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Using glancing angle X-ray diffraction, glow discharge optical emission spectroscopy, and transmission electron microscopy, the crystallization behavior and thermal stability of graded Ta-Si/Ta-Si-N diffusion barriers was analyzed after annealing at various temperatures. For a Ta30Si18N52/Ta73Si27 bilayer and a Ta73Si27/Ta30Si18N52/Ta73Si27 trilayer, nitrogen redistribution within the whole barrier is observed at Tan >= 500 °C. Further heat supply leads to barrier crystallization into Ta2N. Depositing the layer stacks directly onto silicon, a critical temperature of Cu silicide formation was determined. For graded Ta-Si/Ta-Si-N diffusion barriers, this temperature turned out to be between the corresponding values for Ta73Si27 and Ta30Si18N52 single layers. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The electromigration-induced void evolution has been investigated in-situ on fully embedded inlaid copper test structures inside a SEM, utilizing the method described in [1]. After the failure of the test structure or after significant voiding had been observed the cathode via region of the samples was prepared for subsequent TEM and/or EBSD analysis in order to reveal the position of grain boundaries and the orientations of the grains in the neighborhood of a void. It was confirmed that intersections of grain boundaries with interfaces of the interconnect lines or clusters of small grains can act as nucleation sites for initial void formation or as trapping sites on which voids can be stopped. Furthermore, it was found that for interconnects with strengthened top interface, where the diffusion rate is significantly lower due to the changed chemical bonding, that the void movement occurs mainly along the copper/liner interface. Such interconnects show significantly longer lifetimes. In this paper, local alloying of copper interconnects with aluminum is reported. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The ongoing scaling-down of device structures requires new methods for device characterization. High resolution TEM combined with analytical techniques becomes more and more an important tool in cross-sectional on-product characterization and failure analysis. Besides traditional techniques like EDS, EELS and also electron diffraction new analytical techniques which allow chemical analysis in the few nm range with only short acquisition times have been introduced only very recently. Energy filtering transmission electron microscopy (EFTEM) is such a new technique that can be used for both chemical mapping and ELNES mapping. It is shown how these techniques can contribute to problem solving in semiconductor industry. Capabilities and limits of the present analytical TEM techniques are discussed. New challenges for analytical TEM are forecasted based on the expected future design of semiconductor devices. [ABSTRACT FROM AUTHOR]