TEM-Untersuchungen zum Gefüge und zu mechanischen Spannungen in Metallisierungen für SAW-Bauelemente

Higher frequencies in the MHz and GHz range and the increasing miniaturization lead to a higher load of the SAW (surface acoustic wave) metallizations. This higher SAW load and the intrinsic stresses result in a stress induced material transport, called acoustomigration. These microstructural changes can destroy the characteristic of the SAW device. Different Al based material combinations were investigated by different authors to improve the reliability of the metallizations and to delay the cost-intensive change to Cu based metallizations. The Cu based metallizations with TaSiN diffusion barriers were also investigated in this work. The barrier layers are necessary to impede the oxygen diffusion into the Cu layer and the Cu diffusion into the piezoelectric substrate. Also in this work the analytical TEM were used as a tool to investigate these microstructural changes in the SAW electrodes. Chemical changes in the metallizations were analysed by EDXS and EELS. The locally high resolved stress measurement in metallizations is a challenge for the future. The CBED (convergent beam electron diffraction) technique has shown the best resolution, however, it can only be applied to TEM lamellas. The aim of this work was to measure the stress within the SAW metallizations by using the CBED method. With it, we could correlate the microstructural changes with the causing stresses within the metallizations. To qualify the CBED method the thermal expansion of Al and Cu single crystals was measured by using a new model for thin TEM lamallas.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Technische Universität Dresden

Year

2007

Author dc:creator

• Hofmann, Matthias

Contributors dc:contributor

• Wetzig, Klaus
• Gemming, Thomas
• Thomas, Jürgen
• Bartha, Johann
• Dehm, Gerhard

• Oberflächenwellen
• Konvergente Elektronenbeugung
• TaSiN
• AlTi
• Cu
• Akustomigration
• Surface acoustic wave
• Convergent beam electron diffraction
• CBED
• diffusion barrier
• acoustomigration