Elasticity study of very thin Cu films

[摘要] The elastic properties and the surface morphology of Cu/Ta films and Ta/Cu/Ta films sputter-deposited on Si reed substrates were studied for the Cu film thickness, t(Cu), between 7 and 1000nm. A monotonic increase in the internal friction, Q(f)(-1), in the constituent Cu film above 200K was commonly observed. For Cu/Ta films, Young's modulus of a Cu film, E-f, showed good agreement with the theoretical value for t(Cu) >similar to 80 nm and a decrease with decreasing t(Cu) below similar to 80 nm. A decrease in Q(f)(-1) after 400 K annealing, Delta Q(f,400k)(-1) and the surface roughness showed a local minimum and a local maximum near 80 nm, respectively, indicating that the properties of the Cu film were modified by subsequent deposition of a Cu layer (the self capping effect). For Ta/Cu/Ta films, Ta capping brought about an increase in the grain size parallel to the film surface, a decrease in the internal stress and a decrease in Ef but no changes in the grain size normal to the film surface, Q(f)(-1), Delta Q(f,400k)(-1) and the t(Cu)-dependence of the surface roughness. These results are discussed in the light of the anclastic responses of grain boundaries and interface in nano-scale Cu films which may be important for down-sizing of electric devices. (c) 2006 Elsevier B.V. All rights reserved.

[发布日期] 2006-12-20

[效力级别]  Proceedings Paper

[关键词] Cu thin film;Young's modulus;internal friction;internal stress;surface morphology;capping effect