A highly reliable selective CVD-W utilizing SiH4 reduction for VLSI contacts

Selective CVD-W process by using silane (SiH4) reduction of WF6 has been developed for VLSI contacts. The reaction occurs very fast resulting in a deposition rate of as high as 0.6 µm/min, and completely suppresses undesirable phenomena such as encroachment and wormholes. An X-ray diffraction analysis shows that a small W5Si3 peak can be observed although W peaks are dominant. The junction leakage current for the new selective CVD-W process is almost the same as that for conventional AlSi one. Contact resistance of submicron holes is more stable and lower for this process than for the conventional one. This new process has been successfully applied to CMOS 1Mbit DRAM.