Texture and strain in narrow copper damascene interconnect lines: An X-ray diffraction analysis

The behaviour of submicron damascene copper lines raises a number of fundamental issues such as grain growth in narrow trenches, thermomechanical properties of copper in these confined geometries, etc. This experimental study is aimed at evaluating the influence of annealing, polishing and line width on the room temperature strain and texture of narrow copper damascene lines. X-ray diffraction has been performed on arrays of lines with widths ranging between 3 μm and 0.09 μm. Two annealing conditions (150 °C and 400 °C) have been used either prior or after Chemical Mechanical Polishing (CMP). A clear influence of the Cu overburden on the in-line microstructure is evidenced. X-ray diffraction analysis shows that strains in line longitudinal direction are higher in those annealed at 400 °C and decrease with the width of the lines.Effect of CMP on structure and relationship between both texture and strain and temperature of thermal treatments is discussed in light of these observations.