Process and reliability of air-gap Cu interconnect using 90-nm node technology

• Published in: IEEE transactions on electron devices Vol. 52; no. 3; pp. 352 - 359
• Main Authors: Noguchi, J., Sato, K., Konishi, N., Uno, S., Oshima, T., Ishikawa, K., Ashihara, H., Saito, T., Kubo, M., Tamaru, T., Yamada, Y., Aoki, H., Fujiwara, T.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-03-2005; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Air-gaps; Applied sciences; capacitance; CMOS integrated circuits; Copper; Design. Technologies. Operation analysis. Testing; Electric breakdown; Electronics; Etching; Exact sciences and technology; IC interconnections; Integrated circuit interconnections; Integrated circuit metallization; Integrated circuit reliability; Integrated circuits; Leakage currents; Microelectronic fabrication (materials and surfaces technology); reliability; seals; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; stress; stress; Electric breakdown; Dry process; Metallizing; IC interconnections; Air-gaps; Damascene process; Self aligned technology; Time dependence; Microelectronic fabrication; Effective dielectric constant; Interconnection; Complementary MOS technology; seals; Integrated circuit; Air gap; Capacitance; copper; Leakage current; Miniaturization; Reliability; Sacrificial layer; Damaging
• DOI: 10.1109/TED.2005.843886
• EISSN: 1557-9646
• ISSN: 0018-9383

A self-aligned air-gap interconnect process was proposed. The key features include: 1) a simple process using a conventional Cu damascene process; 2) the combination of a sacrificial layer and a dry-etching process that do not cause any damage to Cu wires; 3) a self-aligned, maskless structure for gap formation; and 4) the preservation of mechanical integrity. In this paper, the air-gap Cu metallization was applied to 130- and 90-nm node CMOS. Four levels of Cu/air-gap interconnects were successfully fabricated and the reliability of the technology was investigated. There were distinct improvements of the leakage current and the time-dependent dielectric breakdown characteristic by the application of an air-gap. Moreover, the air-gap interconnect was further improved with a selective W sealing process. This results in a drastic reduction of the capacitance and the effective dielectric constant.