Fabrication of fine copper lines on AZ 5214^TM patterned silicon substrates by selective chemical vapor deposition

Abstract
Copper features with dimensions down to 0.5 µm were fabricated on silicon substrates by selective chemical vapor deposition. For the fabrication oxidized (100) silicon substrates were used, covered with a film grown by LPCVD at 0.1 Torr and 550 °C, from W(CO)₆ decomposition. These substrates were subsequently covered with AZ 5214^TM photosensitive polymer, which has been developed as both positive and negative tone resist. Copper was then chemically vapor deposited on the patterned substrates by 1, 5-cyclooctadiene Cu(I) hexafluoroacetylacetonate decomposition, at 1 Torr and temperatures of 110 and 140 °C. A vertical, cold-wall reactor was used, equipped with a UV lamp permitting photon-assisted deposition. Under UV illumination, copper was deposited on resist covered and uncovered parts of the substrate. In absence of illumination, the metal was selectively grown on the tungsten film only at relatively slow rates (1 and 3.5 nm/min at 110 and 140 °C respectively). Copper films had a granular form with a grain size increasing with temperature (150 and 550 nm at 110 and 140 °C respectively). Afer depositions the resist was removed in oxygen plasma leading to the formation of fine copper features.