Interconnect lines are thin wires inside microelectronic circuits. The material in an interconnect line is subjected to severe mechanical and electrical loading, which causes voids to nucleate and propagate in the line: microelectronic circuits often fail because an interconnect is severed by a crack. Many of the mechanisms of failure are believed to be associated with diffusion of material through the line; driven by variations in elastic strain energy and stress in the solid, by the flow of electric current, and by variations in the free energy of the solid itself. With a view to modelling interconnect failures, we have developed a finite element method that may be used to compute the effects of diffusion and deformation in an electrically conducting, deformable solid. Our analysis accounts for large changes in the shape of the solid due to surface diffusion, grain boundary diffusion, and elastic or inelastic deformation within the grains. The methods of analysis is reviewed in this paper, and selected examples are used to illustrate the capabilities of the method. We compute the rate of growth of a void in an interconnect by coupled grain boundary diffusion and creep; we investigate void migration and evolution by electromigration‐induced surface diffusion; we study the influence of electromigration and stress on hillock formation in unpassivated interconnects, and compute the distribution of stress and plastic strain induced by electromigration in a passivated, polycrystalline interconnect line.
Little population-based data has been published about skin cancers in children and young adults. In this study, 200 cases of melanoma and non-melanoma skin cancers diagnosed under 25 years of age in the North of England from 1968-1995 were obtained from the Northern Region Young Persons' Malignant Disease Registry. The incidence was 1.2 cases per million per year for children (aged 0-14 years) and was 13 cases per million per year for young adults (aged 15-24 years). Melanoma accounted for 138 cases, of which 16 were in subjects aged < 15 years at diagnosis. The incidence of melanoma increased in females at a rate of 5.6 per million per decade (95% confidence interval [CI] 2.2-8.9, P = 0.002), largely due to an increased incidence of primary lower limb tumours. The incidence for males was unchanged. Survival improved significantly over time for both males and females (P < or = 0.02). Of the 62 patients with non-melanoma skin cancers, 66% were diagnosed with primary non-basal cell carcinoma, 13% with dermatofibrosarcoma protuberans, 10% with squamous cell carcinoma and 11% with other tumours. Two cases were iatrogenic second malignancies following treatment for an earlier primary brain tumour. The incidence of non-melanoma skin cancers was significantly higher during 1982-1995 than during 1968-1981 (rate ratio 1.7, 95% CI 1.0-2.8). There were three deaths from non-melanoma skin cancer, and the overall 5 year survival rate was 98% (95% CI 89-100%). The reason for the increasing incidence of both melanoma and non-melanoma skin cancer in young people is unknown, but it is likely that ultraviolet exposure plays an aetiological role. It is important that families continue to be advised of the need for vigilance with regard to childhood sun exposure.
aintrodoctco of ch .d res start contc ners for scl cylctes and parcicetarmoi Total number of hospital admissions for accidental poisonings in children aged 0-4 years in England and Wales from 1970 to 1979 with all medicinal agents (above) and with specified drugs (below).
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