PROBLEMS OF HIGH-RELIABILITY MULTILEVEL VLSI INTERCONNECTIONS

The use of aluminum in VLSI metallization involves a number of factors which limit the reliability of the interconnections. However, this material remains a promising component for multilevel systems. Encouraging results, in particular, are obtained using electron-beam evaporation for the creation of interconnections with so-called "bamboo" structure. The electron-beam evaporation of refractory metals under conditions of ultra-high vacuum also allows one to make high-quality silicide films (TiSi2, CoSi2) using a quite low-temperature process (550-650-degrees-C), which eliminates the appearance of strong stresses in the film at locations of contacts in the silicon. The outlook is for the application of tungsten for barrier layers and interconnections primarily because W has almost three orders of magnitude higher resistance to electromigration than Al. Stimulated deposition from vapor-gas mixture on substrates cooled to a negative substrate temperature are promising for the deposition of planarized dielectric films.