LPCVD Tungsten Filled vias for Multilayer Metallization

Tungsten, deposited in a hot wall LPCVD furnace, was used to fill vias and contact holes. Starting from a planarized silicondioxide surface, vias and contact holes were opened by RIE to the first metallayer. Prior to tungsten deposition, a layer of 500Ã… TiW was sputter-deposited onto the wafers. The thickness of LPCVD tungsten was chosen to result in a planar surface with all the vias filled. In the next step tungsten and TiW were backetched, using a mixture of CF4/O2, thus reestablishing the planarized silicondioxide surface with all the vias and contacts filled with tungsten. Electrical measurements comfirmed good, uniform contacts with low specfic contact resistance. The results were successfully implemented in a commercially available CMOS process.