Gap-filling property of Cu film by chemical vapor deposition

The gap-filling property of Cu deposited by chemical vapor deposition was investigated in 1/4-mu m-wide trenches and 1/4-mu m-diam holes. Attention was paid to the influences on the gap-filling property of both substrate temperature and partial pressure of the source gas. At a low deposition temperature of 180 degrees C, Cu could completely fill a hole with an aspect ratio of 7. A high deposition rate could be obtained at the high substrate temperature and high pal-tial pressure of the source gas. However the coverage probably deteriorated because of the increase in sticking coefficient due to an increase in the reaction rate at high temperature. As the source gas pressure increased, the deposition rate increased and saturated in the high source pressure region. The good gap-tilling property at high source pressures was attributed to the Langmuir-Hinshelwood reaction where almost the same deposition rate is realized from the top to the bottom of the trench. At a high temperature of 215 degrees C, voids were observed at both the center and along the wall of the trench. The voids along the wall were assumed to be formed at the initial stage of deposition. They disappeared with an increase in source gas flow rate. Therefore, the formation of voids could be due to an insufficient supply of source gas. By annealing the Cu film, its properties of increase in grain size and the reduction in the amount of C, O, and F contaminants were improved. After annealing and chemical mechanical polishing treatment, scanning electron microscopy observation showed Cu interconnecting lines with grains larger than the wire width. (C) 1999 American Vacuum Society. [S0734-211 X(99)05505-5].