Integration of chemical vapor deposition Al interconnects in a benzocyclobutene low dielectric constant polymer matrix: A feasibility study

Results are presented from a proof-of-concept study that examined the integ ration of damascene-processed thermal chemical vapor deposited (TCVD) alumi num (Al) interconnects in a benzocyclobutene (BCB) polymer matrix. In a fir st phase, the study identified baseline deposition conditions for the forma tion of structurally and chemically compatible blanket Al/titanium nitride (TiN)/BCB stacks on two types of blanket BCB substrates utilized to simulat e the actual surfaces encountered in typical damascene processing: (1) blan ket BCB films capped with a silicon dioxide SiO2 layer (SiO2-BCB), and (2) plasma reactive ion etched blanket BCB films. The TiN diffusion barrier was grown in two stages. A first (bottom) layer was deposited by physical vapo r deposition (PVD), followed by a CVD-grown top layer. The resulting TCVD A l/CVD TiN/PVD TiN/BCB stacks were stable under thermal stressing up to 325 degreesC for 1 h. In a second phase, an optimized TCVD Al process flow was developed for void-free filling of TiN-coated 320-nm-wide trenches etched i n a BCB matrix. The process flow included the demonstration of a chemical m echanical polishing recipe for planarization of the patterned TCVD Al/CVD T iN/PVD TiN/BCB structures. The resulting findings were incorporated in the fabrication of electrically testable TCVD Al/CVD TiN/PVD TiN/BCB interconne ct structures on 200 mm wafers. Electrical evaluation for shorting and leak age of the test dice produced an adequate yield for the feasibility study o f similar to 71% of screened test sites. The electrical tests also generate d an upper-bound value of 4.2 mu Omega cm for Al Line resistivity, a number that did not include corrections for contact resistance and interfacial sc attering. These findings demonstrate the feasibility of TCVD Al/BCB based m etallization schemes, particularly in terms of chemical, structural, mechan ical, and electrical performance. (C) 2000 American Vacuum Society. [S0734- 211X(00)03705-7].