The ptanarization of metal interconnect Layers has recently been a subject of intensive development effort in semiconductor processing. Although layer thicknesses have not decreased In proportion, lateral dimensions have been reduced to the point that aspect ratios are too large for effective step coverage by conventional film deposition techniques. The most difficult structure to peanarize is submicron contact holes in thick dielectrics.
A dual-Layer CVD blanket tungsten film was shown to be viable for use as an interconnect material in submicron processes. A single-wafer reactor operating at a pressure of 80 Torr was used to deposit the film. The film exhibits superior properties in terms of its basic characteristics. The film completely fits submicron contacts to silicon, yet has a low surface roughness that would minimize concomitant photolithography and etching problems. Film adhesion is excellent, uniformity and reproducibility are >95%, depgsition rate is greater than 400 nm/mmn., stress is below 8×109 dynes/cm2, and resistivity is 11 μ-ohm-cm or less.