An overview is given of transmission electron microscopy techniques to address strain with nm scale spatial resolution. In particular the possibilities and limitations of (large angle) convergent beam electron diffraction ((LA)CBED) and electron diffraction contrast imaging (EDCI) techniques are discussed in detail. It will be shown by a few case studies that unique and quantitative information on local strain distributions can be obtained by the combined use of both (LA)CBED and EDCI in correlation with three dimensional finite element simulations of the strain distributions in the thinned specimen.

The current leakage generated in a localized area that creates a more serious problem to the ULSI devices was investigated. To clarify the origin of such a current leakage generated at a localized small area, an evaluation technique with a high spatial resolution, high sensitivity and a precise positioning is demanded. We have developed the planar point TEM(Transmission Electron Microscope) technique to enable the structure analysis of a localized small area in ULSI devices. Using this technique and AEM(Analytical Electron Microscope), we revealed one cause of current leakage at a small area in a memory device. It was found that one origin of such leakage is caused by heavy metal precipitation on the localized dislocation. The origin of this dislocation generation is a combination of effects from the crystalline damage during the formation of the oxide sidewall spacer by dry etching and the stresses from the oxide sidewall spacer and the field oxide.

This paper reports etching results supporting the identification of the SG1 center as a germanium dangling bond defect at the interface between an oxide and crystalline SiGe. The presence of this defect is significant because, like an analogous center in Si-based systems, it may alter the operation of any microelectronic or micro-optical device which incorporates an interface between SiGe and an overlying oxide. The samples examined are oxygen implanted SiGe layers in which the SG1 center is believed to occur at the interface between oxide precipitates and SiGe. Because of the center's apparent relation to the oxide precipitates distributed through layers of the sample, a depth profile assists in confirming the interfacial nature of the defect. We obtain a depth profile by comparing electron paramagnetic resonance (EPR) spectra of samples etched to decreasing thickness. EPR spectra indicate that the SG1 center decreases with depth in a manner that when correlated to a cross sectional transmission electron micrograph confirms the association with SiO2 and supports its location at the SiGe/SiO2 precipitate interface.

This paper reports on our studies of dislocation formation in trench capacitor DRAM structures. Experimental results on process dependence and layout dependence of dislocation formation in cell layouts with minimum feature sizes from 0.5 μm to 0.25 μm are compared to two-dimensional stress simulations. It is shown that the nucleation and spatial distribution of dislocations can be explained by considering stress fields which are influenced by the overlay of deep trench and shallow trench isolation structures.

Using isotropic elasticity theory it is possible to determine the bulk mismatch in thinned, cross-sectioned heterostructures, where a relaxation occurs along the thinning direction. This is accomplished by measuring, in the central disk of a single Convergent Beam Electron Diffraction (CBED) pattern, the position of the High Order Laue Zone lines, which are sensitive to lattice parameters along different crystallographic directions. The results obtained in both uniform and graded Sil-xGex/Si heterostructures are in good agreement with bulk values deduced from independent techniques.

The stress and microstructure of growing thin films evolve with time if the deposition is interrupted or terminated. To establish the parameters which control both kinetic processes ultra thin Au, Cu and Al layers were sputter deposited on Si membranes and the stress evolution was monitored by a vibrating membrane technique. The related surface morphology was studied by scanning tunneling microscopy. Aging after each deposition causes stress evolution towards higher tension and the evolution of the stress with time follows an exponential law with a characteristic relaxation time of the order of tens of seconds. This time was found to depend strongly on the accumulated film thickness as well as the surface morphology. The intrinsic stress of the growing layer increases with the coverage of the film on substrate. Scanning Tunneling Microscopy (STM) shows that the film grows in a Volmer-Weber (VW) mode and the stress reaches a maximum as the film become continuous.

Impurities control electrical, mechanical, physical, and chemical properties of the materials. We have manipulated their introduction into semiconductors, insulators, and metals to achieve otherwise unattainable properties. More recently, the continued miniaturization of the solid state devices and circuits have challenged the existing interconnection and contact metallization materials and schemes. These have led to an investigation of new multilevel metallization schemes with lower resistivities and higher reliabilities. In addition, efforts are being made to re-examine the use of newer Al-alloys that may satisfy the resistivity and reliability requirements. This paper will briefly review the existing practices, future needs, and current research activities focused to satisfy these future needs.

Surface and interface stresses, which are intrinsic thermodynamic quantities associated with all types of solid surfaces and interfaces are reviewed. A simple model for one type of interface stress is presented. These stresses can strongly influence the structure and mechanical behavior of nanostructured materials such as multilayered materials withultrathin layer thicknesses.

Strain measurement by laser diffraction was used in tensile testing of free-standing Ag/Cu multilayered thin films with repeat lengths between 3 nm and 3 μm. The mean value, for all the films, of the Young modulus was 83.1± 1.2 GPa, and of the Poisson ratio was 0.377±0.015. No variation with bilayer repeat length, and hence no “supermodulus” effect, was observed.

Nanocrystallization from Metglas® 2605 SC and Vitrovac® amorphous ribbons were studied by Mössbauer spectroscopy, transmission electron microscopy and differential scanning calorimetry. The spectra showed spin texture. The relative intensities change to a random distribution of spin orientation. New lines appear indicating new magnetic phases. TEM and DSC observations confirmed the crystallization of nanostructured grains.

Aluminum contacts on chemical vapor deposited (CVD) SiC films were studied to examine variations in the chemical, morphological and electrical properties of the samples. Nitrogen and aluminum doped substrates were prepared to give n-type and p-type SiC epilayers respectively. These preparations were examined by surface sensitive spectroscopies and by atomic force microscopy (AFM). Samples were studied both before and after the deposition of aluminum films to compare differences between SiC(p++)/metal and SiC(n++)/metal contact interfacial properties. Aluminum has generally been found to have good adherence to the n+ epilayer but do not form good ohmic contacts, while metal films deposited on p+ epilayers have had poor adherence but have been found to provide better ohmic character. AFM images revealed nanometer sized clusters, attributed to excess Si on the n+ epilayers, while no clusters were observed on the p+ epilayers. XPS studies of the as-prepared samples indicated that the n+ epilayers had higher concentrations of oxides which may enhance adhesion. The chemical composition and morphology is discussed and correlated to the electrical properties obtained for the various samples.

Transmission Electron Microscopy(TEM) and magnetization measurements were used to study the correlation between size of the iron particles precipitated in glass and their magnetic properties. The iron particles les s than 40 Å in diameter photodeposited in porous Vycor glass(PVG) show superparamagnetic behavior at room temperature. As the size of the particles increases and reaches about 100 Å in diameter, the magnetization curve shows minor hysteresis with a very large coercivity.

The temperature evolution of the crystalline structure of the nanophases found in sol-gel MgO, TiO2 and ZrO2 systems was analyzed by performing x-ray powder diffraction. The structure and concentration of each phase was determined by using the Rietveld technique. The effect of doping MgO and TiO2 systems with platinum was also studied.

Reactive sputtering of gold and selected gold alloys in oxygen and nitrogen plasmas generated in a DC glow discharge was studied. Gold alloys examined were various compositions with gallium, aluminum and silicon. Gold is transported unreacted from a gold target to the substrate in a nitrogen plasma to form polycrystalline films, but gold alloys produce fine dispersions of gold in the corresponding ceramic nitride matrix which was crystalline for gallium and amorphous for silicon and aluminum. This contrasts with the behavior in an oxygen plasma which produces pure gold oxide, Au2O3, from a gold target and gold oxide-silicon oxide nanocomposites from Au/Si alloys. Gold oxide is thermally labile and reverts to the elements at 350 °C. Stress in gold oxide films was detected in the decomposition profile, volatile evolution versus temperature, as an event occurring at a lower temperature. The thermal lability of gold oxide was utilized to generate gold nanocomposites in silica with different metal loading through pyrolysis of the corresponding precursor gold oxide-silica films. The properties of gold oxide and gold nanocomposites are described.

Polymer dominated polyimide/preceramic ceramers have been prepared by two different techniques. Both methods currently offer high potential of generating a novel nanostructure with well consolidated moldings of the multiphased systems. The first method involves microencapsulation of sub-micron polymer particles of LARC• IA (Langley Research Center Improved Adhesive) in a TiO2 coating and the other method utilizes LARCTM IA amic acid and TEOS in a sol-gel process. Each has allowed for the formation of ceramers possessing properties of both inorganic glasses and organic polymers. Processing, thermal characterization, and mechanical properties of the resultant materials will be discussed.