Since the early work of Ilan Blech and Gene Meieran more than 20 years ago, electromigration (mass transport produced in a metallic conductor by current flow) has been recognized as an important reliability hazard for solid-state electronic devices. The continuing shrinkage of dimensions in VLSI devices has resulted in a continuing increase in the current density in the interconnection lines and a corresponding increase in the potential electromigration hazard. Although there have been improvements in the materials and structures used for interconnections, notably the addition of copper to aluminum and the use of layered structures, the provision of an adequate margin of safety has become increasingly difficult and is an important constraint on both device design and process development.

Multilevel metallization is becoming an increasingly interesting area of research as circuit fabrication technologies are scaled down to deep submicron dimensions. The mainstream of today's interconnection technology is AlSiCu metallization. Al-based solutions, however, seem to be limited in resistivity as well as in electromigration performance. Because of its low electrical resistivity and its resistance to electromigration, copper is considered to be a promising new solution for on-chip interconnections. The performance of copper would allow its use in wiring with very small linewidths, as required for ULSI circuits. Before considering copper metallization in ULSI processing, however, major problems still have to be overcome.

Taking into account these considerations, a European project is now devoted to the evaluation of copper-based metallization for ULSI applications. The project, Copper Interconnection (COIN), associates the efforts of seven European partners.

The objectives of COIN are to evaluate and develop a set of optimized solutions which demonstrate to our industrial partners the interest of using on-chip copper metallization. High deposition rates, low temperature processing, thermal stability, reliability, and low cost are the main goals.

The COIN project is devoted to an exploratory study concerning the major issues to be addressed in order to reach the above targets. The choice is to limit, for as long as possible, the modifications of existing multilevel metallization (MLM) structures to a simple replacement of the aluminum by copper interconnection levels. The refractory metal layers in MLM structures (TiSi2, Ti, TiN, W) will be maintained in the copper metallization scheme as will the use of SiO2 as the dielectric material. Another consideration in our approach is the possibility of achieving this substitution with minimum modification to existing fabrication lines. Thus, processes for copper deposition and copper patterning will be developed using existing machines and machine concepts for as long as possible.

Lignocellulosics represent that mass of organic matter produced by land-growing plants in the form of trees, shrubs, and agricultural crops. Lignocellulosics are renewable, and they sustain living conditions on our planet by recycling carbon dioxide to oxygen. Lignocellulosics serve the planet as a carbon sink. Chlorophyll is the essential catalyst and sunlight the necessary energy source that drive this carbon dioxide reduction to an organic mass that varies little from the carbon-to-oxygen ratio of carbon monoxide.

There is, however, no distinct “lignocellulose” molecule. Instead, nature has found it necessary to formulate a multiphase material consisting of cellulose, hemicelluloses, and lignin. The composition of this multiphase material can be likened to a fiber-reinforced organic glass where cellulose serves as lightweight fiber, lignin serves as a continuous (glassy) matrix, and hemicelluloses serve as coupling agents. The overall composition suggests that there is 35–45% cellulose, 25–35% hemicelluloses, 20–25% lignin, and various minor constituents.

In chemical terms, cellulose is a linear homopolysaccharide with a high degree of crystallinity. It consists of 1,4-β-linked D-glucopyranose units connected in syndiotactic fashion (on alternating sides of the main chain). Cellulose molecules in nature occur with molecular weights exceeding 2 million. Hemicelluloses, by contrast, are branched heterosaccharides of lesser molecular weight. They rarely exceed 20,000 daltons. Hemicelluloses are either rich in glucomannan chains (softwoods), or they consist primarily of branched xylans (hardwoods and annual crops). The chemical composition of hemicelluloses is extraordinarily similar to cellulose (i.e., polyanhydro-pyranoside), but their morphological structure is vastly different.

Immobilization and geological isolation are the general goals of nuclear waste disposal. The appropriate isolation of immobilized long-lived radionuclides, mostly actinide elements, from interaction with water for a period of many thousands of years in any given geological formation is a scientific and technological challenge. This challenge can be met by considering a multibarrier concept that appraises engineered, geoengineered, and geological barriers designed to confine the migration of long-lived actinides. Once interaction with water occurs, one may expect many complex geochemical reactions of immobilized actinides; actinides will therefore be distributed into two kinds of chemical states, mobile and immobile species. Reflecting results in laboratory systems, the two species are expected to be chemical partners in equilibrium reactions. In multicomponent geochemical systems, however, the chemistry of the mobile and immobile species of actinides in trace concentration is, in general, masked by geochemical reactions of natural aquatic constituents, which are found in much higher concentrations. The mobile species are either complexed anions or colloidal species, whereas the immobile species are new solid phases of very low solubility, which are thermodynamically better stabilized than in the original host phases.

Until the 18th century, the word “art” meant the product of the artisan (not the artist) and, by extension, also meant the product itself. Objects manufactured by craftsmen had, first of all, a useful function, although they might also have had a symbolic or aesthetic meaning. The concept of aesthetics is actually much older, considering the antiquity of Rome and Greece. And in Egypt, 3,500 years ago, at Saqqara, the first stone pyramid was engraved by scribes expressing their admiration for it.

These artisans were famous for the quality of their work, for their genius in mastering their knowledge. One is reminded of Phidias in Athens, Michelangelo and Julius II, or Leonardo da Vinci and Francois the 1st.

However, the social status of such artists was probably not very different from the status of other exceptional artisans in fields such as jewelry, metallurgy, clothing, music, etc. “Ĺart pour l'art,” a tenet which ignored the function of the object, arose only during the last century. In other words, almost all objects or artifacts in museums were originally devised and built to achieve a very specific and useful function.