over titanium silicide. However, other concerns, including local effects near certain types of contacts, prevent this technology from being used. Current practice is to use the SiH 4 reduction reaction for WF 6 when depositing selective tungsten. Table 5.1 summarizes the film/deposition parameters that are critical for using both blanket and selective CVD tungsten and the analytical techniques used to char- acterize them. References 1 R. Blumenthal and G. C. Smith. Tungsten and Other Refractory Metals for VLSI Applications III. (V. Wells, Ed.) Mat. Res. Soc., Pittsburgh, 1988, p. 47. W. T. Runyan. Semiconductor Measurements and Instrumentation. McGraw-Hill, New York, 1975, p. 71. G. M. Gutierrez, R. S. Blewer, and M. E. Tracy. Tungsten and Other Refractory Metals for VLSI Applications III. (V. Wells, Ed.) Mat. Res. Soc., Pittsburgh, 1988, p. 271. S. Sivaram, S. Chen, D. Liao, R. Shukla, and D. Fraser. Tungsten and Other Refractory Metals for ULSI Applications 1990. (G. Smith and R. Blumenthal, Eds.) Mat. Res. Soc., Pittsburgh, 1991, p. 407. R. Blumenthal, G. Smith, H. Y. Liu, and H. L. Tsai. Tungsten and Other Refractory Metals for VLSI Applications IV. (R. S. Blewer and C. M. McConica, Eds.) Mat. Res. Soc., Pittsburgh, 1989, p. 65. D. R. Bradbury and T. I. Kamins. J. Electrochem. Soc. 133, 1215, 1986. R. W. Cheek, J. A. Kelber, J. Fleming, R. D. Lujan, and R. S. Blewer. Tungsten and Other Refractory Metals for ULSI Applications 1990. (G. Smith and R. Blumenthal, Eds.) Mat. Res. Soc., Pittsburgh, 1991, p. 99. J. R. Creighton and J. W. Rogers. Tungsten and Other Refractory Metals for VLSI Applications III. (V. Wells, Ed.) Mat. Res. Soc., Pittsburgh, 1988, p. 63. S. Tseng, L. Lane, R. Foster, S. Felch, P. Geraghty, and W. L. Smith. Tungsten and Other Refractory Metals for VLSI Applications III. (V. Wells, Ed.) Mat. Res. Soc., Pittsburgh, 1988, p. 303. G. C. Smith, T. D. Bonifield, R. Blumenthal, J. Keenan, and P.-H. Chang. Proceedings. 1987 VLSI Multilevel Interconnect Conf., Santa Clara, CA, 1987, p. 155. 2 3 4 5 6 7 8 9 10 REFERENCES 137