ment of the surface topography of the electrodes by STM, in particular the size and diameter of the columnar-like structure and its evolution during time. It is shown that, for a rounded cap columnar structure, the estimation of the thickness by coulometry and the evaluation of the roughness factor through conventional voltammetry allow one to obtain the value of the surface diffusion coefficient. For Au and Pt the measured values of the surface diffusion coefficients in 0.5M H2SO4 appear to be higher than those reported in vacuum. AcknowledgmentA fellowship from the Consejo Nacional de Investigaciones Cientificas y T6cnicas (Argentina) to R.C.S. is gratefully acknowledged. Financial support was obtained from DGICT through contract number PB86-0606. We are indebted to A. Buendia for skillful technical assistance and to J. GSmez and J. M. G6mez for help in data acquisition and images processing.
Chemical plating techniques have been used in silicon processing for many years for junction delineation and ohmic contact formation. In recent years, interest in this area has been renewed because of the potential use of electroless copper deposition for ultra-large-scale integration (ULSI) metallization and for the formation of thin metal etch masks for deep-ultraviolet lithography. Good deposition selectivity, low operating temperature, high copper purity, good filling characteristics, and planar topography have been among the many advantageous attributes reported from early investigations.In the June 1993 issue of the MRS Bulletin on Copper Metallization, Cho et al. gave an exposition on the use of electroless copper for VLSI. More comprehensive reviews of the electrochemical fundamentals can be found in References 8,9, and 10. This article summarizes the current understanding of various chemical and material aspects of this deposition method in an attempt to give an overview of the film growth characteristics for thin film applications. Because of length limitations, only selected topics are included. The emphasis is on the initiation conditions and the resultant microstructure and properties obtained. We also discuss special considerations for fine pattern formation.The information presented here applies primarily to electroless copper deposition on metals and metal silicides since these are the typical substrate surfaces for metallization in contact vias of ULSI circuits. Strictly speaking, metallization of upper-level interconnects occurs mostly on a dielectric base. However, since copper systems usually require a diffusion barrier to shield the copper from diffusing into the silicon, we can treat the deposition process startingfrom this layer onward.
A systematic enumeration of possible reaction mechanisms consistent with a given set of chemical species and elementary steps is useful in guiding research in heterogeneous reaction systems which are encountered in catalysis and electrochemistry. In this paper, the synthesis of methanol by catalytic hydrogenation of carbon monoxide and the anoidic oxidation of zinc in alkaline solutions are presented as two examples of the usefulness of such an approach. The technique utilized to generate the reaction mechanisms is based upon combinatorial analysis. linear algebra and the principle of microscopic reversibility.In the case of methanol synthesis, it is shown that in addition to the two currently proposed mechanisms, there exist two alternate reaction pathways each of which involves the hydrogenation of a formyl species to form a surface methoxide. One of these mechanisms has recently been proposed for a ZnO catalyst, however there remains an additional mechanism for consideration. For the case of anodic zinc oxidation, it is shown that mechanisms which involve cathodic elementary steps are also possible. To the authors knowledge, these mechanisms have not been previously discussed in the literature.
The ductility of electroless copper generally increases upon low-temperature (100-200 ~ annealing. It is shown in this paper that this phenomenon can be due to either or both of two different physical changes that occur in the deposit during annealing: (i) the decrease in pressure of the hydrogen gas trapped in voids, which results from the outdiffusion of the hydrogen, and (ii) the microstructural change resulting from recrystallization and grain growth. It is also shown that the extent of the grain growth is influenced by the volume occupied by voids and nonvolatile impurities contained within the deposits. In particular, voids and impurities trapped at the grain boundaries can effectively prevent the boundaries from migrating and thus retard recrystallization and grain growth.
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533of NiFe polycrystalline films. The permeability of the samples of head pole configurations can be understood separately for the yoke and the pole tip region and considered as the combination of that of the yoke and the pole tip region. Deterioration of the permeability of the strip samples on the stepped surface can be explained by the stress variation on the slope and the flat surface. The permeability is the combination of that on both surface. The effect of magnetostriction, strip configuration, step region, frequency, and residual stress on the permeability and the domain structure of NiFe films has become clear. In particular, magnetostrictive behavior has been demonstrated clearly. More accurate magnetostriction control is necessary for the thin film heads with narrower track width. AcknowledgmentThe author would like to thank Mr. Katsuki for measuring the stress of NiFe films. ABSTRACTThe ductility of fine-grained (0.1 -0.5 ~m) electroless copper deposits was found to vary with the type of substrates that they were plated on; under identical plating conditions, the ductility of the electroless copper grown on activated plastic substrates was higher than that grown epitaxially on a large-grained copper foil. This ductility difference is shown to originate from a difference in the void structure developed at the grain boundaries of the deposits during film formation.
2363 not correlate to the film microstructure. These surface grooves bore no correlation to grain boundaries. Measurements of grain size and distribution by examining the surface topography using techniques such as SEM and STM/ AFM could produce erroneous results. Additional information from another method, such as TEM, is recommended for verification. Johnston (Advanced Custom Technologies) for depositing the films, Ray Doyte (Materials Technology Center) for preparing the TEM samples, and Andy Zobel (Materials Technology Center) for doing the ion channeling work. ABSTRACTAn investigation was conducted to examine the low temperature (<300~ annealing behavior of two types of finegrained electroless copper deposits. Heat-treatment from continuous oven-annealing was compared to that from thermal cycling in a fluidized sandbath (FSB) unit. It was found that one of the deposits, referred to as type IV electroless copper, showed considerable resistance to recrystallization. Microscopic and chemical analyses indicated that this electroless copper contained a high density of organic inclusions which were effective in pinning grain boundary movement and preventing recrystallization. Type IV electroless copper also had high gaseous hydrogen content. The FSB experiments showed that this entrapped hydrogen could induce a local plastic deformation mechanism and cause internal fatiguing in the copper during thermal cycling. The other deposit, referred to as type I electroless copper, was relatively free of foreign incorporation. This copper recrystallized readily upon annealing. The driving force for grain growth was the surface energy released from elimination of grain boundaries.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 192.236.36.29 Downloaded on 2015-04-09 to IP
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