EFFECTS OF BARRIER LAYER AND PROCESSING CONDITIONS ON THIN-FILM CU MICROSTRUCTURE

The crystallographic texture and grain size of sputtered Cu films were characterized as a function of deposition temperature, barrier layer material, and vacuum conditions. For Cu deposited in a HV chamber, (111) Cu texture was found to weaken with increasing deposition temperatures on W, amorphous C and Ta barrier layers, each deposited at 30 degrees C. Conversely, under identical Cu deposition conditions, texture was found to strengthen with increasing deposition temperature on Ta deposited at 100 degrees C. Median Cu grain size varied parabolically with deposition temperature on all barrier layers and was slightly higher on the 100 degrees C Ta at a given Cu deposition temperature, relative to the other underlayers. For depositions in an UHV chamber, Cu texture was found to strengthen with increasing Cu deposition temperature, independent of Ta deposition temperature. Median Cu grain size, however, was still higher on 100 degrees C Ta than on 30 degrees C Ta. The observed differences between the two different chambers suggest that the trend of weak texture at elevated deposition temperatures may be related to contamination. Characterization of the Ta underlayers revealed that the strengthened texture of Cu films deposited on 100 degrees C Ta is likely related to textural inheritance.