The effect of grain orientation on the relaxation of thermomechanical stress and hillock growth in AI-1%Si conductor layers on silicon substrates

Hillocks are formed sporadically in Al-l%Si sputter layers on SiO₂/Si substrates during heat treatments in the range from 200 to 500°C. The driving force is the relaxation of thermomechanical stress in the grains induced by the thermal expansion mismatch between the metallization layer and the substrate. The orientations of individual grains and hillocks are measured on-line with a medium voltage transmission electron microscope by the Kikuchi pattern method. Thermomechanical stress in the grains is calculated with a biaxial strain model, considering the glide systems of dislocations for the individual grain orientations. In general, hillocks deviate from the ordinary 〈111〉 fiber texture of aluminum sputter layers. The spatial distribution of grain orientations is illustrated by orientation images using Miller indices or Rodrigues vectors.