On-chip copper/low-k interconnects for advanced IC devices: Materials integration and processing optimization studies.

摘要

The performance requirement of Moore's law continues to push the integrated circuits fabrication technology to reduce not only gate delay but also back-end-of-the-line (BEOL) delay. To meet these requirements, the implementation of copper as an interconnect in conjunction with ultra low-k materials as interlevel dielectrics (ILDs) in the fabrication of ULSI circuits has been a main stream. Presented in this dissertation is mainly focusing on the materials integration and processing optimization study of advanced Cu/low-k interconnections.; The dielectric soft-breakdown and conduction mechanisms in PTFE low-k thin films have been studied. Temperature accelerated effects on leakage current and dielectric soft-breakdown behavior in low-k thin films are investigated and analyzed. Frequency dependence of dielectric constant of low-k thin films are also investigated and analyzed with frequency range up to 3 GHz. The extendibility of PVD seed layer for future devices needs to be enhanced with electrochemical techniques. Developing analytical techniques for plating bath is a particular challenge because bath ingredients are difficult to ascertain. The feasibility of using an Ion Chromatography for electrochemical copper Seed Layer Enhancement process metrology is studied. The compatibility of low-k polymer dielectrics with the electrochemical Cu deposition solution is investigated. Also, the drift of copper ions in low-k polymer dielectrics to identify copper barrier requirements for reliable interconnect integration is addressed by means of capacitance-voltage measurement which can quantify uncompensated dielectric charge in a MIS system with high sensitivity.; It is found that the strength against soft-breakdown decreases with increasing temperature and with decreasing low-k film thickness. Ion conduction mechanism is expected to be dominant before soft-breakdown and Schottky conduction mechanism is expected to be dominant after soft-breakdown. The dielectric constant decreases with increasing frequency, and the frequency dependence is more pronounced in thinner low-k films. Frequency dependence of dielectric constant could be attributed to the orientation polarization of polymer chains and thickness dependence could be attributed to the crystallite size of low-k polymers. An Ion Chromatography method is shown to be capable for electrochemical Copper Seed Layer Enhancement process metrology. A strong correlation between the ion chromatograms and the electroplated copper film properties is observed.