Material Characterization of Cu(Ti)-Polyimide Thin Film Stacks

E. Kondoh

ABSTRACT

Copper films containing a small amount of an alloy element (1 wt % Ti) are metallized on spun-on polyimide (PI) films. In order to modify the Cu(Ti)/PI interface, the PI surface is treated with an O₂-containing plasma prior to the Cu(Ti) deposition. The stacked films are characterized with respect to roles of the Ti incorporation and of the PI surface modification. Compared to pure Cu films, the Cu(Ti) films have a remarkably large adhesion strength to PI and show practically no diffusion into the PI layer. In addition, a well-developed (111) texture is observed in the Cu(Ti) films. The relative amount of the (111) component is dependent on the condition of the PI surface treatment. From X-ray photoelectron spectroscopy analyses, it is found that chemical reaction at the Cu(Ti)/PI interface involves metals (Cu, Ti), oxygen, and nitrogen.

References

1. D. Gupta, F. Faupel, and R. Willecke, in Diffusion in amorphous materials, Eds., H.J.a.D. Gupta, (The minerals, metals & materials Society, Pittsburgh, PA, 1993), pp. 189.
2. C.-K. Hu, M.B. Small, F. Kaufman, and D.J. Pearson, in Tungsten and Other Advanced Metals for VLSI/ULSI Applications V, Eds., S.S. Wong and S. Furukawa, (Materials Research Socity, Pittburg, PA, 1989), pp. 369.
3. J. C. Cabral, J.M. Harper, K. Holloway, D.A. Smith, and R.G. Schad, J. Vac. Sci. Technol. A10, 1706 (1992).
4. P.J. Ding, W.A. Lanford, S. Hymes, and S.P. Murarka, J. Appl. Phys. 75, 3627 (1994).
5. D.B. Knorr and K.P. Rodbell, J. Appl. Phys. 79, 2409 (1996).
6. S. W. Russell, S. A. Rafalski, R. L. Spreitzer, J. Li, M. Moinpour, F. Moghadam, and T. L. Alford, Thin Solid Films, 262, 154 (1995).
7. D. Adams, T. L. Alford, N. D. Theodore, and S. W. Russell, Thin Solid Films, 270, 346 (1995).
8. P. S. Ho, P. O. Hahn, J. W. Bartha, G. W. Rubloff, F. K. LeGoues, and B. D. Silverman, J. Vac. Sci. Technol., A3, 739 (1985).
9. R. Haight, R. C. White, B. D. Silverman, and P. S. Ho, J. Vac. Sci. Technol. A6, 2188 (1988).
10. F.S. Ohuchi, L.H. Tjeng, J. v. Elp, H. Eskes, J. Westerink, G.A. Sawatsky, and M.T. Czyzyk, Phys. Rev. B38, 11322 (1988).
11. I. Milosev, H.-H Strehblow, B. Navinsek, and M. Metikos-Hukovic, Surface and Interface Analysis, 23, 529 (1995).
12. D. P. Tracy and D. B. Knorr, J. Electron. Materials, 22, 611 (1993).
13. Y. Inagaki and T. Ito, J. Vac. Sci. Technol., B16, 2745 (1998).
14. A. W. Adamson, Physical Chemistry of Surfaces, 4^th ed., (John Wiley and Sons, New York, 1982).
15. H. Toyoda, T. Kawanoe, M. Hasunuma, H. Kaneko, and M. Miyauchi, in the Proceedings of IEEE International Reliability Physics Symposium, (San Jose, CA, 1994), p. 178.
16. E. Bauer and H. Poppa, Thin Solid Films, 12, 167 (1972).
17. F.D. Egitto, L.J. Matienzo, K.J. Blackwell, and A.R. Knoll, Journal of Adhesion Science and Technology, 8, 411 (1994).
18. N. Inagaki, S. Tasaka, and K. Hibi, Journal of Adhesion Science and Technology, 8, 395 (1994).
19. B. J. Bachman and M. J. Vasile, J. Vac. Sci. Technol. A7, 2709 (1989).

Figure Captions

Figure 1 Adhesion strength of Cu and Cu(Ti) films deposited on PI.

Figure 2 Adhesion strength of Cu and Cu(Ti) films as a function of plasma treatment time.

Figure 3 Atomic force microscope images of PI surfaces after plasma treatments. Notice that the vertical scales are not the same.

Figure 4 Average surface roughness (Ra) of plasma-treated PI surfaces as a function of treatment time.

Figure 5 Rutherford backscattering spectra for Cu(Ti)/PI and Cu/PI specimens. The sold curves show simulation results.

Figure 6 Carbon 1s core spectra of PI surfaces. a) pristine PI and b) after 50Å Cu(Ti) metallization.

Figure 7 Nitrogen 1s core spectra of PI surfaces. a) pristine PI and b) after 50Å Cu(Ti) metallization.

Figure 8 XPS depth profiling for (a) as-deposited and (b) annealed Cu(Ti)/PI-O₂ specimens.

Figure 9 The amounts of the (111), (100) and random texture components in the Cu and Cu(Ti) films.

Figure 10 Resistivity of as-deposited and annealed Cu(Ti) films for various PI treatment conditions.