400.4 eV with a shoulder at ca. 398.2 eV, which most likely is attributed to nitrogen remaining from the polyacrylonitrile (PAN) precursor material. NO treatments only increased the total surface oxygen to 33%, but introduced additional nitrogen species onto the fiber surface compared to O2 plasmas. N(ls) spectra for the NO plasma treated fibers showed, in addition to the two nitrogen species mentioned above, a higher binding energy peak at ca. 405.5 eV, which is assigned to -NO2 species. This peak increased to a maximum intensity after 5 minutes of treatment and then decreased upon further treatment, even though the total nitrogen intensity remained constant at approximately 6%. Subsequent increases in the two lower binding energy species at 400.4 eV and 398.2 eV suggest -NO2 surface species were reduced to species such as amides, nitriles, and amines. Reducing the NO plasma power levels from 25 Watts to 5 Watts resulted in the same three peaks in the N(ls) spectra but required 30 minutes for the -NO2 species to reach a maximum intensity. Scanning electron micrographs (x 10,000 magnification) of fibers treated up to 5 minutes revealed that plasma treatments did not significantly change surface morphology. Small bumps on the surface appeared after longer treatments as the plasma began etching the fiber surface, but even 60 minutes of treatment did not significantly alter the overall fiber diameters.

As a potential micro-actuator material thin film shape memory alloys (SMAs) have drawn attention because of their capability of generating strains of a few percent reversibly. In contrast to SMAs the output strain of traditional actuator material, such as quartz and PZT ferroelectrics, is limited to 100 to 1000 ppm. The authors have investigated the transformation properties and microstructures of thin Ni50Ti50 films on Si. From application point of view, the evaluation of the actuator property should come from direct measurements of the strain output of the film/substrate composite. In the film/substrate composite, the martensitic transformation strains in the SMA thin film are coupled to elastically to the substrate through interface load transfer. Interface properties thus play crucial role on the efficiency of the composite actuators. Since the capability of interface load transfer is determined by the substrate stiffness, experiments were designed to measure the strain output of NiTi/Si composite with varying substrate stiffness. The experiments indicated that the output efficiency of the martensitic transformation strain increases by a factor of 2 when the film/substrate thickness ratio increases from 1/345 to 1/70. The result is favorable for micro-actuator application since much larger film/substrate ratios can be achieved by micro-machining. The absolute value of the transformation strain is about 2 percent which can be improved if the film texture is controlled.

Another problem related to the nature of the film/substrate composite is the thermal stress arising from the difference of the thermal expansivities of the film and substrate. The as deposited films were amorphous with a growth tensile stress ranging from 0.6 GPa to 1 GPa, increasing with the substrate stiffness. The initial recrystallization of the amorphous NiS0Ti,0 film results in an increase of the tensile stress by 80 MPa; however upon completion of the recrystallization process the tensile stress was relaxed. Young’s moduli of the recrystallized austenitic NiTi films were calculated from the thermal stresses arising in the composite samples. It was found that the moduli apparently depend on the substrate thickness. This effect is tentatively interpreted to indicate a sensitivity of the mechanical properties of the film on the grain structure of the recrystallized state which in turn might depend on the constraint due to the substrate. TEM studies will clarify the situation.

It is concluded that the interface stress restrained the efficiency of the martensitic transformation. Since the NiTi film has a high (interface) yield stress, above 1 GPa, it is proposed that the actuation efficiency of the SMA can be improved by reducing the substrate stiffness while maintaining a high load transfer efficiency. If Si is used as a substrate because of its high thermal diffusivity, the actuator design must weight the mechanical actuator output against its speed.

The interfacial compatibility of SiC, Al2O3, and TiC with Ti3Al alloy has been evaluated. Thin films of these three ceramics materials were deposited on Ti3A1 substrates. The thin film diffusion couples were annealed from 600°C to 1000°C, and the thickness of the interfacial layer was obtained from Auger Electron Spectroscopy (AES) concentration depth profiling. The reaction products were identified by X-ray Diffraction (XRD) and AES. In the A12O3/Ti3A1, obvious interdiffusion occurred with some reaction products. In the SiC/Ti3Al, significant interdiffusion and reactions occurred in the interfacial layer, and multilayer reaction zones were found. In the TiC/Ti3Al, the reaction product was primarily the P(Ti3AlC) phase. Kinetic studies of the growth of the interfacial layer showed that SiC reacted most severely with Ti3Al, TiC less so, and AI2O3 the least. The compatibility of these three systems has been assessed.

The fracture energy of Ti/Al203 composite interfaces has been determined by four point bending tests of sandwich specimens for different thicknesses of metal interlayers at 900°C. The interfacial fracture was found to be brittle. An intermetallic reaction product (Ti3Al) was produced at the interface after the diffusion bonding process. When the metal interlayer is thicker, there is more plastic energy dissipation in the metal during the fracture process. Therefore, the interfacial fracture energy increases. This can be seen from the fact that there is a larger plastic zone size with increasing thickness of the metal interlayer. The measured interfacial fracture energy Ti/Al203 ranges from 9.6 J/m2to 45.1 J/m2. The intrinsic interfacial fracture energy is obtained to be 0.26 J/m2. The embrittlement of the interface after the diffusion bonding process causes this value to be smaller than work of adhesion for Ti/Al203 (2.0 J/m2).

Carbon fibers derived from various sources are surface modified by oxygen and nitrogen ion beams generated from a low voltage ion source. The surface analyses by X-ray photoelectron spectroscopy reveal that the ion treatment produces large abundances of various surface functional groups which are dependent on impinging ion energies and irradiation times. In the oxygen beam, the hydroxyl moiety is a dominant surface functionality, but in the nitrogen beam, various moieties containing oxygen and nitrogen are observed. The transverse tensile stresses of the epoxy composites made from the ion treated fibers are found to increase two to four times. The ion beam process yields the highest adhesive strength among all surface treatment methods.

Composites samples containing 80% and 85% organic filler in a polymer-plastizer binder were produced by mixing, extruding, cutting, drying and pressing. Before pressing the extruded material was in some cases coated with a thin layer of graphite (= one micron) for ease in pressing. As part of a general study of these composites the compressive strength, σm, was determined as a function of temperature, strain rate and the thickness of the graphite coating. Without graphite σm increases with decreasing temperature and increasing strain rate. With graphite σm has the same behavior above approximately −10 C, but is independent of both temperature and strain rate below −10 C for a strain rate of 1.0/Sec. In addition, the low temperature value of Om decreases with increasing graphite thickness. The cracking and fracture patterns are temperature and strain rate dependent and are different with and without graphite. These results indicate that the bond produced by pressing the graphite containing material is stronger than the composite above −10 C and weaker below −10 C so that failure initiates in the composite above −10 C and in the bond below −10 C. With decreasing strain rate this transition temperature decreases. The bonding is discussed.

This paper reports the results of solid state wetting studies of graphite by Pb and Au alloyed with Ni. It is shown that additions of Ni ranging from 0 to 0.2 wt%Ni reduce the contact angle of Pb on graphite from 117 to 80°, and that a 5 wt% Ni addition to Au decreases the contact angle of Au on graphite from 131 to 123°. These contact angle changes are used to compute the interfacial energy at both Pb/graphite and Au/graphite interfaces. Direct evidence of Ni segregation at those interfaces is also obtained by crater edge profiling measurements. It is found that the enrichment factor of Ni is much larger in the Pb- than in the Au-based system. Also, for similar changes in interfacial energy, the effects of Ni segregation on contact angle are larger in the Pb- than in the Au-based system. These effects are discussed in terms of the relative surface and interfacial energies in the two systems.

Scanning Tunneling and Atomic Force Microscopy were used to characterize the topography of fractured Au /sapphire interfaces. Variance analysis which quantifies surface morphology was developed and applied to the characterization of the metal fracture surface of the metal/ceramic system. Fracture surface features related to plasticity were quantified and correlated to the fracture energy and energy release rate.

The morphology characteristic of acid-washed and annealed MgO (100) surfaces used as substrates for pulsed-laser deposition (PLD) is studied employing TEM, SEM and AFM. Each of these three microscopal techniques provides information not so readily accessible by and complementary to the other two techniques, leading to a more rounded view of the characteristic morphology of these surfaces.

A novel configuration for Fourier-transform infrared reflection absorption spectroscopy (FT-IR-RAS) has been devised to study the nature of silicon wafer surfaces in the wide IR irradiation region (especially below 1300 cm−1) with high sensitivity. The configuration is basically similar to a conventional one of FT-IR-RAS except that a optical-flat mirror is placed on a silicon wafer surface and the IR beam is incident on the back side of the wafer with a grazing angle. The sensitivity of the novel technique was estimated by the observation of the stretching vibration absorption of the Si-Hx bond (2070-2150 cm−1) on HF/NH4F-treated Si(111) surfaces and Si-O bond (1000-1250 cm−1) of chemically oxidized layer ( ∼0.7 nm ) on Si(111) surfaces. The dependence of Si-Hx absorption peaks intensities on the composition of HF/NH4.F solutions was clearly observed. Furthermore, Si-O bond peak corresponding to the longitudinal optical phonon was also detected.

The structure of thin SiO2 films thermally grown on Si(100) and Si(111) surfaces has been characterized by using infrared internal reflection and x-ray photoelectron spectroscopy. It is found that the infrared absorption peak due to the LO phonon mode originating from the Si-O-Si stretching vibration shows a considerable red shift in the thickness range below 30A. This red shift is interpreted in terms of the compressive stress near the interface.

Simulation of a thin oxide RAS spectrum obtained by using the dielectric function extracted from thick oxide RAS spectra is shown to be a viable method for the comparison of oxide films of differing thickness. Bulk and near-interfacial features of thermally grown SiO2 thin films were studied by this method and it was found that the LO phonon peak at about 1255 cm−1 reflects bulk SiO2 structure and a higher reflectance between 1100 and 1200 cm−1 reflects SiO2/Si interface structure.

Silicon nanocrystallites have been studied in a variety of passivating environments to study the role of surface passivation in visible light emission from the particles. Thin films of Si nanocrystallites have been deposited by a laser ablation supersonic expansion technique. The films show significant room temperature photoluminescence (PL) behavior only after processing to achieve surface passivation. Passivation effects on light emission are studied through PL emission spectroscopy on clusters in the gas phase, as well as films in a variety of passivating media. The intensity of PL emission seems to scale with the extent of surface passivation, but the specific nature of the passivating species is not critical in defining the wavelength of emitted light.