Effect of sputtered TiW deposition conditions on barrier properties for submicron metallization

Reports the results of an orthogonal array study of the step coverage of magnetron sputtered TiW. The authors concentrate on the effect of target power (1-2.5 kW), Ar pressure (4-21 mT), and substrate temperature (100-450 degrees C) on coverage into near vertical wall windows (85 degrees wall angle) with aspect ratio approximately 1.5 (h/w=1.3/0.85) reactive ion etched in a deposited oxide. Scanning electron microscopy (SEM) indicates that coverage defined as the ratio of TiW approximately 1000 AA thick on top of oxide to that in the bottom of the windows, varies between approximately 25-35%. Coverage improves with moderate power approximately 2 kW and temperature approximately 300 degrees C. Ar pressure has a somewhat smaller effect on coverage than either power or temperature. TiW resistivity and stress magnitude also decrease to 0.65-0.7 mu Omega -cm and low 10/sup 9/ dynes/cm/sup 2/ respectively, for the sputtering conditions used to maximize step coverage. Reverse bias diode leakage ( approximately 3000 AA deep n/sup +//p with approximately 1000 AA TiSi/sub 2/ and window contacts) does not degrade for Al/TiW or Al/CVD W/TiW metallization of the window contacts are annealed at 450 degrees C, 30 min., the highest anneal cycle used in this study. Low leakage was measured for a nominal 1000 AA thick TiW deposited with the conditions giving the best and worst window coverage, indicating that approximately 300 AA is an acceptable barrier at >