Pure Al and Cu films evaporated on thin glass and thermally oxidized silicon substrates are subject to changes in temperature Ṫ>100Ks-1. With constant temperature the stress relaxation is between 1 and 10 % of the thermally induced stress. The stationary creep rates are comparable to diffusion controlled power-law creep. The discontinuous grain growth during the T cycling shifts the transient amplitudes and the stationary slopes of stress to negative values. DC resistance measurements indicate the production and annihilation of vacancies.

The adherence and the bond strength of metal-to-ceramic joints are described in terms of the fracture energy Gc and the fracture resistance Kc. Small three- or four-point bend test specimens of 30 to 60 mm length notched or precracked at the metal-ceramic interface are used to determine the Gc and Kc data. Examples of bond strength measurements on metal-to-ceramic joints and plasma-sprayed ceramic layer-metal substrate combinations aim to demonstrate the applicability of the method.

The strength of an interface between two metal surfaces can be drastically affected by the presence of chemical species in the interface. The two surfaces may form the boundary between two grains inside a solid block of metal, the interface between a substrate and a metal film or the interface between two solid bodies brought into physical contact. Interface impurities such as oxygen atoms generally reduce the cohesion between the two surfaces. Conventional fracture experiments have difficulty in determining whether this results from a reduction in the interfacial energy, or a hardening of the interface, either of these making brittle fracture easier. The experiments which we have carried out by contacting two clean and characterised surfaces in ultra high vacuum, enable a direct study to be made of the change in interfacial energy and mechanical behaviour as a result of adsorbed species.

A sharp metal point of about 1μm radius of curvature is contacted against a flat metal specimen and the force of adhesion and contact area (measured from electrical resistance) are determined. The extent of ductile or elastic behaviour of the interface can be determined from the reversibility of the contact area as a function of applied load during separation.

We have shown directly from a contact experiment, that monolayer quantities of oxygen reduce the interfacial energy by a factor of three in the metal contacts studied. Interfacial ductility is only reduced by the presence of oxide layers of the order of 5nm thick.

Load relaxation testing has been demonstrated to be useful for characterizing the time dependent plastic properties of metals. However, for testing of small material volumes, such as thin film metallizations, thin films, and contact surfaces, conventional load relaxation techniques cannot be used. For such applications an indentation test offers an attractive means for obtaining data necessary for materials characterization. This work shows that an indentation load relaxation test is experimentally feasible for thin film testing. Experiments on brass and beryllium copper samples with or without a gold/nickel plating illustrate different relaxation properties of the substrates and the surface layers. Furthermore, results of experiments on some fcc metals suggest rather simple relations between the conventional uniaxial load relaxation (LR) test and the indentation load relaxation (ILR) test.

Interdiffusion of polymer chains plays an important role in establishing good adhesion at polymer interfaces as well as in the kinetics of phase separation and mixing in polymer blends. Reptation, a process in which a given linear chain crawls along a primitive path defined by the topological constraints due to the surrounding chains, is thought to be the most important diffusion mechanism. A reptating chain of Volecular weight M should have a tracer diffusion coefficient given by D =DR =Do M−2, where D depends on the Rouse mobility of the chain and an entang ement molecular weight, Me. Because the topological constraints are assumed to be fixed, DR is independent of the molecular weight P of the polymer into which the M-chains are diffusing. In principle however if M is large enough and P is small enough the M-chain can diffuse by rearrangement of the P-chains surrounding it, a process called constraint release. The D for this process, DCR= αCRDoMe2/(MP3), where αCR is a constant approximately equal to 13, increases strongly with decreasing P. Recent experimental results, which give evidence for both reptation and constraint release, will be reviewed. These results have important implications for the diffusion of nonlinear polymer chains, e.g. stars and rings.

The strength of interfacial bonding between polymers and inorganic substrates is very appreciably enhanced when polymers are acidic and substrates are basic, or vice versa. The interaction is of two kinds, an increased thermodynamic work of adhesion resulting from large exothermic interactions at the interface, and an increased tensile strength resulting from electrical charge injection into the polymer from the substrate.

The exothermic interfacial interactions between acidic and basic sites are easily measured by calorimetry or by infrared spectral shifts. The enthalpies of adsorption can be correlated and predicted by the Drago equation, −Δ H = CACB+ EAEB, where the CA and EA for the acidic member can be measured by enthalpies determined with basic molecular probes of known CB and EB. Heats of adsorption of polymers onto inorganic substrates are precisely predictable with the above equation once E and C values are known for the polymer and substrate.

This paper summarizes recent studies on metal-polymer interfaces for Cu, Ni and Cr on a high temperature polymer, polyimide. First some surface and bulk chemical properties of polyimide are described briefly, as measured with surface spectroscopies and verified by theoretical molecular orbital calculations. Then the chemical bonding and reactivity of the three interfaces are described and discussed in light of experimental observations of electronic structure, composition and interface morphology. The chemical trend of increasing reactivity of the interface is illustrated by comparing results from Cu to Cr.

Two ion beam depth profiling methods have been used to measure the diffusion of polymer chains of molecular weight M into a matrix of polymer of molecular weight P. In the first the displacement xm of Au markers at the original interface of a diffusion couple between polystyrene with P=2×107 and a thin film of PS with M<P is measured using Rutherford backscattering spectrometry. From this modern version of the Kirkendall effect we find x=0.4t8(D*t) 0 5, where D* the tracer diffusion coefficient of the M chains at 174°C, is found to be D*=O.007M−2cm2/sec, in good agreement with the D*=DR expected for the reptation mechanism. Forward recoil spectrometry, a technique in which the energies of recoiling deuterons are detected, is used to obtain concentration profiles, and hence D*, of deuterated PS M-chains diffusing into a hydrogenated PS P-chain matrix. When P>>M, D*=0.008M−2, in good agreement with the marker data. When P<P*(M) however D*; increases greatly as P decreases; P* increases slowly with increasing M. The results are predicted quantitatively by D*=DR+DCR, where DCR=0.10Me2/(Mp 3 ) describes the diffusion of the M-chain by release of its topological constraints (by diffusion of the surrounding P-chains) and Me is an entanglement molecular weight. D* for self-diffusion (M=P) is dominated by reptation except for M's close to Me.

Copper was deposited by electron beam evaporation onto both freshly cleaved bare and polyimide-coated (001) NaCl at substrate temperatures of 20°, 100°, 200° and 300°C at rates of 2 and 20,Åsec−1. For all substrate temperatures and deposition rates investigated, the Volmer-Weber mode of film growth was observed for copper both on polyimide and on NaCl. Comparisons of film growth on the two substrates for a constant substrate temperature revealed differences in film thickness at which copper became continuous or formed a completely coalesced film. It was found that copper grown on polyimide formed continuous and completely coalesced films at smaller film thicknesses than on NaCI. However once a completely coalesced film was obtained, grain growth in the copper films proceeded more rapidly on NaC1 substrates than on polyimide substrates.

Etched metallic conductor lines on metal clad polymeric substrates are used for electronic component interconnections. Significant signal losses are observed for microstrip conductor lines used for interconnecting high Frequency (above 20 GHz) devices. At these frequencies, the electronic signal travels closer to the metal-polymer interface due to the skin effect. Copper-teflon interfaces were characterized by SEM and AES to determine the interfacial properties. Data relating roughness of the copper film to signal losses was compared to theory. Films used to enhance adhesion, were also found, to a lesser extent, to contribute to these losses.

ESCA studies of two molecules which are similar in structure to the PMDA and ODA constituents of the PMDA-ODA polyimide monomer are discussed. Their interaction with in-situ evaporated Cr and Cu films are compared. The PMDA model compound interacts with Cr through the imide group, while very little interaction is observed with Cu. The ODA model compound (oxydianiline) interacts with Cr via the ether linkage and the terminal amino groups, whereas very little interaction is observed with Cu.

Many technologically-important areas rely on properties of ceramic surfaces or interfaces. Some of these properties are simply stability, e.g. resistance to dimension change, to grain-size change, or to change in coverage by a metal layer. Other properties rely on well-defined electronic features, e.g. a suitable density of surface states, of surface defects, or of response to adsorbed species. Still further surface characteristics - the precise geometric structures, the near-surface electric fields, and especially impurity segregation - can strongly influence observed behaviour.

This survey emphasises the insights gained from atomistic modelling of ceramic surfaces and interfaces. The theoretical methods allow one to identify the features determining surface geometry, the degree of surface segregation by impurities, the role of the image charge and the influence of space-charge layers on intrinsic defect levels. The surface distortion affects defects like the surface Fs+ centre (electron trapped at an oxygen vacancy on an oxide) and similar colour centres. Whilst most of the results will be for oxides, parallels with semiconductor systems and the special features of metal-oxide interfaces are mentioned.

The application of surface analysis techniques for the study of fundamental surface and thin film phenomena is described. The topics covered relate to the processing and fabrication of electronic packages and include: evaporation/condensation during the thermal processing of glasses, hydration of glass surfaces and thin films, nitridation of silica films, diffusion behavior in oxides at low temperature, and impurity segregation in thin films. A wide variety of surface analytical methods are exemplified including Auger electron spectroscopy (AES), ion-scattering spectroscopy (ISS), nuclear reaction analysis (NRA), secondary-ion mass spectroscopy (SIMS) and x-ray photoelectron spectroscopy (XPS).

Silicides of transition metals are used in two distinct ways in very large scale integrated circuits: (i) in the contact pads of individual devices on a chip, and (ii) in the interconnection lines. For the latter applications, two particular properties of the silicides make them desirable: their metallic electrical conductivity, and the possibility to produce a protective coating of SiO2 under heat treatment in an oxidizing ambient. Of those two attributes, the second one is particularly attractive because it offers inherent advantages in multilevel metallization schemes. To utilize this feature of silicides successfully, an understanding of the oxidation process is mandatory.

The interfacial zones in copper-magnesium aluminosilicate materials were characterized by several microscopic and microchemical techniques. Interfaces between copper-glass, copper-partially crystallized glass, and copper-fully crystallized glass were studied with the specific goal of determining the oxidation state of copper in various locations in the microstructure of the reaction zones. Optical microscopy, cathodoluminescence, electron probe microanalysis (EPMA), SEM, TEM, and other microtechniques were used. The presence of copper in various oxidation states can be attributed to the thermodynamics and kinetics of the system. Results correlating the observed interfacial microstructure and the thermochemistry of the system are presented.

We have explored the possibility of oxidizing a Au/Si composite layer or a Au-Si alloyed layer on SiO2 substrates to form a highly conductive narrow line with a protective SiO2 layer over it. A number of sample configurations and annealing ambients have been investigated. It was found that co-evaporated Au-Si alloys ( ∼30 at. % Au) showed no oxide formation for annealing temperatures between 200°C and 800°C in a flowing O2 ambient (annealing time ≃ 2.25hrs). Samples with a configuration of SiO2/Au/Si showed mixing of the Au and Si layers, but no appreciable oxide formation until after annealing at 800°C in a flowing O2. Samples with a configuration of SiO2/Si/Au, however, showed uniform and smooth oxide growth on top of the Au layer after annealing in air at 200°C. The structural and electrical properties of the self-confined Au lines will be discussed. This process may be potentially useful for narrow interconnects on VLSl chips.

Lateral concentration profiles of hydrogen (1H) have been measured using nuclear recoil analysis on electrolytically charged metal (V, Nb, Ta) foils subjected to current densities of order 103 amps/cm2 for various times in order to study the electromigration of hydrogen. Initially uniformly loaded foils exhibited a dramatic redistribution of the hydrogen. Numerical analysis of these data using the conventional solution of the electromigration equation is used to extract the hydrogen effective charge (Z*) from the steady state data and the diffusion coefficient from the time-dependent data. The nuclear technique permits rapid and accurate direct concentration measurements capable of distinguishing surface and subsurface transport.

It is demonstrated that the most important geometrical parameter governing the identification of “special” interfaces is the interplanar spacing of the lattice planes parallel to the interfacial plane and not, as often assumed, the inverse density of coincident-site lattice points, Σ. A simple geometrical selection rule for the identification of “special” or “favored” boundaries is formulated on the basis of the interplanar lattice constant.

Rose, Smith, and Ferrante have discovered scaling relations which map the adhesive binding energy calculated by Ferrante and Smith onto a single universal binding energy curve. These binding energies are calculated for all combinations of Al(111), Zn(0001), Mg(0001), and Na(110) in contact. The scaling involves normalizing the energy by the maximum binding energy and normalizing distances by a suitable combination of Thomas-Fermi screening lengths. Rose et al. have also found that the calculated cohesive energies of K, Ba, Cu, Mo, and Sm scale by similar simple relations, suggesting the universal relation may be more general than for the simple free-electron metals for which it was derived. In addition, the scaling length was defined more generally in order to relate it to measurable physical properties. Further this universality can be extended to chemisorption and molecular binding. The implications of this scaling have been explored and have produced some interesting results and verifications. A simple and yet quite accurate prediction of a zero temperature equation of state (volume as a function of pressure for metals and alloys) is presented. Thermal expansion coefficients and melting temperatures are predicted by simple, analytic expressions, and results compare favorably with experiment for a broad range of metals. All of these predictions are made possible by the discovery of universality in binding energy relations for metals. Finally some results of other researchers concerning universality In Van der Waals forces are referred to

When two solid surfaces are brought into contact strong adhesive bond forces can develop between the materials. The magnitude of the forces will depend upon the state of the surfaces, cleanliness and the fundamental properties of the two solids, both surface and bulk. Adhesion between solids is addressed from a theoretical consideration of the electronic nature of the surfaces and experimentally relating bond forces to the nature of the interface resulting from solid state contact. Surface properties correlated with adhesion include, atomic or molecular orientation, reconstruction and segregation as well as the chemistry of the surface specie. Where dissimilar solids are in contact the contribution of each is considered as is the role of their interactive chemistry on bond strength. Bulk properties examined include elastic and plastic behavior in'the surficial regions, cohesive binding energies, crystal structure, crystallographic orientation and state. Materials examined with respect to interfacial adhesive interactions include metals, alloys, ceramics, polymers and diamond. They are reviewed both in single and polycrystalline form. The surfaces of the contacting solids are studied both in the atomic or molecularly clean state and in the presence of selected surface contaminants. Topography effects are obviously complex and their detailed consideration is beyond the scope of this paper.