A selective LPCVD tungsten process using silane reduction for VLSI applications

A selective CVD tungsten process using silane reduction of tungsten hexafluoride has been investigated. A deposition rate as high as 0.6 mu m/min is obtained. The properties of the tungsten films have been investigated by X-ray diffraction, secondary ion mass spectroscopy, and transmission electron microscopy. The tungsten films contain a small amount of Si, which is uniformly distributed as a W/sub 5/Si/sub 3/ phase. The silane reduction process completely suppresses undesirable phenomena, such as Si consumption, lateral encroachment, and wormholes. Measurements have been made of the junction leakage current and the contact resistance. The junction leakage current for this process is almost the same as that for the conventional AlSi process. The contact resistance of submicron holes is more stable and lower for this process than for the conventional one. The new process has been successfully applied to CMOS 1-Mb DRAMs.<
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