Critical influence of plating bath temperature on Cu damascene electrodeposits

The plating bath temperature has a critical influence on the damascene gap fill quality. Scanning electron microscopy studies indicated that over a small temperature range from 20 to 30 degrees C defect-free electroplated Cu fill was obtained. The effect was attributable to the initial nucleation and the chemistry of the plating bath, particularly the functionality of the additives. Secondary ion mass spectroscopy analysis showed different impurity levels of H, C, O, S, and Cl incorporated within the films. X-ray diffraction analysis on blanket Cu films indicated that, although all the Cu films had roughly the same (111) texture strength after plating, after a high temperature anneal at 450 degrees C for 30 min, the films deposited at higher temperatures exhibited much stronger (111) texture than the others. However, x-ray pole figure analysis of Cu lines with 0.35 mu m linewidth and 0.40 mu m spacing indicated roughly the same (111) texture intensity after the anneal. The shortened transformation time and more tensile stress observed on blanket Cu films plated at low temperatures were due to smaller grains and less dense packing of deposits which were formed at low temperature plating. Severe anisotropy of the stress was measured in 0.35 mu m Cu lines where the stress perpendicular to the trench and along the surface normal were only about half of the stress parallel to the trench. This indicates the existence of strong side wall interaction between Cu and the dielectrics. (C) 1999 American Vacuum Society. [S0734-211X(99)04105-0].