Air-Gaps for High-Performance On-Chip Interconnect Part II: Modeling, Fabrication, and Characterization
- 698 Downloads
Air-gaps are the ultimate low-k material in microelectronics due to air having a low dielectric constant close to 1.0. The interconnect capacitance can further be reduced by extending the air-gaps into the interlayer dielectric region to reduce the fringing electric field. An electrostatic model (200 nm half-pitch interconnect with an aspect ratio of 2.0), was used to evaluate the dielectric properties of the air-gap structures. The incorporation of air-gaps into the intrametal dielectric region reduced the capacitance by 39% compared with SiO2. Extending the air-gap 100 nm into the top and bottom interlayer SiO2 region lowered the capacitance by 49%. The ability to fabricate air-gaps and ‹extended air-gaps’ was demonstrated, and the capacitance decrease was experimentally verified. Cu/air-gap and extended Cu/air-gap interconnect structures were fabricated using high-modulus tetracyclododecene (TD)-based sacrificial polymer. The aspect ratio of the air-gap was 1.8 and the air-gap was extended 80 nm and 100 nm into the top and bottom interlevel SiO2 region, respectively. The measured effective dielectric constant (k eff) of the Cu/air-gap and the extended Cu/air-gap structures with SiO2 interlevel dielectric was 2.42 and 2.17, respectively. The effect of moisture uptake within the extended Cu/air-gap structure was investigated. As the relative humidity increased from 4% to 92%, the k eff increased by 7%. Hexamethyldisilazane was used to remove adsorbed moisture and create a hydrophobic termination within the air-cavities, which lowered the effect of humidity on the k eff. A dual Damascene air-gap and extended air-gap fabrication processes were proposed and the challenges of using a sacrificial polymer placeholder approach to form air-cavities are compared to other integration approaches of dual Damascene air-gap.
KeywordsAir-gap low-k Damascene
The authors gratefully acknowledge the support of Promerus LLC.
- 1.TheInternational Technology Roadmap for Semiconductors (2006). http://www.itrs.net/.
- 2.D. Edelstein, J. Heidenreich, R. Goldblatt, W. Cote, C. Uzoh, N. Lustig et al., Technical Digest, IEEE International Electron Devices Meeting (2007), p. 773.Google Scholar
- 4.D.C. Edelstein, Proceedings of the 12th International IEEE VLSI Multilevel Interconnection Conference (1995), p. 301.Google Scholar
- 5.N.P. Hacker, G. Davis, L. Figge, and T. Krajewski, Proc. MRS Symp. Low Dielectric Constant Materials III, Vol. 476, eds. C. Case, P. Kohl, T. Kikkawa, and W. Lee (1997), p. 25.Google Scholar
- 6.Y. Ohoka, Y. Ohba, A. Isobayashi, N. Komai, S. Arakawa, R.␣Kanamura, and S. Kadomura, IITC (San Francisco, CA, 2007), pp. 67–69.Google Scholar
- 7.M. Aimadeddine, V. Jousseaume, V. Arnal, L. Favennec, A.␣Farcy, A. Zenasni, M. Assous, M. Vilmay, S. Jullian, P.␣Maury, V. Delaye, N. Jourdan, T. Vanypre, P. Brun, G.␣Imbert, Y. LeFriec, M. Mellier, H. Chaabouni, L.L. Chapelon, K. Hamioud, F. Volpi, D. Louis, G. Passemard, and J. Torres, IITC (San Francisco, CA, 2007), p. 175.Google Scholar
- 9.S. Park, J. Krotine, S. Allen, and P. Kohl, VMIC (Fremont, CA, 2007).Google Scholar
- 10.R. Daamen, P.H.L. Bancken, D. Ernur Badaroglu, J. Michelon, V.H. Nguyen, G.J.A.M. Verheijden, A. Humbert, J. Waterloos, A. Yang, J.K. Cheng, L. Chen, T. Martens, and R.J.O.M. Hoofman, IITC (San Francisco, CA, 2007), p. 61.Google Scholar
- 11.L.G. Gosset, F. Gaillard, D. Bouchu, R. Gras, J. de Pontcharra, S. Orain, O. Cueto, Ph. Lyan, O. Louveau, G.␣Passemard, and J. Torres, IITC (San Francisco, CA, 2007), p. 58.Google Scholar
- 12.T. Harada, A. Ueki, K. Tomita, K. Hashimoto, J. Shibata, H.␣Okamura, K. Yoshikawa, T. Iseki, M. Higashi, S. Maejima, K. Nomura, K. Goto, T. Shono, S. Muranka, N. Torazawa, S.␣Hirao, M. Matsumoto, T. Sasaki, S. Matsumoto, O. Ogawa, M. Fujisawa, A. Ishii, M. Matsuura, and T. Ueda, IITC (San Francisco, CA, 2007), p. 141.Google Scholar
- 13.R.H. Havemann and S.-P. Jeng, U.S. patent No. 5,461,003 (1995).Google Scholar
- 15.L.G. Gosset, V. Arnal, C. Prindle, R. Hoofman, G. Verheijden, R. Daamen, L. Broussous, F. Fusalba, M. Assous, R. Chatterjee, J. Torres, D. Gravesteijn, and K.C. Yu, IITC (2003), p. 65.Google Scholar
- 22.N. Grove, Characterization of functionalized polynorbornenes as interlevel dielectrics (Ph.D. dissertation, Georgia Institute of Technology, 1997).Google Scholar
- 23.J. Noguchi, T. Oshima, T. Matsumoto, S. Uno, K. Sato, N.␣␣Konishi, T. Saito, M. Miyauchi, S. Hotta, H. Aoki, T.␣Kikuchi, K. Watanabe, and K. Kikushima, IITC (2006), p.␣167.Google Scholar