Stable titanium silicide formation on field oxide after BF2 ion implantation

The use of titanium silicide for low resistivity interconnects in a complem entary metal-oxide-semiconductor process is investigated. After a source-dr ain processing, a wet oxide strip, and a 600 Angstrom Ti deposition, a two- step anneal forms stable TiSi2 in the diffused regions and amorphous silico n gate. Extraneous regions or islands of TiSi2 were found to form on BF2 im planted thick field oxide, and were not present on B-11, n-type (N +), or n onimplanted field areas. The growth and nucleation of TiSi2 in the presence of oxygen is discussed, and an oxygen solubility model is used to explain the nucleation of TiSi2 from a Ti5Si3 interlayer. Two models are presented to explain the availability of Si to form stable TiSi in field oxide region s. In the first, B is shown to promote the formation of oxygen vacancies re sulting in a Si rich oxide, while the second involves oxide network strain from the incorporation of F in the oxide, facilitating Si segregation to th e surface and subsequent availability of Si atoms. (C) 2001 American Vacuum Society.