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08/27/93   11:31   NO 434   07

ISHM '92 Proceedings

[16] rather than the conventional aqueous HF clean, so that contamination by residual moisture is minimized. Another technique for removal of the native oxide is the use of Electron-Cyclotron Resonance (ECR) plasma cleaning with hydrogen [17. One must be aware of the possible creation by-products of any "clean" which is done prior to another processing step, especially when dealing with plasma sources where redeposition of etch species from the oxide etch or other sources of the reactor, e.g. the reactor materials, can occur. An example of the latter is the case where aluminum from the reactor parts is removed by sputtering from those parts and redeposited onto the water surface as AIOX. Wwith the above concerns in mind, one can proceed with the deposition of the nitrided refractory metal. After insuring that the vacuum system ultimate pressure is below 10-5 Pa range in the "throttled" mode (to minimize the possibility of uncontrollable addition of oxygen or nitrogen in the deposited film), the refractory metal deposition is then started with pure metal deposited to about 1/3 the desired thickness. This aids adhesion of the refractory metal to the substrate. Then, nitrogen is introduced into the deposition chamber, preferably as a 25% mixture with argon when sputter deposition is being done, and the deposition is continued to complete another 1/3 of the total thickness of refractory metal desired. Finally, the nitrogen is pimped away and the deposition of pure metal is continued to the final thickness desired. 

This procedure minimized the film stress increase in the refractory metal and allows good adhesion to the substrate and overlying metal. As with any refractory metallization, the intrinsic film stress should be optimized to the device structure. For sputter deposition, the pressure vs. stress relationship of Hoffman and Thornton [18] is recommended. One can determine the approximate level and nature (tensile or compressive) of stress component in the film by visual inspection of a thin (ca. 50 uM thick) beam of silicon which had been coated with the thickness of film required for the fabrication of the device. Adjustment of the sputtering pressure can then be done to reach the desired level and nature of film stress. 

References

1. J. Vossen, J. Vac. Sci. Technol,. 19 p. 761 (1981)
2. C .W. Nelson, "Metallization and glassing of silicon integrated circuits," Proc. Int. Symp. Hybrid Microelectronics, Dallas, TX, Sept. 29, 1969. ISHM, Montgomery, AL, pp. 413-438 (1969)
3. P. R. Fournier, U.S. 3,879,746 (1975). 
4. M.A. Nicolet and M. Bartur, J. Vac. Sci. Technoi., 19, pp.786-793 (1981)
5. R. Remba, I. Suni and M.A. Nicolet, IEEE El.Dev.Lett., EDL-6, pp. 437-438 (1985)
6. J. A. Cunningham, C. R. Fuller and C. T. Haywood, IEEE Trans. Reliab,. 19, pp. 182-187 (1970).
7. R. S. Nowicki, J. M. Harris, M. A. Nocilet and I. V. Mitchell, This Solid Films, 53, 195-205 (1978).
8. 6. R.A.M. Wolters and A.M. Nelllisen, Solid State Techol,. pp. 131-136 (Feb.,1986). 
9. R.S. Nowicki and I. Wang, J. Vac. Sci. Technol., 15, pp. 235-237 (1978)
10. C.C. Lee, G. Roberts, H. Gladstone and G. Vendura, "An All GOld Metal System for Aluminum Gate GaAs FET's" Hewlett-Packard 1977 Semiconductor Technology Conference, Fallen Leaf Lake, California. 
11. R. S. Nowicki and R. P. Henderson, original workers on study published by B. E. P Beeston and A.J. Aronson, MIcroel. Manuf. Test, 9, NO. 6 (1986) 33. 

12. J. E. Baker, R. J. Blattner, S. Nadal, C. A. Evans, Jr. and R.S. Nowicki, This Solid Films, 69, pp. 53-62 (1980).
13. D.W. Harris & R.S. Nowicki, "Applications of AEL in Microelectronics", in Practical Surface Analysis , Eds. D. Briggs and M.P. Seah, (John Wiley and Sons Ltd., England, 1990), pp. 257-310
14. R. S. Nowicki, unpublished study on an electroless nickel blistering problem, 1988. 
15. Metals Handbook., Vol. 5, Ninth Ed., Am. Soc. for Metals, 1985, pp. 219-249. See also J.R. Rairden, C.A. Neugebauer and R.A. Sigsbee, Metal. Trans., pp. 719-722 (1973).
16. T. Hara, private common., pat. pending. 
17. T. Shibata, Y. Nanishi and M. Fujimoto, Jap. J. Appl. Phys.,29, pp.1181-84(1990).
18. J. A. Thornton and D. W. Hoffman. J. Van Sci. Thecnol.,14, pp. 164-168 (1977).

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