A Metal Fill Process
Original Publication Date: 2003-Nov-14
Included in the Prior Art Database: 2003-Nov-14
Rationale: Future CMOS require contact via/plug aspect ratio to decrease with increasing technology generation. For contact fill, the metal of choice has been and remains CVD tungsten from tungsten hexafluoride (WF6) for a variety of reasons. Due to the poor adhesion of CVD W on most dielectrics a glue (adhesion) layer with low contact resistance properties such as titanium is required. In addition, since the flourine from the W will attack titanium to form titanium flouride, a layer of diffusion barrier such as TiN is required. Thus, 3 films namely: titanium, titanium nitride and tungsten are required to fill the contact plugs. As the contact aspect ratio become aggressive, problems such as poor step coverage, "bread-loafing" and voids in the plug(coring) become apparent. Both the Ti and TiN film thicknesses have been reduced drastically in order to fill the plugs void-free. There is therefore a great need for a contact fill process with low defectivity and coring.