CVD aluminum for submicron VLSI metallization

For submicron VLSI metallization, chemical vapor deposition (CVD) of aluminum (Al) combines superior CVD step coverage with low resistivity and long experience with Al. The authors report the step coverage issues, electrical results, and device and process compatibility. CVD Al, 0.3 μm thick, was deposited at 230°C using industrial grade triisobutylaluminum (TIBA) in a prototype ASM Advance 600 CVD Cluster System. The conductivity was 2.9 μΩ-cm and no mobile ions were detected in CV measurement. At >80% film reflectivity, 0.5μm wide lines with 0.65 μm spaces were patterned with I-line lithography and RIE. SEM evaluation showed fully filled 0.65μm diameter windows with 2:1 aspect ratio. Optimizing the window coverage of the nucleation layer was important to ensure reliable CVD Al filling. Interestingly, anomalous filling of 0.75 μm diameter windows by very thin CVD Al layer (0.2 μm) was also observed, which might provide added process robustness. Devices processed with this 0.5 μm CMOS technology showed good results on submicron contact chains, line continuity, and shallow junction compatibility