Linewidth and underlayer influence on texture in submicrometer-wide Al and AlCu lines

The local texture in three types of patterned, thin-film, Al and AlCu interconnections on Si semiconductor devices is investigated by electron backscatter diffraction. Two types of standard planar metal structures were investigated: (1) blanket Al and (2) blanket Al-0.5 wt% Cu on TiN/Ti underlayers. Both were deposited on amorphous SiO2 substrates followed by reactive ion etching to define 0.45-10 μm wide lines and >10×10μm2 pads. Damascene structures were also investigated in which Al-0.5 wt% Cu films were deposited into preformed Ti-lined amorphous SiO2 trenches, 0.3-5.0 μm wide by 0.4 μm deep, followed by chemical-mechanical polishing to remove the metal overburden. For these three types of structures, distinctly different behaviors were observed: the two planar metal samples exhibited either little change or a large increase in their (111) fiber texture strength with decreasing linewidth, while the damascene samples showed a marked decrease in the (111) fiber texture with decreasing linewidth and feature size. In addition, a novel trimodal (111) texture distribution was found in 0.3 μm wide damascene lines in which appreciable TiAl3 formed. © 1998 American Institute of Physics.